Regression in log context tracking

[erikjohnston]

On both matrix.org and jki.re I'm seeing (on latest develop) a lot of:

2021-01-07 18:39:07,534 - synapse.util.metrics - 113 - WARNING - None - Starting metrics collection from sentinel context: metrics will be lost

which may mean a bunch of our metrics are inaccurate

[richvdh]

which may mean a bunch of our metrics are inaccurate

I think the problem has existed for a while: we're just reporting it now.

It will have been introduced by #8935, and I feel like the increased log spam makes this a release-blocker for 1.25.

[richvdh]

scratch that, it will be #8939, which didn't make the release.

[erikjohnston]

Agreed. I think the first step is to get it to log what block is being ignored, since we have the name there that should be easy.

[richvdh]

(it's still a release-blocker, but for 1.26...)

[erikjohnston]

Clearly we need a next-release blocker label...

[erikjohnston]

Looks like it is in v1.25.0rc1

[erikjohnston]

Oh, ignore me somehow I opened the wrong PR....