Hello all, I experienced a situation when TWSocket's handlers confuse application workflow. I have SessionConnected handler async-ly reporting an error and SessionClosed handler async-ly reconnecting/pausing/reporting an error - depends of several conditions. Everything worked fine for months, but today the server I was connecting to went down. Here's the log (Pos/SetState are my methods):
2011-10-12 10:37:39.311 7FD10330 Socket handle created 3572 2011-10-12 10:37:39.311 SocketChangeState wsClosed -> wsOpened 2011-10-12 10:37:39.311 TWSocket will connect to **** 2011-10-12 10:37:39.311 SocketChangeState wsOpened -> wsConnecting 2011-10-12 10:37:40.326 SocketChangeState wsConnecting -> wsConnected 2011-10-12 10:37:40.326 SocketSessionConnected, Connection refused (#10061) // OK. Error on connect. My code commands to report an error and reconnect 2011-10-12 10:37:40.326 PostState: csConnecting -> csError 2011-10-12 10:37:40.326 7FD10330 TCustomWSocket.Shutdown 1 3572 2011-10-12 10:37:40.326 SocketChangeState wsConnected -> wsClosed // ! Oops. The socket was "kinda connected" and then closed 2011-10-12 10:37:40.326 SocketSessionClosed // ! Looks like just an accident closing after successful connect, closing WITHOUT ANY ERROR. So my code commands to fall asleep 2011-10-12 10:37:40.326 PostState: csConnecting -> csSleeping 2011-10-12 10:37:40.326 SetState: csConnecting -> csError // OK. Here the state commanded in SocketSessionConnected is finally set 2011-10-12 10:37:40.326 PostState: csError -> csReconnect // OK. Here we command to retry after an error 2011-10-12 10:37:40.326 SetState: csError -> csSleeping // Oops! Command from SocketSessionClosed has arrived 2011-10-12 10:37:40.326 SetState: csSleeping -> csReconnect // Damn, the previous reconnect command has arrived ... Frankly speaking, there was no serious trouble except for strange high CPU load which I still can't track. But I think the very principle of calling the methods here enables possible troubles. I see two major danger sources here: 1) Despite of error on connect, socket state changes to wsConnected anyway. 2) Close is called without any error code so it looks like an accidental line break. What have I do to handle the descibed situation properly? * I can't use only OnSessionConnected because then I won't catch disconnects after successful connect * I can't use only OnSessionClosed because then I won't realise that an error occured on connect * I can't use both of them because they're messing up. So for now I have to invent some flag to tell the OnSessionClosed that OnSessionConnected has already handled the situation. Maybe you have more clever alternative? -- Anton -- To unsubscribe or change your settings for TWSocket mailing list please goto http://lists.elists.org/cgi-bin/mailman/listinfo/twsocket Visit our website at http://www.overbyte.be
