I've been hunting down a problem that I've finally found the cause of and I'd like to know what's the Twisted way to catch this "error within the code handling the error" type of error.
Basically, in one branch of the errBack, there was a typo. A simple typo that caused an unhandled NameError exception, but only once in a few thousand runs. The exception got caught and "displayed" by Twisted, but it wasn't going anyplace anyone was looking (buried under zillions of lines of logging) and the app continues on as if nothing went wrong. I've put up a simple app that demonstrates the issue: http://pastebin.com/m59217f60 If you put in a 404 error URL, let it run through, you'll see the 404 error printed out, the exception will occur in the background, and the program just keeps on going. If you then hit Ctrl-C, you can see the traceback showing that Twisted caught the NameError . What is the best way to handle programming errors like this in deferreds so they don't slip by, unnoticed? Thanks, S (~/twisted_err)# ./errs_away.py URL: http://www.yahoo.com line = http://www.yahoo.com Got data, len == 9490 URL: http://thereisnodomainnamedthis.com line = http://thereisnodomainnamedthis.com Error: DNS lookup failed: address 'thereisnodomainnamedthis.com' not found: [Errno 8] nodename nor servname provided, or not known. URL: http://www.yahoo.com/non-existent-page line = http://www.yahoo.com/non-existent-page Error: 400 Bad Request <====== This triggers the code with the bad variable URL: ^C <============= manually stop the program ============= Then, you get to see the traceback ================== Unhandled error in Deferred: Traceback (most recent call last): File "/System/Library/Frameworks/Python.framework/Versions/2.6/ Extras/lib/python/twisted/web/client.py", line 143, in handleResponse self.status, self.message, response))) File "/System/Library/Frameworks/Python.framework/Versions/2.6/ Extras/lib/python/twisted/web/client.py", line 309, in noPage self.deferred.errback(reason) File "/System/Library/Frameworks/Python.framework/Versions/2.6/ Extras/lib/python/twisted/internet/defer.py", line 269, in errback self._startRunCallbacks(fail) File "/System/Library/Frameworks/Python.framework/Versions/2.6/ Extras/lib/python/twisted/internet/defer.py", line 312, in _startRunCallbacks self._runCallbacks() --- <exception caught here> --- File "/System/Library/Frameworks/Python.framework/Versions/2.6/ Extras/lib/python/twisted/internet/defer.py", line 328, in _runCallbacks self.result = callback(self.result, *args, **kw) File "./errs_away.py", line 15, in printError print oops # variable's not defined... exceptions.NameError: global name 'oops' is not defined Thanks, S _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
