Fix write lock deadline handling #7
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Related: gorilla#704 |
cce
reviewed
Nov 17, 2021
cce
approved these changes
Nov 17, 2021
cce
approved these changes
Nov 17, 2021
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Issue
The existing code in go-algorand is using two go-routines for reading/writing and a separate go-routine for opening/closing the connections.
When a client connection becomes non-responsive ( i.e. the writer is not returning ), the current implementation tries to close the connection. However, per WebSocket specification, the client is supposed to send a Close message first.
The close message is being sent using the
WriteControlmethod, which is supposed to be able to run concurrently withWriteMessage. However, both reachesConn.writewhere it attempt to acquire a writing lock.Since the
WriteMessage -> Conn.writeis stuck ( but theWriteControldoesn't really know it's stuck indefinitely ), theWriteControl -> Conn.writeget blocks indefinitely as well.Unlike the
WriteMessage, when callingWriteControl, we provide a deadline : a timestamp after which we don't care if the message was actually sent. In this PR, I have added handling that would limit the time theConn.writewould wait to that deadline.From spec perspective, it would be a violation of the WebSocket protocol; however, given that the other party is no longer responsive, a successful writing of a Close message is not possible, it would probably be just fine.