[Twisted-Python] deferreds and hung connections
exarkun at divmod.com
Wed Mar 9 13:34:28 EST 2005
On Wed, 9 Mar 2005 09:28:49 -0800 (PST), Lenny G Arbage <alengarbage at yahoo.com> wrote:
>Suppose I am using twisted.web.client.getPage() to
> retrieve webpages. I am setting a callback and an
> errback for the result, and this all works
> But what about the case where the webserver simply
> hangs with the connection open, never returning with
> either a result or an error?
> I assume that my errback will get called if the socket
> times out and closes (right?). But what if I don't
> want to wait that long -- what if I want to do my own
> timeout after N seconds/minutes?
> I've been looking for examples of how to do this, and
> monkeying with reactor.callLater() with partial
> success. If I save the id from callLater(), I can
> cancel the timeout in callback() or errback().
> However, if the timeout does get fired, I get:
> [Failure instance: Traceback:
> twisted.internet.error.AlreadyCalled, Tried to cancel
> an already-called event.
> Am I going about this the wrong way? Perhaps twisted
> has some built-ins that I'm not aware of to do
> essentially the same thing?
> I have a modified example from the Defer Howto that
> exhibits this behavior. I can post if the above
> explanation isn't enough.
As was recently mentioned on the list, timeout support needs
to be part of the result-generating API. Luckily, in the case
of getPage, it is, as demonstrated by this manhole session:
>>> from twisted.web import client
>>> client.getPage('http://google.com', timeout=0.001)
Deferred #0 failed: 'Getting http://google.com took longer than 0.001
More information about the Twisted-Python