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

Chris Withers chris at simplistix.co.uk
Thu Sep 30 11:10:54 EDT 2010

On 30/09/2010 15:53, Phil Mayers wrote:
>> So, I appear to be back to the case where I can either gracefully handle
>> the exception *or* gracefully handle the errback, but not both?
> It should be possible if using Twisted APIs correctly to reliably
> capture errors.
> If it is not, that is a Twisted bug (or possibly API limitation)
> However, your "test_looping.py" is not using the API correctly; the
> reactor.callLater throws away the call stack, so the error has nowhere
> to go.

Right, but that's what appears to be happening with the "real code", and 
I get the mysterious GeneratorExit...

> Since you're not using reactor.callLater in your real code, the example
> is not valid. Hopefully I'm being more clear here!

Yes, but I do feel a bit like I'm banging my head against a wall too. 
The effect is the same as the real live observed problem, only I can't 
replicate the real problem without an ftp server that only happens to 
accept active connections. I don't have one of those around, and *even* 
if I did, I want to make the scheduler bulletproof, not *just* go and 
fix the one error that has cropped up so far...



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