Mailman 3 February 2008 - Twisted

[Twisted-Python] Twisted.Web, Twisted.Web2, or something else?
by Shawn Smiley 24 Feb '08

24 Feb '08

Hi all, What is the groups opinion on which web library to use as the basis of my system? I've started the work using Twisted.Web, but would like a sanity check before I go too far down this path. The piece of a larger system that I'm working on is basically a generic communication bridge application that will allow various external systems to talk to our system. The initial release of this system is implementing a simple HTTP GET Server that allows the external systems to use a URL to either send small amounts of data to or request data from our system. Here is an example scenario: Our bridge application would be installed on an interactive kiosk. The kiosk presentation would be able to report usage data by calling a URL such as http://localhost:8000/ReportUsage?ScreenID=1234. The bridge application would receive this request, write it to a local data cache for later batch uploading to a central server. The local HTTP Server would return a simple text or XML response to the calling application to indicate success/failure of the request. Eventually we want to have a variety of interfaces that are tailored to specific types of applications. But for right now we're looking at implementing the lowest common denominator which is exchanging information via simple HTTP calls. So getting back to my original question, is Twisted.Web or Twisted.Web2 the better framework to use in this case or is there another framework than Twisted that may work better? NOTE: I'm working in Python 2.5 and Twisted 2.5 if that makes any difference. Primary development is being done on Linux but with the goal of being able to run on Linux, Windows, or Mac. Thanks in advance for your suggestions and comments. -Shawn ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs

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[Twisted-Python] Weekly Bug Summary
by exarkun＠twistedmatrix.com 24 Feb '08

24 Feb '08

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[Twisted-Python] How to make a secure connection between two computers
by Noam Raphael 22 Feb '08

22 Feb '08

Hello, I want to do a pretty simple thing (I think): I have two computers A and B. I want A to connect to B, where both A verifies that it connected to B and B verifies that it was connected from A. The connection should be encrypted. I assume it can be done by SSL and twisted. I tried quite a bit, but it's too confusing. Perhaps someone can give me a tip? (Some openssl commands to create the needed key/certificate files, and an echoserver and echoclient programs would be really great.) Thanks a lot, Noam

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Re: InlineCallback Friendly ? Re: [Twisted-Python] Question
by Andrew Francis 21 Feb '08

21 Feb '08

Hi Jean-Paul: >Depending on the value returned by a method is an API >decision made by whoever implemented the protocol. ... >The only kind of dispatcher which is really hostile >towards inlineCallbacks is the kind which is hostile >towards Deferreds in general - ie, one which requires >a return value and does not support Deferreds. This is extremely *helpful*. From reading the "Evolution of Finger" paper, I am realising that Deferreds are also used in ServerProtocols (this makes sense). >Not really. It's just an API. Unless the return >value isn't allowed to be a Deferred, there's little >difference between using the return >value and ignoring it. ... >The reactor doesn't care. This is all pyAMF stuff. >pyAMF accepts Deferreds (again, near as I can tell) >and treats their eventual result as the response to >the request, sending it off in whatever >way is appropriate for AMF. I notice that I am using an old version of pyAMF. When I tried callbacks, a string representation of the Deferred was sent back to my client. Looking at the latest version (I can't install and use it right now), I see lines like "A Twisted Friendly implement" version and __call__ returns a deferred. Once again Jean-Paul, I find your explanation super helpful and save me time going down the wrong path. Cheers, Andrew ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs

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[Twisted-Python] Question about writing a server that accepts multiple clients with independent processing
by Gabriel Rossetti 21 Feb '08

21 Feb '08

Hello, I am new to Twisted and I'm trying to write a server that accepts multiple client connections and processes them separately. I *think* this is done with a protocol instance per client connection, but I may be 100% wrong. I don't really understand how to do this with twisted. In a threaded server I would : 1) wait for a client connection 2) create a thread and hand it the client connection then the server waits again for the next client connection, the thread executes the protocol, e.g. dialogs with the client until disconnection. I have done this so far using Twisted : 1) created a protocol (the one that would be executed in a separate thread in the example above) 2) created a factory and listen for incoming connections. This works great if I have one connection, but I need multiple connections being processed in parallel (simulated parallelism I guess) Could someone please explain how Twisted works for this or point me to some documentation explaining this? I have searched the docs on the twisted website and google, but I can't find anything explaining this. Thank you, Gabriel

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[Twisted-Python] Help using XmlStreamFactory & XmlStream
by Gabriel Rossetti 21 Feb '08

21 Feb '08

Hello, I am trying to write a Server and Client that use an XML protocol. I saw that there is a XmlStream class and tried to use it, but was unable to. I saw one small example for a client (http://ralphm.net/blog/2005/10), but it raises some questions. First of all, it seams to work compleatly differently that the other server/client examples. I don't understand why there is a need to add observers, and what they are used for. I can't get any of these to work (on either side, client or server): def connectionMade(self): print 'Connected!' def dataReceived(self, data): print data def onDocumentStart(self, rootElement): print "Message start : ", rootElement def onElement(self, element): print "current element : ", element def onDocumentEnd(self, rootElement): print "Message end : ", rootElement I'm kind of lost :-( I'm new to Twisted and I though that I understood how it works (read howtos, turorials, etc, but this one doesn't seam like the others. Can someone please point me to an example, I searched google but no luck. All I need is a simple client-server xml echo example or a better understanding of how it works and how it differs from the other echo examples. Thank you, Gabriel Thank you

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[Twisted-Python] How to say "reverted". (was Re: [Twisted-commits] r22628 - Revert r22624: regression in test_conch.)
by Jonathan Lange 21 Feb '08

21 Feb '08

On Wed, Feb 20, 2008 at 8:41 PM, Thomas Herve <therve(a)wolfwood.twistedmatrix.com> wrote: > Author: therve > Date: Wed Feb 20 02:41:55 2008 > New Revision: 22628 > > Removed: > trunk/twisted/conch/test/test_transport.py > Modified: > trunk/twisted/conch/manhole_ssh.py > trunk/twisted/conch/ssh/factory.py > trunk/twisted/conch/ssh/service.py > trunk/twisted/conch/ssh/transport.py > trunk/twisted/conch/ssh/userauth.py > trunk/twisted/conch/test/test_conch.py > trunk/twisted/conch/test/test_ssh.py > > Log: > Revert r22624: regression in test_conch. > > Refs #2678 Hello all, Thanks to Thomas for being alert enough to spot this regression and energetic enough to revert it. I'm very glad that we have people[1] monitoring the test suite making sure that we can trust trunk. However, I have two suggestions on how we can announce trunk reverts better. I'm not picking on him in particular, this is just the first revert for which I am detached enough to comment sensibly. 1. When reverting a commit to trunk, the commit message should explain what the regression is. The word 'regression' is used sometimes to mean 'test suite failure' and other times to mean 'a feature that I liked works differently now' or 'this is slower than it was'. If it's a test failure, it's useful to know what test, and particularly whether or not the test was related to the change. If it's not a test failure, it's good to know why the "regression" is considered severe enough to back out the change, rather than just fixing it in place. 2. Reverting someone's contribution is bad news for them. We should break the bad news gently. Backing out someone's changes can often send an unintended message of blame, when we actually want to be encouraging people to contribute. "Revert <revno>: regression in <file>." is terse, unspecific and leaves too much unsaid. We can't do anything about the bad news, but we can change the way we break it. Being more specific helps a lot, as does describing what happens next (e.g. "I'll fix it up and land it for you", "Can you please investigate the failure and fix the test, I'll review the fix for you as soon as it's ready.") jml [1] I'll be even happier when we have *machines* monitoring the test suite, but that's another email.

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[Twisted-Python] Question about Using Deferreds in ServerProtocol request Handler
by Andrew Francis 21 Feb '08

21 Feb '08

Hi Folks: Much of what I do with Stackless involves making calls from server requests that in turn, make Twisted calls that return a deferred. i.e., class MyRequestHandler(http.Request): """ let us create a tasklet to do work in the request handler and allow the Reactor to continue """ def process(self): t = stackless.tasklet(self.doWork)() def doWork(self): message = MyRequestHandler.processor.getPage("") self.write(message) self.finish() return I have been able to do the same thing with an inlineCallback class MyRequestHandler(http.Request): @defer.inlineCallbacks def process(self): try: result = yield client.getPage("http://www.google.com") except Exception, err: log.err(err, "process getPage call failed") else: self.setHeader('Content-Type', 'text/html') self.write(result) self.finish() (although this works, the technique is not general for all protocols) However, how is this done with just deferreds and callbacks without Stackless or inlineCallbacks? Cheers, Andrew ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

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InlineCallback Friendly ? Re: [Twisted-Python] Question about Using in ServerProtocol request Handler
by Andrew Francis 20 Feb '08

20 Feb '08

Hi Jean-Paul: >However, how is this done with just deferreds and >callbacks without Stackless or inlineCallbacks? Thanks for the response. And thanks for the explanation of inlineCallbacks. Annotating your example, I get the following: def process(self): def callback(result): print "second" self.setHeader('Content-Type', 'text/html') self.write(result) self.finish() def errback(err): err.trap(Exception) log.err(err, "process getPage call failed") try: d = client.getPage("http://www.google.com") except Exception: d = failure.Failure() d.addCallbacks(callback, errback) print "first" running this I get what I expected "first" "second" This example I can follow. The server protocol handler terminates. The callback eventually fires. Since the callback has a reference to the request, it can write back the response. Bear with me, I am just starting to read up on protocols... What I am unclear on, is why some Server Protocols depend on 'return' and others don't (I assume with HTTP, you can stream a response). What is the right way to design a ServerProtocol? Is there an 'inclineCallback' friendly protocol Unless I am fundamentally missing something it seems that there are advantages to designing a Server Protocol not to depend on 'return' As I alluded to in other posts, I get confused over this variation. This is pyAMF class pyAMFTest(TwistedGateway): def __init__(self): super(TubeTest, self).__init__() return def echo(self, x): print x return x pretend I wish to do a callRemote(...) def echo(self, x): def callback(result): print "second" """ How do I return x? """ def errback(err): err.trap(Exception) log.err(err, "process getPage call failed") try: proxy = .... d = proxy.callRemote(...) except Exception: d = failure.Failure() d.addCallbacks(callback, errback) print "first" In this case, how is 'x' transmitted back to the reactor and the client? What is the proper way of structuring this code. By the way, the inlineCallback and the Stackless versions also have problems handling this. This is starting to stimulate my interest in writing a Stackless solution that handles this case.... Cheers, Andrew ____________________________________________________________________________________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping

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Silly Error [Twisted-Python] Question about Twistd and PYTHONPATH
by Andrew Francis 20 Feb '08

20 Feb '08

Hi Matthew: >I guess your Reporter class is in another module. >I ran into the same situation a few days ago and >finally made it work > like >this: >import sys >sys.path.append('.') Thanks for the response. My error seemed to be much sillier - somehow the top level __init__.py was missing! Arrrgh.... Cheers, Andrew ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs

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