On Wed, Sep 26, 2012 at 7:46 PM, Jonathan Vanasco <twisted-pyt...@2xlp.com>wrote:
> while migrating some functionality to a deferred callback chain and > debugging my app, i noticed this oddity... > > if a function doesn't have the proper args/kwargs definition, no error is > raised and everything just hangs > > ... > then the reactor just seems to hang. > > if i kill the process, then the Unhandled Error and Traceback message > prints. > If i wait until the next interval that the timerservice runs, then the > Unhandled Error and Traceback message will print then ( but that could be > minutes/hours later ). > > has anyone else noticed this before ? > The reactor isn't hanging, it's running just fine. The problem is you expect the Deferred's error to be logged immediately, which is not guaranteed; the error is only logged if the object is garbage collected, which may take a while, or never happen if you've kept extra references around. The latter can happen by accident. > are there any good ways around this , other than setting the timer service > to be within seconds during bugtesting ? > 1. Add a logging errback to all Deferreds at the end of the callback chain: d.addErrback(log.err). 2. Less effective, but also helpful, is making sure you delete all unnecessary references to a Deferred once you've fired it, to make sure it gets garbage collected: self.d.callback(None) del self.d # remove extra reference that prevents garbage collection http://bit.ly/NS6ptj explains the issue. -- Itamar Turner-Trauring, Future Foundries LLC http://futurefoundries.com/ — Twisted consulting, training and support.
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