[Twisted-Python] run queries in deffered, but not in transaction

[Pet]

On Thu, Sep 17, 2009 at 4:35 AM, Matt Perry <matt at unshift.net> wrote:
> Make sure you're using the @inlineCallbacks decorator and the yield
> statement referenced previously.  Without those you're just adding several
> callbacks to the same Deferred; with them, the function will wait until the
> Deferred fires before continuing.
>
> def logRequest(self, *arg, **kw):
>    obj = copy.deepcopy(kw['obj'])
>
>    d = self.db.runInteraction(obj.first)
>
>    d.addCallback(self.db.runInteraction, obj.second, param1, param2)
>    d.addErrback(log.err)
>
>    d.addCallback(self.db.runInteraction, obj.third)
>    d.addErrback(log.err)
>
>
> Note that "d" is the same Deferred throughout.  If you change it to:
>
> @inlineCallbacks
> def logRequest(self, *arg, **kw):
>    obj = copy.deepcopy(kw['obj'])
>
>    firstDeferred = self.db.runInteraction(obj.first)
>    yield firstDeferred
>
>   # code here won't get resumed until "firstDeferred" has a result
>   print firstDeferred.result
>
>   secondDeferred = self.db.runInteraction(obj.second)
>   yield secondDeferred
>
>   # same as above, code won't get executed until "secondDeferred" has a
> result
>
> then you'll get the behavior you're looking for.
>
> See
> http://twistedmatrix.com/documents/8.2.0/api/twisted.internet.defer.html#inlineCallbacks
> for some more information.
>

Matt and Jean-Paul,

thank you for help!

Pet

>    - Matt
>
>
>
> On Wed, Sep 16, 2009 at 12:18 PM, Pet <petshmidt at googlemail.com> wrote:
>>
>> On Tue, Sep 15, 2009 at 6:21 PM, Pet <petshmidt at googlemail.com> wrote:
>> > On Tue, Sep 15, 2009 at 5:19 PM, Mark Visser <markv at lumierevfx.com>
>> > wrote:
>> >> exarkun at twistedmatrix.com wrote:
>> >>> On 10:37 am, petshmidt at googlemail.com wrote:
>> >>>>
>> >>>> I'd like to run several queries in background, some of them may fail.
>> >>>>
>> >>>
>> >>> If you have a function along the lines of this one:
>> >>>
>> >>>     def someInteractions(db):
>> >>>         interactions = [
>> >>>             db.runInteraction(one),
>> >>>             db.runInteraction(two),
>> >>>             db.runInteraction(three)]
>> >>>
>> >>> Then a failure in one shouldn't affect two or three; likewise for any
>> >>> other failure or combination of failures.  They are naturally (ugh,
>> >>> not
>> >>> a good word, but I can't think of a better one) independent.  You have
>> >>> to go out of your way to associate them somehow.
>> >>>
>> >> I think he might mean he wants them to run sequentially, even if one
>> >> fails.
>> >>
>> >> You can do that explicitly via @inlineCallbacks like this:
>> >>
>> >> @inlineCallbacks
>> >> def someInteractions(db):
>> >>    try:
>> >>        yield db.runInteraction(one)
>> >>    except:
>> >>       pass
>> >>
>> >>    try:
>> >>        yield db.runInteraction(two)
>> >>    except:
>> >>       pass
>> >>
>> >>    try:
>> >>        yield db.runInteraction(three)
>> >>    except:
>> >>       pass
>> >>
>> >> Or with callback/errbacks, like this:
>> >>
>> >> def someInteractions(db)
>> >>        d = db.runInteraction(one).addBoth(db.runInteraction,
>> >> two).addBoth(db.runInteraction, three)
>> >
>>
>> Hi,
>>
>>
>> I've tried to do following:
>>
>> def logRequest(self, *arg, **kw):
>>    obj = copy.deepcopy(kw['obj'])
>>
>>    d = self.db.runInteraction(obj.first)
>>
>>    d.addCallback(self.db.runInteraction, obj.second, param1, param2)
>>    d.addErrback(log.err)
>>
>>    d.addCallback(self.db.runInteraction, obj.third)
>>    d.addErrback(log.err)
>>
>>
>> unfortunately it doesn't work in that way, because I suppose, obj is
>> destroyed if second or third interaction starts.
>> Is there a way to solve this?
>>
>> Thanks, Pet
>>
>> > Hi Mark!
>> >
>> > Yes, I'd like run them sequentially, it was not clear for me, how to
>> > do it in one deferred.
>> >
>> > I will try your suggestions out.
>> >
>> > Thanks for help!
>> >
>> > Pet
>> >
>> >>
>> >> addBoth is a convenience method that adds the same function as a
>> >> callback and an errback:
>> >>
>> >>
>> >> http://twistedmatrix.com/documents/8.2.0/api/twisted.internet.defer.Deferred.html#addBoth
>> >>
>> >> --
>> >> Mark Visser, Software Director
>> >> Lumière VFX
>> >> Email: markv at lumierevfx.com
>> >> Phone: +1-514-316-1080 x3030
>> >>
>> >>
>> >> _______________________________________________
>> >> Twisted-Python mailing list
>> >> Twisted-Python at twistedmatrix.com
>> >> http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
>> >>
>> >
>>
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