[Twisted-Python] serializing inline callbacks

[Axel Rau]

Am 18.02.2014 um 20:03 schrieb Dustin J. Mitchell <dustin at v.igoro.us>:

> I'm suggesting that there are lots more problems with your code than
> the one you have identified.  Any method which is decorated with
Sure. This is my 1st project with twisted. (-;

> @defer.inlineCallbacks will return a Deferred,
This is the missing clue.

>  and you need to handle
> every Deferred somehow.  Generally (although not always, as lvh has
> said) you do that by yielding it.
> 
> Your code should be
I have that implemented, but B does not call C:
> 
> ----
>    def render_GET(self, request):
>        ...
>        d = self.A()
>        d.addErrback(request.processingFailed)
>        return NOT_DONE_YET
> 
>    @inlineCallbacks
>    def A(self):
>        ...
>        tmp = yield subprocess(args)
>        ...
>        yield self.B()
> 
>    @inlineCallbacks
>    def B(self):
>        ...
>        tmp = yield subprocess(args)
>        ...
>        yield self.C()
> =====================================> stops here
>    def C(self):
>        ...
>        x = yield self.D(...)
>        y = yield self.D(...)
>        z = yield self.D(...)
>        ...
>        yield self.E()
> 
>    @inlineCallbacks
>    def D(self):
>        ...
>        tmp = yield subprocess(args)
>        ...
>        returnValue(tmp)
> 
> 
>    @inlineCallbacks
>    def E(self):
>        ...
>        tmp = yield subprocess(args)
>        ...
>        request.write(...)
>        request.finished()
> 
> ----
> 
> Here you see that all of the Deferreds are handled, either by yielding
> them or, in the case of the Deferred from A, by adding an errback that
> will conveniently format an HTML error response.

This is B:
- - - -
    @inlineCallbacks
    def imageMap(self):
        """
        return client side image maps
        """
        args = list(self.basecmd)
        args.extend((
            '-g', conf.graphlist[self.station][0], '-I', '-m', '-d', '-d', '-d', '-d'))
        map = yield util.subprocess(args)
        self.request.write(bytes(map))
        yield self.navigation()
        if debug: log.msg('imageMap ended')
- - - -
and begin of C:
- - - -
    def navigation(self):
        """
        Compute links for navigation (up, left, right arrows or)
        week, month, year) and place them on the page.
        """
        if debug: log.msg('In navigation.'). . .
- - - -
I see log message ‚imageMap ended‘ , but not 'In navigation.'
Any further advice?

Thanks for your patience,
Axel
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