On Wed, Nov 14, 2018 at 3:50 AM Chris Withers <ch...@withers.org> wrote:
> Right, so, I've been trying to get the technique in > https://jml.io/pages/how-to-disconnect-in-twisted-really.html to work > for me. > > No hating please, most of my testing in the past has involved hitting a > relational database, so there's already a TCP connection flying around, > one more won't make any difference. > > jml's example, exactly as-is on that page, hangs around 30-40% of the > time when running on my macOS laptop. From changing the teardown to look > like this: > > def tearDown(self): > ds = defer.maybeDeferred(self.serverPort.stopListening) > dc = defer.maybeDeferred(self.clientConnection.disconnect) > print() > > ds.addCallback(lambda _: print('serverPort.stopListening')) > dc.addCallback(lambda _: > print('self.clientConnection.disconnect')) > self.clientDisconnected.addCallback(lambda _: > print('self.clientDisconnected')) > self.serverDisconnected.addCallback(lambda _: > print('self.serverDisconnected')) > self.serverDisconnected.addErrback(lambda _: > print('self.serverDisconnected:', _)) > return defer.gatherResults([ds, dc, self.clientDisconnected, > self.serverDisconnected]) > > ...it appears that it's the serverDisconnected deferred that's failing > to fire. I can't reproduce this on Linux as of yet, so I'm guessing this > is a difference between the SelectReactor used on macOS and the > EPollReactor used on Linux. > > What's the best way to go about debugging a non-firing deferred like this? > Track it backwards towards the earliest/lowest possible source of the event. You've already started this: you noticed that the result of `gatherResults` doesn't fire and you investigate somehow and learned that this is because `serverDisconnected` didn't fire. Now keep going. Why didn't `serverDisconnected` fire? It looks like it should be fired by `ServerProtocol.connectionLost`. Does that method ever get called? If so, you've now identified the break in the chain and you just have to figure out why `connectionLost` doesn't manage to make `serverDisconnected` fire. If not, keep going. What code calls `ServerProtocol.connectionLost` - does that run, etc. Repeat until you find the break. > > Anyone know what this might be? > I know that macOS often delivers events in a different order compared to Linux. This has sometimes caused problems, particularly in the test suite. I can't quite see how that would explain this behavior though so maybe it's something else. It might be useful to share your version of Python, Twisted, macOS, and the reactor you're using, in case anyone wants to try to replicate. Jean-Paul > > cheers, > > Chris > > _______________________________________________ > Twisted-Python mailing list > Twisted-Python@twistedmatrix.com > https://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python >
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