[Twisted-Python] dumb question on qt4reactor

[Kevin Horn]

It might be, but I can't think of a reason off hand why it ever _should_
be.  I can kind of see how it might work, but if your "async" process ever
takes longer than your callLater delay it will break, and probably quite
horribly.


On Wed, Jul 9, 2014 at 12:11 PM, Kevin Mcintyre <kebin70 at gmail.com> wrote:

> Another "Oh right" twisted moment.  callInThread instead of callLater?
>
> This is a case where I've been laying tracks for 2 years without totally
> understanding the train that was eventually coming down the tracks.  I
> guess I implicitly understood by wanting to move to a separate reactor as a
> separate thread, and in the past when I've used callLater it's encapsulated
> non-blocking code.
>
> In this sense is callLater ever utilized as a pseudo asynchronous method?
>
>
>
> On Sat, Jul 5, 2014 at 5:24 PM, <exarkun at twistedmatrix.com> wrote:
>
>> On 5 Jul, 08:35 pm, kebin70 at gmail.com wrote:
>>
>>> calling reactor.callLater within qt4reactor in an attempt to async non
>>> webkit work but not seeing expected behavior.  Webkit locks while the
>>> callLater function executes.
>>>
>>
>> `callLater` does not make a blocking function into a non-blocking one. It
>> just calls a function after a specified delay.  If the function blocks,
>> then the reactor will block when it gets around to calling it.
>>
>> If you need to call blocking APIs you may need to call them in a separate
>> thread (Twisted includes a threadpool that can help you with this) or a
>> separate process (Twisted has some APIs for launching and interacting with
>> other processes, too).  Of course, the ideal solution is often to find a
>> non-blocking equivalent to the blocking API and use that instead (for
>> example, I know that txaws is a project that exists - perhaps it can do the
>> things to S3 that you want to do).
>>
>> Jean-Paul
>>
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>
>
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-- 
--
Kevin Horn
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