Re: [Twisted-Python] The Real Error (tm) [was Re: how to write a safe catch-all]

Oct. 1, 2010


      On 30/09/2010 18:01, Phil Mayers wrote:
...
It is more than a little confusing, and I'm sure frustrating.
I've tried to produce something like this locally, but cannot.
The very first message in this thread (28th Sept, 14:48) and my email of 
30th Sept, 14:36 both had scripts attached which do exactly this..
...
Let me see if I understand the problem in full.
You have an @inlineCallbacks-decorated generator which is the target of
a LoopingCall, like so:
@inlineCallbacks
def loop():
    try:
      somework()
    except:
      log.err()
lc = task.LoopingCall(loop)
Almost:

     @inlineCallbacks
     def loop(self):
         # Check for files to send on schedule
         yield self.checkSchedule()

     @inlineCallbacks
     def checkSchedule(self):
        try:
            yield somework()
        except Exception:
            log.err(None,'Unhandled exception ...')

...although I'm currently changing the loop function to be:

     def loop(self):
	self.checkSchedule()

...as this appears to give me what I want, until something proves 
otherwise...
...
You want this loop function to catch&  log all exceptions resulting from
work it initiates.
Yep, errbacks, internal twisted bugs, whatever. As long as they're 
logged by something, preferabyl the try-except above, I don't mind.
What absolutely must not cannot ever happen is for the scheduler to die ;-)
...
Your "somework" function calls, amongst other things, an
@inlineCallbacks-decorated worker function:
@inlineCallbacks
def sendTransmission(...):
    try:
      yield maybeDeferred(feed.initiateTransmission)
    except:
      ...some handling
Yep.
...
You are seeing two errors:
1. A GeneratorExit exception. This appears (if I'm reading your
logging right) to be caught by your logging?
Yep.
...
2. A ConnectionLost exception. This is not caught by your logging, and
is propagating up to the reactor, and giving "Unhandled Error"
Correct.

Re: [Twisted-Python] The Real Error (tm) [was Re: how to write a safe catch-all]

Chris Withers