[Twisted-Python] Dealing with an intermittent PB server

Phil Mayers p.mayers at imperial.ac.uk
Thu Feb 17 18:24:19 EST 2005

On Thu, Feb 17, 2005 at 11:31:24AM -0800, Dave Cook wrote:
>On Thu, 17 Feb 2005 01:05:22 +0000, Phil Mayers <p.mayers at imperial.ac.uk> wrote:
>>     try:
>>       self.root.callRemote('start').addCallbacks(self.start2, self.err)
>I never get this far.  In my code:
>    def data_tableList(self, ctx, data):
>        ...
>        d = self.pbClientFactory.login(creds).addCallbacks(self._cbLogin,
>        return d
>Neither _cbLogin or _ebLogin ever get called, so there's no possiblity
>of the DeadReferenceError getting called.  I guess this could be a

That's odd. Even if Nevow discarded the deferred (not sure - I don't use 
it in data/render mode, my app is 100% livepage!) the callback/errback 
should still get called by the reactor.

If I call "start" in my example with the server down, I get a Failure to 
errback with "errno 111 connection refused" (I see it in the LivePage, 
via my "alert" function)

Is there any possibility there's a firewall between the Nevow middle and 
PB backend that's making TCP RST or ICMPs not work?

>Nevow bug (I hate bugging people if it's just my misunderstanding)?  I
>think what I'll do is keep a reference to the original SSLClient
>object and check client.running before I try factory.login().

Wait, SSL? Hmm. Have you tried running over straight TCP just to see if 
there's a difference (I'm thinking error handling propagation etc. given 
the layered nature of SSL and comments seen on this list to the effect 
of the Twisted SSL implementation complexity)

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