How to detect non-graceful disconnect of Twisted on Linux?

Question

I wrote a server based on Twisted, and I encountered a problem, some of the clients are disconnected not gracefully. For example, the user pulls out the network cable.

For a while, the client on Windows is disconnected (the connectionLost is called, and it is also written in Twisted). And on the Linux server side, my connectionLost of twisted is never triggered. Even it try to writes data to client when the connection is lost. Why Twisted can't detect those non-graceful disconnection (even write data to client) on Linux? How to makes Twisted detect non-graceful disconnections? Because the feature Twisted can't detect non-graceful, I have lots of zombie user on my server.

---- Update ----

I thought it might be the feature of socket of unix-like os, so, what is the behavior of socket on unix-like for handling situation like this?

Thanks. Victor Lin.

Answer 1

You're describing the behavior of TCP connections on an unreliable network. Twisted is merely exposing this behavior: after all, when you set up a TCP connection with Twisted, it is nothing more than a TCP connection.

You're mistaken when you say that the connectionLost callback isn't invoked even if you try to send data over it. After two minutes, the underlying TCP connection will disappear and Twisted will inform you of this by calling connectionLost.

If you need to detect this condition more quickly than that, then you can implement your own timeouts using reactor.callLater.

Answer 2

Hi Victor,

Seconding what Jean-Paul said, if you need more fine grained TCP connection management, just use reactor.CallLater. We have exactly that implementation on a Twisted/wxPython trading platform, and it works a treat. You might also want to tweak the behaviour of the ReconnectingClientFactory in order to achieve the results I understand your looking for.