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Split homeserver creation and setup (#19015)

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### Background

As part of Element's plan to support a light form of vhosting (virtual
host) (multiple instances of Synapse in the same Python process), we're
currently diving into the details and implications of running multiple
instances of Synapse in the same Python process.

"Clean tenant provisioning" tracked internally by
https://github.com/element-hq/synapse-small-hosts/issues/221


### Partial startup problem

In the context of Synapse Pro for Small Hosts, since the Twisted reactor
is already running (from the `multi_synapse` shard process itself), when
provisioning a homeserver tenant, the `reactor.callWhenRunning(...)`
callbacks will be invoked immediately. This includes the Synapse's
[`start`](0615b64bb4/synapse/app/homeserver.py (L418-L429))
callback which sets up everything (including listeners, background
tasks, etc). If we encounter an error at this point, we are partially
setup but the exception will [bubble back to
us](8be122186b/multi_synapse/app/shard.py (L114-L121))
without us having a handle to the homeserver yet so we can't call
`hs.shutdown()` and clean everything up.


### What does this PR do?

Structures Synapse so we split creating the homeserver instance from
setting everything up. This way we have access to `hs` if anything goes
wrong during setup and can subsequently `hs.shutdown()` to clean
everything up.
This commit is contained in:
Eric Eastwood
2025-10-09 13:12:10 -05:00
committed by GitHub
parent d440cfc9e2
commit 715cc5ee37
4 changed files with 74 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
tests/app/test_homeserver_start.py
View File

@@ -37,7 +37,13 @@ class HomeserverAppStartTestCase(ConfigFileTestCase):
self.add_lines_to_config([" main:", " host: 127.0.0.1", " port: 1234"])
# Ensure that starting master process with worker config raises an exception
with self.assertRaises(ConfigError):
# Do a normal homeserver creation and setup
homeserver_config = synapse.app.homeserver.load_or_generate_config(
["-c", self.config_file]
)
synapse.app.homeserver.setup(homeserver_config)
# XXX: The error will be raised at this point
hs = synapse.app.homeserver.create_homeserver(homeserver_config)
# Continue with the setup. We don't expect this to run because we raised
# earlier, but in the future, the code could be refactored to raise the
# error in a different place.
synapse.app.homeserver.setup(hs)

8
tests/config/test_registration_config.py
View File

@@ -112,7 +112,13 @@ class RegistrationConfigTestCase(ConfigFileTestCase):
# Test that allowing open registration without verification raises an error
with self.assertRaises(ConfigError):
# Do a normal homeserver creation and setup
homeserver_config = synapse.app.homeserver.load_or_generate_config(
["-c", self.config_file]
)
synapse.app.homeserver.setup(homeserver_config)
# XXX: The error will be raised at this point
hs = synapse.app.homeserver.create_homeserver(homeserver_config)
# Continue with the setup. We don't expect this to run because we raised
# earlier, but in the future, the code could be refactored to raise the
# error in a different place.
synapse.app.homeserver.setup(hs)