Ping thread never exits

[Yuras]

After upgrading snap and websockets I see memory leak in my application. To reproduce, create simple websockets server:

wsApp :: Snap ()
wsApp = WebSockets.runWebSocketsSnap $ \pc -> do
  print "client"
  c <- WebSockets.acceptRequest pc
  threadDelay (10000000)
  print "done"

Then run in with +RTS -S -RTS, make a number of connections and check memory usage. It grows even if the handler exists after 10 seconds. Disabling the built-in ping thread fixes the issue:

wsApp :: Snap ()
wsApp = WebSockets.runWebSocketsSnap $ \pc -> do
  print "client"
  c <- WebSockets.acceptRequest pc
    { WebSockets.pendingOnAccept = const $ return ()
    }
  threadDelay (10000000)
  print "done"

My conclusion: ping thread doesn't exit for some reason.

[jaspervdj]

This is surprising -- an exception should be raised when it tries to write to the socket.

I'll see if we can circumvent the problem by explicitly killing the thread -- that's a bit better anyway since we can get rid of the thread faster.