Fixup

Newsfile
Speed up calculation of remote hosts
2023-07-20 13:26:14 +01:00 · 2023-07-20 13:21:58 +01:00 · 2023-07-20 13:19:16 +01:00 · 2023-07-20 11:07:58 +01:00 · 2023-07-20 10:46:37 +01:00 · 2023-07-19 17:00:33 +00:00
204 changed files with 8268 additions and 6381 deletions
--- a/.ci/scripts/calculate_jobs.py
+++ b/.ci/scripts/calculate_jobs.py
@@ -29,11 +29,12 @@ IS_PR = os.environ["GITHUB_REF"].startswith("refs/pull/")

 # First calculate the various trial jobs.
 #
-# For each type of test we only run on Py3.7 on PRs
+# For PRs, we only run each type of test with the oldest Python version supported (which
+# is Python 3.8 right now)

 trial_sqlite_tests = [
    {
-        "python-version": "3.7",
+        "python-version": "3.8",
        "database": "sqlite",
        "extras": "all",
    }
@@ -46,13 +47,13 @@ if not IS_PR:
            "database": "sqlite",
            "extras": "all",
        }
-        for version in ("3.8", "3.9", "3.10", "3.11")
+        for version in ("3.9", "3.10", "3.11")
    )


 trial_postgres_tests = [
    {
-        "python-version": "3.7",
+        "python-version": "3.8",
        "database": "postgres",
        "postgres-version": "11",
        "extras": "all",
@@ -71,7 +72,7 @@ if not IS_PR:

 trial_no_extra_tests = [
    {
-        "python-version": "3.7",
+        "python-version": "3.8",
        "database": "sqlite",
        "extras": "",
    }
@@ -133,11 +134,6 @@ if not IS_PR:
                "sytest-tag": "testing",
                "postgres": "postgres",
            },
-            {
-                "sytest-tag": "buster",
-                "postgres": "multi-postgres",
-                "workers": "workers",
-            },
        ]
    )

--- a/.github/workflows/release-artifacts.yml
+++ b/.github/workflows/release-artifacts.yml
@@ -144,7 +144,7 @@ jobs:

      - name: Only build a single wheel on PR
        if: startsWith(github.ref, 'refs/pull/')
-        run: echo "CIBW_BUILD="cp37-manylinux_${{ matrix.arch }}"" >> $GITHUB_ENV
+        run: echo "CIBW_BUILD="cp38-manylinux_${{ matrix.arch }}"" >> $GITHUB_ENV

      - name: Build wheels
        run: python -m cibuildwheel --output-dir wheelhouse
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -320,7 +320,7 @@ jobs:

      - uses: actions/setup-python@v4
        with:
-          python-version: '3.7'
+          python-version: '3.8'

      - name: Prepare old deps
        if: steps.cache-poetry-old-deps.outputs.cache-hit != 'true'
@@ -362,7 +362,7 @@ jobs:
    runs-on: ubuntu-latest
    strategy:
      matrix:
-        python-version: ["pypy-3.7"]
+        python-version: ["pypy-3.8"]
        extras: ["all"]

    steps:
@@ -399,8 +399,8 @@ jobs:
      env:
        SYTEST_BRANCH: ${{ github.head_ref }}
        POSTGRES: ${{ matrix.job.postgres && 1}}
-        MULTI_POSTGRES: ${{ (matrix.job.postgres == 'multi-postgres') && 1}}
-        ASYNCIO_REACTOR: ${{ (matrix.job.reactor == 'asyncio') && 1 }}
+        MULTI_POSTGRES: ${{ (matrix.job.postgres == 'multi-postgres') || '' }}
+        ASYNCIO_REACTOR: ${{ (matrix.job.reactor == 'asyncio') || '' }}
        WORKERS: ${{ matrix.job.workers && 1 }}
        BLACKLIST: ${{ matrix.job.workers && 'synapse-blacklist-with-workers' }}
        TOP: ${{ github.workspace }}
@@ -477,7 +477,7 @@ jobs:
    strategy:
      matrix:
        include:
-          - python-version: "3.7"
+          - python-version: "3.8"
            postgres-version: "11"

          - python-version: "3.11"
--- a/.github/workflows/twisted_trunk.yml
+++ b/.github/workflows/twisted_trunk.yml
@@ -96,7 +96,11 @@ jobs:
    if: needs.check_repo.outputs.should_run_workflow == 'true'
    runs-on: ubuntu-latest
    container:
-      image: matrixdotorg/sytest-synapse:buster
+      # We're using ubuntu:focal because it uses Python 3.8 which is our minimum supported Python version.
+      # This job is a canary to warn us about unreleased twisted changes that would cause problems for us if
+      # they were to be released immediately. For simplicity's sake (and to save CI runners) we use the oldest
+      # version, assuming that any incompatibilities on newer versions would also be present on the oldest.
+      image: matrixdotorg/sytest-synapse:focal
      volumes:
        - ${{ github.workspace }}:/src

--- a/.gitignore
+++ b/.gitignore
@@ -34,6 +34,7 @@ __pycache__/
 /logs
 /media_store/
 /uploads
+/homeserver-config-overrides.d

 # For direnv users
 /.envrc
--- a/CHANGES.md
+++ b/CHANGES.md
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -13,9 +13,9 @@ dependencies = [

 [[package]]
 name = "anyhow"
-version = "1.0.71"
+version = "1.0.72"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9c7d0618f0e0b7e8ff11427422b64564d5fb0be1940354bfe2e0529b18a9d9b8"
+checksum = "3b13c32d80ecc7ab747b80c3784bce54ee8a7a0cc4fbda9bf4cda2cf6fe90854"

 [[package]]
 name = "arc-swap"
@@ -182,9 +182,9 @@ dependencies = [

 [[package]]
 name = "proc-macro2"
-version = "1.0.52"
+version = "1.0.64"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d0e1ae9e836cc3beddd63db0df682593d7e2d3d891ae8c9083d2113e1744224"
+checksum = "78803b62cbf1f46fde80d7c0e803111524b9877184cfe7c3033659490ac7a7da"
 dependencies = [
 "unicode-ident",
 ]
@@ -229,9 +229,9 @@ dependencies = [

 [[package]]
 name = "pyo3-log"
-version = "0.8.2"
+version = "0.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c94ff6535a6bae58d7d0b85e60d4c53f7f84d0d0aa35d6a28c3f3e70bfe51444"
+checksum = "f47b0777feb17f61eea78667d61103758b243a871edc09a7786500a50467b605"
 dependencies = [
 "arc-swap",
 "log",
@@ -273,9 +273,9 @@ dependencies = [

 [[package]]
 name = "quote"
-version = "1.0.26"
+version = "1.0.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4424af4bf778aae2051a77b60283332f386554255d722233d09fbfc7e30da2fc"
+checksum = "573015e8ab27661678357f27dc26460738fd2b6c86e46f386fde94cb5d913105"
 dependencies = [
 "proc-macro2",
 ]
@@ -291,9 +291,21 @@ dependencies = [

 [[package]]
 name = "regex"
-version = "1.8.4"
+version = "1.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d0ab3ca65655bb1e41f2a8c8cd662eb4fb035e67c3f78da1d61dffe89d07300f"
+checksum = "b2eae68fc220f7cf2532e4494aded17545fce192d59cd996e0fe7887f4ceb575"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "83d3daa6976cffb758ec878f108ba0e062a45b2d6ca3a2cca965338855476caf"
 dependencies = [
 "aho-corasick",
 "memchr",
@@ -302,9 +314,9 @@ dependencies = [

 [[package]]
 name = "regex-syntax"
-version = "0.7.2"
+version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "436b050e76ed2903236f032a59761c1eb99e1b0aead2c257922771dab1fc8c78"
+checksum = "2ab07dc67230e4a4718e70fd5c20055a4334b121f1f9db8fe63ef39ce9b8c846"

 [[package]]
 name = "ryu"
@@ -320,29 +332,29 @@ checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"

 [[package]]
 name = "serde"
-version = "1.0.164"
+version = "1.0.171"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9e8c8cf938e98f769bc164923b06dce91cea1751522f46f8466461af04c9027d"
+checksum = "30e27d1e4fd7659406c492fd6cfaf2066ba8773de45ca75e855590f856dc34a9"
 dependencies = [
 "serde_derive",
 ]

 [[package]]
 name = "serde_derive"
-version = "1.0.164"
+version = "1.0.171"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d9735b638ccc51c28bf6914d90a2e9725b377144fc612c49a611fddd1b631d68"
+checksum = "389894603bd18c46fa56231694f8d827779c0951a667087194cf9de94ed24682"
 dependencies = [
 "proc-macro2",
 "quote",
- "syn 2.0.10",
+ "syn 2.0.25",
 ]

 [[package]]
 name = "serde_json"
-version = "1.0.96"
+version = "1.0.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "057d394a50403bcac12672b2b18fb387ab6d289d957dab67dd201875391e52f1"
+checksum = "d03b412469450d4404fe8499a268edd7f8b79fecb074b0d812ad64ca21f4031b"
 dependencies = [
 "itoa",
 "ryu",
@@ -374,9 +386,9 @@ dependencies = [

 [[package]]
 name = "syn"
-version = "2.0.10"
+version = "2.0.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5aad1363ed6d37b84299588d62d3a7d95b5a5c2d9aad5c85609fda12afaa1f40"
+checksum = "15e3fc8c0c74267e2df136e5e5fb656a464158aa57624053375eb9c8c6e25ae2"
 dependencies = [
 "proc-macro2",
 "quote",
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,3 +3,4 @@

 [workspace]
 members = ["rust"]
+resolver = "2"
--- a/changelog.d/15708.feature
+++ b/changelog.d/15708.feature
@@ -0,0 +1 @@
+Add Unix Socket support for HTTP Replication Listeners. Document and provide usage instructions for utilizing Unix sockets in Synapse. Contributed by Jason Little.
--- a/changelog.d/15820.bugfix
+++ b/changelog.d/15820.bugfix
@@ -0,0 +1 @@
+Fix long-standing bug where remote invites weren't correctly pushed.
--- a/changelog.d/15884.misc
+++ b/changelog.d/15884.misc
@@ -0,0 +1 @@
+Mark `get_user_in_directory` private since it is only used in tests. Also remove the cache from it.
--- a/changelog.d/15887.misc
+++ b/changelog.d/15887.misc
@@ -0,0 +1 @@
+Fix background schema updates failing over a large upgrade gap.
--- a/changelog.d/15909.misc
+++ b/changelog.d/15909.misc
@@ -0,0 +1 @@
+Document which Python version runs on a given Linux distribution so we can more easily clean up later.
--- a/changelog.d/15911.feature
+++ b/changelog.d/15911.feature
@@ -0,0 +1 @@
+Allow `+` in Matrix IDs, per [MSC4009](https://github.com/matrix-org/matrix-spec-proposals/pull/4009).
--- a/changelog.d/15912.feature
+++ b/changelog.d/15912.feature
@@ -0,0 +1 @@
+Support room version 11 from [MSC3820](https://github.com/matrix-org/matrix-spec-proposals/pull/3820).
--- a/changelog.d/15913.feature
+++ b/changelog.d/15913.feature
@@ -0,0 +1 @@
+Allow configuring the set of workers to proxy outbound federation traffic through via `outbound_federation_restricted_to`.
--- a/changelog.d/15921.doc
+++ b/changelog.d/15921.doc
@@ -0,0 +1 @@
+Better clarify how to run a worker instance (pass both configs).
--- a/changelog.d/15922.misc
+++ b/changelog.d/15922.misc
@@ -0,0 +1 @@
+Add details to warning in log when we fail to fetch an alias.
--- a/changelog.d/15924.feature
+++ b/changelog.d/15924.feature
@@ -0,0 +1 @@
+Add Unix Socket support for HTTP Replication Listeners. Document and provide usage instructions for utilizing Unix sockets in Synapse. Contributed by Jason Little.
--- a/changelog.d/15925.bugfix
+++ b/changelog.d/15925.bugfix
@@ -0,0 +1 @@
+Fix a bug introduced in 1.86.0 where Synapse starting with an empty `experimental_features` configuration setting.
--- a/changelog.d/15926.misc
+++ b/changelog.d/15926.misc
@@ -0,0 +1 @@
+Remove unneeded `__init__`.
--- a/changelog.d/15928.removal
+++ b/changelog.d/15928.removal
@@ -0,0 +1 @@
+Remove support for calling the `/register` endpoint with an unspecced `user` property for application services.
--- a/changelog.d/15933.misc
+++ b/changelog.d/15933.misc
@@ -0,0 +1 @@
+Fix bug with read/write lock implementation. This is currently unused so has no observable effects.
--- a/changelog.d/15938.doc
+++ b/changelog.d/15938.doc
@@ -0,0 +1 @@
+Improve the documentation for the login as a user admin API.
--- a/changelog.d/15940.misc
+++ b/changelog.d/15940.misc
@@ -0,0 +1 @@
+Unbreak the nix development environment by pinning the Rust version to 1.70.0.
--- a/changelog.d/15952.misc
+++ b/changelog.d/15952.misc
@@ -0,0 +1 @@
+Update presence metrics to differentiate remote vs local users.
--- a/changelog.d/15958.misc
+++ b/changelog.d/15958.misc
@@ -0,0 +1 @@
+Fix bug with read/write lock implementation. This is currently unused so has no observable effects.
--- a/changelog.d/15960.misc
+++ b/changelog.d/15960.misc
@@ -0,0 +1 @@
+Ensure a long state res does not starve CPU by occasionally yielding to the reactor.
--- a/changelog.d/15968.misc
+++ b/changelog.d/15968.misc
@@ -0,0 +1 @@
+Reduce the amount of state we pull out.
--- a/changelog.d/15969.feature
+++ b/changelog.d/15969.feature
@@ -0,0 +1 @@
+Allow configuring the set of workers to proxy outbound federation traffic through via `outbound_federation_restricted_to`.
--- a/changelog.d/15970.misc
+++ b/changelog.d/15970.misc
@@ -0,0 +1 @@
+Speed up calculation of remote hosts.
--- a/contrib/lnav/synapse-log-format.json
+++ b/contrib/lnav/synapse-log-format.json
@@ -29,7 +29,7 @@
        "level": "error"
      },
      {
-        "line": "my-matrix-server-federation-sender-1 | 2023-01-25 20:56:20,995 - synapse.http.matrixfederationclient - 709 - WARNING - federation_transaction_transmission_loop-3 - {PUT-O-3} [example.com] Request failed: PUT matrix://example.com/_matrix/federation/v1/send/1674680155797: HttpResponseException('403: Forbidden')",
+        "line": "my-matrix-server-federation-sender-1 | 2023-01-25 20:56:20,995 - synapse.http.matrixfederationclient - 709 - WARNING - federation_transaction_transmission_loop-3 - {PUT-O-3} [example.com] Request failed: PUT matrix-federation://example.com/_matrix/federation/v1/send/1674680155797: HttpResponseException('403: Forbidden')",
        "level": "warning"
      },
      {
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,27 @@
+matrix-synapse-py3 (1.88.0) stable; urgency=medium
+
+  * New Synapse release 1.88.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 18 Jul 2023 13:59:28 +0100
+
+matrix-synapse-py3 (1.88.0~rc1) stable; urgency=medium
+
+  * New Synapse release 1.88.0rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 11 Jul 2023 10:20:19 +0100
+
+matrix-synapse-py3 (1.87.0) stable; urgency=medium
+
+  * New Synapse release 1.87.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 04 Jul 2023 16:24:00 +0100
+
+matrix-synapse-py3 (1.87.0~rc1) stable; urgency=medium
+
+  * New synapse release 1.87.0rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 27 Jun 2023 15:27:04 +0000
+
 matrix-synapse-py3 (1.86.0) stable; urgency=medium

  * New Synapse release 1.86.0.
--- a/docker/Dockerfile-dhvirtualenv
+++ b/docker/Dockerfile-dhvirtualenv
@@ -28,12 +28,12 @@ FROM docker.io/library/${distro} as builder

 RUN apt-get update -qq -o Acquire::Languages=none
 RUN env DEBIAN_FRONTEND=noninteractive apt-get install \
-        -yqq --no-install-recommends \
-        build-essential \
-        ca-certificates \
-        devscripts \
-        equivs \
-        wget
+    -yqq --no-install-recommends \
+    build-essential \
+    ca-certificates \
+    devscripts \
+    equivs \
+    wget

 # fetch and unpack the package
 # We are temporarily using a fork of dh-virtualenv due to an incompatibility with Python 3.11, which ships with
@@ -62,33 +62,29 @@ FROM docker.io/library/${distro}
 ARG distro=""
 ENV distro ${distro}

-# Python < 3.7 assumes LANG="C" means ASCII-only and throws on printing unicode
-# http://bugs.python.org/issue19846
-ENV LANG C.UTF-8
-
 # Install the build dependencies
 #
 # NB: keep this list in sync with the list of build-deps in debian/control
 # TODO: it would be nice to do that automatically.
 RUN apt-get update -qq -o Acquire::Languages=none \
    && env DEBIAN_FRONTEND=noninteractive apt-get install \
-        -yqq --no-install-recommends -o Dpkg::Options::=--force-unsafe-io \
-        build-essential \
-        curl \
-        debhelper \
-        devscripts \
-        libsystemd-dev \
-        lsb-release \
-        pkg-config \
-        python3-dev \
-        python3-pip \
-        python3-setuptools \
-        python3-venv \
-        sqlite3 \
-        libpq-dev \
-        libicu-dev \
-        pkg-config \
-        xmlsec1
+    -yqq --no-install-recommends -o Dpkg::Options::=--force-unsafe-io \
+    build-essential \
+    curl \
+    debhelper \
+    devscripts \
+    libsystemd-dev \
+    lsb-release \
+    pkg-config \
+    python3-dev \
+    python3-pip \
+    python3-setuptools \
+    python3-venv \
+    sqlite3 \
+    libpq-dev \
+    libicu-dev \
+    pkg-config \
+    xmlsec1

 # Install rust and ensure it's in the PATH
 ENV RUSTUP_HOME=/rust
--- a/docker/complement/conf/workers-shared-extra.yaml.j2
+++ b/docker/complement/conf/workers-shared-extra.yaml.j2
@@ -92,8 +92,6 @@ allow_device_name_lookup_over_federation: true
 ## Experimental Features ##

 experimental_features:
-  # Enable history backfilling support
-  msc2716_enabled: true
  # client-side support for partial state in /send_join responses
  faster_joins: true
  # Enable support for polls
--- a/docker/conf-workers/nginx.conf.j2
+++ b/docker/conf-workers/nginx.conf.j2
@@ -35,7 +35,11 @@ server {

    # Send all other traffic to the main process
    location ~* ^(\\/_matrix|\\/_synapse) {
+{% if using_unix_sockets %}
+        proxy_pass http://unix:/run/main_public.sock;
+{% else %}
        proxy_pass http://localhost:8080;
+{% endif %}
        proxy_set_header X-Forwarded-For $remote_addr;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header Host $host;
--- a/docker/conf-workers/shared.yaml.j2
+++ b/docker/conf-workers/shared.yaml.j2
@@ -6,6 +6,9 @@
 {% if enable_redis %}
 redis:
    enabled: true
+    {% if using_unix_sockets %}
+    path: /tmp/redis.sock
+    {% endif %}
 {% endif %}

 {% if appservice_registrations is not none %}
--- a/docker/conf-workers/supervisord.conf.j2
+++ b/docker/conf-workers/supervisord.conf.j2
@@ -19,7 +19,11 @@ username=www-data
 autorestart=true

 [program:redis]
+{% if using_unix_sockets %}
+command=/usr/local/bin/prefix-log /usr/local/bin/redis-server --unixsocket /tmp/redis.sock
+{% else %}
 command=/usr/local/bin/prefix-log /usr/local/bin/redis-server
+{% endif %}
 priority=1
 stdout_logfile=/dev/stdout
 stdout_logfile_maxbytes=0
--- a/docker/conf-workers/worker.yaml.j2
+++ b/docker/conf-workers/worker.yaml.j2
@@ -8,7 +8,11 @@ worker_name: "{{ name }}"

 worker_listeners:
  - type: http
+{% if using_unix_sockets %}
+    path: "/run/worker.{{ port }}"
+{% else %}
    port: {{ port }}
+{% endif %}
 {% if listener_resources %}
    resources:
      - names:
--- a/docker/conf/homeserver.yaml
+++ b/docker/conf/homeserver.yaml
@@ -36,12 +36,17 @@ listeners:

  # Allow configuring in case we want to reverse proxy 8008
  # using another process in the same container
+{% if SYNAPSE_USE_UNIX_SOCKET %}
+  # Unix sockets don't care about TLS or IP addresses or ports
+  - path: '/run/main_public.sock'
+    type: http
+{% else %}
  - port: {{ SYNAPSE_HTTP_PORT or 8008 }}
    tls: false
    bind_addresses: ['::']
    type: http
    x_forwarded: false
-
+{% endif %}
    resources:
      - names: [client]
        compress: true
@@ -57,8 +62,11 @@ database:
    user: "{{ POSTGRES_USER or "synapse" }}"
    password: "{{ POSTGRES_PASSWORD }}"
    database: "{{ POSTGRES_DB or "synapse" }}"
+{% if not SYNAPSE_USE_UNIX_SOCKET %}
+{# Synapse will use a default unix socket for Postgres when host/port is not specified (behavior from `psycopg2`). #}
    host: "{{ POSTGRES_HOST or "db" }}"
    port: "{{ POSTGRES_PORT or "5432" }}"
+{% endif %}
    cp_min: 5
    cp_max: 10
 {% else %}
--- a/docker/configure_workers_and_start.py
+++ b/docker/configure_workers_and_start.py
@@ -74,6 +74,9 @@ MAIN_PROCESS_HTTP_LISTENER_PORT = 8080
 MAIN_PROCESS_INSTANCE_NAME = "main"
 MAIN_PROCESS_LOCALHOST_ADDRESS = "127.0.0.1"
 MAIN_PROCESS_REPLICATION_PORT = 9093
+# Obviously, these would only be used with the UNIX socket option
+MAIN_PROCESS_UNIX_SOCKET_PUBLIC_PATH = "/run/main_public.sock"
+MAIN_PROCESS_UNIX_SOCKET_PRIVATE_PATH = "/run/main_private.sock"

 # A simple name used as a placeholder in the WORKERS_CONFIG below. This will be replaced
 # during processing with the name of the worker.
@@ -244,7 +247,6 @@ WORKERS_CONFIG: Dict[str, Dict[str, Any]] = {
            "^/_matrix/client/(api/v1|r0|v3|unstable)/join/",
            "^/_matrix/client/(api/v1|r0|v3|unstable)/knock/",
            "^/_matrix/client/(api/v1|r0|v3|unstable)/profile/",
-            "^/_matrix/client/(v1|unstable/org.matrix.msc2716)/rooms/.*/batch_send",
        ],
        "shared_extra_conf": {},
        "worker_extra_conf": "",
@@ -408,11 +410,15 @@ def add_worker_roles_to_shared_config(
        )

        # Map of stream writer instance names to host/ports combos
-        instance_map[worker_name] = {
-            "host": "localhost",
-            "port": worker_port,
-        }
-
+        if os.environ.get("SYNAPSE_USE_UNIX_SOCKET", False):
+            instance_map[worker_name] = {
+                "path": f"/run/worker.{worker_port}",
+            }
+        else:
+            instance_map[worker_name] = {
+                "host": "localhost",
+                "port": worker_port,
+            }
    # Update the list of stream writers. It's convenient that the name of the worker
    # type is the same as the stream to write. Iterate over the whole list in case there
    # is more than one.
@@ -424,10 +430,15 @@ def add_worker_roles_to_shared_config(

            # Map of stream writer instance names to host/ports combos
            # For now, all stream writers need http replication ports
-            instance_map[worker_name] = {
-                "host": "localhost",
-                "port": worker_port,
-            }
+            if os.environ.get("SYNAPSE_USE_UNIX_SOCKET", False):
+                instance_map[worker_name] = {
+                    "path": f"/run/worker.{worker_port}",
+                }
+            else:
+                instance_map[worker_name] = {
+                    "host": "localhost",
+                    "port": worker_port,
+                }


 def merge_worker_template_configs(
@@ -719,17 +730,29 @@ def generate_worker_files(
    # Note that yaml cares about indentation, so care should be taken to insert lines
    # into files at the correct indentation below.

+    # Convenience helper for if using unix sockets instead of host:port
+    using_unix_sockets = environ.get("SYNAPSE_USE_UNIX_SOCKET", False)
    # First read the original config file and extract the listeners block. Then we'll
    # add another listener for replication. Later we'll write out the result to the
    # shared config file.
-    listeners = [
-        {
-            "port": MAIN_PROCESS_REPLICATION_PORT,
-            "bind_address": MAIN_PROCESS_LOCALHOST_ADDRESS,
-            "type": "http",
-            "resources": [{"names": ["replication"]}],
-        }
-    ]
+    listeners: List[Any]
+    if using_unix_sockets:
+        listeners = [
+            {
+                "path": MAIN_PROCESS_UNIX_SOCKET_PRIVATE_PATH,
+                "type": "http",
+                "resources": [{"names": ["replication"]}],
+            }
+        ]
+    else:
+        listeners = [
+            {
+                "port": MAIN_PROCESS_REPLICATION_PORT,
+                "bind_address": MAIN_PROCESS_LOCALHOST_ADDRESS,
+                "type": "http",
+                "resources": [{"names": ["replication"]}],
+            }
+        ]
    with open(config_path) as file_stream:
        original_config = yaml.safe_load(file_stream)
        original_listeners = original_config.get("listeners")
@@ -770,7 +793,17 @@ def generate_worker_files(

    # A list of internal endpoints to healthcheck, starting with the main process
    # which exists even if no workers do.
-    healthcheck_urls = ["http://localhost:8080/health"]
+    # This list ends up being part of the command line to curl, (curl added support for
+    # Unix sockets in version 7.40).
+    if using_unix_sockets:
+        healthcheck_urls = [
+            f"--unix-socket {MAIN_PROCESS_UNIX_SOCKET_PUBLIC_PATH} "
+            # The scheme and hostname from the following URL are ignored.
+            # The only thing that matters is the path `/health`
+            "http://localhost/health"
+        ]
+    else:
+        healthcheck_urls = ["http://localhost:8080/health"]

    # Get the set of all worker types that we have configured
    all_worker_types_in_use = set(chain(*requested_worker_types.values()))
@@ -807,8 +840,12 @@ def generate_worker_files(
        # given worker_type needs to stay assigned and not be replaced.
        worker_config["shared_extra_conf"].update(shared_config)
        shared_config = worker_config["shared_extra_conf"]
-
-        healthcheck_urls.append("http://localhost:%d/health" % (worker_port,))
+        if using_unix_sockets:
+            healthcheck_urls.append(
+                f"--unix-socket /run/worker.{worker_port} http://localhost/health"
+            )
+        else:
+            healthcheck_urls.append("http://localhost:%d/health" % (worker_port,))

        # Update the shared config with sharding-related options if necessary
        add_worker_roles_to_shared_config(
@@ -827,6 +864,7 @@ def generate_worker_files(
            "/conf/workers/{name}.yaml".format(name=worker_name),
            **worker_config,
            worker_log_config_filepath=log_config_filepath,
+            using_unix_sockets=using_unix_sockets,
        )

        # Save this worker's port number to the correct nginx upstreams
@@ -847,8 +885,13 @@ def generate_worker_files(
    nginx_upstream_config = ""
    for upstream_worker_base_name, upstream_worker_ports in nginx_upstreams.items():
        body = ""
-        for port in upstream_worker_ports:
-            body += f"    server localhost:{port};\n"
+        if using_unix_sockets:
+            for port in upstream_worker_ports:
+                body += f"    server unix:/run/worker.{port};\n"
+
+        else:
+            for port in upstream_worker_ports:
+                body += f"    server localhost:{port};\n"

        # Add to the list of configured upstreams
        nginx_upstream_config += NGINX_UPSTREAM_CONFIG_BLOCK.format(
@@ -878,10 +921,15 @@ def generate_worker_files(
    # If there are workers, add the main process to the instance_map too.
    if workers_in_use:
        instance_map = shared_config.setdefault("instance_map", {})
-        instance_map[MAIN_PROCESS_INSTANCE_NAME] = {
-            "host": MAIN_PROCESS_LOCALHOST_ADDRESS,
-            "port": MAIN_PROCESS_REPLICATION_PORT,
-        }
+        if using_unix_sockets:
+            instance_map[MAIN_PROCESS_INSTANCE_NAME] = {
+                "path": MAIN_PROCESS_UNIX_SOCKET_PRIVATE_PATH,
+            }
+        else:
+            instance_map[MAIN_PROCESS_INSTANCE_NAME] = {
+                "host": MAIN_PROCESS_LOCALHOST_ADDRESS,
+                "port": MAIN_PROCESS_REPLICATION_PORT,
+            }

    # Shared homeserver config
    convert(
@@ -891,6 +939,7 @@ def generate_worker_files(
        appservice_registrations=appservice_registrations,
        enable_redis=workers_in_use,
        workers_in_use=workers_in_use,
+        using_unix_sockets=using_unix_sockets,
    )

    # Nginx config
@@ -901,6 +950,7 @@ def generate_worker_files(
        upstream_directives=nginx_upstream_config,
        tls_cert_path=os.environ.get("SYNAPSE_TLS_CERT"),
        tls_key_path=os.environ.get("SYNAPSE_TLS_KEY"),
+        using_unix_sockets=using_unix_sockets,
    )

    # Supervisord config
@@ -910,6 +960,7 @@ def generate_worker_files(
        "/etc/supervisor/supervisord.conf",
        main_config_path=config_path,
        enable_redis=workers_in_use,
+        using_unix_sockets=using_unix_sockets,
    )

    convert(
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -419,7 +419,7 @@ The following query parameters are available:

 * `from` (required) - The token to start returning events from. This token can be obtained from a prev_batch
  or next_batch token returned by the /sync endpoint, or from an end token returned by a previous request to this endpoint.
-* `to` - The token to spot returning events at.
+* `to` - The token to stop returning events at.
 * `limit` - The maximum number of events to return. Defaults to `10`.
 * `filter` - A JSON RoomEventFilter to filter returned events with.
 * `dir` - The direction to return events from. Either `f` for forwards or `b` for backwards. Setting
--- a/docs/admin_api/user_admin_api.md
+++ b/docs/admin_api/user_admin_api.md
@@ -242,6 +242,9 @@ The following parameters should be set in the URL:

 - `dir` - Direction of media order. Either `f` for forwards or `b` for backwards.
  Setting this value to `b` will reverse the above sort order. Defaults to `f`.
+- `not_user_type` - Exclude certain user types, such as bot users, from the request.
+   Can be provided multiple times. Possible values are `bot`, `support` or "empty string".
+   "empty string" here means to exclude users without a type.

 Caution. The database only has indexes on the columns `name` and `creation_ts`.
 This means that if a different sort order is used (`is_guest`, `admin`,
@@ -729,7 +732,8 @@ POST /_synapse/admin/v1/users/<user_id>/login

 An optional `valid_until_ms` field can be specified in the request body as an
 integer timestamp that specifies when the token should expire. By default tokens
-do not expire.
+do not expire. Note that this API does not allow a user to login as themselves
+(to create more tokens).

 A response body like the following is returned:

@@ -1180,7 +1184,7 @@ The following parameters should be set in the URL:
 - `user_id` - The fully qualified MXID: for example, `@user:server.com`. The user must
  be local.

-### Check username availability
+## Check username availability

 Checks to see if a username is available, and valid, for the server. See [the client-server 
 API](https://matrix.org/docs/spec/client_server/r0.6.0#get-matrix-client-r0-register-available)
@@ -1198,7 +1202,7 @@ GET /_synapse/admin/v1/username_available?username=$localpart
 The request and response format is the same as the
 [/_matrix/client/r0/register/available](https://matrix.org/docs/spec/client_server/r0.6.0#get-matrix-client-r0-register-available) API.

-### Find a user based on their ID in an auth provider
+## Find a user based on their ID in an auth provider

 The API is:

@@ -1237,7 +1241,7 @@ Returns a `404` HTTP status code if no user was found, with a response body like
 _Added in Synapse 1.68.0._


-### Find a user based on their Third Party ID (ThreePID or 3PID)
+## Find a user based on their Third Party ID (ThreePID or 3PID)

 The API is:

--- a/docs/changelogs/CHANGES-2022.md
+++ b/docs/changelogs/CHANGES-2022.md
--- a/docs/deprecation_policy.md
+++ b/docs/deprecation_policy.md
@@ -23,7 +23,7 @@ people building from source should ensure they can fetch recent versions of Rust
 (e.g. by using [rustup](https://rustup.rs/)).

 The oldest supported version of SQLite is the version
-[provided](https://packages.debian.org/buster/libsqlite3-0) by
+[provided](https://packages.debian.org/bullseye/libsqlite3-0) by
 [Debian oldstable](https://wiki.debian.org/DebianOldStable).

 Context
--- a/docs/development/contributing_guide.md
+++ b/docs/development/contributing_guide.md
@@ -322,7 +322,7 @@ The following command will let you run the integration test with the most common
 configuration:

 ```sh
-$ docker run --rm -it -v /path/where/you/have/cloned/the/repository\:/src:ro -v /path/to/where/you/want/logs\:/logs matrixdotorg/sytest-synapse:buster
+$ docker run --rm -it -v /path/where/you/have/cloned/the/repository\:/src:ro -v /path/to/where/you/want/logs\:/logs matrixdotorg/sytest-synapse:focal
 ```
 (Note that the paths must be full paths! You could also write `$(realpath relative/path)` if needed.)

@@ -370,6 +370,7 @@ The above will run a monolithic (single-process) Synapse with SQLite as the data
    See the [worker documentation](../workers.md) for additional information on workers.
 - Passing `ASYNCIO_REACTOR=1` as an environment variable to use the Twisted asyncio reactor instead of the default one.
 - Passing `PODMAN=1` will use the [podman](https://podman.io/) container runtime, instead of docker.
+- Passing `UNIX_SOCKETS=1` will utilise Unix socket functionality for Synapse, Redis, and Postgres(when applicable).

 To increase the log level for the tests, set `SYNAPSE_TEST_LOG_LEVEL`, e.g:
 ```sh
--- a/docs/development/synapse_architecture/faster_joins.md
+++ b/docs/development/synapse_architecture/faster_joins.md
@@ -6,7 +6,7 @@ This is a work-in-progress set of notes with two goals:

 See also [MSC3902](https://github.com/matrix-org/matrix-spec-proposals/pull/3902).

-The key idea is described by [MSC706](https://github.com/matrix-org/matrix-spec-proposals/pull/3902). This allows servers to
+The key idea is described by [MSC3706](https://github.com/matrix-org/matrix-spec-proposals/pull/3706). This allows servers to
 request a lightweight response to the federation `/send_join` endpoint.
 This is called a **faster join**, also known as a **partial join**. In these
 notes we'll usually use the word "partial" as it matches the database schema.
--- a/docs/modules/spam_checker_callbacks.md
+++ b/docs/modules/spam_checker_callbacks.md
@@ -348,6 +348,42 @@ callback returns `False`, Synapse falls through to the next one. The value of th
 callback that does not return `False` will be used. If this happens, Synapse will not call
 any of the subsequent implementations of this callback.

+
+### `check_login_for_spam`
+
+_First introduced in Synapse v1.87.0_
+
+```python
+async def check_login_for_spam(
+    user_id: str,
+    device_id: Optional[str],
+    initial_display_name: Optional[str],
+    request_info: Collection[Tuple[Optional[str], str]],
+    auth_provider_id: Optional[str] = None,
+) -> Union["synapse.module_api.NOT_SPAM", "synapse.module_api.errors.Codes"]
+```
+
+Called when a user logs in.
+
+The arguments passed to this callback are:
+
+* `user_id`: The user ID the user is logging in with
+* `device_id`: The device ID the user is re-logging into.
+* `initial_display_name`: The device display name, if any.
+* `request_info`: A collection of tuples, which first item is a user agent, and which
+  second item is an IP address. These user agents and IP addresses are the ones that were
+  used during the login process.
+* `auth_provider_id`: The identifier of the SSO authentication provider, if any.
+
+If multiple modules implement this callback, they will be considered in order. If a
+callback returns `synapse.module_api.NOT_SPAM`, Synapse falls through to the next one.
+The value of the first callback that does not return `synapse.module_api.NOT_SPAM` will
+be used. If this happens, Synapse will not call any of the subsequent implementations of
+this callback.
+
+*Note:* This will not be called when a user registers.
+
+
 ## Example

 The example below is a module that implements the spam checker callback
--- a/docs/setup/installation.md
+++ b/docs/setup/installation.md
@@ -200,7 +200,7 @@ When following this route please make sure that the [Platform-specific prerequis
 System requirements:

 - POSIX-compliant system (tested on Linux & OS X)
- Python 3.7 or later, up to Python 3.11.
+- Python 3.8 or later, up to Python 3.11.
 - At least 1GB of free RAM if you want to join large public rooms like #matrix:matrix.org

 If building on an uncommon architecture for which pre-built wheels are
--- a/docs/systemd-with-workers/workers/background_worker.yaml
+++ b/docs/systemd-with-workers/workers/background_worker.yaml
@@ -1,8 +1,4 @@
 worker_app: synapse.app.generic_worker
 worker_name: background_worker

-# The replication listener on the main synapse process.
-worker_replication_host: 127.0.0.1
-worker_replication_http_port: 9093
-
 worker_log_config: /etc/matrix-synapse/background-worker-log.yaml
--- a/docs/systemd-with-workers/workers/event_persister.yaml
+++ b/docs/systemd-with-workers/workers/event_persister.yaml
@@ -1,9 +1,5 @@
 worker_app: synapse.app.generic_worker
-worker_name: event_persister1 
-
-# The replication listener on the main synapse process.
-worker_replication_host: 127.0.0.1
-worker_replication_http_port: 9093
+worker_name: event_persister1

 worker_listeners:
  - type: http
--- a/docs/systemd-with-workers/workers/federation_sender.yaml
+++ b/docs/systemd-with-workers/workers/federation_sender.yaml
@@ -1,8 +1,4 @@
 worker_app: synapse.app.federation_sender
 worker_name: federation_sender1

-# The replication listener on the main synapse process.
-worker_replication_host: 127.0.0.1
-worker_replication_http_port: 9093
-
 worker_log_config: /etc/matrix-synapse/federation-sender-log.yaml
--- a/docs/systemd-with-workers/workers/media_worker.yaml
+++ b/docs/systemd-with-workers/workers/media_worker.yaml
@@ -1,10 +1,6 @@
 worker_app: synapse.app.media_repository
 worker_name: media_worker

-# The replication listener on the main synapse process.
-worker_replication_host: 127.0.0.1
-worker_replication_http_port: 9093
-
 worker_listeners:
  - type: http
    port: 8085
--- a/docs/systemd-with-workers/workers/pusher_worker.yaml
+++ b/docs/systemd-with-workers/workers/pusher_worker.yaml
@@ -1,8 +1,4 @@
 worker_app: synapse.app.pusher
 worker_name: pusher_worker1

-# The replication listener on the main synapse process.
-worker_replication_host: 127.0.0.1
-worker_replication_http_port: 9093
-
 worker_log_config: /etc/matrix-synapse/pusher-worker-log.yaml
--- a/docs/upgrade.md
+++ b/docs/upgrade.md
@@ -87,6 +87,43 @@ process, for example:
    wget https://packages.matrix.org/debian/pool/main/m/matrix-synapse-py3/matrix-synapse-py3_1.3.0+stretch1_amd64.deb
    dpkg -i matrix-synapse-py3_1.3.0+stretch1_amd64.deb
    ```
+
+# Upgrading to v1.89.0
+
+## Removal of unspecced `user` property for `/register`
+
+Application services can no longer call `/register` with a `user` property to create new users.
+The standard `username` property should be used instead. See the
+[Application Service specification](https://spec.matrix.org/v1.7/application-service-api/#server-admin-style-permissions)
+for more information.
+
+
+# Upgrading to v1.88.0
+
+## Minimum supported Python version
+
+The minimum supported Python version has been increased from v3.7 to v3.8.
+You will need Python 3.8 to run Synapse v1.88.0 (due out July 18th, 2023).
+
+If you use current versions of the Matrix.org-distributed Debian
+packages or Docker images, no action is required.
+
+## Removal of `worker_replication_*` settings
+
+As mentioned previously in [Upgrading to v1.84.0](#upgrading-to-v1840), the following deprecated settings
+are being removed in this release of Synapse:
+
+* [`worker_replication_host`](https://matrix-org.github.io/synapse/v1.86/usage/configuration/config_documentation.html#worker_replication_host)
+* [`worker_replication_http_port`](https://matrix-org.github.io/synapse/v1.86/usage/configuration/config_documentation.html#worker_replication_http_port)
+* [`worker_replication_http_tls`](https://matrix-org.github.io/synapse/v1.86/usage/configuration/config_documentation.html#worker_replication_http_tls)
+
+Please ensure that you have migrated to using `main` on your shared configuration's `instance_map`
+(or create one if necessary). This is required if you have ***any*** workers at all;
+administrators of single-process (monolith) installations don't need to do anything.
+
+For an illustrative example, please see [Upgrading to v1.84.0](#upgrading-to-v1840) below.
+
+
 # Upgrading to v1.86.0

 ## Minimum supported Rust version
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -462,6 +462,20 @@ See the docs [request log format](../administration/request_log.md).
 * `additional_resources`: Only valid for an 'http' listener. A map of
   additional endpoints which should be loaded via dynamic modules.

+Unix socket support (_Added in Synapse 1.89.0_):
+* `path`: A path and filename for a Unix socket. Make sure it is located in a
+  directory with read and write permissions, and that it already exists (the directory
+  will not be created). Defaults to `None`.
+  * **Note**: The use of both `path` and `port` options for the same `listener` is not
+    compatible.
+  * The `x_forwarded` option defaults to true  when using Unix sockets and can be omitted.
+  * Other options that would not make sense to use with a UNIX socket, such as 
+    `bind_addresses` and `tls` will be ignored and can be removed.
+* `mode`: The file permissions to set on the UNIX socket. Defaults to `666`
+* **Note:** Must be set as `type: http` (does not support `metrics` and `manhole`). 
+  Also make sure that `metrics` is not included in `resources` -> `names`
+
+
 Valid resource names are:

 * `client`: the client-server API (/_matrix/client), and the synapse admin API (/_synapse/admin). Also implies `media` and `static`.
@@ -474,7 +488,7 @@ Valid resource names are:

 * `media`: the media API (/_matrix/media).

-* `metrics`: the metrics interface. See [here](../../metrics-howto.md).
+* `metrics`: the metrics interface. See [here](../../metrics-howto.md). (Not compatible with Unix sockets)

 * `openid`: OpenID authentication. See [here](../../openid.md).

@@ -533,6 +547,22 @@ listeners:
    bind_addresses: ['::1', '127.0.0.1']
    type: manhole
 ```
+Example configuration #3:
+```yaml
+listeners:
+  # Unix socket listener: Ideal for Synapse deployments behind a reverse proxy, offering
+  # lightweight interprocess communication without TCP/IP overhead, avoid port
+  # conflicts, and providing enhanced security through system file permissions.
+  #
+  # Note that x_forwarded will default to true, when using a UNIX socket. Please see
+  # https://matrix-org.github.io/synapse/latest/reverse_proxy.html.
+  #
+  - path: /var/run/synapse/main_public.sock
+    type: http
+    resources:
+      - names: [client, federation]
+```
+
 ---
 ### `manhole_settings`

@@ -1196,6 +1226,32 @@ Example configuration:
 allow_device_name_lookup_over_federation: true
 ```
 ---
+### `federation`
+
+The federation section defines some sub-options related to federation.
+
+The following options are related to configuring timeout and retry logic for one request,
+independently of the others.
+Short retry algorithm is used when something or someone will wait for the request to have an
+answer, while long retry is used for requests that happen in the background,
+like sending a federation transaction.
+
+* `client_timeout`: timeout for the federation requests. Default to 60s.
+* `max_short_retry_delay`: maximum delay to be used for the short retry algo. Default to 2s.
+* `max_long_retry_delay`: maximum delay to be used for the short retry algo. Default to 60s.
+* `max_short_retries`: maximum number of retries for the short retry algo. Default to 3 attempts.
+* `max_long_retries`: maximum number of retries for the long retry algo. Default to 10 attempts.
+
+Example configuration:
+```yaml
+federation:
+  client_timeout: 180s
+  max_short_retry_delay: 7s
+  max_long_retry_delay: 100s
+  max_short_retries: 5
+  max_long_retries: 20
+```
+---
 ## Caching

 Options related to caching.
@@ -3904,13 +3960,14 @@ federation_sender_instances:
 ---
 ### `instance_map`

-When using workers this should be a map from [`worker_name`](#worker_name) to the
-HTTP replication listener of the worker, if configured, and to the main process.
-Each worker declared under [`stream_writers`](../../workers.md#stream-writers) needs
-a HTTP replication listener, and that listener should be included in the `instance_map`.
-The main process also needs an entry on the `instance_map`, and it should be listed under
-`main` **if even one other worker exists**. Ensure the port matches with what is declared 
-inside the `listener` block for a `replication` listener.
+When using workers this should be a map from [`worker_name`](#worker_name) to the HTTP
+replication listener of the worker, if configured, and to the main process. Each worker
+declared under [`stream_writers`](../../workers.md#stream-writers) and
+[`outbound_federation_restricted_to`](#outbound_federation_restricted_to) needs a HTTP
+replication listener, and that listener should be included in the `instance_map`. The
+main process also needs an entry on the `instance_map`, and it should be listed under
+`main` **if even one other worker exists**. Ensure the port matches with what is
+declared inside the `listener` block for a `replication` listener.


 Example configuration:
@@ -3923,6 +3980,14 @@ instance_map:
    host: localhost
    port: 8034
 ```
+Example configuration(#2, for UNIX sockets):
+```yaml
+instance_map:
+  main:
+    path: /var/run/synapse/main_replication.sock
+  worker1:
+    path: /var/run/synapse/worker1_replication.sock
+```
 ---
 ### `stream_writers`

@@ -3940,6 +4005,24 @@ stream_writers:
  typing: worker1
 ```
 ---
+### `outbound_federation_restricted_to`
+
+When using workers, you can restrict outbound federation traffic to only go through a
+specific subset of workers. Any worker specified here must also be in the
+[`instance_map`](#instance_map).
+[`worker_replication_secret`](#worker_replication_secret) must also be configured to
+authorize inter-worker communication.
+
+```yaml
+outbound_federation_restricted_to:
+  - federation_sender1
+  - federation_sender2
+```
+
+Also see the [worker
+documentation](../../workers.md#restrict-outbound-federation-traffic-to-a-specific-set-of-workers)
+for more info.
+---
 ### `run_background_tasks_on`

 The [worker](../../workers.md#background-tasks) that is used to run
@@ -4064,51 +4147,6 @@ Example configuration:
 worker_name: generic_worker1
 ```
 ---
-### `worker_replication_host`
-*Deprecated as of version 1.84.0. Place `host` under `main` entry on the [`instance_map`](#instance_map) in your shared yaml configuration instead.*
-
-The HTTP replication endpoint that it should talk to on the main Synapse process.
-The main Synapse process defines this with a `replication` resource in
-[`listeners` option](#listeners).
-
-Example configuration:
-```yaml
-worker_replication_host: 127.0.0.1
-```
---
-### `worker_replication_http_port`
-*Deprecated as of version 1.84.0. Place `port` under `main` entry on the [`instance_map`](#instance_map) in your shared yaml configuration instead.*
-
-The HTTP replication port that it should talk to on the main Synapse process.
-The main Synapse process defines this with a `replication` resource in
-[`listeners` option](#listeners).
-
-Example configuration:
-```yaml
-worker_replication_http_port: 9093
-```
---
-### `worker_replication_http_tls`
-*Deprecated as of version 1.84.0. Place `tls` under `main` entry on the [`instance_map`](#instance_map) in your shared yaml configuration instead.*
-
-Whether TLS should be used for talking to the HTTP replication port on the main
-Synapse process.
-The main Synapse process defines this with the `tls` option on its [listener](#listeners) that
-has the `replication` resource enabled.
-
-**Please note:** by default, it is not safe to expose replication ports to the
-public Internet, even with TLS enabled.
-See [`worker_replication_secret`](#worker_replication_secret).
-
-Defaults to `false`.
-
-*Added in Synapse 1.72.0.*
-
-Example configuration:
-```yaml
-worker_replication_http_tls: true
-```
---
 ### `worker_listeners`

 A worker can handle HTTP requests. To do so, a `worker_listeners` option
@@ -4127,6 +4165,18 @@ worker_listeners:
    resources:
      - names: [client, federation]
 ```
+Example configuration(#2, using UNIX sockets with a `replication` listener):
+```yaml
+worker_listeners:
+  - type: http
+    path: /var/run/synapse/worker_public.sock
+    resources:
+      - names: [client, federation]
+  - type: http
+    path: /var/run/synapse/worker_replication.sock
+    resources:
+      - names: [replication]
+```
 ---
 ### `worker_manhole`

--- a/docs/workers.md
+++ b/docs/workers.md
@@ -95,9 +95,12 @@ for the main process
 * Secondly, you need to enable
 [redis-based replication](usage/configuration/config_documentation.md#redis)
 * You will need to add an [`instance_map`](usage/configuration/config_documentation.md#instance_map) 
-with the `main` process defined, as well as the relevant connection information from 
-it's HTTP `replication` listener (defined in step 1 above). Note that the `host` defined 
-is the address the worker needs to look for the `main` process at, not necessarily the same address that is bound to.
+with the `main` process defined, as well as the relevant connection information from
+it's HTTP `replication` listener (defined in step 1 above).
+  * Note that the `host` defined is the address the worker needs to look for the `main`
+  process at, not necessarily the same address that is bound to.
+  * If you are using Unix sockets for the `replication` resource, make sure to
+  use a `path` to the socket file instead of a `port`.
 * Optionally, a [shared secret](usage/configuration/config_documentation.md#worker_replication_secret)
 can be used to authenticate HTTP traffic between workers. For example:

@@ -145,9 +148,6 @@ In the config file for each worker, you must specify:
   with an `http` listener.
 * **Synapse 1.72 and older:** if handling the `^/_matrix/client/v3/keys/upload` endpoint, the HTTP URI for
   the main process (`worker_main_http_uri`). This config option is no longer required and is ignored when running Synapse 1.73 and newer.
- * **Synapse 1.83 and older:** The HTTP replication endpoint that the worker should talk to on the main synapse process
-   ([`worker_replication_host`](usage/configuration/config_documentation.md#worker_replication_host) and
-   [`worker_replication_http_port`](usage/configuration/config_documentation.md#worker_replication_http_port)). If using Synapse 1.84 and newer, these are not needed if `main` is defined on the [shared configuration](#shared-configuration) `instance_map`

 For example:

@@ -177,11 +177,11 @@ The following applies to Synapse installations that have been installed from sou

 You can start the main Synapse process with Poetry by running the following command:
 ```console
-poetry run synapse_homeserver -c [your homeserver.yaml]
+poetry run synapse_homeserver --config-file [your homeserver.yaml]
 ```
 For worker setups, you can run the following command
 ```console
-poetry run synapse_worker -c [your worker.yaml]
+poetry run synapse_worker --config-file [your homeserver.yaml] --config-file [your worker.yaml]
 ```
 ## Available worker applications

@@ -232,7 +232,6 @@ information.
    ^/_matrix/client/v1/rooms/.*/hierarchy$
    ^/_matrix/client/(v1|unstable)/rooms/.*/relations/
    ^/_matrix/client/v1/rooms/.*/threads$
-    ^/_matrix/client/unstable/org.matrix.msc2716/rooms/.*/batch_send$
    ^/_matrix/client/unstable/im.nheko.summary/rooms/.*/summary$
    ^/_matrix/client/(r0|v3|unstable)/account/3pid$
    ^/_matrix/client/(r0|v3|unstable)/account/whoami$
@@ -532,6 +531,30 @@ the stream writer for the `presence` stream:

    ^/_matrix/client/(api/v1|r0|v3|unstable)/presence/

+#### Restrict outbound federation traffic to a specific set of workers
+
+The
+[`outbound_federation_restricted_to`](usage/configuration/config_documentation.md#outbound_federation_restricted_to)
+configuration is useful to make sure outbound federation traffic only goes through a
+specified subset of workers. This allows you to set more strict access controls (like a
+firewall) for all workers and only allow the `federation_sender`'s to contact the
+outside world.
+
+```yaml
+instance_map:
+    main:
+        host: localhost
+        port: 8030
+    federation_sender1:
+        host: localhost
+        port: 8034
+
+outbound_federation_restricted_to:
+  - federation_sender1
+
+worker_replication_secret: "secret_secret"
+```
+
 #### Background tasks

 There is also support for moving background tasks to a separate
--- a/flake.lock
+++ b/flake.lock
@@ -22,27 +22,6 @@
        "type": "github"
      }
    },
-    "fenix": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ],
-        "rust-analyzer-src": "rust-analyzer-src"
-      },
-      "locked": {
-        "lastModified": 1682490133,
-        "narHash": "sha256-tR2Qx0uuk97WySpSSk4rGS/oH7xb5LykbjATcw1vw1I=",
-        "owner": "nix-community",
-        "repo": "fenix",
-        "rev": "4e9412753ab75ef0e038a5fe54a062fb44c27c6a",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-community",
-        "repo": "fenix",
-        "type": "github"
-      }
-    },
    "flake-compat": {
      "flake": false,
      "locked": {
@@ -74,6 +53,24 @@
        "type": "github"
      }
    },
+    "flake-utils_2": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1681202837,
+        "narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "cfacdce06f30d2b68473a46042957675eebb3401",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
    "gitignore": {
      "inputs": {
        "nixpkgs": [
@@ -200,6 +197,22 @@
        "type": "github"
      }
    },
+    "nixpkgs_3": {
+      "locked": {
+        "lastModified": 1681358109,
+        "narHash": "sha256-eKyxW4OohHQx9Urxi7TQlFBTDWII+F+x2hklDOQPB50=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "96ba1c52e54e74c3197f4d43026b3f3d92e83ff9",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
    "pre-commit-hooks": {
      "inputs": {
        "flake-compat": [
@@ -231,25 +244,27 @@
    "root": {
      "inputs": {
        "devenv": "devenv",
-        "fenix": "fenix",
        "nixpkgs": "nixpkgs_2",
-        "systems": "systems"
+        "rust-overlay": "rust-overlay",
+        "systems": "systems_2"
      }
    },
-    "rust-analyzer-src": {
-      "flake": false,
+    "rust-overlay": {
+      "inputs": {
+        "flake-utils": "flake-utils_2",
+        "nixpkgs": "nixpkgs_3"
+      },
      "locked": {
-        "lastModified": 1682426789,
-        "narHash": "sha256-UqnLmJESRZE0tTEaGbRAw05Hm19TWIPA+R3meqi5I4w=",
-        "owner": "rust-lang",
-        "repo": "rust-analyzer",
-        "rev": "943d2a8a1ca15e8b28a1f51f5a5c135e3728da04",
+        "lastModified": 1689302058,
+        "narHash": "sha256-yD74lcHTrw4niXcE9goJLbzsgyce48rQQoy5jK5ZK40=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "7b8dbbf4c67ed05a9bf3d9e658c12d4108bc24c8",
        "type": "github"
      },
      "original": {
-        "owner": "rust-lang",
-        "ref": "nightly",
-        "repo": "rust-analyzer",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
        "type": "github"
      }
    },
@@ -267,6 +282,21 @@
        "repo": "default",
        "type": "github"
      }
+    },
+    "systems_2": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
    }
  },
  "root": "root",
--- a/flake.nix
+++ b/flake.nix
@@ -46,20 +46,20 @@
    systems.url = "github:nix-systems/default";
    # A development environment manager built on Nix. See https://devenv.sh.
    devenv.url = "github:cachix/devenv/main";
-    # Rust toolchains and rust-analyzer nightly.
-    fenix = {
-      url = "github:nix-community/fenix";
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
+    # Rust toolchain.
+    rust-overlay.url = "github:oxalica/rust-overlay";
  };

-  outputs = { self, nixpkgs, devenv, systems, ... } @ inputs:
+  outputs = { self, nixpkgs, devenv, systems, rust-overlay, ... } @ inputs:
    let
      forEachSystem = nixpkgs.lib.genAttrs (import systems);
    in {
      devShells = forEachSystem (system:
        let
-          pkgs = nixpkgs.legacyPackages.${system};
+          overlays = [ (import rust-overlay) ];
+          pkgs = import nixpkgs {
+            inherit system overlays;
+          };
        in {
          # Everything is configured via devenv - a Nix module for creating declarative
          # developer environments. See https://devenv.sh/reference/options/ for a list
@@ -76,6 +76,20 @@
                # Configure packages to install.
                # Search for package names at https://search.nixos.org/packages?channel=unstable
                packages = with pkgs; [
+                  # The rust toolchain and related tools.
+                  # This will install the "default" profile of rust components.
+                  # https://rust-lang.github.io/rustup/concepts/profiles.html
+                  #
+                  # NOTE: We currently need to set the Rust version unnecessarily high
+                  # in order to work around https://github.com/matrix-org/synapse/issues/15939
+                  (rust-bin.stable."1.70.0".default.override {
+                    # Additionally install the "rust-src" extension to allow diving into the
+                    # Rust source code in an IDE (rust-analyzer will also make use of it).
+                    extensions = [ "rust-src" ];
+                  })
+                  # The rust-analyzer language server implementation.
+                  rust-analyzer
+
                  # Native dependencies for running Synapse.
                  icu
                  libffi
@@ -124,12 +138,11 @@
                # Install dependencies for the additional programming languages
                # involved with Synapse development.
                #
-                # * Rust is used for developing and running Synapse.
                # * Golang is needed to run the Complement test suite.
                # * Perl is needed to run the SyTest test suite.
+                # * Rust is used for developing and running Synapse.
+                #   It is installed manually with `packages` above.
                languages.go.enable = true;
-                languages.rust.enable = true;
-                languages.rust.version = "stable";
                languages.perl.enable = true;

                # Postgres is needed to run Synapse with postgres support and
@@ -178,7 +191,7 @@
                  EOF
                '';
                # Start synapse when `devenv up` is run.
-                processes.synapse.exec = "poetry run python -m synapse.app.homeserver -c homeserver.yaml --config-directory homeserver-config-overrides.d";
+                processes.synapse.exec = "poetry run python -m synapse.app.homeserver -c homeserver.yaml -c homeserver-config-overrides.d";

                # Define the perl modules we require to run SyTest.
                #
--- a/poetry.lock
+++ b/poetry.lock
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -89,7 +89,7 @@ manifest-path = "rust/Cargo.toml"

 [tool.poetry]
 name = "matrix-synapse"
-version = "1.86.0"
+version = "1.88.0"
 description = "Homeserver for the Matrix decentralised comms protocol"
 authors = ["Matrix.org Team and Contributors <packages@matrix.org>"]
 license = "Apache-2.0"
@@ -147,7 +147,7 @@ synapse_review_recent_signups = "synapse._scripts.review_recent_signups:main"
 update_synapse_database = "synapse._scripts.update_synapse_database:main"

 [tool.poetry.dependencies]
-python = "^3.7.1"
+python = "^3.8.0"

 # Mandatory Dependencies
 # ----------------------
@@ -203,11 +203,9 @@ ijson = ">=3.1.4"
 matrix-common = "^1.3.0"
 # We need packaging.requirements.Requirement, added in 16.1.
 packaging = ">=16.1"
-# At the time of writing, we only use functions from the version `importlib.metadata`
-# which shipped in Python 3.8. This corresponds to version 1.4 of the backport.
-importlib_metadata = { version = ">=1.4", python = "<3.8" }
 # This is the most recent version of Pydantic with available on common distros.
-pydantic = ">=1.7.4"
+# We are currently incompatible with >=2.0.0: (https://github.com/matrix-org/synapse/issues/15858)
+pydantic = "^1.7.4"

 # This is for building the rust components during "poetry install", which
 # currently ignores the `build-system.requires` directive (c.f.
@@ -311,7 +309,7 @@ all = [
 # We pin black so that our tests don't start failing on new releases.
 isort = ">=5.10.1"
 black = ">=22.3.0"
-ruff = "0.0.265"
+ruff = "0.0.277"

 # Typechecking
 lxml-stubs = ">=0.4.0"
@@ -375,7 +373,15 @@ build-backend = "poetry.core.masonry.api"

 [tool.cibuildwheel]
 # Skip unsupported platforms (by us or by Rust).
-skip = "cp36* *-musllinux_i686 pp*aarch64 *-musllinux_aarch64"
+# See https://cibuildwheel.readthedocs.io/en/stable/options/#build-skip for the list of build targets.
+# We skip:
+#  - CPython 3.6 and 3.7: EOLed
+#  - PyPy 3.7: we only support Python 3.8+
+#  - musllinux i686: excluded to reduce number of wheels we build.
+#    c.f. https://github.com/matrix-org/synapse/pull/12595#discussion_r963107677
+#  - PyPy on Aarch64 and musllinux on aarch64: too slow to build.
+#    c.f. https://github.com/matrix-org/synapse/pull/14259
+skip = "cp36* cp37* pp37* *-musllinux_i686 pp*aarch64 *-musllinux_aarch64"

 # We need a rust compiler
 before-all =  "curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain stable -y --profile minimal"
--- a/rust/src/push/base_rules.rs
+++ b/rust/src/push/base_rules.rs
@@ -142,7 +142,7 @@ pub const BASE_APPEND_OVERRIDE_RULES: &[PushRule] = &[
        default_enabled: true,
    },
    PushRule {
-        rule_id: Cow::Borrowed("global/override/.m.is_user_mention"),
+        rule_id: Cow::Borrowed("global/override/.m.rule.is_user_mention"),
        priority_class: 5,
        conditions: Cow::Borrowed(&[Condition::Known(
            KnownCondition::ExactEventPropertyContainsType(EventPropertyIsTypeCondition {
@@ -163,7 +163,7 @@ pub const BASE_APPEND_OVERRIDE_RULES: &[PushRule] = &[
        default_enabled: true,
    },
    PushRule {
-        rule_id: Cow::Borrowed("global/override/.m.is_room_mention"),
+        rule_id: Cow::Borrowed("global/override/.m.rule.is_room_mention"),
        priority_class: 5,
        conditions: Cow::Borrowed(&[
            Condition::Known(KnownCondition::EventPropertyIs(EventPropertyIsCondition {
--- a/scripts-dev/build_debian_packages.py
+++ b/scripts-dev/build_debian_packages.py
@@ -22,15 +22,18 @@ from typing import Collection, Optional, Sequence, Set

 # These are expanded inside the dockerfile to be a fully qualified image name.
 # e.g. docker.io/library/debian:bullseye
+#
+# If an EOL is forced by a Python version and we're dropping support for it, make sure
+# to remove references to the distibution across Synapse (search for "bullseye" for
+# example)
 DISTS = (
-    "debian:buster",  # oldstable: EOL 2022-08
-    "debian:bullseye",
-    "debian:bookworm",
-    "debian:sid",
-    "ubuntu:focal",  # 20.04 LTS (our EOL forced by Py38 on 2024-10-14)
-    "ubuntu:jammy",  # 22.04 LTS (EOL 2027-04)
-    "ubuntu:kinetic",  # 22.10 (EOL 2023-07-20)
-    "ubuntu:lunar",  # 23.04 (EOL 2024-01)
+    "debian:bullseye",  # (EOL ~2024-07) (our EOL forced by Python 3.9 is 2025-10-05)
+    "debian:bookworm",  # (EOL not specified yet) (our EOL forced by Python 3.11 is 2027-10-24)
+    "debian:sid",  # (EOL not specified yet) (our EOL forced by Python 3.11 is 2027-10-24)
+    "ubuntu:focal",  # 20.04 LTS (EOL 2025-04) (our EOL forced by Python 3.8 is 2024-10-14)
+    "ubuntu:jammy",  # 22.04 LTS (EOL 2027-04) (our EOL forced by Python 3.10 is 2026-10-04)
+    "ubuntu:kinetic",  # 22.10 (EOL 2023-07-20) (our EOL forced by Python 3.10 is 2026-10-04)
+    "ubuntu:lunar",  # 23.04 (EOL 2024-01) (our EOL forced by Python 3.11 is 2027-10-24)
 )

 DESC = """\
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -214,7 +214,7 @@ fi

 extra_test_args=()

-test_tags="synapse_blacklist,msc3787,msc3874,msc3890,msc3391,msc3930,faster_joins"
+test_tags="synapse_blacklist,msc3874,msc3890,msc3391,msc3930,faster_joins"

 # All environment variables starting with PASS_ will be shared.
 # (The prefix is stripped off before reaching the container.)
@@ -246,10 +246,6 @@ else
  else
    export PASS_SYNAPSE_COMPLEMENT_DATABASE=sqlite
  fi
-
-  # The tests for importing historical messages (MSC2716)
-  # only pass with monoliths, currently.
-  test_tags="$test_tags,msc2716"
 fi

 if [[ -n "$ASYNCIO_REACTOR" ]]; then
@@ -257,6 +253,10 @@ if [[ -n "$ASYNCIO_REACTOR" ]]; then
  export PASS_SYNAPSE_COMPLEMENT_USE_ASYNCIO_REACTOR=true
 fi

+if [[ -n "$UNIX_SOCKETS" ]]; then
+  # Enable full on Unix socket mode for Synapse, Redis and Postgresql
+  export PASS_SYNAPSE_USE_UNIX_SOCKET=1
+fi

 if [[ -n "$SYNAPSE_TEST_LOG_LEVEL" ]]; then
  # Set the log level to what is desired
--- a/scripts-dev/federation_client.py
+++ b/scripts-dev/federation_client.py
@@ -136,11 +136,11 @@ def request(
        authorization_headers.append(header)
        print("Authorization: %s" % header, file=sys.stderr)

-    dest = "matrix://%s%s" % (destination, path)
+    dest = "matrix-federation://%s%s" % (destination, path)
    print("Requesting %s" % dest, file=sys.stderr)

    s = requests.Session()
-    s.mount("matrix://", MatrixConnectionAdapter())
+    s.mount("matrix-federation://", MatrixConnectionAdapter())

    headers: Dict[str, str] = {
        "Authorization": authorization_headers[0],
--- a/synapse/init.py
+++ b/synapse/init.py
@@ -25,8 +25,8 @@ from synapse.util.rust import check_rust_lib_up_to_date
 from synapse.util.stringutils import strtobool

 # Check that we're not running on an unsupported Python version.
-if sys.version_info < (3, 7):
-    print("Synapse requires Python 3.7 or above.")
+if sys.version_info < (3, 8):
+    print("Synapse requires Python 3.8 or above.")
    sys.exit(1)

 # Allow using the asyncio reactor via env var.
--- a/synapse/_scripts/synapse_port_db.py
+++ b/synapse/_scripts/synapse_port_db.py
@@ -61,6 +61,7 @@ from synapse.storage.databases.main.deviceinbox import DeviceInboxBackgroundUpda
 from synapse.storage.databases.main.devices import DeviceBackgroundUpdateStore
 from synapse.storage.databases.main.e2e_room_keys import EndToEndRoomKeyBackgroundStore
 from synapse.storage.databases.main.end_to_end_keys import EndToEndKeyBackgroundStore
+from synapse.storage.databases.main.event_federation import EventFederationWorkerStore
 from synapse.storage.databases.main.event_push_actions import EventPushActionsStore
 from synapse.storage.databases.main.events_bg_updates import (
    EventsBackgroundUpdatesStore,
@@ -196,6 +197,11 @@ IGNORED_TABLES = {
    "ui_auth_sessions",
    "ui_auth_sessions_credentials",
    "ui_auth_sessions_ips",
+    # Ignore the worker locks table, as a) there shouldn't be any acquired locks
+    # after porting, and b) the circular foreign key constraints make it hard to
+    # port.
+    "worker_read_write_locks_mode",
+    "worker_read_write_locks",
 }


@@ -239,6 +245,7 @@ class Store(
    PresenceBackgroundUpdateStore,
    ReceiptsBackgroundUpdateStore,
    RelationsWorkerStore,
+    EventFederationWorkerStore,
 ):
    def execute(self, f: Callable[..., R], *args: Any, **kwargs: Any) -> Awaitable[R]:
        return self.db_pool.runInteraction(f.__name__, f, *args, **kwargs)
@@ -803,7 +810,9 @@ class Porter:
            )
            # Map from table name to args passed to `handle_table`, i.e. a tuple
            # of: `postgres_size`, `table_size`, `forward_chunk`, `backward_chunk`.
-            tables_to_port_info_map = {r[0]: r[1:] for r in setup_res}
+            tables_to_port_info_map = {
+                r[0]: r[1:] for r in setup_res if r[0] not in IGNORED_TABLES
+            }

            # Step 5. Do the copying.
            #
@@ -1369,6 +1378,9 @@ def main() -> None:
        sys.stderr.write("Database must use the 'psycopg2' connector.\n")
        sys.exit(3)

+    # Don't run the background tasks that get started by the data stores.
+    hs_config["run_background_tasks_on"] = "some_other_process"
+
    config = HomeServerConfig()
    config.parse_config_dict(hs_config, "", "")

--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -123,10 +123,6 @@ class EventTypes:
    SpaceChild: Final = "m.space.child"
    SpaceParent: Final = "m.space.parent"

-    MSC2716_INSERTION: Final = "org.matrix.msc2716.insertion"
-    MSC2716_BATCH: Final = "org.matrix.msc2716.batch"
-    MSC2716_MARKER: Final = "org.matrix.msc2716.marker"
-
    Reaction: Final = "m.reaction"


@@ -222,16 +218,6 @@ class EventContentFields:
    # Used in m.room.guest_access events.
    GUEST_ACCESS: Final = "guest_access"

-    # Used on normal messages to indicate they were historically imported after the fact
-    MSC2716_HISTORICAL: Final = "org.matrix.msc2716.historical"
-    # For "insertion" events to indicate what the next batch ID should be in
-    # order to connect to it
-    MSC2716_NEXT_BATCH_ID: Final = "next_batch_id"
-    # Used on "batch" events to indicate which insertion event it connects to
-    MSC2716_BATCH_ID: Final = "batch_id"
-    # For "marker" events
-    MSC2716_INSERTION_EVENT_REFERENCE: Final = "insertion_event_reference"
-
    # The authorising user for joining a restricted room.
    AUTHORISING_USER: Final = "join_authorised_via_users_server"

--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -217,6 +217,13 @@ class InvalidAPICallError(SynapseError):
        super().__init__(HTTPStatus.BAD_REQUEST, msg, Codes.BAD_JSON)


+class InvalidProxyCredentialsError(SynapseError):
+    """Error raised when the proxy credentials are invalid."""
+
+    def __init__(self, msg: str, errcode: str = Codes.UNKNOWN):
+        super().__init__(401, msg, errcode)
+
+
 class ProxiedRequestError(SynapseError):
    """An error from a general matrix endpoint, eg. from a proxied Matrix API call.

--- a/synapse/api/room_versions.py
+++ b/synapse/api/room_versions.py
@@ -78,41 +78,29 @@ class RoomVersion:
    # MSC2209: Check 'notifications' key while verifying
    # m.room.power_levels auth rules.
    limit_notifications_power_levels: bool
-    # MSC2175: No longer include the creator in m.room.create events.
-    msc2175_implicit_room_creator: bool
-    # MSC2174/MSC2176: Apply updated redaction rules algorithm, move redacts to
-    # content property.
-    msc2176_redaction_rules: bool
-    # MSC3083: Support the 'restricted' join_rule.
-    msc3083_join_rules: bool
-    # MSC3375: Support for the proper redaction rules for MSC3083. This mustn't
-    #          be enabled if MSC3083 is not.
-    msc3375_redaction_rules: bool
-    # MSC2403: Allows join_rules to be set to 'knock', changes auth rules to allow sending
-    # m.room.membership event with membership 'knock'.
-    msc2403_knocking: bool
-    # MSC2716: Adds m.room.power_levels -> content.historical field to control
-    # whether "insertion", "chunk", "marker" events can be sent
-    msc2716_historical: bool
-    # MSC2716: Adds support for redacting "insertion", "chunk", and "marker" events
-    msc2716_redactions: bool
+    # No longer include the creator in m.room.create events.
+    implicit_room_creator: bool
+    # Apply updated redaction rules algorithm from room version 11.
+    updated_redaction_rules: bool
+    # Support the 'restricted' join rule.
+    restricted_join_rule: bool
+    # Support for the proper redaction rules for the restricted join rule. This requires
+    # restricted_join_rule to be enabled.
+    restricted_join_rule_fix: bool
+    # Support the 'knock' join rule.
+    knock_join_rule: bool
    # MSC3389: Protect relation information from redaction.
    msc3389_relation_redactions: bool
-    # MSC3787: Adds support for a `knock_restricted` join rule, mixing concepts of
-    # knocks and restricted join rules into the same join condition.
-    msc3787_knock_restricted_join_rule: bool
-    # MSC3667: Enforce integer power levels
-    msc3667_int_only_power_levels: bool
-    # MSC3821: Do not redact the third_party_invite content field for membership events.
-    msc3821_redaction_rules: bool
+    # Support the 'knock_restricted' join rule.
+    knock_restricted_join_rule: bool
+    # Enforce integer power levels
+    enforce_int_power_levels: bool
    # MSC3931: Adds a push rule condition for "room version feature flags", making
    # some push rules room version dependent. Note that adding a flag to this list
    # is not enough to mark it "supported": the push rule evaluator also needs to
    # support the flag. Unknown flags are ignored by the evaluator, making conditions
    # fail if used.
    msc3931_push_features: Tuple[str, ...]  # values from PushRuleRoomFlag
-    # MSC3989: Redact the origin field.
-    msc3989_redaction_rules: bool


 class RoomVersions:
@@ -125,19 +113,15 @@ class RoomVersions:
        special_case_aliases_auth=True,
        strict_canonicaljson=False,
        limit_notifications_power_levels=False,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=False,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=False,
+        restricted_join_rule_fix=False,
+        knock_join_rule=False,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V2 = RoomVersion(
        "2",
@@ -148,19 +132,15 @@ class RoomVersions:
        special_case_aliases_auth=True,
        strict_canonicaljson=False,
        limit_notifications_power_levels=False,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=False,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=False,
+        restricted_join_rule_fix=False,
+        knock_join_rule=False,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V3 = RoomVersion(
        "3",
@@ -171,19 +151,15 @@ class RoomVersions:
        special_case_aliases_auth=True,
        strict_canonicaljson=False,
        limit_notifications_power_levels=False,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=False,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=False,
+        restricted_join_rule_fix=False,
+        knock_join_rule=False,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V4 = RoomVersion(
        "4",
@@ -194,19 +170,15 @@ class RoomVersions:
        special_case_aliases_auth=True,
        strict_canonicaljson=False,
        limit_notifications_power_levels=False,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=False,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=False,
+        restricted_join_rule_fix=False,
+        knock_join_rule=False,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V5 = RoomVersion(
        "5",
@@ -217,19 +189,15 @@ class RoomVersions:
        special_case_aliases_auth=True,
        strict_canonicaljson=False,
        limit_notifications_power_levels=False,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=False,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=False,
+        restricted_join_rule_fix=False,
+        knock_join_rule=False,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V6 = RoomVersion(
        "6",
@@ -240,42 +208,15 @@ class RoomVersions:
        special_case_aliases_auth=False,
        strict_canonicaljson=True,
        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=False,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=False,
+        restricted_join_rule_fix=False,
+        knock_join_rule=False,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
-    )
-    MSC2176 = RoomVersion(
-        "org.matrix.msc2176",
-        RoomDisposition.UNSTABLE,
-        EventFormatVersions.ROOM_V4_PLUS,
-        StateResolutionVersions.V2,
-        enforce_key_validity=True,
-        special_case_aliases_auth=False,
-        strict_canonicaljson=True,
-        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=True,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=False,
-        msc2716_historical=False,
-        msc2716_redactions=False,
-        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
-        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V7 = RoomVersion(
        "7",
@@ -286,19 +227,15 @@ class RoomVersions:
        special_case_aliases_auth=False,
        strict_canonicaljson=True,
        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=False,
+        restricted_join_rule_fix=False,
+        knock_join_rule=True,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V8 = RoomVersion(
        "8",
@@ -309,19 +246,15 @@ class RoomVersions:
        special_case_aliases_auth=False,
        strict_canonicaljson=True,
        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=True,
+        restricted_join_rule_fix=False,
+        knock_join_rule=True,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V9 = RoomVersion(
        "9",
@@ -332,65 +265,15 @@ class RoomVersions:
        special_case_aliases_auth=False,
        strict_canonicaljson=True,
        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=True,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=True,
+        restricted_join_rule_fix=True,
+        knock_join_rule=True,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=False,
+        enforce_int_power_levels=False,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
-    )
-    MSC3787 = RoomVersion(
-        "org.matrix.msc3787",
-        RoomDisposition.UNSTABLE,
-        EventFormatVersions.ROOM_V4_PLUS,
-        StateResolutionVersions.V2,
-        enforce_key_validity=True,
-        special_case_aliases_auth=False,
-        strict_canonicaljson=True,
-        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=True,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
-        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=True,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
-        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
-    )
-    MSC3821 = RoomVersion(
-        "org.matrix.msc3821.opt1",
-        RoomDisposition.UNSTABLE,
-        EventFormatVersions.ROOM_V4_PLUS,
-        StateResolutionVersions.V2,
-        enforce_key_validity=True,
-        special_case_aliases_auth=False,
-        strict_canonicaljson=True,
-        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=True,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
-        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=True,
-        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    V10 = RoomVersion(
        "10",
@@ -401,42 +284,15 @@ class RoomVersions:
        special_case_aliases_auth=False,
        strict_canonicaljson=True,
        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=True,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=True,
+        restricted_join_rule_fix=True,
+        knock_join_rule=True,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=True,
-        msc3667_int_only_power_levels=True,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=True,
+        enforce_int_power_levels=True,
        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
-    )
-    MSC2716v4 = RoomVersion(
-        "org.matrix.msc2716v4",
-        RoomDisposition.UNSTABLE,
-        EventFormatVersions.ROOM_V4_PLUS,
-        StateResolutionVersions.V2,
-        enforce_key_validity=True,
-        special_case_aliases_auth=False,
-        strict_canonicaljson=True,
-        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=False,
-        msc3375_redaction_rules=False,
-        msc2403_knocking=True,
-        msc2716_historical=True,
-        msc2716_redactions=True,
-        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=False,
-        msc3667_int_only_power_levels=False,
-        msc3821_redaction_rules=False,
-        msc3931_push_features=(),
-        msc3989_redaction_rules=False,
    )
    MSC1767v10 = RoomVersion(
        # MSC1767 (Extensible Events) based on room version "10"
@@ -448,66 +304,34 @@ class RoomVersions:
        special_case_aliases_auth=False,
        strict_canonicaljson=True,
        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=True,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=False,
+        updated_redaction_rules=False,
+        restricted_join_rule=True,
+        restricted_join_rule_fix=True,
+        knock_join_rule=True,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=True,
-        msc3667_int_only_power_levels=True,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=True,
+        enforce_int_power_levels=True,
        msc3931_push_features=(PushRuleRoomFlag.EXTENSIBLE_EVENTS,),
-        msc3989_redaction_rules=False,
    )
-    MSC3989 = RoomVersion(
-        "org.matrix.msc3989",
-        RoomDisposition.UNSTABLE,
+    V11 = RoomVersion(
+        "11",
+        RoomDisposition.STABLE,
        EventFormatVersions.ROOM_V4_PLUS,
        StateResolutionVersions.V2,
        enforce_key_validity=True,
        special_case_aliases_auth=False,
        strict_canonicaljson=True,
        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=False,
-        msc2176_redaction_rules=False,
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=True,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
+        implicit_room_creator=True,  # Used by MSC3820
+        updated_redaction_rules=True,  # Used by MSC3820
+        restricted_join_rule=True,
+        restricted_join_rule_fix=True,
+        knock_join_rule=True,
        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=True,
-        msc3667_int_only_power_levels=True,
-        msc3821_redaction_rules=False,
+        knock_restricted_join_rule=True,
+        enforce_int_power_levels=True,
        msc3931_push_features=(),
-        msc3989_redaction_rules=True,
-    )
-    MSC3820opt2 = RoomVersion(
-        # Based upon v10
-        "org.matrix.msc3820.opt2",
-        RoomDisposition.UNSTABLE,
-        EventFormatVersions.ROOM_V4_PLUS,
-        StateResolutionVersions.V2,
-        enforce_key_validity=True,
-        special_case_aliases_auth=False,
-        strict_canonicaljson=True,
-        limit_notifications_power_levels=True,
-        msc2175_implicit_room_creator=True,  # Used by MSC3820
-        msc2176_redaction_rules=True,  # Used by MSC3820
-        msc3083_join_rules=True,
-        msc3375_redaction_rules=True,
-        msc2403_knocking=True,
-        msc2716_historical=False,
-        msc2716_redactions=False,
-        msc3389_relation_redactions=False,
-        msc3787_knock_restricted_join_rule=True,
-        msc3667_int_only_power_levels=True,
-        msc3821_redaction_rules=True,  # Used by MSC3820
-        msc3931_push_features=(),
-        msc3989_redaction_rules=True,  # Used by MSC3820
    )


@@ -520,15 +344,11 @@ KNOWN_ROOM_VERSIONS: Dict[str, RoomVersion] = {
        RoomVersions.V4,
        RoomVersions.V5,
        RoomVersions.V6,
-        RoomVersions.MSC2176,
        RoomVersions.V7,
        RoomVersions.V8,
        RoomVersions.V9,
-        RoomVersions.MSC3787,
        RoomVersions.V10,
-        RoomVersions.MSC2716v4,
-        RoomVersions.MSC3989,
-        RoomVersions.MSC3820opt2,
+        RoomVersions.V11,
    )
 }

@@ -557,12 +377,12 @@ MSC3244_CAPABILITIES = {
        RoomVersionCapability(
            "knock",
            RoomVersions.V7,
-            lambda room_version: room_version.msc2403_knocking,
+            lambda room_version: room_version.knock_join_rule,
        ),
        RoomVersionCapability(
            "restricted",
            RoomVersions.V9,
-            lambda room_version: room_version.msc3083_join_rules,
+            lambda room_version: room_version.restricted_join_rule,
        ),
    )
 }
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -386,6 +386,7 @@ def listen_unix(


 def listen_http(
+    hs: "HomeServer",
    listener_config: ListenerConfig,
    root_resource: Resource,
    version_string: str,
@@ -406,6 +407,7 @@ def listen_http(
        version_string,
        max_request_body_size=max_request_body_size,
        reactor=reactor,
+        hs=hs,
    )

    if isinstance(listener_config, TCPListenerConfig):
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -83,7 +83,6 @@ from synapse.storage.databases.main.receipts import ReceiptsWorkerStore
 from synapse.storage.databases.main.registration import RegistrationWorkerStore
 from synapse.storage.databases.main.relations import RelationsWorkerStore
 from synapse.storage.databases.main.room import RoomWorkerStore
-from synapse.storage.databases.main.room_batch import RoomBatchStore
 from synapse.storage.databases.main.roommember import RoomMemberWorkerStore
 from synapse.storage.databases.main.search import SearchStore
 from synapse.storage.databases.main.session import SessionStore
@@ -120,7 +119,6 @@ class GenericWorkerStore(
    # the races it creates aren't too bad.
    KeyStore,
    RoomWorkerStore,
-    RoomBatchStore,
    DirectoryWorkerStore,
    PushRulesWorkerStore,
    ApplicationServiceTransactionWorkerStore,
@@ -223,6 +221,7 @@ class GenericWorkerServer(HomeServer):
        root_resource = create_resource_tree(resources, OptionsResource())

        _base.listen_http(
+            self,
            listener_config,
            root_resource,
            self.version_string,
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -139,6 +139,7 @@ class SynapseHomeServer(HomeServer):
            root_resource = OptionsResource()

        ports = listen_http(
+            self,
            listener_config,
            create_resource_tree(resources, root_resource),
            self.version_string,
--- a/synapse/config/auth.py
+++ b/synapse/config/auth.py
@@ -31,7 +31,7 @@ class AuthConfig(Config):

        # The default value of password_config.enabled is True, unless msc3861 is enabled.
        msc3861_enabled = (
-            config.get("experimental_features", {})
+            (config.get("experimental_features") or {})
            .get("msc3861", {})
            .get("enabled", False)
        )
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -247,9 +247,6 @@ class ExperimentalConfig(Config):
        # MSC3026 (busy presence state)
        self.msc3026_enabled: bool = experimental.get("msc3026_enabled", False)

-        # MSC2716 (importing historical messages)
-        self.msc2716_enabled: bool = experimental.get("msc2716_enabled", False)
-
        # MSC3244 (room version capabilities)
        self.msc3244_enabled: bool = experimental.get("msc3244_enabled", True)

@@ -385,9 +382,6 @@ class ExperimentalConfig(Config):
        # Check that none of the other config options conflict with MSC3861 when enabled
        self.msc3861.check_config_conflicts(self.root)

-        # MSC4009: E.164 Matrix IDs
-        self.msc4009_e164_mxids = experimental.get("msc4009_e164_mxids", False)
-
        # MSC4010: Do not allow setting m.push_rules account data.
        self.msc4010_push_rules_account_data = experimental.get(
            "msc4010_push_rules_account_data", False
--- a/synapse/config/federation.py
+++ b/synapse/config/federation.py
@@ -22,6 +22,8 @@ class FederationConfig(Config):
    section = "federation"

    def read_config(self, config: JsonDict, **kwargs: Any) -> None:
+        federation_config = config.setdefault("federation", {})
+
        # FIXME: federation_domain_whitelist needs sytests
        self.federation_domain_whitelist: Optional[dict] = None
        federation_domain_whitelist = config.get("federation_domain_whitelist", None)
@@ -49,5 +51,19 @@ class FederationConfig(Config):
            "allow_device_name_lookup_over_federation", False
        )

+        # Allow for the configuration of timeout, max request retries
+        # and min/max retry delays in the matrix federation client.
+        self.client_timeout_ms = Config.parse_duration(
+            federation_config.get("client_timeout", "60s")
+        )
+        self.max_long_retry_delay_ms = Config.parse_duration(
+            federation_config.get("max_long_retry_delay", "60s")
+        )
+        self.max_short_retry_delay_ms = Config.parse_duration(
+            federation_config.get("max_short_retry_delay", "2s")
+        )
+        self.max_long_retries = federation_config.get("max_long_retries", 10)
+        self.max_short_retries = federation_config.get("max_short_retries", 3)
+

 _METRICS_FOR_DOMAINS_SCHEMA = {"type": "array", "items": {"type": "string"}}
--- a/synapse/config/workers.py
+++ b/synapse/config/workers.py
@@ -15,7 +15,7 @@

 import argparse
 import logging
-from typing import Any, Dict, List, Union
+from typing import Any, Dict, List, Optional, Union

 import attr
 from pydantic import BaseModel, Extra, StrictBool, StrictInt, StrictStr
@@ -41,11 +41,17 @@ Synapse version. Please use ``%s: name_of_worker`` instead.

 _MISSING_MAIN_PROCESS_INSTANCE_MAP_DATA = """
 Missing data for a worker to connect to main process. Please include '%s' in the
-`instance_map` declared in your shared yaml configuration, or optionally(as a deprecated
-solution) in every worker's yaml as various `worker_replication_*` settings as defined
-in workers documentation here:
+`instance_map` declared in your shared yaml configuration as defined in configuration
+documentation here:
+`https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#instance_map`
+"""
+
+WORKER_REPLICATION_SETTING_DEPRECATED_MESSAGE = """
+'%s' is no longer a supported worker setting, please place '%s' onto your shared
+configuration under `main` inside the `instance_map`. See workers documentation here:
 `https://matrix-org.github.io/synapse/latest/workers.html#worker-configuration`
 """
+
 # This allows for a handy knob when it's time to change from 'master' to
 # something with less 'history'
 MAIN_PROCESS_INSTANCE_NAME = "master"
@@ -88,7 +94,7 @@ class ConfigModel(BaseModel):
        allow_mutation = False


-class InstanceLocationConfig(ConfigModel):
+class InstanceTcpLocationConfig(ConfigModel):
    """The host and port to talk to an instance via HTTP replication."""

    host: StrictStr
@@ -104,6 +110,23 @@ class InstanceLocationConfig(ConfigModel):
        return f"{self.host}:{self.port}"


+class InstanceUnixLocationConfig(ConfigModel):
+    """The socket file to talk to an instance via HTTP replication."""
+
+    path: StrictStr
+
+    def scheme(self) -> str:
+        """Hardcode a retrievable scheme"""
+        return "unix"
+
+    def netloc(self) -> str:
+        """Nicely format the address location data"""
+        return f"{self.path}"
+
+
+InstanceLocationConfig = Union[InstanceTcpLocationConfig, InstanceUnixLocationConfig]
+
+
@attr.s
 class WriterLocations:
    """Specifies the instances that write various streams.
@@ -148,6 +171,27 @@ class WriterLocations:
    )


+@attr.s(auto_attribs=True)
+class OutboundFederationRestrictedTo:
+    """Whether we limit outbound federation to a certain set of instances.
+
+    Attributes:
+        instances: optional list of instances that can make outbound federation
+            requests. If None then all instances can make federation requests.
+        locations: list of instance locations to connect to proxy via.
+    """
+
+    instances: Optional[List[str]]
+    locations: List[InstanceLocationConfig] = attr.Factory(list)
+
+    def __contains__(self, instance: str) -> bool:
+        # It feels a bit dirty to return `True` if `instances` is `None`, but it makes
+        # sense in downstream usage in the sense that if
+        # `outbound_federation_restricted_to` is not configured, then any instance can
+        # talk to federation (no restrictions so always return `True`).
+        return self.instances is None or instance in self.instances
+
+
 class WorkerConfig(Config):
    """The workers are processes run separately to the main synapse process.
    They have their own pid_file and listener configuration. They use the
@@ -216,22 +260,37 @@ class WorkerConfig(Config):
        )

        # A map from instance name to host/port of their HTTP replication endpoint.
-        # Check if the main process is declared. Inject it into the map if it's not,
-        # based first on if a 'main' block is declared then on 'worker_replication_*'
-        # data. If both are available, default to instance_map. The main process
-        # itself doesn't need this data as it would never have to talk to itself.
+        # Check if the main process is declared. The main process itself doesn't need
+        # this data as it would never have to talk to itself.
        instance_map: Dict[str, Any] = config.get("instance_map", {})

        if self.instance_name is not MAIN_PROCESS_INSTANCE_NAME:
+            # TODO: The next 3 condition blocks can be deleted after some time has
+            #  passed and we're ready to stop checking for these settings.
            # The host used to connect to the main synapse
            main_host = config.get("worker_replication_host", None)
+            if main_host:
+                raise ConfigError(
+                    WORKER_REPLICATION_SETTING_DEPRECATED_MESSAGE
+                    % ("worker_replication_host", main_host)
+                )

            # The port on the main synapse for HTTP replication endpoint
            main_port = config.get("worker_replication_http_port")
+            if main_port:
+                raise ConfigError(
+                    WORKER_REPLICATION_SETTING_DEPRECATED_MESSAGE
+                    % ("worker_replication_http_port", main_port)
+                )

            # The tls mode on the main synapse for HTTP replication endpoint.
            # For backward compatibility this defaults to False.
            main_tls = config.get("worker_replication_http_tls", False)
+            if main_tls:
+                raise ConfigError(
+                    WORKER_REPLICATION_SETTING_DEPRECATED_MESSAGE
+                    % ("worker_replication_http_tls", main_tls)
+                )

            # For now, accept 'main' in the instance_map, but the replication system
            # expects 'master', force that into being until it's changed later.
@@ -241,30 +300,20 @@ class WorkerConfig(Config):
                ]
                del instance_map[MAIN_PROCESS_INSTANCE_MAP_NAME]

-            # This is the backwards compatibility bit that handles the
-            # worker_replication_* bits using setdefault() to not overwrite anything.
-            elif main_host is not None and main_port is not None:
-                instance_map.setdefault(
-                    MAIN_PROCESS_INSTANCE_NAME,
-                    {
-                        "host": main_host,
-                        "port": main_port,
-                        "tls": main_tls,
-                    },
-                )
-
            else:
                # If we've gotten here, it means that the main process is not on the
-                # instance_map and that not enough worker_replication_* variables
-                # were declared in the worker's yaml.
+                # instance_map.
                raise ConfigError(
                    _MISSING_MAIN_PROCESS_INSTANCE_MAP_DATA
                    % MAIN_PROCESS_INSTANCE_MAP_NAME
                )

+        # type-ignore: the expression `Union[A, B]` is not a Type[Union[A, B]] currently
        self.instance_map: Dict[
            str, InstanceLocationConfig
-        ] = parse_and_validate_mapping(instance_map, InstanceLocationConfig)
+        ] = parse_and_validate_mapping(
+            instance_map, InstanceLocationConfig  # type: ignore[arg-type]
+        )

        # Map from type of streams to source, c.f. WriterLocations.
        writers = config.get("stream_writers") or {}
@@ -357,6 +406,28 @@ class WorkerConfig(Config):
            new_option_name="update_user_directory_from_worker",
        )

+        outbound_federation_restricted_to = config.get(
+            "outbound_federation_restricted_to", None
+        )
+        self.outbound_federation_restricted_to = OutboundFederationRestrictedTo(
+            outbound_federation_restricted_to
+        )
+        if outbound_federation_restricted_to:
+            if not self.worker_replication_secret:
+                raise ConfigError(
+                    "`worker_replication_secret` must be configured when using `outbound_federation_restricted_to`."
+                )
+
+            for instance in outbound_federation_restricted_to:
+                if instance not in self.instance_map:
+                    raise ConfigError(
+                        "Instance %r is configured in 'outbound_federation_restricted_to' but does not appear in `instance_map` config."
+                        % (instance,)
+                    )
+                self.outbound_federation_restricted_to.locations.append(
+                    self.instance_map[instance]
+                )
+
    def _should_this_worker_perform_duty(
        self,
        config: Dict[str, Any],
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -126,7 +126,7 @@ def validate_event_for_room_version(event: "EventBase") -> None:
            raise AuthError(403, "Event not signed by sending server")

    is_invite_via_allow_rule = (
-        event.room_version.msc3083_join_rules
+        event.room_version.restricted_join_rule
        and event.type == EventTypes.Member
        and event.membership == Membership.JOIN
        and EventContentFields.AUTHORISING_USER in event.content
@@ -339,13 +339,6 @@ def check_state_dependent_auth_rules(
    if event.type == EventTypes.Redaction:
        check_redaction(event.room_version, event, auth_dict)

-    if (
-        event.type == EventTypes.MSC2716_INSERTION
-        or event.type == EventTypes.MSC2716_BATCH
-        or event.type == EventTypes.MSC2716_MARKER
-    ):
-        check_historical(event.room_version, event, auth_dict)
-
    logger.debug("Allowing! %s", event)


@@ -359,13 +352,10 @@ LENIENT_EVENT_BYTE_LIMITS_ROOM_VERSIONS = {
    RoomVersions.V4,
    RoomVersions.V5,
    RoomVersions.V6,
-    RoomVersions.MSC2176,
    RoomVersions.V7,
    RoomVersions.V8,
    RoomVersions.V9,
-    RoomVersions.MSC3787,
    RoomVersions.V10,
-    RoomVersions.MSC2716v4,
    RoomVersions.MSC1767v10,
 }

@@ -457,7 +447,7 @@ def _check_create(event: "EventBase") -> None:

    # 1.4 If content has no creator field, reject if the room version requires it.
    if (
-        not event.room_version.msc2175_implicit_room_creator
+        not event.room_version.implicit_room_creator
        and EventContentFields.ROOM_CREATOR not in event.content
    ):
        raise AuthError(403, "Create event lacks a 'creator' property")
@@ -494,7 +484,7 @@ def _is_membership_change_allowed(
        key = (EventTypes.Create, "")
        create = auth_events.get(key)
        if create and event.prev_event_ids()[0] == create.event_id:
-            if room_version.msc2175_implicit_room_creator:
+            if room_version.implicit_room_creator:
                creator = create.sender
            else:
                creator = create.content[EventContentFields.ROOM_CREATOR]
@@ -517,7 +507,7 @@ def _is_membership_change_allowed(
    caller_invited = caller and caller.membership == Membership.INVITE
    caller_knocked = (
        caller
-        and room_version.msc2403_knocking
+        and room_version.knock_join_rule
        and caller.membership == Membership.KNOCK
    )

@@ -617,9 +607,9 @@ def _is_membership_change_allowed(
        elif join_rule == JoinRules.PUBLIC:
            pass
        elif (
-            room_version.msc3083_join_rules and join_rule == JoinRules.RESTRICTED
+            room_version.restricted_join_rule and join_rule == JoinRules.RESTRICTED
        ) or (
-            room_version.msc3787_knock_restricted_join_rule
+            room_version.knock_restricted_join_rule
            and join_rule == JoinRules.KNOCK_RESTRICTED
        ):
            # This is the same as public, but the event must contain a reference
@@ -649,9 +639,9 @@ def _is_membership_change_allowed(

        elif (
            join_rule == JoinRules.INVITE
-            or (room_version.msc2403_knocking and join_rule == JoinRules.KNOCK)
+            or (room_version.knock_join_rule and join_rule == JoinRules.KNOCK)
            or (
-                room_version.msc3787_knock_restricted_join_rule
+                room_version.knock_restricted_join_rule
                and join_rule == JoinRules.KNOCK_RESTRICTED
            )
        ):
@@ -685,9 +675,9 @@ def _is_membership_change_allowed(
                "You don't have permission to ban",
                errcode=Codes.INSUFFICIENT_POWER,
            )
-    elif room_version.msc2403_knocking and Membership.KNOCK == membership:
+    elif room_version.knock_join_rule and Membership.KNOCK == membership:
        if join_rule != JoinRules.KNOCK and (
-            not room_version.msc3787_knock_restricted_join_rule
+            not room_version.knock_restricted_join_rule
            or join_rule != JoinRules.KNOCK_RESTRICTED
        ):
            raise AuthError(403, "You don't have permission to knock")
@@ -823,38 +813,6 @@ def check_redaction(
    raise AuthError(403, "You don't have permission to redact events")


-def check_historical(
-    room_version_obj: RoomVersion,
-    event: "EventBase",
-    auth_events: StateMap["EventBase"],
-) -> None:
-    """Check whether the event sender is allowed to send historical related
-    events like "insertion", "batch", and "marker".
-
-    Returns:
-        None
-
-    Raises:
-        AuthError if the event sender is not allowed to send historical related events
-        ("insertion", "batch", and "marker").
-    """
-    # Ignore the auth checks in room versions that do not support historical
-    # events
-    if not room_version_obj.msc2716_historical:
-        return
-
-    user_level = get_user_power_level(event.user_id, auth_events)
-
-    historical_level = get_named_level(auth_events, "historical", 100)
-
-    if user_level < historical_level:
-        raise UnstableSpecAuthError(
-            403,
-            'You don\'t have permission to send send historical related events ("insertion", "batch", and "marker")',
-            errcode=Codes.INSUFFICIENT_POWER,
-        )
-
-
 def _check_power_levels(
    room_version_obj: RoomVersion,
    event: "EventBase",
@@ -876,7 +834,7 @@ def _check_power_levels(
    # Reject events with stringy power levels if required by room version
    if (
        event.type == EventTypes.PowerLevels
-        and room_version_obj.msc3667_int_only_power_levels
+        and room_version_obj.enforce_int_power_levels
    ):
        for k, v in event.content.items():
            if k in {
@@ -1012,7 +970,7 @@ def get_user_power_level(user_id: str, auth_events: StateMap["EventBase"]) -> in
        key = (EventTypes.Create, "")
        create_event = auth_events.get(key)
        if create_event is not None:
-            if create_event.room_version.msc2175_implicit_room_creator:
+            if create_event.room_version.implicit_room_creator:
                creator = create_event.sender
            else:
                creator = create_event.content[EventContentFields.ROOM_CREATOR]
@@ -1150,7 +1108,7 @@ def auth_types_for_event(
                )
                auth_types.add(key)

-        if room_version.msc3083_join_rules and membership == Membership.JOIN:
+        if room_version.restricted_join_rule and membership == Membership.JOIN:
            if EventContentFields.AUTHORISING_USER in event.content:
                key = (
                    EventTypes.Member,
--- a/synapse/events/init.py
+++ b/synapse/events/init.py
@@ -198,7 +198,6 @@ class _EventInternalMetadata:
    soft_failed: DictProperty[bool] = DictProperty("soft_failed")
    proactively_send: DictProperty[bool] = DictProperty("proactively_send")
    redacted: DictProperty[bool] = DictProperty("redacted")
-    historical: DictProperty[bool] = DictProperty("historical")

    txn_id: DictProperty[str] = DictProperty("txn_id")
    """The transaction ID, if it was set when the event was created."""
@@ -288,14 +287,6 @@ class _EventInternalMetadata:
        """
        return self._dict.get("redacted", False)

-    def is_historical(self) -> bool:
-        """Whether this is a historical message.
-        This is used by the batchsend historical message endpoint and
-        is needed to and mark the event as backfilled and skip some checks
-        like push notifications.
-        """
-        return self._dict.get("historical", False)
-
    def is_notifiable(self) -> bool:
        """Whether this event can trigger a push notification"""
        return not self.is_outlier() or self.is_out_of_band_membership()
@@ -355,7 +346,7 @@ class EventBase(metaclass=abc.ABCMeta):
    @property
    def redacts(self) -> Optional[str]:
        """MSC2176 moved the redacts field into the content."""
-        if self.room_version.msc2176_redaction_rules:
+        if self.room_version.updated_redaction_rules:
            return self.content.get("redacts")
        return self.get("redacts")

--- a/synapse/events/builder.py
+++ b/synapse/events/builder.py
@@ -175,7 +175,7 @@ class EventBuilder:

        # MSC2174 moves the redacts property to the content, it is invalid to
        # provide it as a top-level property.
-        if self._redacts is not None and not self.room_version.msc2176_redaction_rules:
+        if self._redacts is not None and not self.room_version.updated_redaction_rules:
            event_dict["redacts"] = self._redacts

        if self._origin_server_ts is not None:
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from abc import ABC, abstractmethod
-from typing import TYPE_CHECKING, List, Optional, Tuple
+from typing import TYPE_CHECKING, Dict, List, Optional, Tuple

 import attr
 from immutabledict import immutabledict
@@ -107,33 +107,32 @@ class EventContext(UnpersistedEventContextBase):
        state_delta_due_to_event: If `state_group` and `state_group_before_event` are not None
            then this is the delta of the state between the two groups.

-        prev_group: If it is known, ``state_group``'s prev_group. Note that this being
-            None does not necessarily mean that ``state_group`` does not have
-            a prev_group!
+        state_group_deltas: If not empty, this is a dict collecting a mapping of the state
+            difference between state groups.

-            If the event is a state event, this is normally the same as
-            ``state_group_before_event``.
+            The keys are a tuple of two integers: the initial group and final state group.
+            The corresponding value is a state map representing the state delta between
+            these state groups.

-            If ``state_group`` is None (ie, the event is an outlier), ``prev_group``
-            will always also be ``None``.
+            The dictionary is expected to have at most two entries with state groups of:

-            Note that this *not* (necessarily) the state group associated with
-            ``_prev_state_ids``.
+            1. The state group before the event and after the event.
+            2. The state group preceding the state group before the event and the
+               state group before the event.

-        delta_ids: If ``prev_group`` is not None, the state delta between ``prev_group``
-            and ``state_group``.
+            This information is collected and stored as part of an optimization for persisting
+            events.

        partial_state: if True, we may be storing this event with a temporary,
            incomplete state.
    """

    _storage: "StorageControllers"
+    state_group_deltas: Dict[Tuple[int, int], StateMap[str]]
    rejected: Optional[str] = None
    _state_group: Optional[int] = None
    state_group_before_event: Optional[int] = None
    _state_delta_due_to_event: Optional[StateMap[str]] = None
-    prev_group: Optional[int] = None
-    delta_ids: Optional[StateMap[str]] = None
    app_service: Optional[ApplicationService] = None

    partial_state: bool = False
@@ -145,16 +144,14 @@ class EventContext(UnpersistedEventContextBase):
        state_group_before_event: Optional[int],
        state_delta_due_to_event: Optional[StateMap[str]],
        partial_state: bool,
-        prev_group: Optional[int] = None,
-        delta_ids: Optional[StateMap[str]] = None,
+        state_group_deltas: Dict[Tuple[int, int], StateMap[str]],
    ) -> "EventContext":
        return EventContext(
            storage=storage,
            state_group=state_group,
            state_group_before_event=state_group_before_event,
            state_delta_due_to_event=state_delta_due_to_event,
-            prev_group=prev_group,
-            delta_ids=delta_ids,
+            state_group_deltas=state_group_deltas,
            partial_state=partial_state,
        )

@@ -163,7 +160,7 @@ class EventContext(UnpersistedEventContextBase):
        storage: "StorageControllers",
    ) -> "EventContext":
        """Return an EventContext instance suitable for persisting an outlier event"""
-        return EventContext(storage=storage)
+        return EventContext(storage=storage, state_group_deltas={})

    async def persist(self, event: EventBase) -> "EventContext":
        return self
@@ -183,13 +180,15 @@ class EventContext(UnpersistedEventContextBase):
            "state_group": self._state_group,
            "state_group_before_event": self.state_group_before_event,
            "rejected": self.rejected,
-            "prev_group": self.prev_group,
+            "state_group_deltas": _encode_state_group_delta(self.state_group_deltas),
            "state_delta_due_to_event": _encode_state_dict(
                self._state_delta_due_to_event
            ),
-            "delta_ids": _encode_state_dict(self.delta_ids),
            "app_service_id": self.app_service.id if self.app_service else None,
            "partial_state": self.partial_state,
+            # add dummy delta_ids and prev_group for backwards compatibility
+            "delta_ids": None,
+            "prev_group": None,
        }

    @staticmethod
@@ -204,17 +203,24 @@ class EventContext(UnpersistedEventContextBase):
        Returns:
            The event context.
        """
+        # workaround for backwards/forwards compatibility: if the input doesn't have a value
+        # for "state_group_deltas" just assign an empty dict
+        state_group_deltas = input.get("state_group_deltas", None)
+        if state_group_deltas:
+            state_group_deltas = _decode_state_group_delta(state_group_deltas)
+        else:
+            state_group_deltas = {}
+
        context = EventContext(
            # We use the state_group and prev_state_id stuff to pull the
            # current_state_ids out of the DB and construct prev_state_ids.
            storage=storage,
            state_group=input["state_group"],
            state_group_before_event=input["state_group_before_event"],
-            prev_group=input["prev_group"],
+            state_group_deltas=state_group_deltas,
            state_delta_due_to_event=_decode_state_dict(
                input["state_delta_due_to_event"]
            ),
-            delta_ids=_decode_state_dict(input["delta_ids"]),
            rejected=input["rejected"],
            partial_state=input.get("partial_state", False),
        )
@@ -349,7 +355,7 @@ class UnpersistedEventContext(UnpersistedEventContextBase):
    _storage: "StorageControllers"
    state_group_before_event: Optional[int]
    state_group_after_event: Optional[int]
-    state_delta_due_to_event: Optional[dict]
+    state_delta_due_to_event: Optional[StateMap[str]]
    prev_group_for_state_group_before_event: Optional[int]
    delta_ids_to_state_group_before_event: Optional[StateMap[str]]
    partial_state: bool
@@ -380,26 +386,16 @@ class UnpersistedEventContext(UnpersistedEventContextBase):

        events_and_persisted_context = []
        for event, unpersisted_context in amended_events_and_context:
-            if event.is_state():
-                context = EventContext(
-                    storage=unpersisted_context._storage,
-                    state_group=unpersisted_context.state_group_after_event,
-                    state_group_before_event=unpersisted_context.state_group_before_event,
-                    state_delta_due_to_event=unpersisted_context.state_delta_due_to_event,
-                    partial_state=unpersisted_context.partial_state,
-                    prev_group=unpersisted_context.state_group_before_event,
-                    delta_ids=unpersisted_context.state_delta_due_to_event,
-                )
-            else:
-                context = EventContext(
-                    storage=unpersisted_context._storage,
-                    state_group=unpersisted_context.state_group_after_event,
-                    state_group_before_event=unpersisted_context.state_group_before_event,
-                    state_delta_due_to_event=unpersisted_context.state_delta_due_to_event,
-                    partial_state=unpersisted_context.partial_state,
-                    prev_group=unpersisted_context.prev_group_for_state_group_before_event,
-                    delta_ids=unpersisted_context.delta_ids_to_state_group_before_event,
-                )
+            state_group_deltas = unpersisted_context._build_state_group_deltas()
+
+            context = EventContext(
+                storage=unpersisted_context._storage,
+                state_group=unpersisted_context.state_group_after_event,
+                state_group_before_event=unpersisted_context.state_group_before_event,
+                state_delta_due_to_event=unpersisted_context.state_delta_due_to_event,
+                partial_state=unpersisted_context.partial_state,
+                state_group_deltas=state_group_deltas,
+            )
            events_and_persisted_context.append((event, context))
        return events_and_persisted_context

@@ -452,11 +448,11 @@ class UnpersistedEventContext(UnpersistedEventContextBase):

        # if the event isn't a state event the state group doesn't change
        if not self.state_delta_due_to_event:
-            state_group_after_event = self.state_group_before_event
+            self.state_group_after_event = self.state_group_before_event

        # otherwise if it is a state event we need to get a state group for it
        else:
-            state_group_after_event = await self._storage.state.store_state_group(
+            self.state_group_after_event = await self._storage.state.store_state_group(
                event.event_id,
                event.room_id,
                prev_group=self.state_group_before_event,
@@ -464,16 +460,81 @@ class UnpersistedEventContext(UnpersistedEventContextBase):
                current_state_ids=None,
            )

+        state_group_deltas = self._build_state_group_deltas()
+
        return EventContext.with_state(
            storage=self._storage,
-            state_group=state_group_after_event,
+            state_group=self.state_group_after_event,
            state_group_before_event=self.state_group_before_event,
            state_delta_due_to_event=self.state_delta_due_to_event,
+            state_group_deltas=state_group_deltas,
            partial_state=self.partial_state,
-            prev_group=self.state_group_before_event,
-            delta_ids=self.state_delta_due_to_event,
        )

+    def _build_state_group_deltas(self) -> Dict[Tuple[int, int], StateMap]:
+        """
+        Collect deltas between the state groups associated with this context
+        """
+        state_group_deltas = {}
+
+        # if we know the state group before the event and after the event, add them and the
+        # state delta between them to state_group_deltas
+        if self.state_group_before_event and self.state_group_after_event:
+            # if we have the state groups we should have the delta
+            assert self.state_delta_due_to_event is not None
+            state_group_deltas[
+                (
+                    self.state_group_before_event,
+                    self.state_group_after_event,
+                )
+            ] = self.state_delta_due_to_event
+
+        # the state group before the event may also have a state group which precedes it, if
+        # we have that and the state group before the event, add them and the state
+        # delta between them to state_group_deltas
+        if (
+            self.prev_group_for_state_group_before_event
+            and self.state_group_before_event
+        ):
+            # if we have both state groups we should have the delta between them
+            assert self.delta_ids_to_state_group_before_event is not None
+            state_group_deltas[
+                (
+                    self.prev_group_for_state_group_before_event,
+                    self.state_group_before_event,
+                )
+            ] = self.delta_ids_to_state_group_before_event
+
+        return state_group_deltas
+
+
+def _encode_state_group_delta(
+    state_group_delta: Dict[Tuple[int, int], StateMap[str]]
+) -> List[Tuple[int, int, Optional[List[Tuple[str, str, str]]]]]:
+    if not state_group_delta:
+        return []
+
+    state_group_delta_encoded = []
+    for key, value in state_group_delta.items():
+        state_group_delta_encoded.append((key[0], key[1], _encode_state_dict(value)))
+
+    return state_group_delta_encoded
+
+
+def _decode_state_group_delta(
+    input: List[Tuple[int, int, List[Tuple[str, str, str]]]]
+) -> Dict[Tuple[int, int], StateMap[str]]:
+    if not input:
+        return {}
+
+    state_group_deltas = {}
+    for state_group_1, state_group_2, state_dict in input:
+        state_map = _decode_state_dict(state_dict)
+        assert state_map is not None
+        state_group_deltas[(state_group_1, state_group_2)] = state_map
+
+    return state_group_deltas
+

 def _encode_state_dict(
    state_dict: Optional[StateMap[str]],
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -108,13 +108,9 @@ def prune_event_dict(room_version: RoomVersion, event_dict: JsonDict) -> JsonDic
        "origin_server_ts",
    ]

-    # Room versions from before MSC2176 had additional allowed keys.
-    if not room_version.msc2176_redaction_rules:
-        allowed_keys.extend(["prev_state", "membership"])
-
-    # Room versions before MSC3989 kept the origin field.
-    if not room_version.msc3989_redaction_rules:
-        allowed_keys.append("origin")
+    # Earlier room versions from had additional allowed keys.
+    if not room_version.updated_redaction_rules:
+        allowed_keys.extend(["prev_state", "membership", "origin"])

    event_type = event_dict["type"]

@@ -127,9 +123,9 @@ def prune_event_dict(room_version: RoomVersion, event_dict: JsonDict) -> JsonDic

    if event_type == EventTypes.Member:
        add_fields("membership")
-        if room_version.msc3375_redaction_rules:
+        if room_version.restricted_join_rule_fix:
            add_fields(EventContentFields.AUTHORISING_USER)
-        if room_version.msc3821_redaction_rules:
+        if room_version.updated_redaction_rules:
            # Preserve the signed field under third_party_invite.
            third_party_invite = event_dict["content"].get("third_party_invite")
            if isinstance(third_party_invite, collections.abc.Mapping):
@@ -141,13 +137,13 @@ def prune_event_dict(room_version: RoomVersion, event_dict: JsonDict) -> JsonDic

    elif event_type == EventTypes.Create:
        # MSC2176 rules state that create events cannot be redacted.
-        if room_version.msc2176_redaction_rules:
+        if room_version.updated_redaction_rules:
            return event_dict

        add_fields("creator")
    elif event_type == EventTypes.JoinRules:
        add_fields("join_rule")
-        if room_version.msc3083_join_rules:
+        if room_version.restricted_join_rule:
            add_fields("allow")
    elif event_type == EventTypes.PowerLevels:
        add_fields(
@@ -161,24 +157,15 @@ def prune_event_dict(room_version: RoomVersion, event_dict: JsonDict) -> JsonDic
            "redact",
        )

-        if room_version.msc2176_redaction_rules:
+        if room_version.updated_redaction_rules:
            add_fields("invite")

-        if room_version.msc2716_historical:
-            add_fields("historical")
-
    elif event_type == EventTypes.Aliases and room_version.special_case_aliases_auth:
        add_fields("aliases")
    elif event_type == EventTypes.RoomHistoryVisibility:
        add_fields("history_visibility")
-    elif event_type == EventTypes.Redaction and room_version.msc2176_redaction_rules:
+    elif event_type == EventTypes.Redaction and room_version.updated_redaction_rules:
        add_fields("redacts")
-    elif room_version.msc2716_redactions and event_type == EventTypes.MSC2716_INSERTION:
-        add_fields(EventContentFields.MSC2716_NEXT_BATCH_ID)
-    elif room_version.msc2716_redactions and event_type == EventTypes.MSC2716_BATCH:
-        add_fields(EventContentFields.MSC2716_BATCH_ID)
-    elif room_version.msc2716_redactions and event_type == EventTypes.MSC2716_MARKER:
-        add_fields(EventContentFields.MSC2716_INSERTION_EVENT_REFERENCE)

    # Protect the rel_type and event_id fields under the m.relates_to field.
    if room_version.msc3389_relation_redactions:
@@ -486,6 +473,15 @@ def serialize_event(
    if config.as_client_event:
        d = config.event_format(d)

+    # If the event is a redaction, copy the redacts field from the content to
+    # top-level for backwards compatibility.
+    if (
+        e.type == EventTypes.Redaction
+        and e.room_version.updated_redaction_rules
+        and e.redacts is not None
+    ):
+        d["redacts"] = e.redacts
+
    only_event_fields = config.only_event_fields
    if only_event_fields:
        if not isinstance(only_event_fields, list) or not all(
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -231,7 +231,7 @@ async def _check_sigs_on_pdu(
    # If this is a join event for a restricted room it may have been authorised
    # via a different server from the sending server. Check those signatures.
    if (
-        room_version.msc3083_join_rules
+        room_version.restricted_join_rule
        and pdu.type == EventTypes.Member
        and pdu.membership == Membership.JOIN
        and EventContentFields.AUTHORISING_USER in pdu.content
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -260,7 +260,9 @@ class FederationClient(FederationBase):
        use_unstable = False
        for user_id, one_time_keys in query.items():
            for device_id, algorithms in one_time_keys.items():
-                if any(count > 1 for count in algorithms.values()):
+                # If more than one algorithm is requested, attempt to use the unstable
+                # endpoint.
+                if sum(algorithms.values()) > 1:
                    use_unstable = True
                if algorithms:
                    # For the stable query, choose only the first algorithm.
@@ -296,6 +298,7 @@ class FederationClient(FederationBase):
        else:
            logger.debug("Skipping unstable claim client keys API")

+        # TODO Potentially attempt multiple queries and combine the results?
        return await self.transport_layer.claim_client_keys(
            user, destination, content, timeout
        )
@@ -980,7 +983,7 @@ class FederationClient(FederationBase):
            if not room_version:
                raise UnsupportedRoomVersionError()

-            if not room_version.msc2403_knocking and membership == Membership.KNOCK:
+            if not room_version.knock_join_rule and membership == Membership.KNOCK:
                raise SynapseError(
                    400,
                    "This room version does not support knocking",
@@ -1066,7 +1069,7 @@ class FederationClient(FederationBase):
            # * Ensure the signatures are good.
            #
            # Otherwise, fallback to the provided event.
-            if room_version.msc3083_join_rules and response.event:
+            if room_version.restricted_join_rule and response.event:
                event = response.event

                valid_pdu = await self._check_sigs_and_hash_and_fetch_one(
@@ -1192,7 +1195,7 @@ class FederationClient(FederationBase):

        # MSC3083 defines additional error codes for room joins.
        failover_errcodes = None
-        if room_version.msc3083_join_rules:
+        if room_version.restricted_join_rule:
            failover_errcodes = (
                Codes.UNABLE_AUTHORISE_JOIN,
                Codes.UNABLE_TO_GRANT_JOIN,
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -806,7 +806,7 @@ class FederationServer(FederationBase):
            raise IncompatibleRoomVersionError(room_version=room_version.identifier)

        # Check that this room supports knocking as defined by its room version
-        if not room_version.msc2403_knocking:
+        if not room_version.knock_join_rule:
            raise SynapseError(
                403,
                "This room version does not support knocking",
@@ -909,7 +909,7 @@ class FederationServer(FederationBase):
                errcode=Codes.NOT_FOUND,
            )

-        if membership_type == Membership.KNOCK and not room_version.msc2403_knocking:
+        if membership_type == Membership.KNOCK and not room_version.knock_join_rule:
            raise SynapseError(
                403,
                "This room version does not support knocking",
@@ -933,7 +933,7 @@ class FederationServer(FederationBase):
        # the event is valid to be sent into the room. Currently this is only done
        # if the user is being joined via restricted join rules.
        if (
-            room_version.msc3083_join_rules
+            room_version.restricted_join_rule
            and event.membership == Membership.JOIN
            and EventContentFields.AUTHORISING_USER in event.content
        ):
@@ -1016,7 +1016,9 @@ class FederationServer(FederationBase):
            for user_id, device_keys in result.items():
                for device_id, keys in device_keys.items():
                    for key_id, key in keys.items():
-                        json_result.setdefault(user_id, {})[device_id] = {key_id: key}
+                        json_result.setdefault(user_id, {}).setdefault(device_id, {})[
+                            key_id
+                        ] = key

        logger.info(
            "Claimed one-time-keys: %s",
--- a/synapse/federation/sender/init.py
+++ b/synapse/federation/sender/init.py
@@ -109,10 +109,8 @@ was enabled*, Catch-Up Mode is exited and we return to `_transaction_transmissio

 If a remote server is unreachable over federation, we back off from that server,
 with an exponentially-increasing retry interval.
-Whilst we don't automatically retry after the interval, we prevent making new attempts
-until such time as the back-off has cleared.
-Once the back-off is cleared and a new PDU or EDU arrives for transmission, the transmission
-loop resumes and empties the queue by making federation requests.
+We automatically retry after the retry interval expires (roughly, the logic to do so
+being triggered every minute).

 If the backoff grows too large (> 1 hour), the in-memory queue is emptied (to prevent
 unbounded growth) and Catch-Up Mode is entered.
@@ -145,7 +143,6 @@ from prometheus_client import Counter
 from typing_extensions import Literal

 from twisted.internet import defer
-from twisted.internet.interfaces import IDelayedCall

 import synapse.metrics
 from synapse.api.presence import UserPresenceState
@@ -184,14 +181,18 @@ sent_pdus_destination_dist_total = Counter(
    "Total number of PDUs queued for sending across all destinations",
 )

-# Time (in s) after Synapse's startup that we will begin to wake up destinations
-# that have catch-up outstanding.
-CATCH_UP_STARTUP_DELAY_SEC = 15
+# Time (in s) to wait before trying to wake up destinations that have
+# catch-up outstanding. This will also be the delay applied at startup
+# before trying the same.
+# Please note that rate limiting still applies, so while the loop is
+# executed every X seconds the destinations may not be wake up because
+# they are being rate limited following previous attempt failures.
+WAKEUP_RETRY_PERIOD_SEC = 60

 # Time (in s) to wait in between waking up each destination, i.e. one destination
-# will be woken up every <x> seconds after Synapse's startup until we have woken
-# every destination has outstanding catch-up.
-CATCH_UP_STARTUP_INTERVAL_SEC = 5
+# will be woken up every <x> seconds until we have woken every destination
+# has outstanding catch-up.
+WAKEUP_INTERVAL_BETWEEN_DESTINATIONS_SEC = 5


 class AbstractFederationSender(metaclass=abc.ABCMeta):
@@ -415,12 +416,10 @@ class FederationSender(AbstractFederationSender):
            / hs.config.ratelimiting.federation_rr_transactions_per_room_per_second
        )

-        # wake up destinations that have outstanding PDUs to be caught up
-        self._catchup_after_startup_timer: Optional[
-            IDelayedCall
-        ] = self.clock.call_later(
-            CATCH_UP_STARTUP_DELAY_SEC,
+        # Regularly wake up destinations that have outstanding PDUs to be caught up
+        self.clock.looping_call(
            run_as_background_process,
+            WAKEUP_RETRY_PERIOD_SEC * 1000.0,
            "wake_destinations_needing_catchup",
            self._wake_destinations_needing_catchup,
        )
@@ -966,7 +965,6 @@ class FederationSender(AbstractFederationSender):

            if not destinations_to_wake:
                # finished waking all destinations!
-                self._catchup_after_startup_timer = None
                break

            last_processed = destinations_to_wake[-1]
@@ -983,4 +981,4 @@ class FederationSender(AbstractFederationSender):
                    last_processed,
                )
                self.wake_destination(destination)
-                await self.clock.sleep(CATCH_UP_STARTUP_INTERVAL_SEC)
+                await self.clock.sleep(WAKEUP_INTERVAL_BETWEEN_DESTINATIONS_SEC)
--- a/synapse/federation/transport/server/federation.py
+++ b/synapse/federation/transport/server/federation.py
@@ -432,15 +432,6 @@ class FederationV2SendJoinServlet(BaseFederationServerServlet):

    PREFIX = FEDERATION_V2_PREFIX

-    def __init__(
-        self,
-        hs: "HomeServer",
-        authenticator: Authenticator,
-        ratelimiter: FederationRateLimiter,
-        server_name: str,
-    ):
-        super().__init__(hs, authenticator, ratelimiter, server_name)
-
    async def on_PUT(
        self,
        origin: str,
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -277,7 +277,9 @@ class DirectoryHandler:
            except RequestSendFailed:
                raise SynapseError(502, "Failed to fetch alias")
            except CodeMessageException as e:
-                logging.warning("Error retrieving alias")
+                logging.warning(
+                    "Error retrieving alias %s -> %s %s", room_alias, e.code, e.msg
+                )
                if e.code == 404:
                    fed_result = None
                else:
--- a/synapse/handlers/event_auth.py
+++ b/synapse/handlers/event_auth.py
@@ -277,7 +277,7 @@ class EventAuthHandler:
            True if the proper room version and join rules are set for restricted access.
        """
        # This only applies to room versions which support the new join rule.
-        if not room_version.msc3083_join_rules:
+        if not room_version.restricted_join_rule:
            return False

        # If there's no join rule, then it defaults to invite (so this doesn't apply).
@@ -292,7 +292,7 @@ class EventAuthHandler:
            return True

        # also check for MSC3787 behaviour
-        if room_version.msc3787_knock_restricted_join_rule:
+        if room_version.knock_restricted_join_rule:
            return content_join_rule == JoinRules.KNOCK_RESTRICTED

        return False
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -105,14 +105,12 @@ backfill_processing_before_timer = Histogram(
 )


+# TODO: We can refactor this away now that there is only one backfill point again
 class _BackfillPointType(Enum):
    # a regular backwards extremity (ie, an event which we don't yet have, but which
    # is referred to by other events in the DAG)
    BACKWARDS_EXTREMITY = enum.auto()

-    # an MSC2716 "insertion event"
-    INSERTION_PONT = enum.auto()
-

@attr.s(slots=True, auto_attribs=True, frozen=True)
 class _BackfillPoint:
@@ -273,32 +271,10 @@ class FederationHandler:
            )
        ]

-        insertion_events_to_be_backfilled: List[_BackfillPoint] = []
-        if self.hs.config.experimental.msc2716_enabled:
-            insertion_events_to_be_backfilled = [
-                _BackfillPoint(event_id, depth, _BackfillPointType.INSERTION_PONT)
-                for event_id, depth in await self.store.get_insertion_event_backward_extremities_in_room(
-                    room_id=room_id,
-                    current_depth=current_depth,
-                    # We only need to end up with 5 extremities combined with
-                    # the backfill points to make the `/backfill` request ...
-                    # (see the other comment above for more context).
-                    limit=50,
-                )
-            ]
-        logger.debug(
-            "_maybe_backfill_inner: backwards_extremities=%s insertion_events_to_be_backfilled=%s",
-            backwards_extremities,
-            insertion_events_to_be_backfilled,
-        )
-
        # we now have a list of potential places to backpaginate from. We prefer to
        # start with the most recent (ie, max depth), so let's sort the list.
        sorted_backfill_points: List[_BackfillPoint] = sorted(
-            itertools.chain(
-                backwards_extremities,
-                insertion_events_to_be_backfilled,
-            ),
+            backwards_extremities,
            key=lambda e: -int(e.depth),
        )

@@ -411,10 +387,7 @@ class FederationHandler:
            #   event but not anything before it. This would require looking at the
            #   state *before* the event, ignoring the special casing certain event
            #   types have.
-            if bp.type == _BackfillPointType.INSERTION_PONT:
-                event_ids_to_check = [bp.event_id]
-            else:
-                event_ids_to_check = await self.store.get_successor_events(bp.event_id)
+            event_ids_to_check = await self.store.get_successor_events(bp.event_id)

            events_to_check = await self.store.get_events_as_list(
                event_ids_to_check,
@@ -984,7 +957,7 @@ class FederationHandler:
        # Note that this requires the /send_join request to come back to the
        # same server.
        prev_event_ids = None
-        if room_version.msc3083_join_rules:
+        if room_version.restricted_join_rule:
            # Note that the room's state can change out from under us and render our
            # nice join rules-conformant event non-conformant by the time we build the
            # event. When this happens, our validation at the end fails and we respond
@@ -1608,9 +1581,7 @@ class FederationHandler:
            event.content["third_party_invite"]["signed"]["token"],
        )
        original_invite = None
-        prev_state_ids = await context.get_prev_state_ids(
-            StateFilter.from_types([(EventTypes.ThirdPartyInvite, None)])
-        )
+        prev_state_ids = await context.get_prev_state_ids(StateFilter.from_types([key]))
        original_invite_id = prev_state_ids.get(key)
        if original_invite_id:
            original_invite = await self.store.get_event(
@@ -1663,7 +1634,7 @@ class FederationHandler:
        token = signed["token"]

        prev_state_ids = await context.get_prev_state_ids(
-            StateFilter.from_types([(EventTypes.ThirdPartyInvite, None)])
+            StateFilter.from_types([(EventTypes.ThirdPartyInvite, token)])
        )
        invite_event_id = prev_state_ids.get((EventTypes.ThirdPartyInvite, token))

--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -601,18 +601,6 @@ class FederationEventHandler:
                room_id, [(event, context)]
            )

-            # If we're joining the room again, check if there is new marker
-            # state indicating that there is new history imported somewhere in
-            # the DAG. Multiple markers can exist in the current state with
-            # unique state_keys.
-            #
-            # Do this after the state from the remote join was persisted (via
-            # `persist_events_and_notify`). Otherwise we can run into a
-            # situation where the create event doesn't exist yet in the
-            # `current_state_events`
-            for e in state:
-                await self._handle_marker_event(origin, e)
-
            return stream_id_after_persist

    async def update_state_for_partial_state_event(
@@ -915,13 +903,6 @@ class FederationEventHandler:
            )
        )

-        # We construct the event lists in source order from `/backfill` response because
-        # it's a) easiest, but also b) the order in which we process things matters for
-        # MSC2716 historical batches because many historical events are all at the same
-        # `depth` and we rely on the tenuous sort that the other server gave us and hope
-        # they're doing their best. The brittle nature of this ordering for historical
-        # messages over federation is one of the reasons why we don't want to continue
-        # on MSC2716 until we have online topological ordering.
        events_with_failed_pull_attempts, fresh_events = partition(
            new_events, lambda e: e.event_id in event_ids_with_failed_pull_attempts
        )
@@ -1460,8 +1441,6 @@ class FederationEventHandler:

        await self._run_push_actions_and_persist_event(event, context, backfilled)

-        await self._handle_marker_event(origin, event)
-
        if backfilled or context.rejected:
            return

@@ -1559,94 +1538,6 @@ class FederationEventHandler:
        except Exception:
            logger.exception("Failed to resync device for %s", sender)

-    @trace
-    async def _handle_marker_event(self, origin: str, marker_event: EventBase) -> None:
-        """Handles backfilling the insertion event when we receive a marker
-        event that points to one.
-
-        Args:
-            origin: Origin of the event. Will be called to get the insertion event
-            marker_event: The event to process
-        """
-
-        if marker_event.type != EventTypes.MSC2716_MARKER:
-            # Not a marker event
-            return
-
-        if marker_event.rejected_reason is not None:
-            # Rejected event
-            return
-
-        # Skip processing a marker event if the room version doesn't
-        # support it or the event is not from the room creator.
-        room_version = await self._store.get_room_version(marker_event.room_id)
-        create_event = await self._store.get_create_event_for_room(marker_event.room_id)
-        if not room_version.msc2175_implicit_room_creator:
-            room_creator = create_event.content.get(EventContentFields.ROOM_CREATOR)
-        else:
-            room_creator = create_event.sender
-        if not room_version.msc2716_historical and (
-            not self._config.experimental.msc2716_enabled
-            or marker_event.sender != room_creator
-        ):
-            return
-
-        logger.debug("_handle_marker_event: received %s", marker_event)
-
-        insertion_event_id = marker_event.content.get(
-            EventContentFields.MSC2716_INSERTION_EVENT_REFERENCE
-        )
-
-        if insertion_event_id is None:
-            # Nothing to retrieve then (invalid marker)
-            return
-
-        already_seen_insertion_event = await self._store.have_seen_event(
-            marker_event.room_id, insertion_event_id
-        )
-        if already_seen_insertion_event:
-            # No need to process a marker again if we have already seen the
-            # insertion event that it was pointing to
-            return
-
-        logger.debug(
-            "_handle_marker_event: backfilling insertion event %s", insertion_event_id
-        )
-
-        await self._get_events_and_persist(
-            origin,
-            marker_event.room_id,
-            [insertion_event_id],
-        )
-
-        insertion_event = await self._store.get_event(
-            insertion_event_id, allow_none=True
-        )
-        if insertion_event is None:
-            logger.warning(
-                "_handle_marker_event: server %s didn't return insertion event %s for marker %s",
-                origin,
-                insertion_event_id,
-                marker_event.event_id,
-            )
-            return
-
-        logger.debug(
-            "_handle_marker_event: succesfully backfilled insertion event %s from marker event %s",
-            insertion_event,
-            marker_event,
-        )
-
-        await self._store.insert_insertion_extremity(
-            insertion_event_id, marker_event.room_id
-        )
-
-        logger.debug(
-            "_handle_marker_event: insertion extremity added for %s from marker event %s",
-            insertion_event,
-            marker_event,
-        )
-
    async def backfill_event_id(
        self, destinations: List[str], room_id: str, event_id: str
    ) -> PulledPduInfo:
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -60,7 +60,6 @@ from synapse.replication.http.send_event import ReplicationSendEventRestServlet
 from synapse.replication.http.send_events import ReplicationSendEventsRestServlet
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
 from synapse.types import (
-    MutableStateMap,
    PersistedEventPosition,
    Requester,
    RoomAlias,
@@ -573,7 +572,6 @@ class EventCreationHandler:
        state_event_ids: Optional[List[str]] = None,
        require_consent: bool = True,
        outlier: bool = False,
-        historical: bool = False,
        depth: Optional[int] = None,
        state_map: Optional[StateMap[str]] = None,
        for_batch: bool = False,
@@ -599,7 +597,7 @@ class EventCreationHandler:
            allow_no_prev_events: Whether to allow this event to be created an empty
                list of prev_events. Normally this is prohibited just because most
                events should have a prev_event and we should only use this in special
-                cases like MSC2716.
+                cases (previously useful for MSC2716).
            prev_event_ids:
                the forward extremities to use as the prev_events for the
                new event.
@@ -614,13 +612,10 @@ class EventCreationHandler:
                If non-None, prev_event_ids must also be provided.

            state_event_ids:
-                The full state at a given event. This is used particularly by the MSC2716
-                /batch_send endpoint. One use case is with insertion events which float at
-                the beginning of a historical batch and don't have any `prev_events` to
-                derive from; we add all of these state events as the explicit state so the
-                rest of the historical batch can inherit the same state and state_group.
-                This should normally be left as None, which will cause the auth_event_ids
-                to be calculated based on the room state at the prev_events.
+                The full state at a given event. This was previously used particularly
+                by the MSC2716 /batch_send endpoint. This should normally be left as
+                None, which will cause the auth_event_ids to be calculated based on the
+                room state at the prev_events.

            require_consent: Whether to check if the requester has
                consented to the privacy policy.
@@ -629,10 +624,6 @@ class EventCreationHandler:
                it's from an arbitrary point and floating in the DAG as
                opposed to being inline with the current DAG.

-            historical: Indicates whether the message is being inserted
-                back in time around some existing events. This is used to skip
-                a few checks and mark the event as backfilled.
-
            depth: Override the depth used to order the event in the DAG.
                Should normally be set to None, which will cause the depth to be calculated
                based on the prev_events.
@@ -717,8 +708,6 @@ class EventCreationHandler:

        builder.internal_metadata.outlier = outlier

-        builder.internal_metadata.historical = historical
-
        event, unpersisted_context = await self.create_new_client_event(
            builder=builder,
            requester=requester,
@@ -749,7 +738,7 @@ class EventCreationHandler:
                prev_event_id = state_map.get((EventTypes.Member, event.sender))
            else:
                prev_state_ids = await unpersisted_context.get_prev_state_ids(
-                    StateFilter.from_types([(EventTypes.Member, None)])
+                    StateFilter.from_types([(EventTypes.Member, event.sender)])
                )
                prev_event_id = prev_state_ids.get((EventTypes.Member, event.sender))
            prev_event = (
@@ -871,7 +860,7 @@ class EventCreationHandler:
            return None

        prev_state_ids = await context.get_prev_state_ids(
-            StateFilter.from_types([(event.type, None)])
+            StateFilter.from_types([(event.type, event.state_key)])
        )
        prev_event_id = prev_state_ids.get((event.type, event.state_key))
        if not prev_event_id:
@@ -947,7 +936,6 @@ class EventCreationHandler:
        txn_id: Optional[str] = None,
        ignore_shadow_ban: bool = False,
        outlier: bool = False,
-        historical: bool = False,
        depth: Optional[int] = None,
    ) -> Tuple[EventBase, int]:
        """
@@ -961,19 +949,16 @@ class EventCreationHandler:
            allow_no_prev_events: Whether to allow this event to be created an empty
                list of prev_events. Normally this is prohibited just because most
                events should have a prev_event and we should only use this in special
-                cases like MSC2716.
+                cases (previously useful for MSC2716).
            prev_event_ids:
                The event IDs to use as the prev events.
                Should normally be left as None to automatically request them
                from the database.
            state_event_ids:
-                The full state at a given event. This is used particularly by the MSC2716
-                /batch_send endpoint. One use case is with insertion events which float at
-                the beginning of a historical batch and don't have any `prev_events` to
-                derive from; we add all of these state events as the explicit state so the
-                rest of the historical batch can inherit the same state and state_group.
-                This should normally be left as None, which will cause the auth_event_ids
-                to be calculated based on the room state at the prev_events.
+                The full state at a given event. This was previously used particularly
+                by the MSC2716 /batch_send endpoint. This should normally be left as
+                None, which will cause the auth_event_ids to be calculated based on the
+                room state at the prev_events.
            ratelimit: Whether to rate limit this send.
            txn_id: The transaction ID.
            ignore_shadow_ban: True if shadow-banned users should be allowed to
@@ -981,9 +966,6 @@ class EventCreationHandler:
            outlier: Indicates whether the event is an `outlier`, i.e. if
                it's from an arbitrary point and floating in the DAG as
                opposed to being inline with the current DAG.
-            historical: Indicates whether the message is being inserted
-                back in time around some existing events. This is used to skip
-                a few checks and mark the event as backfilled.
            depth: Override the depth used to order the event in the DAG.
                Should normally be set to None, which will cause the depth to be calculated
                based on the prev_events.
@@ -1053,7 +1035,6 @@ class EventCreationHandler:
                    prev_event_ids=prev_event_ids,
                    state_event_ids=state_event_ids,
                    outlier=outlier,
-                    historical=historical,
                    depth=depth,
                )
                context = await unpersisted_context.persist(event)
@@ -1145,7 +1126,7 @@ class EventCreationHandler:
            allow_no_prev_events: Whether to allow this event to be created an empty
                list of prev_events. Normally this is prohibited just because most
                events should have a prev_event and we should only use this in special
-                cases like MSC2716.
+                cases (previously useful for MSC2716).
            prev_event_ids:
                the forward extremities to use as the prev_events for the
                new event.
@@ -1158,13 +1139,10 @@ class EventCreationHandler:
                based on the room state at the prev_events.

            state_event_ids:
-                The full state at a given event. This is used particularly by the MSC2716
-                /batch_send endpoint. One use case is with insertion events which float at
-                the beginning of a historical batch and don't have any `prev_events` to
-                derive from; we add all of these state events as the explicit state so the
-                rest of the historical batch can inherit the same state and state_group.
-                This should normally be left as None, which will cause the auth_event_ids
-                to be calculated based on the room state at the prev_events.
+                The full state at a given event. This was previously used particularly
+                by the MSC2716 /batch_send endpoint. This should normally be left as
+                None, which will cause the auth_event_ids to be calculated based on the
+                room state at the prev_events.

            depth: Override the depth used to order the event in the DAG.
                Should normally be set to None, which will cause the depth to be calculated
@@ -1261,52 +1239,6 @@ class EventCreationHandler:
            if builder.internal_metadata.outlier:
                event.internal_metadata.outlier = True
                context = EventContext.for_outlier(self._storage_controllers)
-            elif (
-                event.type == EventTypes.MSC2716_INSERTION
-                and state_event_ids
-                and builder.internal_metadata.is_historical()
-            ):
-                # Add explicit state to the insertion event so it has state to derive
-                # from even though it's floating with no `prev_events`. The rest of
-                # the batch can derive from this state and state_group.
-                #
-                # TODO(faster_joins): figure out how this works, and make sure that the
-                #   old state is complete.
-                #   https://github.com/matrix-org/synapse/issues/13003
-                metadata = await self.store.get_metadata_for_events(state_event_ids)
-
-                state_map_for_event: MutableStateMap[str] = {}
-                for state_id in state_event_ids:
-                    data = metadata.get(state_id)
-                    if data is None:
-                        # We're trying to persist a new historical batch of events
-                        # with the given state, e.g. via
-                        # `RoomBatchSendEventRestServlet`. The state can be inferred
-                        # by Synapse or set directly by the client.
-                        #
-                        # Either way, we should have persisted all the state before
-                        # getting here.
-                        raise Exception(
-                            f"State event {state_id} not found in DB,"
-                            " Synapse should have persisted it before using it."
-                        )
-
-                    if data.state_key is None:
-                        raise Exception(
-                            f"Trying to set non-state event {state_id} as state"
-                        )
-
-                    state_map_for_event[(data.event_type, data.state_key)] = state_id
-
-                # TODO(faster_joins): check how MSC2716 works and whether we can have
-                #   partial state here
-                #   https://github.com/matrix-org/synapse/issues/13003
-                context = await self.state.calculate_context_info(
-                    event,
-                    state_ids_before_event=state_map_for_event,
-                    partial_state=False,
-                )
-
            else:
                context = await self.state.calculate_context_info(event)

@@ -1633,12 +1565,14 @@ class EventCreationHandler:
                if state_entry.state_group in self._external_cache_joined_hosts_updates:
                    return

-                state = await state_entry.get_state(
+                await state_entry.get_state(
                    self._storage_controllers.state, StateFilter.all()
                )
                with opentracing.start_active_span("get_joined_hosts"):
-                    joined_hosts = await self.store.get_joined_hosts(
-                        event.room_id, state, state_entry
+                    stream_ordering = event.internal_metadata.stream_ordering
+                    assert stream_ordering is not None
+                    joined_hosts = await self._storage_controllers.state.get_joined_remote_hosts_for_event(
+                        event.room_id, event.event_id, stream_ordering
                    )

                # Note that the expiry times must be larger than the expiry time in
@@ -1876,28 +1810,6 @@ class EventCreationHandler:
                            403, "Redacting server ACL events is not permitted"
                        )

-                    # Add a little safety stop-gap to prevent people from trying to
-                    # redact MSC2716 related events when they're in a room version
-                    # which does not support it yet. We allow people to use MSC2716
-                    # events in existing room versions but only from the room
-                    # creator since it does not require any changes to the auth
-                    # rules and in effect, the redaction algorithm . In the
-                    # supported room version, we add the `historical` power level to
-                    # auth the MSC2716 related events and adjust the redaction
-                    # algorthim to keep the `historical` field around (redacting an
-                    # event should only strip fields which don't affect the
-                    # structural protocol level).
-                    is_msc2716_event = (
-                        original_event.type == EventTypes.MSC2716_INSERTION
-                        or original_event.type == EventTypes.MSC2716_BATCH
-                        or original_event.type == EventTypes.MSC2716_MARKER
-                    )
-                    if not room_version_obj.msc2716_historical and is_msc2716_event:
-                        raise AuthError(
-                            403,
-                            "Redacting MSC2716 events is not supported in this room version",
-                        )
-
                event_types = event_auth.auth_types_for_event(event.room_version, event)
                prev_state_ids = await context.get_prev_state_ids(
                    StateFilter.from_types(event_types)
@@ -1935,58 +1847,12 @@ class EventCreationHandler:
                if prev_state_ids:
                    raise AuthError(403, "Changing the room create event is forbidden")

-            if event.type == EventTypes.MSC2716_INSERTION:
-                room_version = await self.store.get_room_version_id(event.room_id)
-                room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
-
-                create_event = await self.store.get_create_event_for_room(event.room_id)
-                if not room_version_obj.msc2175_implicit_room_creator:
-                    room_creator = create_event.content.get(
-                        EventContentFields.ROOM_CREATOR
-                    )
-                else:
-                    room_creator = create_event.sender
-
-                # Only check an insertion event if the room version
-                # supports it or the event is from the room creator.
-                if room_version_obj.msc2716_historical or (
-                    self.config.experimental.msc2716_enabled
-                    and event.sender == room_creator
-                ):
-                    next_batch_id = event.content.get(
-                        EventContentFields.MSC2716_NEXT_BATCH_ID
-                    )
-                    conflicting_insertion_event_id = None
-                    if next_batch_id:
-                        conflicting_insertion_event_id = (
-                            await self.store.get_insertion_event_id_by_batch_id(
-                                event.room_id, next_batch_id
-                            )
-                        )
-                    if conflicting_insertion_event_id is not None:
-                        # The current insertion event that we're processing is invalid
-                        # because an insertion event already exists in the room with the
-                        # same next_batch_id. We can't allow multiple because the batch
-                        # pointing will get weird, e.g. we can't determine which insertion
-                        # event the batch event is pointing to.
-                        raise SynapseError(
-                            HTTPStatus.BAD_REQUEST,
-                            "Another insertion event already exists with the same next_batch_id",
-                            errcode=Codes.INVALID_PARAM,
-                        )
-
-            # Mark any `m.historical` messages as backfilled so they don't appear
-            # in `/sync` and have the proper decrementing `stream_ordering` as we import
-            backfilled = False
-            if event.internal_metadata.is_historical():
-                backfilled = True
-
        assert self._storage_controllers.persistence is not None
        (
            persisted_events,
            max_stream_token,
        ) = await self._storage_controllers.persistence.persist_events(
-            events_and_context, backfilled=backfilled
+            events_and_context,
        )

        events_and_pos = []
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -40,6 +40,11 @@ if TYPE_CHECKING:

 logger = logging.getLogger(__name__)

+# How many single event gaps we tolerate returning in a `/messages` response before we
+# backfill and try to fill in the history. This is an arbitrarily picked number so feel
+# free to tune it in the future.
+BACKFILL_BECAUSE_TOO_MANY_GAPS_THRESHOLD = 3
+

@attr.s(slots=True, auto_attribs=True)
 class PurgeStatus:
@@ -486,35 +491,35 @@ class PaginationHandler:
                        room_id, room_token.stream
                    )

-                if not use_admin_priviledge and membership == Membership.LEAVE:
-                    # If they have left the room then clamp the token to be before
-                    # they left the room, to save the effort of loading from the
-                    # database.
+            # If they have left the room then clamp the token to be before
+            # they left the room, to save the effort of loading from the
+            # database.
+            if (
+                pagin_config.direction == Direction.BACKWARDS
+                and not use_admin_priviledge
+                and membership == Membership.LEAVE
+            ):
+                # This is only None if the room is world_readable, in which case
+                # "Membership.JOIN" would have been returned and we should never hit
+                # this branch.
+                assert member_event_id

-                    # This is only None if the room is world_readable, in which
-                    # case "JOIN" would have been returned.
-                    assert member_event_id
-
-                    leave_token = await self.store.get_topological_token_for_event(
-                        member_event_id
-                    )
-                    assert leave_token.topological is not None
-
-                    if leave_token.topological < curr_topo:
-                        from_token = from_token.copy_and_replace(
-                            StreamKeyType.ROOM, leave_token
-                        )
-
-                await self.hs.get_federation_handler().maybe_backfill(
-                    room_id,
-                    curr_topo,
-                    limit=pagin_config.limit,
+                leave_token = await self.store.get_topological_token_for_event(
+                    member_event_id
                )
+                assert leave_token.topological is not None
+
+                if leave_token.topological < curr_topo:
+                    from_token = from_token.copy_and_replace(
+                        StreamKeyType.ROOM, leave_token
+                    )

            to_room_key = None
            if pagin_config.to_token:
                to_room_key = pagin_config.to_token.room_key

+            # Initially fetch the events from the database. With any luck, we can return
+            # these without blocking on backfill (handled below).
            events, next_key = await self.store.paginate_room_events(
                room_id=room_id,
                from_key=from_token.room_key,
@@ -524,6 +529,94 @@ class PaginationHandler:
                event_filter=event_filter,
            )

+            if pagin_config.direction == Direction.BACKWARDS:
+                # We use a `Set` because there can be multiple events at a given depth
+                # and we only care about looking at the unique continum of depths to
+                # find gaps.
+                event_depths: Set[int] = {event.depth for event in events}
+                sorted_event_depths = sorted(event_depths)
+
+                # Inspect the depths of the returned events to see if there are any gaps
+                found_big_gap = False
+                number_of_gaps = 0
+                previous_event_depth = (
+                    sorted_event_depths[0] if len(sorted_event_depths) > 0 else 0
+                )
+                for event_depth in sorted_event_depths:
+                    # We don't expect a negative depth but we'll just deal with it in
+                    # any case by taking the absolute value to get the true gap between
+                    # any two integers.
+                    depth_gap = abs(event_depth - previous_event_depth)
+                    # A `depth_gap` of 1 is a normal continuous chain to the next event
+                    # (1 <-- 2 <-- 3) so anything larger indicates a missing event (it's
+                    # also possible there is no event at a given depth but we can't ever
+                    # know that for sure)
+                    if depth_gap > 1:
+                        number_of_gaps += 1
+
+                    # We only tolerate a small number single-event long gaps in the
+                    # returned events because those are most likely just events we've
+                    # failed to pull in the past. Anything longer than that is probably
+                    # a sign that we're missing a decent chunk of history and we should
+                    # try to backfill it.
+                    #
+                    # XXX: It's possible we could tolerate longer gaps if we checked
+                    # that a given events `prev_events` is one that has failed pull
+                    # attempts and we could just treat it like a dead branch of history
+                    # for now or at least something that we don't need the block the
+                    # client on to try pulling.
+                    #
+                    # XXX: If we had something like MSC3871 to indicate gaps in the
+                    # timeline to the client, we could also get away with any sized gap
+                    # and just have the client refetch the holes as they see fit.
+                    if depth_gap > 2:
+                        found_big_gap = True
+                        break
+                    previous_event_depth = event_depth
+
+                # Backfill in the foreground if we found a big gap, have too many holes,
+                # or we don't have enough events to fill the limit that the client asked
+                # for.
+                missing_too_many_events = (
+                    number_of_gaps > BACKFILL_BECAUSE_TOO_MANY_GAPS_THRESHOLD
+                )
+                not_enough_events_to_fill_response = len(events) < pagin_config.limit
+                if (
+                    found_big_gap
+                    or missing_too_many_events
+                    or not_enough_events_to_fill_response
+                ):
+                    did_backfill = (
+                        await self.hs.get_federation_handler().maybe_backfill(
+                            room_id,
+                            curr_topo,
+                            limit=pagin_config.limit,
+                        )
+                    )
+
+                    # If we did backfill something, refetch the events from the database to
+                    # catch anything new that might have been added since we last fetched.
+                    if did_backfill:
+                        events, next_key = await self.store.paginate_room_events(
+                            room_id=room_id,
+                            from_key=from_token.room_key,
+                            to_key=to_room_key,
+                            direction=pagin_config.direction,
+                            limit=pagin_config.limit,
+                            event_filter=event_filter,
+                        )
+                else:
+                    # Otherwise, we can backfill in the background for eventual
+                    # consistency's sake but we don't need to block the client waiting
+                    # for a costly federation call and processing.
+                    run_as_background_process(
+                        "maybe_backfill_in_the_background",
+                        self.hs.get_federation_handler().maybe_backfill,
+                        room_id,
+                        curr_topo,
+                        limit=pagin_config.limit,
+                    )
+
            next_token = from_token.copy_and_replace(StreamKeyType.ROOM, next_key)

        # if no events are returned from pagination, that implies
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -95,13 +95,12 @@ bump_active_time_counter = Counter("synapse_handler_presence_bump_active_time",
 get_updates_counter = Counter("synapse_handler_presence_get_updates", "", ["type"])

 notify_reason_counter = Counter(
-    "synapse_handler_presence_notify_reason", "", ["reason"]
+    "synapse_handler_presence_notify_reason", "", ["locality", "reason"]
 )
 state_transition_counter = Counter(
-    "synapse_handler_presence_state_transition", "", ["from", "to"]
+    "synapse_handler_presence_state_transition", "", ["locality", "from", "to"]
 )

-
 # If a user was last active in the last LAST_ACTIVE_GRANULARITY, consider them
 # "currently_active"
 LAST_ACTIVE_GRANULARITY = 60 * 1000
@@ -567,8 +566,8 @@ class WorkerPresenceHandler(BasePresenceHandler):
        for new_state in states:
            old_state = self.user_to_current_state.get(new_state.user_id)
            self.user_to_current_state[new_state.user_id] = new_state
-
-            if not old_state or should_notify(old_state, new_state):
+            is_mine = self.is_mine_id(new_state.user_id)
+            if not old_state or should_notify(old_state, new_state, is_mine):
                state_to_notify.append(new_state)

        stream_id = token
@@ -1499,23 +1498,31 @@ class PresenceHandler(BasePresenceHandler):
            )


-def should_notify(old_state: UserPresenceState, new_state: UserPresenceState) -> bool:
+def should_notify(
+    old_state: UserPresenceState, new_state: UserPresenceState, is_mine: bool
+) -> bool:
    """Decides if a presence state change should be sent to interested parties."""
+    user_location = "remote"
+    if is_mine:
+        user_location = "local"
+
    if old_state == new_state:
        return False

    if old_state.status_msg != new_state.status_msg:
-        notify_reason_counter.labels("status_msg_change").inc()
+        notify_reason_counter.labels(user_location, "status_msg_change").inc()
        return True

    if old_state.state != new_state.state:
-        notify_reason_counter.labels("state_change").inc()
-        state_transition_counter.labels(old_state.state, new_state.state).inc()
+        notify_reason_counter.labels(user_location, "state_change").inc()
+        state_transition_counter.labels(
+            user_location, old_state.state, new_state.state
+        ).inc()
        return True

    if old_state.state == PresenceState.ONLINE:
        if new_state.currently_active != old_state.currently_active:
-            notify_reason_counter.labels("current_active_change").inc()
+            notify_reason_counter.labels(user_location, "current_active_change").inc()
            return True

        if (
@@ -1524,12 +1531,16 @@ def should_notify(old_state: UserPresenceState, new_state: UserPresenceState) ->
        ):
            # Only notify about last active bumps if we're not currently active
            if not new_state.currently_active:
-                notify_reason_counter.labels("last_active_change_online").inc()
+                notify_reason_counter.labels(
+                    user_location, "last_active_change_online"
+                ).inc()
                return True

    elif new_state.last_active_ts - old_state.last_active_ts > LAST_ACTIVE_GRANULARITY:
        # Always notify for a transition where last active gets bumped.
-        notify_reason_counter.labels("last_active_change_not_online").inc()
+        notify_reason_counter.labels(
+            user_location, "last_active_change_not_online"
+        ).inc()
        return True

    return False
@@ -1989,7 +2000,7 @@ def handle_update(
        )

    # Check whether the change was something worth notifying about
-    if should_notify(prev_state, new_state):
+    if should_notify(prev_state, new_state, is_mine):
        new_state = new_state.copy_and_replace(last_federation_update_ts=now)
        persist_and_notify = True

--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -143,15 +143,10 @@ class RegistrationHandler:
        assigned_user_id: Optional[str] = None,
        inhibit_user_in_use_error: bool = False,
    ) -> None:
-        if types.contains_invalid_mxid_characters(
-            localpart, self.hs.config.experimental.msc4009_e164_mxids
-        ):
-            extra_chars = (
-                "=_-./+" if self.hs.config.experimental.msc4009_e164_mxids else "=_-./"
-            )
+        if types.contains_invalid_mxid_characters(localpart):
            raise SynapseError(
                400,
-                f"User ID can only contain characters a-z, 0-9, or '{extra_chars}'",
+                "User ID can only contain characters a-z, 0-9, or '=_-./+'",
                Codes.INVALID_USERNAME,
            )

--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -1116,7 +1116,7 @@ class RoomCreationHandler:
        preset_config, config = self._room_preset_config(room_config)

        # MSC2175 removes the creator field from the create event.
-        if not room_version.msc2175_implicit_room_creator:
+        if not room_version.implicit_room_creator:
            creation_content["creator"] = creator_id
        creation_event, unpersisted_creation_context = await create_event(
            EventTypes.Create, creation_content, False
--- a/synapse/handlers/room_batch.py
+++ b/synapse/handlers/room_batch.py
@@ -1,466 +0,0 @@
-import logging
-from typing import TYPE_CHECKING, List, Tuple
-
-from synapse.api.constants import EventContentFields, EventTypes
-from synapse.appservice import ApplicationService
-from synapse.http.servlet import assert_params_in_dict
-from synapse.types import JsonDict, Requester, UserID, create_requester
-from synapse.util.stringutils import random_string
-
-if TYPE_CHECKING:
-    from synapse.server import HomeServer
-
-logger = logging.getLogger(__name__)
-
-
-class RoomBatchHandler:
-    def __init__(self, hs: "HomeServer"):
-        self.hs = hs
-        self.store = hs.get_datastores().main
-        self._state_storage_controller = hs.get_storage_controllers().state
-        self.event_creation_handler = hs.get_event_creation_handler()
-        self.room_member_handler = hs.get_room_member_handler()
-        self.auth = hs.get_auth()
-
-    async def inherit_depth_from_prev_ids(self, prev_event_ids: List[str]) -> int:
-        """Finds the depth which would sort it after the most-recent
-        prev_event_id but before the successors of those events. If no
-        successors are found, we assume it's an historical extremity part of the
-        current batch and use the same depth of the prev_event_ids.
-
-        Args:
-            prev_event_ids: List of prev event IDs
-
-        Returns:
-            Inherited depth
-        """
-        (
-            most_recent_prev_event_id,
-            most_recent_prev_event_depth,
-        ) = await self.store.get_max_depth_of(prev_event_ids)
-
-        # We want to insert the historical event after the `prev_event` but before the successor event
-        #
-        # We inherit depth from the successor event instead of the `prev_event`
-        # because events returned from `/messages` are first sorted by `topological_ordering`
-        # which is just the `depth` and then tie-break with `stream_ordering`.
-        #
-        # We mark these inserted historical events as "backfilled" which gives them a
-        # negative `stream_ordering`. If we use the same depth as the `prev_event`,
-        # then our historical event will tie-break and be sorted before the `prev_event`
-        # when it should come after.
-        #
-        # We want to use the successor event depth so they appear after `prev_event` because
-        # it has a larger `depth` but before the successor event because the `stream_ordering`
-        # is negative before the successor event.
-        assert most_recent_prev_event_id is not None
-        successor_event_ids = await self.store.get_successor_events(
-            most_recent_prev_event_id
-        )
-
-        # If we can't find any successor events, then it's a forward extremity of
-        # historical messages and we can just inherit from the previous historical
-        # event which we can already assume has the correct depth where we want
-        # to insert into.
-        if not successor_event_ids:
-            depth = most_recent_prev_event_depth
-        else:
-            (
-                _,
-                oldest_successor_depth,
-            ) = await self.store.get_min_depth_of(successor_event_ids)
-
-            depth = oldest_successor_depth
-
-        return depth
-
-    def create_insertion_event_dict(
-        self, sender: str, room_id: str, origin_server_ts: int
-    ) -> JsonDict:
-        """Creates an event dict for an "insertion" event with the proper fields
-        and a random batch ID.
-
-        Args:
-            sender: The event author MXID
-            room_id: The room ID that the event belongs to
-            origin_server_ts: Timestamp when the event was sent
-
-        Returns:
-            The new event dictionary to insert.
-        """
-
-        next_batch_id = random_string(8)
-        insertion_event = {
-            "type": EventTypes.MSC2716_INSERTION,
-            "sender": sender,
-            "room_id": room_id,
-            "content": {
-                EventContentFields.MSC2716_NEXT_BATCH_ID: next_batch_id,
-                EventContentFields.MSC2716_HISTORICAL: True,
-            },
-            "origin_server_ts": origin_server_ts,
-        }
-
-        return insertion_event
-
-    async def create_requester_for_user_id_from_app_service(
-        self, user_id: str, app_service: ApplicationService
-    ) -> Requester:
-        """Creates a new requester for the given user_id
-        and validates that the app service is allowed to control
-        the given user.
-
-        Args:
-            user_id: The author MXID that the app service is controlling
-            app_service: The app service that controls the user
-
-        Returns:
-            Requester object
-        """
-
-        await self.auth.validate_appservice_can_control_user_id(app_service, user_id)
-
-        return create_requester(user_id, app_service=app_service)
-
-    async def get_most_recent_full_state_ids_from_event_id_list(
-        self, event_ids: List[str]
-    ) -> List[str]:
-        """Find the most recent event_id and grab the full state at that event.
-        We will use this as a base to auth our historical messages against.
-
-        Args:
-            event_ids: List of event ID's to look at
-
-        Returns:
-            List of event ID's
-        """
-
-        (
-            most_recent_event_id,
-            _,
-        ) = await self.store.get_max_depth_of(event_ids)
-        # mapping from (type, state_key) -> state_event_id
-        assert most_recent_event_id is not None
-        prev_state_map = await self._state_storage_controller.get_state_ids_for_event(
-            most_recent_event_id
-        )
-        # List of state event ID's
-        full_state_ids = list(prev_state_map.values())
-
-        return full_state_ids
-
-    async def persist_state_events_at_start(
-        self,
-        state_events_at_start: List[JsonDict],
-        room_id: str,
-        initial_state_event_ids: List[str],
-        app_service_requester: Requester,
-    ) -> List[str]:
-        """Takes all `state_events_at_start` event dictionaries and creates/persists
-        them in a floating state event chain which don't resolve into the current room
-        state. They are floating because they reference no prev_events which disconnects
-        them from the normal DAG.
-
-        Args:
-            state_events_at_start:
-            room_id: Room where you want the events persisted in.
-            initial_state_event_ids:
-                The base set of state for the historical batch which the floating
-                state chain will derive from. This should probably be the state
-                from the `prev_event` defined by `/batch_send?prev_event_id=$abc`.
-            app_service_requester: The requester of an application service.
-
-        Returns:
-            List of state event ID's we just persisted
-        """
-        assert app_service_requester.app_service
-
-        state_event_ids_at_start = []
-        state_event_ids = initial_state_event_ids.copy()
-
-        # Make the state events float off on their own by specifying no
-        # prev_events for the first one in the chain so we don't have a bunch of
-        # `@mxid joined the room` noise between each batch.
-        prev_event_ids_for_state_chain: List[str] = []
-
-        for index, state_event in enumerate(state_events_at_start):
-            assert_params_in_dict(
-                state_event, ["type", "origin_server_ts", "content", "sender"]
-            )
-
-            logger.debug(
-                "RoomBatchSendEventRestServlet inserting state_event=%s", state_event
-            )
-
-            event_dict = {
-                "type": state_event["type"],
-                "origin_server_ts": state_event["origin_server_ts"],
-                "content": state_event["content"],
-                "room_id": room_id,
-                "sender": state_event["sender"],
-                "state_key": state_event["state_key"],
-            }
-
-            # Mark all events as historical
-            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
-
-            # TODO: This is pretty much the same as some other code to handle inserting state in this file
-            if event_dict["type"] == EventTypes.Member:
-                membership = event_dict["content"].get("membership", None)
-                event_id, _ = await self.room_member_handler.update_membership(
-                    await self.create_requester_for_user_id_from_app_service(
-                        state_event["sender"], app_service_requester.app_service
-                    ),
-                    target=UserID.from_string(event_dict["state_key"]),
-                    room_id=room_id,
-                    action=membership,
-                    content=event_dict["content"],
-                    historical=True,
-                    # Only the first event in the state chain should be floating.
-                    # The rest should hang off each other in a chain.
-                    allow_no_prev_events=index == 0,
-                    prev_event_ids=prev_event_ids_for_state_chain,
-                    # The first event in the state chain is floating with no
-                    # `prev_events` which means it can't derive state from
-                    # anywhere automatically. So we need to set some state
-                    # explicitly.
-                    #
-                    # Make sure to use a copy of this list because we modify it
-                    # later in the loop here. Otherwise it will be the same
-                    # reference and also update in the event when we append
-                    # later.
-                    state_event_ids=state_event_ids.copy(),
-                )
-            else:
-                (
-                    event,
-                    _,
-                ) = await self.event_creation_handler.create_and_send_nonmember_event(
-                    await self.create_requester_for_user_id_from_app_service(
-                        state_event["sender"], app_service_requester.app_service
-                    ),
-                    event_dict,
-                    historical=True,
-                    # Only the first event in the state chain should be floating.
-                    # The rest should hang off each other in a chain.
-                    allow_no_prev_events=index == 0,
-                    prev_event_ids=prev_event_ids_for_state_chain,
-                    # The first event in the state chain is floating with no
-                    # `prev_events` which means it can't derive state from
-                    # anywhere automatically. So we need to set some state
-                    # explicitly.
-                    #
-                    # Make sure to use a copy of this list because we modify it
-                    # later in the loop here. Otherwise it will be the same
-                    # reference and also update in the event when we append later.
-                    state_event_ids=state_event_ids.copy(),
-                )
-                event_id = event.event_id
-
-            state_event_ids_at_start.append(event_id)
-            state_event_ids.append(event_id)
-            # Connect all the state in a floating chain
-            prev_event_ids_for_state_chain = [event_id]
-
-        return state_event_ids_at_start
-
-    async def persist_historical_events(
-        self,
-        events_to_create: List[JsonDict],
-        room_id: str,
-        inherited_depth: int,
-        initial_state_event_ids: List[str],
-        app_service_requester: Requester,
-    ) -> List[str]:
-        """Create and persists all events provided sequentially. Handles the
-        complexity of creating events in chronological order so they can
-        reference each other by prev_event but still persists in
-        reverse-chronoloical order so they have the correct
-        (topological_ordering, stream_ordering) and sort correctly from
-        /messages.
-
-        Args:
-            events_to_create: List of historical events to create in JSON
-                dictionary format.
-            room_id: Room where you want the events persisted in.
-            inherited_depth: The depth to create the events at (you will
-                probably by calling inherit_depth_from_prev_ids(...)).
-            initial_state_event_ids:
-                This is used to set explicit state for the insertion event at
-                the start of the historical batch since it's floating with no
-                prev_events to derive state from automatically.
-            app_service_requester: The requester of an application service.
-
-        Returns:
-            List of persisted event IDs
-        """
-        assert app_service_requester.app_service
-
-        # We expect the first event in a historical batch to be an insertion event
-        assert events_to_create[0]["type"] == EventTypes.MSC2716_INSERTION
-        # We expect the last event in a historical batch to be an batch event
-        assert events_to_create[-1]["type"] == EventTypes.MSC2716_BATCH
-
-        # Make the historical event chain float off on its own by specifying no
-        # prev_events for the first event in the chain which causes the HS to
-        # ask for the state at the start of the batch later.
-        prev_event_ids: List[str] = []
-
-        event_ids = []
-        events_to_persist = []
-        for index, ev in enumerate(events_to_create):
-            assert_params_in_dict(ev, ["type", "origin_server_ts", "content", "sender"])
-
-            assert self.hs.is_mine_id(ev["sender"]), "User must be our own: %s" % (
-                ev["sender"],
-            )
-
-            event_dict = {
-                "type": ev["type"],
-                "origin_server_ts": ev["origin_server_ts"],
-                "content": ev["content"],
-                "room_id": room_id,
-                "sender": ev["sender"],  # requester.user.to_string(),
-                "prev_events": prev_event_ids.copy(),
-            }
-
-            # Mark all events as historical
-            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
-
-            event, unpersisted_context = await self.event_creation_handler.create_event(
-                await self.create_requester_for_user_id_from_app_service(
-                    ev["sender"], app_service_requester.app_service
-                ),
-                event_dict,
-                # Only the first event (which is the insertion event) in the
-                # chain should be floating. The rest should hang off each other
-                # in a chain.
-                allow_no_prev_events=index == 0,
-                prev_event_ids=event_dict.get("prev_events"),
-                # Since the first event (which is the insertion event) in the
-                # chain is floating with no `prev_events`, it can't derive state
-                # from anywhere automatically. So we need to set some state
-                # explicitly.
-                state_event_ids=initial_state_event_ids if index == 0 else None,
-                historical=True,
-                depth=inherited_depth,
-            )
-            context = await unpersisted_context.persist(event)
-            assert context._state_group
-
-            # Normally this is done when persisting the event but we have to
-            # pre-emptively do it here because we create all the events first,
-            # then persist them in another pass below. And we want to share
-            # state_groups across the whole batch so this lookup needs to work
-            # for the next event in the batch in this loop.
-            await self.store.store_state_group_id_for_event_id(
-                event_id=event.event_id,
-                state_group_id=context._state_group,
-            )
-
-            logger.debug(
-                "RoomBatchSendEventRestServlet inserting event=%s, prev_event_ids=%s",
-                event,
-                prev_event_ids,
-            )
-
-            events_to_persist.append((event, context))
-            event_id = event.event_id
-
-            event_ids.append(event_id)
-            prev_event_ids = [event_id]
-
-        # Persist events in reverse-chronological order so they have the
-        # correct stream_ordering as they are backfilled (which decrements).
-        # Events are sorted by (topological_ordering, stream_ordering)
-        # where topological_ordering is just depth.
-        for event, context in reversed(events_to_persist):
-            # This call can't raise `PartialStateConflictError` since we forbid
-            # use of the historical batch API during partial state
-            await self.event_creation_handler.handle_new_client_event(
-                await self.create_requester_for_user_id_from_app_service(
-                    event.sender, app_service_requester.app_service
-                ),
-                events_and_context=[(event, context)],
-            )
-
-        return event_ids
-
-    async def handle_batch_of_events(
-        self,
-        events_to_create: List[JsonDict],
-        room_id: str,
-        batch_id_to_connect_to: str,
-        inherited_depth: int,
-        initial_state_event_ids: List[str],
-        app_service_requester: Requester,
-    ) -> Tuple[List[str], str]:
-        """
-        Handles creating and persisting all of the historical events as well as
-        insertion and batch meta events to make the batch navigable in the DAG.
-
-        Args:
-            events_to_create: List of historical events to create in JSON
-                dictionary format.
-            room_id: Room where you want the events created in.
-            batch_id_to_connect_to: The batch_id from the insertion event you
-                want this batch to connect to.
-            inherited_depth: The depth to create the events at (you will
-                probably by calling inherit_depth_from_prev_ids(...)).
-            initial_state_event_ids:
-                This is used to set explicit state for the insertion event at
-                the start of the historical batch since it's floating with no
-                prev_events to derive state from automatically. This should
-                probably be the state from the `prev_event` defined by
-                `/batch_send?prev_event_id=$abc` plus the outcome of
-                `persist_state_events_at_start`
-            app_service_requester: The requester of an application service.
-
-        Returns:
-            Tuple containing a list of created events and the next_batch_id
-        """
-
-        # Connect this current batch to the insertion event from the previous batch
-        last_event_in_batch = events_to_create[-1]
-        batch_event = {
-            "type": EventTypes.MSC2716_BATCH,
-            "sender": app_service_requester.user.to_string(),
-            "room_id": room_id,
-            "content": {
-                EventContentFields.MSC2716_BATCH_ID: batch_id_to_connect_to,
-                EventContentFields.MSC2716_HISTORICAL: True,
-            },
-            # Since the batch event is put at the end of the batch,
-            # where the newest-in-time event is, copy the origin_server_ts from
-            # the last event we're inserting
-            "origin_server_ts": last_event_in_batch["origin_server_ts"],
-        }
-        # Add the batch event to the end of the batch (newest-in-time)
-        events_to_create.append(batch_event)
-
-        # Add an "insertion" event to the start of each batch (next to the oldest-in-time
-        # event in the batch) so the next batch can be connected to this one.
-        insertion_event = self.create_insertion_event_dict(
-            sender=app_service_requester.user.to_string(),
-            room_id=room_id,
-            # Since the insertion event is put at the start of the batch,
-            # where the oldest-in-time event is, copy the origin_server_ts from
-            # the first event we're inserting
-            origin_server_ts=events_to_create[0]["origin_server_ts"],
-        )
-        next_batch_id = insertion_event["content"][
-            EventContentFields.MSC2716_NEXT_BATCH_ID
-        ]
-        # Prepend the insertion event to the start of the batch (oldest-in-time)
-        events_to_create = [insertion_event] + events_to_create
-
-        # Create and persist all of the historical events
-        event_ids = await self.persist_historical_events(
-            events_to_create=events_to_create,
-            room_id=room_id,
-            inherited_depth=inherited_depth,
-            initial_state_event_ids=initial_state_event_ids,
-            app_service_requester=app_service_requester,
-        )
-
-        return event_ids, next_batch_id
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -362,7 +362,6 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
        content: Optional[dict] = None,
        require_consent: bool = True,
        outlier: bool = False,
-        historical: bool = False,
        origin_server_ts: Optional[int] = None,
    ) -> Tuple[str, int]:
        """
@@ -378,16 +377,13 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
            allow_no_prev_events: Whether to allow this event to be created an empty
                list of prev_events. Normally this is prohibited just because most
                events should have a prev_event and we should only use this in special
-                cases like MSC2716.
+                cases (previously useful for MSC2716).
            prev_event_ids: The event IDs to use as the prev events
            state_event_ids:
-                The full state at a given event. This is used particularly by the MSC2716
-                /batch_send endpoint. One use case is the historical `state_events_at_start`;
-                since each is marked as an `outlier`, the `EventContext.for_outlier()` won't
-                have any `state_ids` set and therefore can't derive any state even though the
-                prev_events are set so we need to set them ourself via this argument.
-                This should normally be left as None, which will cause the auth_event_ids
-                to be calculated based on the room state at the prev_events.
+                The full state at a given event. This was previously used particularly
+                by the MSC2716 /batch_send endpoint. This should normally be left as
+                None, which will cause the auth_event_ids to be calculated based on the
+                room state at the prev_events.
            depth: Override the depth used to order the event in the DAG.
                Should normally be set to None, which will cause the depth to be calculated
                based on the prev_events.
@@ -400,9 +396,6 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
            outlier: Indicates whether the event is an `outlier`, i.e. if
                it's from an arbitrary point and floating in the DAG as
                opposed to being inline with the current DAG.
-            historical: Indicates whether the message is being inserted
-                back in time around some existing events. This is used to skip
-                a few checks and mark the event as backfilled.
            origin_server_ts: The origin_server_ts to use if a new event is created. Uses
                the current timestamp if set to None.

@@ -477,11 +470,10 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                    depth=depth,
                    require_consent=require_consent,
                    outlier=outlier,
-                    historical=historical,
                )
                context = await unpersisted_context.persist(event)
                prev_state_ids = await context.get_prev_state_ids(
-                    StateFilter.from_types([(EventTypes.Member, None)])
+                    StateFilter.from_types([(EventTypes.Member, user_id)])
                )

                prev_member_event_id = prev_state_ids.get(
@@ -585,7 +577,6 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
        new_room: bool = False,
        require_consent: bool = True,
        outlier: bool = False,
-        historical: bool = False,
        allow_no_prev_events: bool = False,
        prev_event_ids: Optional[List[str]] = None,
        state_event_ids: Optional[List[str]] = None,
@@ -610,22 +601,16 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
            outlier: Indicates whether the event is an `outlier`, i.e. if
                it's from an arbitrary point and floating in the DAG as
                opposed to being inline with the current DAG.
-            historical: Indicates whether the message is being inserted
-                back in time around some existing events. This is used to skip
-                a few checks and mark the event as backfilled.
            allow_no_prev_events: Whether to allow this event to be created an empty
                list of prev_events. Normally this is prohibited just because most
                events should have a prev_event and we should only use this in special
-                cases like MSC2716.
+                cases (previously useful for MSC2716).
            prev_event_ids: The event IDs to use as the prev events
            state_event_ids:
-                The full state at a given event. This is used particularly by the MSC2716
-                /batch_send endpoint. One use case is the historical `state_events_at_start`;
-                since each is marked as an `outlier`, the `EventContext.for_outlier()` won't
-                have any `state_ids` set and therefore can't derive any state even though the
-                prev_events are set so we need to set them ourself via this argument.
-                This should normally be left as None, which will cause the auth_event_ids
-                to be calculated based on the room state at the prev_events.
+                The full state at a given event. This was previously used particularly
+                by the MSC2716 /batch_send endpoint. This should normally be left as
+                None, which will cause the auth_event_ids to be calculated based on the
+                room state at the prev_events.
            depth: Override the depth used to order the event in the DAG.
                Should normally be set to None, which will cause the depth to be calculated
                based on the prev_events.
@@ -667,7 +652,6 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                        new_room=new_room,
                        require_consent=require_consent,
                        outlier=outlier,
-                        historical=historical,
                        allow_no_prev_events=allow_no_prev_events,
                        prev_event_ids=prev_event_ids,
                        state_event_ids=state_event_ids,
@@ -691,7 +675,6 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
        new_room: bool = False,
        require_consent: bool = True,
        outlier: bool = False,
-        historical: bool = False,
        allow_no_prev_events: bool = False,
        prev_event_ids: Optional[List[str]] = None,
        state_event_ids: Optional[List[str]] = None,
@@ -718,22 +701,16 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
            outlier: Indicates whether the event is an `outlier`, i.e. if
                it's from an arbitrary point and floating in the DAG as
                opposed to being inline with the current DAG.
-            historical: Indicates whether the message is being inserted
-                back in time around some existing events. This is used to skip
-                a few checks and mark the event as backfilled.
            allow_no_prev_events: Whether to allow this event to be created an empty
                list of prev_events. Normally this is prohibited just because most
                events should have a prev_event and we should only use this in special
-                cases like MSC2716.
+                cases (previously useful for MSC2716).
            prev_event_ids: The event IDs to use as the prev events
            state_event_ids:
-                The full state at a given event. This is used particularly by the MSC2716
-                /batch_send endpoint. One use case is the historical `state_events_at_start`;
-                since each is marked as an `outlier`, the `EventContext.for_outlier()` won't
-                have any `state_ids` set and therefore can't derive any state even though the
-                prev_events are set so we need to set them ourself via this argument.
-                This should normally be left as None, which will cause the auth_event_ids
-                to be calculated based on the room state at the prev_events.
+                The full state at a given event. This was previously used particularly
+                by the MSC2716 /batch_send endpoint. This should normally be left as
+                None, which will cause the auth_event_ids to be calculated based on the
+                room state at the prev_events.
            depth: Override the depth used to order the event in the DAG.
                Should normally be set to None, which will cause the depth to be calculated
                based on the prev_events.
@@ -877,7 +854,6 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                content=content,
                require_consent=require_consent,
                outlier=outlier,
-                historical=historical,
                origin_server_ts=origin_server_ts,
            )

@@ -1364,7 +1340,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
            requester = types.create_requester(target_user)

        prev_state_ids = await context.get_prev_state_ids(
-            StateFilter.from_types([(EventTypes.GuestAccess, None)])
+            StateFilter.from_types([(EventTypes.GuestAccess, "")])
        )
        if event.membership == Membership.JOIN:
            if requester.is_guest:
@@ -1386,11 +1362,14 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
            ratelimit=ratelimit,
        )

-        prev_member_event_id = prev_state_ids.get(
-            (EventTypes.Member, event.state_key), None
-        )
-
        if event.membership == Membership.LEAVE:
+            prev_state_ids = await context.get_prev_state_ids(
+                StateFilter.from_types([(EventTypes.Member, event.state_key)])
+            )
+            prev_member_event_id = prev_state_ids.get(
+                (EventTypes.Member, event.state_key), None
+            )
+
            if prev_member_event_id:
                prev_member_event = await self.store.get_event(prev_member_event_id)
                if prev_member_event.membership == Membership.JOIN:
@@ -1498,7 +1477,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
        # put the server which owns the alias at the front of the server list.
        if room_alias.domain in servers:
            servers.remove(room_alias.domain)
-        servers.insert(0, room_alias.domain)
+            servers.insert(0, room_alias.domain)

        return RoomID.from_string(room_id), servers

--- a/synapse/handlers/room_summary.py
+++ b/synapse/handlers/room_summary.py
@@ -564,9 +564,9 @@ class RoomSummaryHandler:
            join_rule = join_rules_event.content.get("join_rule")
            if (
                join_rule == JoinRules.PUBLIC
-                or (room_version.msc2403_knocking and join_rule == JoinRules.KNOCK)
+                or (room_version.knock_join_rule and join_rule == JoinRules.KNOCK)
                or (
-                    room_version.msc3787_knock_restricted_join_rule
+                    room_version.knock_restricted_join_rule
                    and join_rule == JoinRules.KNOCK_RESTRICTED
                )
            ):
--- a/synapse/handlers/saml.py
+++ b/synapse/handlers/saml.py
@@ -27,9 +27,9 @@ from synapse.http.servlet import parse_string
 from synapse.http.site import SynapseRequest
 from synapse.module_api import ModuleApi
 from synapse.types import (
+    MXID_LOCALPART_ALLOWED_CHARACTERS,
    UserID,
    map_username_to_mxid_localpart,
-    mxid_localpart_allowed_characters,
 )
 from synapse.util.iterutils import chunk_seq

@@ -371,7 +371,7 @@ class SamlHandler:


 DOT_REPLACE_PATTERN = re.compile(
-    "[^%s]" % (re.escape("".join(mxid_localpart_allowed_characters)),)
+    "[^%s]" % (re.escape("".join(MXID_LOCALPART_ALLOWED_CHARACTERS)),)
 )


--- a/Show More
+++ b/Show More
				`@@ -0,0 +1 @@`
				`Add Unix Socket support for HTTP Replication Listeners. Document and provide usage instructions for utilizing Unix sockets in Synapse. Contributed by Jason Little.`
				`@@ -0,0 +1 @@`
				`Fix long-standing bug where remote invites weren't correctly pushed.`
				`@@ -0,0 +1 @@`
				Mark `get_user_in_directory` private since it is only used in tests. Also remove the cache from it.
				`@@ -0,0 +1 @@`
				`Fix background schema updates failing over a large upgrade gap.`
				`@@ -0,0 +1 @@`
				`Document which Python version runs on a given Linux distribution so we can more easily clean up later.`
				`@@ -0,0 +1 @@`
				Allow `+` in Matrix IDs, per [MSC4009](https://github.com/matrix-org/matrix-spec-proposals/pull/4009).
				`@@ -0,0 +1 @@`
				`Support room version 11 from [MSC3820](https://github.com/matrix-org/matrix-spec-proposals/pull/3820).`
				`@@ -0,0 +1 @@`
				Allow configuring the set of workers to proxy outbound federation traffic through via `outbound_federation_restricted_to`.
				`@@ -0,0 +1 @@`
				`Better clarify how to run a worker instance (pass both configs).`
				`@@ -0,0 +1 @@`
				`Add details to warning in log when we fail to fetch an alias.`