[GitHub] massakam opened a new pull request #3172: Modify producer handler of WebSocket to send ack to client asynchrono…

[GitBox <gi...@apache.org>]

massakam opened a new pull request #3172: Modify producer handler of WebSocket to send ack to client asynchrono…
URL: https://github.com/apache/pulsar/pull/3172
 
 
   …usly
   
   ### Motivation
   
   Recently, the WebSocket proxy in our Pulsar cluster hangs occasionally. A lot of connections in the CLOSE_WAIT state occur and the WebSocket proxy can not respond at all to requests from clients.
   
   When checking the thread dump at this time, the IO thread is waiting forever for ack to be sent to the client.
   https://gist.github.com/massakam/b0cffaf5f7361b94ec2a4dd13c672143#file-websocket_blocked_thread-txt
   
   Some similar issues have been reported in the Jetty repository:
   https://github.com/eclipse/jetty.project/issues/272
   https://github.com/eclipse/jetty.project/issues/2061
   
   The cause is still unknown, but this phenomenon seems to occur only when using blocking writes.
   https://github.com/eclipse/jetty.project/issues/2061#issuecomment-420002658
   
   ### Modifications
   
   When WebSocket proxy sends ack to client, it uses asynchronous write instead of blocking write.
   
   ### Result
   
   It can be expected to avoid WebSocket hanging, but there is no confirmation.

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