Prevent WebSocket._thread from speed-reading closed sockets#3
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rdash-fenix wants to merge 1 commit intoch-iv:mainfrom
Open
Prevent WebSocket._thread from speed-reading closed sockets#3rdash-fenix wants to merge 1 commit intoch-iv:mainfrom
rdash-fenix wants to merge 1 commit intoch-iv:mainfrom
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Noticed that a program I was writing in flask had a very high CPU usage,
py-spyand some tinkering led me to discover it was an endless loop in WebSocket._thread. I could repeatably cause the fault condition by opening the endpoint incurland then killing it so it could not send a close message.Per python's socket documentation, calls to
recv()on a closed socket do not yield anOSErrorlike one would expect, but instead simply return an emptybytesinstance. Between this and wsproto's parser just returningNonewhen it receives an emptybytesinstance, you have a loop that pegs the CPU.My patch simply adds a check for an empty return, and injects the OSError the code is otherwise expecting. The other case where
recv()could return no bytes is if a zero-length datagram was received (which would not be possible/valid given websocket's use of TCP), so this simple check should be safe.Passed against the test suite, and functions correctly against both of the provided examples (as well as the codebase where I discovered it).