### 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).
Related to https://github.com/element-hq/synapse/issues/18905
These fixes were split off from
https://github.com/element-hq/synapse/pull/18828 where @devonh was
seeing some test failures because `timeout_deferred(...)` is being
updated to use `Clock` utilities instead of raw `reactor` methods. This
test was failing in that branch/PR until we made this new version that
handles the logcontexts properly.
While the previous version of this test does pass on `develop`, it was
using what appears completely wrong assertions, assumptions, and bad
patterns to make it happen (see diff comments below)
---
Test originally introduced in https://github.com/matrix-org/synapse/pull/4407
The main change here is to add a helper function
`gather_optional_coroutines`, which works in a similar way as
`yieldable_gather_results` but takes a set of coroutines rather than a
function
This will mainly be useful when dealing with module callbacks, which are
all typed as returning `Awaitable`s instead of coroutines or
`Deferred`s.
Signed-off-by: Sean Quah <seanq@element.io>
`delay_cancellation` behaves like `stop_cancellation`, except it
delays `CancelledError`s until the original `Deferred` resolves.
This is handy for unifying cleanup paths and ensuring that uncancelled
coroutines don't use finished logcontexts.
Signed-off-by: Sean Quah <seanq@element.io>
* fix incorrect unwrapFirstError import
this was being imported from the wrong place
* Refactor `concurrently_execute` to use `yieldable_gather_results`
* Improve exception handling in `yieldable_gather_results`
Try to avoid swallowing so many stack traces.
* mark unwrapFirstError deprecated
* changelog
