On 5 Aug, 03:59 pm, peter.westl...@pobox.com wrote: >Background: I have a client program that calls callRemote, but the >Deferred that callRemote returns is not fired. This is an intermittent >error that only happens after some hours of traffic. > >By putting some logging into AMP, it's apparent that the server gets >as far as sending the reply using BoxDispatcher._safeEmit. The >original version of that ignores connection errors, but I overrode it >with one that doesn't: > >[snip] > >On the client, BoxDispatcher._answerReceived logs all replies: > >[snip] > >Likewise _errorReceived. > >I always see both log.msgs or neither, so it isn't something going >wrong in the callback. > >The client sends a request. >The server sends a reply with the same tag, and logs a message. >Until it goes wrong, the client receives the reply and logs it. >When it goes wrong, the client does not see the reply. > >The protocol has the unfired Deferred in _outstandingRequests, >with the missing tag as key. > >All this suggests that the problem is either in the low-level >network code, or somewhere in the network between the client >and server. But doesn't TCP/IP tell you if a packet doesn't >get through?
It doesn't really /tell/ you. But if there is some issue with the network that prevents packet delivery for long enough, then the connection breaks (giving you a connectionLost call in Twisted, which should errback your Deferred). > >I tried tracing the packets using a python-pycapy script (attached), >but it showed more packets disappearing than actually were. It might be simpler to use something like wireshark, which already knows how to do TCP stream re-assembly and such. I know this isn't much of a suggestion, but it's the only thing that really comes to mind. Jean-Paul _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
