[Twisted-Python] Catching error in protocol.ReconnectingClientFactory

[Adrian Overbury]

On 26/06/2012, at 7:47 AM, Martin <martin at webscio.net> wrote:

> On 25/06/12 22:27, Adrian Overbury wrote:
>> On 25/06/2012, at 10:16 PM, Martin <martin at webscio.net> wrote:
>> 
>>> On 14/06/12 12:38, Martin wrote:
>>>> Hi, thanks for your reply.
>>>> 
>>>> Indeed, the ReconnectingClientFactory is being sent the Failure object to
>>>> 
>>>> def clientConnectionLost(self, connector, reason):
>>>>        log.msg('Lost connection. Reason: %s' % reason)
>>>> protocol.ReconnectingClientFactory.clientConnectionLost(self,
>>>> connector, reason)
>>>> 
>>>> where "reason" is the Failure object that is "unhandled". is there
>>>> anything I could do to it there to make it handled?
>>>> 
>>>> Also, the documentation in
>>>> http://twistedmatrix.com/documents/current/core/howto/defer.html says
>>>> that one can do d.addErrback(err.log) to deal with unhandled errors,
>>>> but what is d?
>>>> 
>>>> In general, I'm not doing anything special.. I'm creating a
>>>> ReconnectingClientFactory and connecting it to a server..
>>>> f = MyReconnectingClientFactory(..)
>>>> reactor.connectSSL(url, port, f, ssl.ClientContextFactory())
>>>> reactor.run()
>>>> 
>>>> Basically it. Any thoughts? Thanks a lot!
>>>>> On Jun 11, 2012, at 8:01 AM, Martin wrote:
>>>>> 
>>>>>> Hi there,
>>>>>> 
>>>>>> I've been looking around for a solution for several hours now, and
>>>>>> maybe
>>>>>> I'm just missing something..
>>>>>> 
>>>>>> I've a factory that implements protocol.ReconnectingClientFactory which
>>>>>> works just fine, however, whenever the program ends running, I get a
>>>>>> bunch of Unhandled error in Deferred messages in my log for each
>>>>>> disconnection that occurred during runtime, such as Failure:
>>>>>> twisted.internet.error.ConnectionLost: ...
>>>>>> 
>>>>>> Is there any way I could somehow "handle" these during runtime, so that
>>>>>> my log wouldn't be spammed with this at the end.. (or avoid it being
>>>>>> spammed somehow..)
>>>>> These messages are coming from some code which is issuing Deferreds,
>>>>> not from ReconnectingClientFactory.  You need to add an errback to
>>>>> those Deferreds in your application code.  There's no way to write a
>>>>> catch-all, just like there's no way to write a catch-all that can
>>>>> stop exceptions from being raised in basic Python.
>>>>> 
>>>>> I can't say more without a code example, preferably
>>>>> a<http://sscce.org/>.
>>>>> 
>>>>> -glyph
>>>>> 
>>>>> 
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>>>>> 
>>>>> 
>>> No suggestions as to how I could get rid of this? :(
>>> 
>>> 
>> I believe glyph gave you the answer to that already.  In your example above of d.addErrBack, d is the deferred object.  Each of those needs to have an errback handler attached to it.  If you don't want to see anything out of them, simply don't print anything.
>> 
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>> 
> Well, kind of - I know that I need to do addErrBack on the deferred 
> objects, I kind of knew that when I asked the original question having 
> read the documentation on deferreds. What I still don't know though is 
> how am I supposed to catch these deferreds - that is not being explained 
> anywhere in the documentation I'm afraid.
> 
> 

The page and bookmark http://twistedmatrix.com/documents/current/core/howto/defer.html#auto4 explains it pretty well.  When there's an error your errback function is called and a failure object is passed to it.  You can handle it, drop it or pass it on as you please or seem appropriate.  Hope  that helps.

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