tornado: Fix race condition on handler._request #22220
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Commit 6fd1a55 (zulip#21469) introduced an await point where get_events_backend calls fetch_events in order to switch threads. This opened the possibility that, in the window between the connect_handler call in fetch_events and the old location of this assignment in get_events_backend, an event could arrive, causing ClientDescriptor.add_event to crash on missing handler._request. Fix this by assigning handler._request earlier. Signed-off-by: Anders Kaseorg <anders@zulip.com>
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The 0.1 second delay was sometimes not long enough to guarantee we hit the async response path, resulting in a nondeterministic coverage failure. Signed-off-by: Anders Kaseorg <anders@zulip.com>
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Merged, thanks @andersk! |
This was referenced Jul 6, 2022
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Commit 6fd1a55 (#21469) introduced an await point where
get_events_backendcallsfetch_eventsin order to switch threads. This opened the possibility that, in the window between theconnect_handlercall infetch_eventsand the old location of this assignment inget_events_backend, an event could arrive, causingClientDescriptor.add_eventto crash on missinghandler._request. Fix this by assigninghandler._requestearlier.I found this by trying to improve #22058 (cc @asah) to avoid relying on a fixed timeout. So this improved test now also serves as a test case for this race condition.