Split homeserver creation and setup #19015
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As we already have the reactor running in the case of Synapse Pro for Small Hosts and `setup()` should handle everything
…round_tasks`" This reverts commit 211765f. (do this in another PR)
MadLittleMods
commented
Oct 3, 2025
synapse/app/homeserver.py
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| # TODO: This should be moved to `SynapseHomeServer.start_background_tasks` (this | ||
| # way it matches the behavior of only running on `main`) |
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This is a future TODO
MadLittleMods
commented
Oct 3, 2025
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| async def start() -> None: | ||
| async def _start_when_reactor_running() -> None: | ||
| # TODO: Feels like this should be moved somewhere else. |
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This is a future TODO
MadLittleMods
commented
Oct 7, 2025
| "You have specified `worker_app` in the config but are attempting to start a non-worker " | ||
| "instance. Please use `python -m synapse.app.generic_worker` instead (or remove the option if this is the main process)." | ||
| ) | ||
| sys.exit(1) |
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Removed this exit as it's unreachable since we raise just above
3 tasks
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Split homeserver creation and setup
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_synapseshard process itself), when provisioning a homeserver tenant, thereactor.callWhenRunning(...)callbacks will be invoked immediately. This includes the Synapse'sstartcallback 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 without us having a handle to the homeserver yet so we can't callhs.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
hsif anything goes wrong during setup and can subsequentlyhs.shutdown()to clean everything up.Dev notes
Refactor with
start_background_tasks: #18886Pull Request Checklist
EventStoretoEventWorkerStore.".code blocks.