Investigate Sentry error: TaskStopped

[callahad]

Our monitoring for Syngal on matrix.org occasionally sees an error:

Unexpected exception from twisted.web.client.FileBodyProducer.stopProducing

The traceback is:

TaskStopped: null
  File "twisted/web/_newclient.py", line 197, in _callAppFunction
    function()
  File "twisted/web/client.py", line 1161, in stopProducing
    self._task.stop()
  File "twisted/internet/task.py", line 497, in stop
    self._checkFinish()
  File "twisted/internet/task.py", line 507, in _checkFinish
    raise self._completionState

So... what causes this to happen? Can we handle the error more gracefully?

(For Element employees, this is https://sentry.matrix.org/sentry/sygnal-matrixorg/issues/15235/)

[H-Shay]

I am wondering if this error is related to this issue: https://twistedmatrix.com/trac/ticket/9929

[clokep]

I think this needs this code from Synapse ported to Sygnal: https://github.com/matrix-org/synapse/blob/15090de85075c9d7d54479b4bfd79057de64059b/synapse/http/__init__.py#L43-L54

[richvdh]

I think this needs this code from Synapse ported to Sygnal: https://github.com/matrix-org/synapse/blob/15090de85075c9d7d54479b4bfd79057de64059b/synapse/http/__init__.py#L43-L54

I would love it if we could shove all this sort of thing in a matrix-twisted-utils library or something so that we don't have to implement it individually in each of synapse, sygnal and sydent.

[clokep]

In this case it seems like we could also try to fix the Twisted bug?

[richvdh]

well, true.