Mailman 3 June 2008 - Twisted

[Twisted-Python] Twisted Community Code
by Duncan McGreggor 05 Jun '08

05 Jun '08

Inspired by the discussion from the recent thread about community code, a concise string couplet to represent Twisted, and trademarks, I've created a space on Launchpad for Twisted Community Code: https://launchpad.net/tx Anyone can create a project and add it to this "super project" -- hopefully, they will only do so if their code is based on and uses Twisted :-) Also: I'd like to thank Phil Christensen for taking a leadership role in this new space. Thanks Phil! I'll be blogging about this soon, but I wanted to give everyone on this list first notice :-) d

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[Twisted-Python] Using twisted to manage processes
by Brian Granger 05 Jun '08

05 Jun '08

Hi, We have been using Twisted for a long time with IPython and we are needing a nice general and cross platform way of managing processes (spawning, sending signals, etc.). I am aware of Twisted's process management API and it looks like it would fit the bill rather well for us. But, I am wondering how cross platform it is. We need to be able to write code that works on Linux, OS X, AIX and Win32. More specifically, I know 0 about process control on Win32 and want to make sure that Windows users will be able to use this stuff. So, will the process management stuff work on Win32? Are there any issues I need to be aware of on Win32 that the Twisted API won't quite handle? Thanks, Brian

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[Twisted-Python] [ANN] Foolscap-0.2.8 released
by Brian Warner 05 Jun '08

05 Jun '08

I've just released Foolscap-0.2.8 . This is a minor bugfix release, which also updates the setuptools-visible dependencies in a way that makes it slightly easier for other projects (like Tahoe) to declare that they need foolscap's cryptographic properties. The full release notes are attached below. Foolscap is a Twisted-friendly remote object protocol, a descendant of Perspective Broker, with improved security properties, third-party references, adaptable serialization, and other useful features. Please visit http://foolscap.lothar.com/trac for more details. have a groovy day, -Brian * Release 0.2.8 (04 Jun 2008) ** Compatibility: exactly the same as 0.2.6 ** setuptools dependencies updated Foolscap (when built with setuptools) now uses the "extras_require" feature to declare that it needs pyOpenSSL if you want to use the "secure_connections" feature. This makes easy_install easier to use in projects that depend upon Foolscap (and also insist upon using secure connections): they do not need to declare a dependency on pyOpenSSL themselves, instead they declare a dependency on "Foolscap[secure_connections]". See the following documentation for more details: http://peak.telecommunity.com/DevCenter/setuptools#declaring-extras-optiona… ** New RemoteReference.getPeer() method The new rref.getPeer() method will return address information about the far end of the connection, allowing you to determine their IP address and port number. This may be useful for debugging or diagnostic purposes. ** Minor bugs fixed Tub.registerReference() with both name= and furlFile= arguments now works even when the furlFile= already exists. Tubs which have been shutdown now give more useful error messages when you (incorrectly) try to use them again. Previously a bug caused them to emit a TypeError.

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[Twisted-Python] RE: How do I get the reactor to stop on an exception
by Gerrat Rickert 04 Jun '08

04 Jun '08

Thanks for the quick responses, Jean-Paul & Itamar. It looks like turning my app into a twistd plugin seems to be the preferred method (well, quashing bugs quickly and permanently with Unit Tests is obviously the preferred method :o) !) Itamar, >When using twistd or trial, you can simply use the debug command-line >option for that (-b). Without those, >twisted.python.failure.setDebugMode(True) or something, I forget the exact >invocation. There is a twisted.python.failure.startDebugMode(), but it doesn't seem to stop the reactor on exceptions (I'm not directly using Deferred's, so maybe that's the reason). I'm mostly using Twisted for it's robust Networking protocols (ok, and a bit of scheduling), and I can't say enough good things about how well it works. I also know Twisted has many more parts to it than the small subset I'm using, but it seems unfortunate to me that including any part of Twisted in a program means that all exceptions are trapped -whether or not the exception has anything to do with Twisted. Regular Python (sans Twisted) doesn't trap exceptions, but I'm sure there are many good reasons for doing so with Twisted (you don't have to list them - I'm not being facetious). I just think it would be useful to be able to set a flag somewhere to stop this behaviour. I will definitely remove this after, but adding a 'raise' statement to the except clause of the RunUntilCurrent method of ReactorBase in base.py seems to do exactly what I want. ...would zero percent be on the high side for the chances of having a Twisted developer make some sort of flag available that would turn this on? (or equivalent functionality) ...just askin... Thanks again for your help/advice guys, Gerrat

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[Twisted-Python] How do I get the reactor to stop on an exception
by Gerrat Rickert 04 Jun '08

04 Jun '08

I'm running a rather involved simulation using twisted, and it would be preferable if I could get the reactor to just drop me into the interpreter on any exception so I could examine the current state of things. I set os.environ['PYTHONINSPECT'] = '1', but the reactor seems to trap any exceptions and just merrily carry on - logging my tracebacks to a file, but continuing to run - modifying the current state of things and making it harder to track down bugs. Is there an easy way to prevent the reactor from trapping exceptions? Thanks, Gerrat

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[Twisted-Python] Idiom for database access within iterator/generator?
by Justin Warren 03 Jun '08

03 Jun '08

Greetings twisted gurus! I'm hoping someone with a better algorithmic brain than I could offer some advice on a good way to do something in a twisty/pythonic way. The pseudocode for what I want to do is: for item in generator_that_fetches_rows_from_database: ... do_stuff() ... where generator_that_fetches_rows_from_database is an object that uses enterprise.adbapi (or anything else) to fetch rows from a database and return them to the for..in.. loop. Now, I'm probably looking at this from too much of a blocking code perspective, rather than setting up a Deferred() chain of some sort, but rather than hacking something functional but ugly, it occurs to me that someone is bound to have done this before. It would be nice if the database accessing object could fetch rows as required, via cursors or whatever, rather than sucking an entire table into memory and then doling out one row at a time... which is what I've got working at the moment. The morbidly curious can recoil in horror at the current code in the SQLIterator class here: http://modipy.seafelt.com/browser/trunk/lib/modipy/iterator.py Any free clues? -- Justin Warren <daedalus(a)eigenmagic.com>

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[Twisted-Python] How to detect dead client connections in twisted
by Alvin Delagon 03 Jun '08

03 Jun '08

I've been using xmlstream for quite sometime now and I noticed one such problem where my server doesn't detect clients that went to hardware shutdown without closing the socket. I also reproduced it using a simple twisted TCP server: #!/usr/bin/python from twisted.internet import protocol from twisted.internet import reactor class EchoProtocol(protocol.Protocol): def __init__(self): pass def connectionMade(self): print "Client Connected Detected!" def connectionLost(self, reason): print "Client Connection Lost!" def dataReceived(self, data): self.transport.write(data) factory = protocol.Factory() factory.protocol = EchoProtocol reactor.listenTCP(8000, factory) reactor.run() Using a different machine, telnet to the echo server and then shut down the computer (without exiting telnet). It seems that the connectionLost function doesn't get called. I even had an XMPP account appeared online on our XMPP server for almost three days even though I shut down the PC hosting my client. Should we implement a Hearbeat functionality? Thank you in advance! Alvin Delagon -- http://www.alvinatorsplayground.blogspot.com/

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[Twisted-Python] exceptions.SystemError: unknown opcode
by Miguel Filho 02 Jun '08

02 Jun '08

Hello list, I have a twisted application in production for some time now, running under Fedora Core 6, Python 2.4.4 and twisted 2.4. I know, a little outdated. The process was running fine for some weeks without any problems, although I got this exception in my logs and I really have no idea what it means. The process did not die and is still running ok. 2008/05/13 16:03 BRT [-] Traceback (most recent call last): File "/usr/lib/python2.4/site-packages/twisted/application/app.py", line 278, in run runApp(config) File "/usr/lib/python2.4/site-packages/twisted/scripts/twistd.py", line 197, in runApp app.runReactorWithLogging(config, oldstdout, oldstderr) File "/usr/lib/python2.4/site-packages/twisted/application/app.py", line 131, in runReactorWithLogging reactor.run() File "/usr/lib/python2.4/site-packages/twisted/internet/posixbase.py", line 218, in run self.mainLoop() --- <exception caught here> --- File "/usr/lib/python2.4/site-packages/twisted/internet/posixbase.py", line 229, in mainLoop self.doIteration(t) exceptions.SystemError: unknown opcode Regards, Miguel

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[Twisted-Python] Creating a protocol-agnostic chatbot with Twisted words
by Jo Vermeulen 02 Jun '08

02 Jun '08

Hello, I am trying to create a chat bot that can work over both the XMPP and the MSN protocol using Twisted words. I have a couple of questions as a Twisted newbie :-) Is there any documentation on how to create a protocol-agnostic chatbot with Twisted words? Or are there applications using Twisted words that offer multiple front-ends? I have a XMPP version working, but had some problems finding my way around a few features. I don't know how to get a list of contacts, or initiatiate a group chat. Even if I succeed in doing this, would it be possible to generalize this for both XMPP and MSN? Finally, I was wondering how mature Twisted words is. It seems to work well for XMPP, but how mature is the MSN support? Are there other libraries I could consider, or is it possible to generalize other libraries within Twisted? Thanks in advance! -- Jo Vermeulen

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[Twisted-Python] Weekly Bug Summary
by exarkun＠twistedmatrix.com 01 Jun '08

01 Jun '08

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