Mailman 3 January 2009 - Twisted

[Twisted-Python] Best place to put application code
by John Aherne Jan. 14, 2009

Jan. 14, 2009

One thing that has been puzzling me is where is the best place to put application code. The case I am using is straightforward TCP server with client connections making simple requests and waiting for responses retrieved from database tables to be sent back. Reading the docs and looking at various examples provided in books and documentation has left me a bit confused. Is there a best practice for where application code should go - either the protcocol class or the factory class or somewhere … [View More]else. Does it actually matter. Is there any downside to putting application code in the protocol or factory. What pitfalls are there for either approach. I see examples where application code appears in both classes, but the examples are very small so may not be indicative of what should be done. In the docs I see reference to most of the code will be written in the protocol class, but that seems to be referring to actually writing protocols not application code. It also says that when the protocol needs to call application code to make it a method call - not to mix protocol and application code. This could just mean creating some methods in the protocol class to handle the task. However, if the application code needs to run for 10-12 seconds looking up database tables and accumulating results and waiting on deferreds, should all this code reside in the protocol class or the factory. If I keep it in the protocol, then I already have my client connection to write back to. So that seems to be the place to keep the code. If I put the code in the factory, then I need to pass the client connection so it can write back to the client. Or is there another way of doing this I have missed. . The factory seems to be the place where other classes can be passed in and the protocol can call them via self.factory. That seems to imply that application code should be put into the factory, but I can't see any way of passing back information from deferred results to the call from protocol. It's ok if it was just a simple method call that returns a result, but if the code has to run a series of deferreds then it will be the called method that will have the result and it will need a means of writing this back to the client. I don't think I can signal the protocol to say I now have the result.Of course I could easily be mistaken. So please correct. Of course if I passs the client connection to the factory, then it can use this to write back. But that means passing around the client connection. Should I avoid doing that or is that not a problem. I hope I have explained myself clearly. I'm just looking for some guidance and pointers to what is best to do or what is best to avoid. Regards John Aherne [View Less]

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[Twisted-Python] IPushProducer problem
by Gabriel Rossetti Jan. 14, 2009

Jan. 14, 2009

Hello everyone, I implemented a push-produce a while back and I though it works, but it didn't. When the msgs where spaced out, it worked, but if several msgs were sent one after the other, then things go bad (the msgs get mixed up)... I found this thread : http://www.twistedmatrix.com/pipermail/twisted-python/2007-March/014983.html and I think I ave the same problem, my code looks a bit like his : def pauseProducing(self): """ Pause the producer """ … [View More]

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[Twisted-Python] connectTCP() passing a ClientFactory: how to get the local port of the created client socket?
by Alessio Pace Jan. 13, 2009

Jan. 13, 2009

Hi, I'm having some difficulties in trying to figure out how to get a reference to the connector or anyway the local port to which a client socket is bound in a reactor.connectTCP() call, where the bindAddress is not passed as parameter, thus letting the OS pick an available port. In fact in the ClientFactory has a buildProtocol(self, addr) method, but 'addr' is the address of the remote endpoint of the client socket created.. Thanks in advance for any suggestion. Regards, Alessio Pace.

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[Twisted-Python] Manhole and StandardIO
by Zoran Bosnjak Jan. 13, 2009

Jan. 13, 2009

Hello all, I would like to have a simple console python interactive shell, powered by twisted. I am looking for something like this... --- from twisted.internet import reactor, stdio from twisted.conch.manhole import Manhole stdio.StandardIO(Manhole()) reactor.run() --- ... but it does not work. Please advice. Thanks, Zoran

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[Twisted-Python] How to listen on and connect from same TCP port with Twisted?
by Alessio Pace Jan. 12, 2009

Jan. 12, 2009

Hi, I would lilke tro listen on a given TCP port and initiate multiple TCP client connections from the same port, but I'm encountering the classical: <class 'twisted.internet.error.ConnectBindError'>: Couldn't bind: 98: Address already in use My code is: ###################################### factory = Factory() # an almost empy subclass of Protocol factory.protocol = TCPServer reactor.listenTCP(12345, factory) # ClientFactory subclass which simply instantiate … [View More]

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[Twisted-Python] connectionLost not always getting called?
by Rob Bredow Jan. 12, 2009

Jan. 12, 2009

I've implemented a twisted server using the basic.lineReceiver class. The client is a socket based client implemented in flash and the connections are long-lived (minutes or hours). To handle cleaning up the players when they disconnect, I'm using the connectionLost function in my player class. 99% of the time, things work as expected. However in rare cases, connectionLost is not getting called when the flash-based client disappears. Even completely quitting the client's web-browser does … [View More]

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[Twisted-Python] [Q] Naming Service for Twisted Servers
by V S P Jan. 12, 2009

Jan. 12, 2009

Hi, I am sorry I am reasking the same question I asked before (but I did not get any replies) Basically wanted to know -- for running Twisted on multiple servers is there such a thing as a "Naming" server that would register all the currently running twisted servers -- so that asynchronious event dispatching can be done in some round-robin to available twisted servers thank you in advance -- V S P toreason(a)fastmail.fm -- http://www.fastmail.fm - And now for something completely different┘

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[Twisted-Python] Weekly Bug Summary
by exarkun＠twistedmatrix.com Jan. 11, 2009

Jan. 11, 2009

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[Twisted-Python] [Job] Senior Programmer - SQL, Python, C/C++, PHP
by Markus Wanner Jan. 7, 2009

Jan. 7, 2009

Hello, I'm pleased to announce the following position in our team of talented engineers. I personally enjoy working here and recommend this job to the dynamic, motivated self-starter looking for his/ her next career step in the open source world. Please feel free to forward this to anybody interested. Based in beautiful Berlin, we are a medium sized but growing database solutions provider for various industries and the public sector. Our main product is easydb, a customizable web-based front-… [View More]

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[Twisted-Python] ANN: Twisted 8.2 released
by Christopher Armstrong Jan. 6, 2009

Jan. 6, 2009

Version 8.2 of Twisted is now out (actually, it's been out for over a week now!). You can download it (in Windows, Mac, and source forms) at: http://twistedmatrix.com/ Twisted 8.2 is a major feature release, also including many important bug fixes: * twistd now has a --umask option for specifying the umask * Log observers can now be configured in .tac files * ProcessProtocols can now implement processExited to get reliable notification of a process exiting * FTPClient has many more … [View More]

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Re: [Twisted-Python] Perspective broker and inlineCallbacks exception handling problem
by Terry Jones Jan. 6, 2009

Jan. 6, 2009

Hi Maik I'm not an expert on inlineCallbacks, but I know enough to give something of an answer. > I am developing a basic client/server application based on twisted. > For communication purposes I am using perspective broker. I have > problems with inlineCallbacks and remotely raised errors: > > My client code looks like this (pseudo code): > > class Client: > @defer.inlineCallbacks > def login(self, prms): > self.factory = pb.PBClientFactory() > … [View More]reactor.connect(host, port) > self.perspective = yield self.factory.login() > self.services = yield self.perspective.callRemote('getClientServices') > > When using this class in application, I want to handle errors raised remotely: > > @defer.inlineCallbacks > def main(): > client = Client() > try: > yield client.login(prms) > except Exception, e: > print 'Handled exception:', e > > However, no matter what is raised on remote side, except block is > never used. The first thing to say is that you shouldn't send us pseudo code. It will help you understand what's going on if you write a small example and play with it. And that will help us help you because we'll be able to see exactly what's going on and run your code ourselves. Without a real example, it's hard to give a concrete answer. There are quite a few subtleties involved in using inlineCallbacks, and you're using it twice. Below is some working code that has something like the calling pattern you seem to be trying to set up. If I cause _login to raise an exception, it IS propagated all the way back to the except Exception clause. > But if I change the code to plain except, exception is handled: > > @defer.inlineCallbacks > def main(): > client = Client() > try: > client.login(prms) > except: > print 'Some error occurred' Note that in the above snippet, you're using inlineCallbacks but you're not yielding anything. If you try calling this main() function, it will give you an exception: Failure instance: Traceback: <type 'exceptions.AttributeError'>: 'NoneType' object has no attribute 'send' That's just an example of the subtleties (and it's not so sublte in this case), and underlines why you should send us real code. Are you actually trying to call main()? > If I rewrite this function using classic deferred style, it works as > excepted (prints error with the correct type): > > def eb_failure(failure): > print type(failure), failure > > def cb_success(result): > print 'OK', result > > def main(): > client = Client() > d = client.login(prms) > d.addCallbacks(cb_success, eb_failure) Right. But that code is very different from what's going on behind the scenes when you use inlineCallbacks. > I am purposely raising errors derived from pb.Error. Using the > inlineCallbacks version I can only inspect remote errors with > sys.exc_info(), and that results in a plain string object, which > includes the classname of the original error like > 'myerror.MyAuthenticationError' How do you raise the error? Let's see the code. > What am I doing wrong? Is there a way to resolve this? Sure. But we need to know more first. Below is some code that might be useful. It's also worth trying to figure out how inlineCallbacks does its magic. Terry --- #!/usr/bin/python from twisted.internet import defer, reactor def _login(d): try: hello except Exception: d.errback() else: d.callback(True) def login(): d = defer.Deferred() reactor.callLater(1, _login, d) return d class Client: @defer.inlineCallbacks def login(self, prms): yield login() @defer.inlineCallbacks def main(): client = Client() try: yield client.login(33) except Exception, e: print 'Handled exception:', e def ok(result): print "ok", result def nok(failure): print "nok", failure def stop(_): reactor.stop() def go(): x = main() x.addCallback(ok) x.addErrback(nok) x.addBoth(stop) if __name__ == '__main__': reactor.callLater(0, go) reactor.run() [View Less]

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Re: [Twisted-Python] Looping
by Terry Jones Jan. 6, 2009

Jan. 6, 2009

>>>>> "Robert" == Robert Hancock <hancock.robert(a)gmail.com> writes: Robert> I want to put this into a loop and run it as a daemon, but the Robert> looping is causing me a problem. I've tried making the above into Robert> a procedure (minus the stop working call back and reactor.run()) Robert> and it does not run. Any suggestions on how to encapsulate this Robert> into loop would be gratefully appreciated. It's hard to help unless you post more of your … [View More]

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[Twisted-Python] Perspective broker and inlineCallbacks exception handling problem
by Maik Friedmann Jan. 5, 2009

Jan. 5, 2009

Hello, I am developing a basic client/server application based on twisted. For communication purposes I am using perspective broker. I have problems with inlineCallbacks and remotely raised errors: My client code looks like this (pseudo code): class Client: @defer.inlineCallbacks def login(self, prms): self.factory = pb.PBClientFactory() reactor.connect(host, port) self.perspective = yield self.factory.login() self.services = yield self.perspective.callRemote('… [View More]

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[Twisted-Python] Looping
by Robert Hancock Jan. 5, 2009

Jan. 5, 2009

I have a process that takes a list of URLs, uses client.getPage() to retrieve the data, writes the contents to disk, and then moves the file to another directory. # get feed list - this is a list tuples # url, name, username, password url_tuples = feed_list(feed_file) global C_URLS d = defer.succeed(log_start(log)) for tup_url in url_tuples: C_URLS += 1 d.addCallback(get_page, tup_url) d.addErrback(get_page_error, tup_url[0]) d.… [View More]

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[Twisted-Python] Weekly Bug Summary
by exarkun＠twistedmatrix.com Jan. 4, 2009

Jan. 4, 2009

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[Twisted-Python] ssh v1 support
by Deniz Pecel Jan. 3, 2009

Jan. 3, 2009

Hi List Does twisted support ssh v1? thanks

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