Mailman 3 April 2004 - Twisted

Re: [Twisted-Python] why deferred.setTimeout is not my favorite API method
by exarkun＠divmod.com April 18, 2004

April 18, 2004

On Sun, 18 Apr 2004 10:25:34 +1000, Andrew Bennetts <andrew-twisted(a)puzzling.org> wrote: > > [snip] > > I don't see why allowing users of Deferreds to just say > "d.setTimeout(5)" is a bad thing? > > [snip] I tend to prefer "foo(x, y, timeout=z)" over "foo(x, y).setTimeout(z)". As both require explicit support from the implementor of "foo" (as you correctly note is the only way .setTimeout() can actually work), it seems unnecessary to special-case this form of … [View More]

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Re: [Twisted-Python] why deferred.setTimeout is not my favorite API method
by exarkun＠divmod.com April 17, 2004

April 17, 2004

On Sat, 17 Apr 2004 18:22:50 -0400, Jonathan Simms <slyphon(a)twistedmatrix.com> wrote: > > [snip] > > ------------------------------------------------------ > > d = iReturnADeferred() > > def onTimeout(): > handleTimeoutCondition() > > delayedCall = reactor.callLater(timeoutLen, onTimeout) > > def success(value): > handleSuccess() > > def nonTimeoutFailure(reason): > handleErrorCondition() > > def cancelTimeout(… [View More]val): > if delayedCall.active(): > delayedCall.cancel() return val > > d.addBoth(cancelTimeout) > d.addCallback(success) > d.addErrback(nonTimeoutFailure) > > ------------------------------------------------------- While I think the above is very close to being correct (it even fooled me into thinking it was correct for several minutes, during which I composed an alternate email expounding on how we might simplify users' lives by extracting the common portions of the above into a helper function), ultimately even it does not solve all the issues relating to timing out Deferreds. The problem is simply that "onTimeout" in the above code cannot be correctly defined by anyone except the person who defined "iReturnADeferred". The above pattern may be useful for framework implementors, but not users. Framework implementors typically (though not always) understand how to handle timeout issues, so this is of little help. I think that users asking for help with setTimeout or with timing out Deferreds need to be handled in one of two ways: 1) Direct them to APIs related to the features they wish to use with timeouts that already support timeouts directly (ie, not through setTimeout calls on the Deferreds they return). Examples of such APIs include twisted.web.client.getPage and twisted.names.client.lookupAddress. 2) If APIs for the feature they wish to use do not support timeouts, explain this. Recommend that the user submit a patch or open an issue on the bug tracker, and/or apologize to them that Twisted is not yet perfect in every respect. > [snip] > > It makes no sense to leave a sharp, pointy thing lying around for users > to hurt themselves with, and to constantly tell them "DON'T USE THAT". > I think that deprecating setTimeout is a good thing, even if several years must pass before we can actually remove it. In addition to the reasons Jonathan gave, I will add this: setTimeout() is the only part of Deferreds that tie them to twisted.internet. If it is removed, defer.py could (other issues, such as backwards compatibility and user consternation aside) be moved to the twisted.python package. It also makes it that much easier to use Deferreds with a non-Twisted reactor. Jp [View Less]

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[Twisted-Python] On splitting Twisted into subprojects
by Mary Gardiner April 17, 2004

April 17, 2004

Note: Cross-posted to twisted-web and twisted-python. Decide between them for your follow-ups please :) This is intended to spark a little more discussion on splitting Twisted into subprojects, as discussed on Aussie-time on IRC (Jerub, jml, spiv and myself). It seems like the twisted-web project are planning to split off fairly soon: see http://twistedmatrix.com/pipermail/twisted-web/2004-April/000312.html It's pretty likely that this split will go ahead without any kind of imposed-… [View More]

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[Twisted-Python] Minor question wrt threading pools
by Mike C. Fletcher April 17, 2004

April 17, 2004

I'm sitting down to move more of our application into Twisted and have come across a minor question that I'm thinking would be a good addition to the threading howto. In particular, starting a thread-pool seems to start the threads as non-daemon threads, so that on completion of the main reactor loop the threads are still hanging around (AFAICS, anyway, the app sits hung waiting for the background threads to complete). It would be useful to know: * How to start threads in the … [View More]

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Re: [Twisted-Python] pb: async call in remote method
by Brian Warner April 16, 2004

April 16, 2004

> def remote_getValue(self, someParam) > result = processAsyncRequest(someParam) > return notYetReceivedResult > > Is it possible to somehow defer (funny heh) the response that > remote_getValue should send back to the client until the result from > processAsyncRequest arrives? Yes, and in fact a Deferred is precisely what you use to do it. When a remote_* method returns a Deferred, the PB internals know they should add a callback to it, and they will refrain … [View More]

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[Twisted-Python] pb: async call in remote method
by Sorin C. April 16, 2004

April 16, 2004

Hi all, I have a client and server that talk to each other through pb. The situation is the following: The client calls a remote method: """ d = obj.callRemote('getValue', someParam) d.addCallback(self.gotValue) """ On the server side: """ class PbValue(pb.Referenceable): def remote_getValue(self, someParam) result = processAsyncRequest(someParam) return notYetReceivedResult """ The problem is that processAsyncRequest is asynchronous, sends a request to another server (not Python) … [View More]

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Re: [Twisted-Python] New user, help needed with raw UDP packets
by exarkun＠divmod.com April 16, 2004

April 16, 2004

On Fri, 16 Apr 2004 09:34:49 -0400, Itamar Shtull-Trauring <itamar(a)itamarst.org> wrote: >On Fri, 2004-04-16 at 03:00, Richard Taylor wrote: > > > I have been looking at how to subclass usp.Port to get what I want but I have > > come up against a problem that looks like a show stopper to me. It does not > > look like Python's socket library supports SOCK_RAW. I may be mistaken, but I > > think that I need to put the socket into RAW mode to get the … [View More]

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[Twisted-Python] running local process to share serial port to many tcp clients
by Denis Barmenkov April 16, 2004

April 16, 2004

Hello! Is there some example/tutorial, how top create twisted application for sharing unique resource? I have some hardware module, which connects to Linux computer via serial port. Simple protocol also exists: after writing some data to device, it think ;), then returns response. And my question is: how can I write separate process, which acts as serial_device proxy? And how to implement interaction between twisted.internet.protocol.Protocol's descendants and this device-sharing … [View More]

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[Twisted-Python] explanation of the chatserver.py example
by George Patterson April 16, 2004

April 16, 2004

I have trying to write a chat server that will selectively send out messages to some clients. Anyway, looking around for a framework to start from and learn more about Python and other modules I stumbled upon chatserver.py twisted.sourceforge.net But I can't find what some of the aspects the MyChat class does. From: http://twisted.sourceforge.net/TwistedDocs-1.2.0/examples/chatserver.py class MyChat(basic.LineReceiver): def connectionMade(self): print "Got new client!" … [View More]

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[Twisted-Python] Re: [Twisted-commits] r10475 - Use writeSequence instead of silly for-loop.
by exarkun＠divmod.com April 15, 2004

April 15, 2004

On Thu, 15 Apr 2004 13:27:56 -0400, James Y Knight <foom(a)fuhm.net> wrote: > > On Apr 5, 2004, at 10:36 AM, Andrew Bennetts wrote: > > > This is of course quite silly, and I suspect a nice performance > enhancement could be achieved by making FileDescriptor.dataBuffer be a > list of strings, rather than a single string. That would both cause > multiple writes in a row to not allocate new strings, and allow > writeSequence to be implemented sanely. Been … [View More]

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