[Twisted-web] Error output for bad deferred method signatures?

Tommi Virtanen tv at twistedmatrix.com
Fri Dec 2 01:11:18 MST 2005

Lenny G Arbage wrote:
> I'm wondering though, if there is a way to do this
> globally without specifying another errBack for every
> deferred I call (which, right now numbers about 60 in
> my little app)?  This would be useful for debugging
> only, of course -- but that's where I'd like to save
> the several hours trying to figure out why my
> callbacks weren't firing for the next time I forget to
> check that all err/callbacks have the correct
> signatures.

There already is a global debug output if nothing handled
the error (last errback run should return e.g. None).
The traceback is dumped to the log. But it is only run
when the Deferred is garbace collected, so if something
that has infinite lifetime holds a reference to it, it
won't be triggered until shutdown. There's no way to do
this globally earlier, because you don't know whether
a new errback will be added later..

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