Fix lints

```
builtins.AssertionError: Expected `looping_call` callback from the reactor to start with the sentinel logcontext but saw task-_resumable_task-0-IBzAmHUoepQfLnEA. In other words, another task shouldn't have leaked their logcontext to us.
```

changelog.d/19036.misc

@@ -1 +1 @@
-Move `start_doing_background_updates()` to `SynapseHomeServer.start_background_tasks()`.
+Move `start_doing_background_updates()` to `HomeServer.start_background_tasks()`.

changelog.d/19057.misc

@@ -0,0 +1 @@
+Move `start_doing_background_updates()` to `HomeServer.start_background_tasks()`.

synapse/app/homeserver.py

@@ -317,11 +317,6 @@ class SynapseHomeServer(HomeServer):
                 # during parsing
                 logger.warning("Unrecognized listener type: %s", listener.type)
 
-    def start_background_tasks(self) -> None:
-        super().start_background_tasks()
-
-        self.get_datastores().main.db_pool.updates.start_doing_background_updates()
-
 
 def load_or_generate_config(argv_options: List[str]) -> HomeServerConfig:
     """

synapse/server.py

@@ -646,6 +646,7 @@ class HomeServer(metaclass=abc.ABCMeta):
         self.get_task_scheduler()
         self.get_common_usage_metrics_manager().setup()
         start_phone_stats_home(self)
+        self.get_datastores().main.db_pool.updates.start_doing_background_updates()
 
     def get_reactor(self) -> ISynapseReactor:
         """

synapse/util/task_scheduler.py

@@ -53,8 +53,8 @@ running_tasks_gauge = LaterGauge(
 class TaskScheduler:
     """
     This is a simple task scheduler designed for resumable tasks. Normally,
-    you'd use `run_in_background` to start a background task or Twisted's
-    `deferLater` if you want to run it later.
+    you'd use `run_in_background` to start a background task or `clock.call_later`
+    if you want to run it later.
 
     The issue is that these tasks stop completely and won't resume if Synapse is
     shut down for any reason.

tests/rest/admin/test_room.py

@@ -27,7 +27,6 @@ from unittest.mock import AsyncMock, Mock
 
 from parameterized import parameterized
 
-from twisted.internet.task import deferLater
 from twisted.internet.testing import MemoryReactor
 
 import synapse.rest.admin
@@ -861,7 +860,7 @@ class DeleteRoomV2TestCase(unittest.HomeserverTestCase):
         # Mock PaginationHandler.purge_room to sleep for 100s, so we have time to do a second call
         # before the purge is over. Note that it doesn't purge anymore, but we don't care.
         async def purge_room(room_id: str, force: bool) -> None:
-            await deferLater(self.hs.get_reactor(), 100, lambda: None)
+            await self.hs.get_clock().sleep(100)
 
         self.pagination_handler.purge_room = AsyncMock(side_effect=purge_room)  # type: ignore[method-assign]
 

tests/unittest.py

@@ -73,12 +73,12 @@ from synapse.http.server import JsonResource, OptionsResource
 from synapse.http.site import SynapseRequest, SynapseSite
 from synapse.logging.context import (
     SENTINEL_CONTEXT,
-    LoggingContext,
     current_context,
     set_current_context,
 )
 from synapse.rest import RegisterServletsFunc
 from synapse.server import HomeServer
+from synapse.storage.background_updates import UpdaterStatus
 from synapse.storage.keys import FetchKeyResult
 from synapse.types import ISynapseReactor, JsonDict, Requester, UserID, create_requester
 from synapse.util.clock import Clock
@@ -108,6 +108,11 @@ P = ParamSpec("P")
 R = TypeVar("R")
 S = TypeVar("S")
 
+BACKGROUND_UPDATE_TIMEOUT_SECONDS = 5
+"""
+We expect this to be pretty immediate as we're working with an empty database.
+"""
+
 
 class _TypedFailure(Generic[_ExcType], Protocol):
     """Extension to twisted.Failure, where the 'value' has a certain type."""
@@ -490,7 +495,11 @@ class HomeserverTestCase(TestCase):
 
     def wait_for_background_updates(self) -> None:
         """Block until all background database updates have completed."""
-        store = self.hs.get_datastores().main
+        self._wait_for_background_updates(self.hs)
+
+    def _wait_for_background_updates(self, hs: HomeServer) -> None:
+        """Block until all background database updates have completed."""
+        store = hs.get_datastores().main
         while not self.get_success(
             store.db_pool.updates.has_completed_background_updates()
         ):
@@ -677,10 +686,6 @@ class HomeserverTestCase(TestCase):
         # construct a homeserver with a matching name.
         server_name = config_obj.server.server_name
 
-        async def run_bg_updates() -> None:
-            with LoggingContext(name="run_bg_updates", server_name=server_name):
-                self.get_success(stor.db_pool.updates.run_background_updates(False))
-
         hs = setup_test_homeserver(
             cleanup_func=self.addCleanup,
             server_name=server_name,
@@ -689,11 +694,48 @@ class HomeserverTestCase(TestCase):
             clock=clock,
             **extra_homeserver_attributes,
         )
-        stor = hs.get_datastores().main
 
-        # Run the database background updates, when running against "master".
-        if hs.__class__.__name__ == "TestHomeServer":
-            self.get_success(run_bg_updates())
+        # Wait for the database background updates to complete. This is important
+        # because tests assume that the database is using the latest schema.
+        #
+        # We could use `self._wait_for_background_updates(hs)` to accomplish the same
+        # thing but we don't want to start or drive the background updates here. We want
+        # to ensure the homeserver itself is doing that.
+        start_time_s = time.time()
+        store = hs.get_datastores().main
+        while not self.get_success(
+            # This check is slightly naive. It only checks if there is anything left in
+            # the `background_updates` database table so it is possible that the
+            # homeserver mistakenly never registered any background updates to be run.
+            # Since `register_background_xxx(...)` is done across the codebase, we can't
+            # really assert that everything was registered as expected.
+            store.db_pool.updates.has_completed_background_updates()
+        ):
+            # Timeout if it takes too long. This should be pretty immediate as we're
+            # working with an empty database.
+            current_time_s = time.time()
+            if current_time_s - start_time_s > BACKGROUND_UPDATE_TIMEOUT_SECONDS:
+                background_update_status = store.db_pool.updates.get_status()
+
+                # Add some better context when we give up
+                extra_message = ""
+                if background_update_status == UpdaterStatus.NOT_STARTED:
+                    extra_message = (
+                        "Did you forget to `start_doing_background_updates()`?"
+                    )
+                elif background_update_status == UpdaterStatus.RUNNING_UPDATE:
+                    extra_message = "Background updates were still running when we gave up. Are they stuck?"
+                else:
+                    extra_message = (
+                        f"Background update status was {background_update_status}."
+                    )
+
+                raise AssertionError(
+                    f"Timed out waiting for background updates to complete ({BACKGROUND_UPDATE_TIMEOUT_SECONDS}s). "
+                    + extra_message
+                )
+
+            self.pump(by=0.1)
 
         return hs
 

tests/util/test_task_scheduler.py

@@ -20,9 +20,10 @@
 #
 from typing import List, Optional, Tuple
 
-from twisted.internet.task import deferLater
+from twisted.internet.defer import Deferred
 from twisted.internet.testing import MemoryReactor
 
+from synapse.logging.context import make_deferred_yieldable
 from synapse.server import HomeServer
 from synapse.types import JsonMapping, ScheduledTask, TaskStatus
 from synapse.util.clock import Clock
@@ -87,7 +88,7 @@ class TestTaskScheduler(HomeserverTestCase):
         self, task: ScheduledTask
     ) -> Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]:
         # Sleep for a second
-        await deferLater(self.reactor, 1, lambda: None)
+        await self.hs.get_clock().sleep(1)
         return TaskStatus.COMPLETE, None, None
 
     def test_schedule_lot_of_tasks(self) -> None:
@@ -170,8 +171,10 @@ class TestTaskScheduler(HomeserverTestCase):
             return TaskStatus.COMPLETE, {"success": True}, None
         else:
             await self.task_scheduler.update_task(task.id, result={"in_progress": True})
+            # Create a deferred which we will never complete
+            incomplete_d: Deferred = Deferred()
             # Await forever to simulate an aborted task because of a restart
-            await deferLater(self.reactor, 2**16, lambda: None)
+            await make_deferred_yieldable(incomplete_d)
             # This should never been called
             return TaskStatus.ACTIVE, None, None