On 10:57 am, facundobati...@gmail.com wrote:
Hello!
I've just subscribed to the list, but I'm using Twisted from a while
ago.
I need to do something, and wasn't able to find out how to do it.
Well, I
*did* find out, but it's a horrible hack, and actually depends on
something
that may be a bug, so it's worth asking here about this :)
In a project I'm doing [0], I want to catch all problems (unhandled
exceptions), log them and show them in stderr after a bit massaging.
My
first approach was to hook me in sys.excepthook, and it worked on some
cases. But I saw some cases where it didn't [1].
Right. Instead of letting any exception from application code abort the
process entirely, most places in Twisted catch and log unexpected
exceptions.
Specifically, when the exception was inside a deferred, it didn't call
excepthook.
Another case where this will happen is if a protocol's dataReceived
method raises an exception. Or if a function passed to
reactor.callLater raises an exception.
Why not? I started to check the code, and found the following
snippet, at the end of Deferred._run_callbacks, in defer.py:
if isinstance(self.result, failure.Failure):
self.result.cleanFailure()
if self._debugInfo is None:
self._debugInfo = DebugInfo()
self._debugInfo.failResult = self.result
From this, I have two questions:
1. The rest of the code only instantiates and uses DebugInfo
"if self.debug". Why this part of the code doesn't care about the
self.debug flag and always uses it? Is it intended and DebugInfo()
not being used for debug is a misname left there for historical
reasons? Should I open a bug about this?
It's correct as is. DebugInfo is used for a few things. Tracking
unhandled errors is one of them, and it is always enabled, whether
"Deferred debugging" is on or not.
2. I did the following (ugly) hack to achieve my results:
import twisted.internet.defer
# ugliest thing I saw in a *long* time
class MyDebugInfo(object):
def _error_happened(self, failure):
msg = failure.getTraceback()
_expose_exception(msg)
failResult = property(fset=_error_happened)
twisted.internet.defer.DebugInfo = MyDebugInfo
Is there a better way to do this? Actually, this is working
correctly,
but I don't know if it's the right way to do it, and don't want to
depend of DebugInfo() being called always in this case.
You should add a log observer that watches for errors.
http://twistedmatrix.com/documents/9.0.0/core/howto/logging.html
Jean-Paul
Thank you very much!
[0] http://launchpad.net/magicicada
[1] http://bugs.launchpad.net/magicicada/+bug/665681
--
.� � Facundo
Blog: http://www.taniquetil.com.ar/plog/
PyAr: http://www.python.org/ar/
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