Mailman 3 June 2011 - Twisted

[Twisted-Python] How to safely stop a chain of deferreds
by tomw 30 Jun '11

30 Jun '11

Hi, in a GUI application I'm using quite a comprehensive chain of deferreds and I'm running the mainloop from the glib2reactor. At a certain point of my application I need to terminate the entire chain of deferreds to make sure that no more data is loaded and processed. Stopping the reactor does not work as the entire GUI would terminate, too. I tried to cancel the first deferred, hoping that the cancel event will be forwarded to the next deferred in the chain or at least invoke an errback, but for some reason it does not work and the deferreds seem to run forever. Any ideas on how to solve this issue? Many thanks, -- tomw <tomw(a)ubilix.com>

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[Twisted-Python] Does twisted have plan to support python 3.x?
by gelin yan 29 Jun '11

29 Jun '11

I heard that Python 3.3 may support coroutine natively via yield generator. I am interested in how this thing can affect twisted development. The most compelling feature of twisted for me is to support a large set of protocols and the most important...it can run on windows flawlessly. Other solutions like gevent, eventlet or etc usually are unable to run on windows. Regards gelin yan

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[Twisted-Python] jQuery.Deferred - why did they have to go and change the interface?
by Richard Wall 28 Jun '11

28 Jun '11

I'm in the process of switching some of my Javascript code from MochiKit.Async.Deferred to the recently introduced jQuery.Deferred. Does anyone else hate the confusing new method names they've chosen? Why couldn't they just stick with the tried and tested interface...aargh...it really pisses me off! * http://api.jquery.com/category/deferred-object/ * http://mochi.github.com/mochikit/doc/html/MochiKit/Async.html#fn-deferred * http://bazaar.launchpad.net/~richardw/jarmon/jquery-deferred/revision/73 -RichardW.

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Re: [Twisted-Python] How to safely stop a chain of deferreds
by Terry Jones 28 Jun '11

28 Jun '11

Hi Tom > in a GUI application I'm using quite a comprehensive chain of deferreds > and I'm running the mainloop from the glib2reactor. At a certain point of > my application I need to terminate the entire chain of deferreds to make > sure that no more data is loaded and processed. Stopping the reactor does > not work as the entire GUI would terminate, too. I tried to cancel the > first deferred, hoping that the cancel event will be forwarded to the > next deferred in the chain or at least invoke an errback, but for some > reason it does not work and the deferreds seem to run forever. Any ideas > on how to solve this issue? It's a bit hard to know how to help without more detail. Code you paste some code somewhere? I'm sorry if this sounds picky, but your description is a bit vague. E.g., there's no such thing as a "chain of deferreds" (do you mean chain of callbacks on a single deferred? or a callbacks that return deferreds etc?) and e.g., "deferreds seem to run forever" but deferreds don't run at all, callbacks do. If you can make it a bit more precise I'll be happy to try to help. Terry

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[Twisted-Python] How to wait for a transport to write some data before loosing the connection
by emmanuel CAZENAVE 28 Jun '11

28 Jun '11

Hi, I wrote a server using a protocol that inherit from 'basic.LineReceiver'. In some circonstances I need to reject the data send by the client and to close the connection. Here is how I do that: class MyProtocol(basic.LineReceiver): ........ def error(self, error_msg): self.transport.write(error_msg) self.transport.loseConnection() Sometimes it works: the client gets notify of the error and the connection is closed properly. And some other times, the client does not received the error notification and the server closes the connection, which causes the client (wich is not written using twisted, but with the socket module from the standard lib) to crash with 'socket.error: (10054, 'Connection reset by peer')'. As I red somewhere in the docs or in the mailing list, self.transort.write does can return before it really writes the data. So how could I do, without using blocking code, to wait until self.transort.write effectively writes the data to avoid closing the connection with unwritten data ? Thanks you. Emmanuel

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[Twisted-Python] A resizable dispatch queue for Twisted (updated)
by Terry Jones 28 Jun '11

28 Jun '11

I've made some changes to txRDQ, and just blogged about the class: http://bit.ly/lD5zIT Summary of changes: A put on the queue now gets you a deferred. There's a new Job class that the deferred fires or errs with. The deferreds can be cancelled. Jobs can be given priorities and can be . On the admin side, the pending and underway methods return lists of job instances (which can be re-prioritized, canceled, and independently watched). Shutdown now allows you to cancel underway jobs. The code also contains a DeferredPriorityQueue which will likely be independently of interest to some, and might make its way into Twisted? Code at https://launchpad.net/txrdq Terry

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[Twisted-Python] twisted.cred implementation for LDAP, anyone?
by Ilja Livenson 27 Jun '11

27 Jun '11

Hi, I wonder if there are kind people here, who have implemented authN against LDAP backend with twisted.cred and would be ok sharing the code? Or even better - if this code could somehow make it into the core package of Twisted. thanks, Ilja

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[Twisted-Python] Deferred flow control examples
by Tristan Seligmann 27 Jun '11

27 Jun '11

When trying to help people understand how to use Deferred.add{Callback,Errback,Callbacks,Both} I've found it useful on a number of occasions to illustrate flow control with Deferreds by comparison with synchronous code. I realised there wasn't really anyway that a "complete" set of examples was collected, so I wrote this blog post: http://mithrandi.net/blog/2011/06/flow-control-with-deferreds-by-example/ I'd appreciate it if people could take a moment to review the examples (I think they're all correct, but maybe I made a mistake somewhere), suggest any important examples I missed, and let me know if they find this approach generally useful. -- mithrandi, i Ainil en-Balandor, a faer Ambar

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[Twisted-Python] Weekly Bug Summary
by exarkun＠twistedmatrix.com 26 Jun '11

26 Jun '11

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[Twisted-Python] New Twisted Tutorial
by Orestis Markou 25 Jun '11

25 Jun '11

Hello, I've started porting my training slides into a written tutorial, making changes along the way based on the audience reactions. You can find it here: https://github.com/orestis/twisted-tutorial It's missing a couple of chapters like errbacks or examples on how to use threads for CPU-intensive tasks, but it's already 6500 words long. Everyone is encouraged to comment on specific lines or fork and change stuff. It's not in any particular format, though at some points it resembles ReST. I think it'd make a great addition to the existing Twisted documentation so unless anyone objects, let's make it so. Once I get to a proper internet connection, I will upload the training slides as well (though they are not very useful on their own). Many thanks to everyone that helped, and especially to lvh and jerub who attended the training (twice!) and helped with the tricky bits. Orestis

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