On 28/09/2010 15:21, exarkun@twistedmatrix.com wrote:
But, more crucially, the looping call then appears to stop.
The function you're looping over returns a Deferred that never fires. The LoopingCall isn't stopped, it's waiting for the Deferred.
So, inlineCallbacks/generator things will only process errbacks, not actual exceptions raised inside asyncronous code called from them?!
What can I do to get the exception logged and then everything handled sanely such that the looping call can continue and my lopp function will keep getting called once every second rather than stopping?
When you do reactor.callLater(n, f), you put f into an execution context where the only thing that will happen to exceptions it raises is that they will be logged.
Okay, the script was a simplification of the "real problem" to try and give the list a "smallest failing example to try and help with". The real logging looks like this: 2010-09-27 15:30:16,340 ERROR : log (24331|7f2e47b4d6e0): Unhandled exception sending schedule transmission Traceback (most recent call last): File "Twisted-8.2.0-py2.5-linux-x86_64.egg/twisted/python/context.py", line 37, in callWithContext return func(*args,**kw) File "Twisted-8.2.0-py2.5-linux-x86_64.egg/twisted/internet/selectreactor.py", line 146, in _doReadOrWrite why = getattr(selectable, method)() File "Twisted-8.2.0-py2.5-linux-x86_64.egg/twisted/internet/tcp.py", line 631, in doConnect self.failIfNotConnected(error.getConnectError((err, strerror(err)))) File "Twisted-8.2.0-py2.5-linux-x86_64.egg/twisted/internet/tcp.py", line 588, in failIfNotConnected del self.connector --- <exception caught here> --- File "ourcode.py", line 180, in checkSchedule yield self.sendTransmissions(...) exceptions.GeneratorExit: 2010-09-27 15:30:28,428 ERROR : log (24331|7f2e47b4d6e0): Unhandled error in Deferred: 2010-09-27 15:30:28,584 ERROR : log (24331|7f2e47b4d6e0): Unhandled Error Traceback (most recent call last): Failure: twisted.protocols.ftp.FTPError: ('Connection Failed', <twisted.python.failure.Failure <class 'twisted.internet.error.ConnectError'>>) I don't quite follow what the above is trying to tell me, other than an FTP connection failed. However, I don't understand why that results in a GeneratorExit rather than an errback of the original exception being caught by the top level handler in the loop() function (switching back to the example terminology for simplicity). I also don't understand why an unhandled deferred is being logged rather than fed back into the handler I built for it!
exception, then you have to arrange for that. You can do this by wrapping f with another function that handles the exception and sends it where you want.
Well, as far as I can tell, that's what I'm trying to do. However, the thing failing in the real world is in code I don't "own" (looks like twisted's inards...) and I'd like to be able to cater for any failure, unforseen or not (barring say a SyntaxError ;-)) and still have the loop() call keep doing its thing. How can I do that? Chris