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Prevent logging context going missing on federation request timeout (#10810) In `MatrixFederationHttpClient._send_request()`, we make a HTTP request using an `Agent`, wrap that request in a timeout and await the resulting `Deferred`. On its own, the `Agent` performing the HTTP request correctly stashes and restores the logging context while waiting. The addition of the timeout introduces a path where the logging context is not restored when execution resumes. To address this, we wrap the timeout `Deferred` in a `make_deferred_yieldable()` to stash the logging context and restore it on completion of the `await`. However this is not sufficient, since by the time we construct the timeout `Deferred`, the `Agent` has already stashed and cleared the logging context when using `make_deferred_yieldable()` to produce its `Deferred` for the request. Hence, we wrap the `Agent` request in a `run_in_background()` to "fork" and preserve the logging context so that we can stash and restore it when `await`ing the timeout `Deferred`. This approach is similar to the one used with `defer.gatherResults`. Note that the code is still not fully correct. When a timeout occurs, the request remains running in the background (existing behavior which is nothing to do with the new call to `run_in_background`) and may re-start the logging context after it has finished.

2021-09-14 14:01:30 +02:00

Fix a case where logging contexts would go missing when federation requests time out.