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Move start_doing_background_updates() to SynapseHomeServer.start_background_tasks() #19036

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Merged
merged 3 commits into from
Oct 10, 2025
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Move start_doing_background_updates() to SynapseHomeServer.start_background_tasks() #19036

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327da0d
Move `start_doing_background_updates()` to `SynapseHomeServer.start_b…
MadLittleMods Oct 9, 2025
a00eef7
Add changelog
MadLittleMods Oct 9, 2025
b5fcd46
Merge branch 'develop' into madlittlemods/move-start-background-updates
MadLittleMods Oct 10, 2025
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1 change: 1 addition & 0 deletions changelog.d/19036.misc
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Move `start_doing_background_updates()` to `SynapseHomeServer.start_background_tasks()`.
10 changes: 5 additions & 5 deletions synapse/app/homeserver.py
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Expand Up @@ -317,6 +317,11 @@ def start_listening(self) -> None:
# 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()
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The one difference here is that previously, start_doing_background_updates() only ran on the main Synapse instance.

But start_background_tasks() runs on the worker that supposed to run_background_tasks.

synapse/synapse/app/_base.py

Lines 683 to 684 in 47fb4b4

if hs.config.worker.run_background_tasks:
hs.start_background_tasks()

Is that okay? Nothing is immediately coming to mind on why this would be bad.

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seems OK to me too

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Actually, I think there is a flaw with this setup.

SynapseHomeServer is for the main Synapse instance. We have SynapseHomeServer.start_background_tasks() setup to call start_doing_background_updates() but if the run_background_tasks_on is set to anything else besides main, then we will never run SynapseHomeServer.start_background_tasks() specifically.

What we actually need to do is just move this to HomeServer.start_background_tasks() instead. We want start_doing_background_updates() to run on whatever homeserver is configured to run_background_tasks_on

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This is being addressed in #19057

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Deciding to revert this PR in the meantime -> #19059

While I figure out all of the intricacies in the test infrastructure from moving it to the correct spot. Will re-introduce things in #19057



def load_or_generate_config(argv_options: List[str]) -> HomeServerConfig:
"""
Expand Down Expand Up @@ -430,11 +435,6 @@ async def _start_when_reactor_running() -> None:

await _base.start(hs, freeze)

# TODO: This should be moved to `SynapseHomeServer.start_background_tasks` (not
# `HomeServer.start_background_tasks`) (this way it matches the behavior of only
# running on `main`)
hs.get_datastores().main.db_pool.updates.start_doing_background_updates()

# Register a callback to be invoked once the reactor is running
register_start(hs, _start_when_reactor_running)

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