Message: 1
Date: Thu, 17 May 2012 00:58:57 +0200
From: Louis <[email protected]>
Subject: [Twisted-Python] Synchronous calls using Twisted?
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
> Hello,
> I am writing an application, which architecture is (I hope my
>beautiful drawing is not messed up):
> +-------------+ +------------+ +-----------+
> | Core Server |---| Web Server |---| Web client|
> +-------------+ +------------+ +-----------+
>...
> Do you think Twisted is the right tool for my use case, or am I doing
>an ugly hack to do what I want, which means I should rather use another
>tool?
I am not sure why inline generators won't work?
Over the years, I use Stackless Python with Twisted. I use Twisted for many of
the reasons you describe. For myself there is another dimension: I find that a
lot of the code I write are orchestrations - that is in order to compute
something, I have to make a few network calls sequentially.
I use a technique that Christopher Armstrong (what happened to him?) called a
blockOn. For the sake of being academic (roll your eyes here), this is an
example of an obscure design pattern called "Half-sync/Half-async."
Essentially one does the following:
def blockOn(deferred):
ch = stackless.channel()
def cb(result):
ch.send(result)
deferred.addBoth(cb)
return ch.receive()
Of course, there is a bit more, like the Twisted reactor is running in its own
tasklet. But this has the effect of nicely allowing one to use Twisted in a
synchronous fashion. If you don't feel like installing Stackless Python, then
you can use stackless.py (not the new version that uses continuations) with the
greenlet package.
Here is a link to a complete example
http://andrewfr.wordpress.com/2011/11/30/the-santa-claus-problem-with-join-patterns/
Cheers,
Andrew
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