Eric Eastwood 5143f93dc9 Fix server_name in logging context for multiple Synapse instances in one process (#18868) ... ### 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. "Per-tenant logging" tracked internally by https://github.com/element-hq/synapse-small-hosts/issues/48 ### Prior art Previously, we exposed `server_name` by providing a static logging `MetadataFilter` that injected the values: 205d9e4fc4/synapse/config/logger.py (L216) While this can work fine for the normal case of one Synapse instance per Python process, this configures things globally and isn't compatible when we try to start multiple Synapse instances because each subsequent tenant will overwrite the previous tenant. ### What does this PR do? We remove the `MetadataFilter` and replace it by tracking the `server_name` in the `LoggingContext` and expose it with our existing [`LoggingContextFilter`](205d9e4fc4/synapse/logging/context.py (L584-L622)) that we already use to expose information about the `request`. This means that the `server_name` value follows wherever we log as expected even when we have multiple Synapse instances running in the same process. ### A note on logcontext Anywhere, Synapse mistakenly uses the `sentinel` logcontext to log something, we won't know which server sent the log. We've been fixing up `sentinel` logcontext usage as tracked by https://github.com/element-hq/synapse/issues/18905 Any further `sentinel` logcontext usage we find in the future can be fixed piecemeal as normal. d2a966f922/docs/log_contexts.md (L71-L81) ### Testing strategy 1. Adjust your logging config to include `%(server_name)s` in the format ```yaml formatters: precise: format: '%(asctime)s - %(server_name)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s' ``` 1. Start Synapse: `poetry run synapse_homeserver --config-path homeserver.yaml` 1. Make some requests (`curl http://localhost:8008/_matrix/client/versions`, etc) 1. Open the homeserver logs and notice the `server_name` in the logs as expected. `unknown_server_from_sentinel_context` is expected for the `sentinel` logcontext (things outside of Synapse).		2025-09-26 17:10:48 -05:00
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transport	Introduce Clock.call_when_running(...) to include logcontext by default (#18944)	2025-09-22 10:27:59 -05:00
__init__.py	Implementation of server_acls	2018-07-04 19:06:20 +01:00
test_complexity.py	Format files with Ruff (#17643)	2024-09-02 12:39:04 +01:00
test_federation_catch_up.py	Introduce Clock.call_when_running(...) to include logcontext by default (#18944)	2025-09-22 10:27:59 -05:00
test_federation_client.py	Introduce Clock.call_when_running(...) to include logcontext by default (#18944)	2025-09-22 10:27:59 -05:00
test_federation_devices.py	Introduce Clock.call_when_running(...) to include logcontext by default (#18944)	2025-09-22 10:27:59 -05:00
test_federation_media.py	Introduce Clock.call_when_running(...) to include logcontext by default (#18944)	2025-09-22 10:27:59 -05:00
test_federation_out_of_band_membership.py	Introduce Clock.call_when_running(...) to include logcontext by default (#18944)	2025-09-22 10:27:59 -05:00
test_federation_sender.py	Introduce Clock.call_when_running(...) to include logcontext by default (#18944)	2025-09-22 10:27:59 -05:00
test_federation_server.py	Fix server_name in logging context for multiple Synapse instances in one process (#18868)	2025-09-26 17:10:48 -05:00