Mailman 3 September 2005 - Twisted

[Twisted-Python] conch.forwarding tutorial
by Yves Glodt 06 Sep '05

06 Sep '05

Hello, can somebody point me at a conch.forwarding tutorial or code example? best regards, Yves

1 0

[Twisted-Python] unsubscribe
by Chris Driscoll 06 Sep '05

06 Sep '05

1 0

Re: [Twisted-Python] Re: Disabling PB (de)serialization
by Brian Warner 06 Sep '05

06 Sep '05

>> Well, you can uncomment the cBanana hook in the PB code, and they will >> be much faster. :-) > > Oooh, seriously? Where do I do that? Hm, I thought cBanana was the default? It might depend upon how you build/install Twisted.. there are platforms on which the optional C extensions are just skipped. Oh, there it is.. twisted/spread/banana.py, towards the end, just grep for 'import cBanana'. Exarkun commented that out last year. Eh, give it a try, see if it helps. I'd be a little bit worried about segfaulting, or exposing such a port to a hostile party. But I honestly haven't looked at that code for two years. cBanana implements the lowest layer of serialization/deserialization in C, so it will be a little bit faster. If your data consists of a lot of strings and ints, the speedup will probably be greater than if it consists of a lot of interconnected lists and tuples. It would be neat to have some actual benchmarks of the speedup, though. newpb is designed to make it possible to write Slicers/Unslicers in C, and in fact to allow the base-level Protocol to be implemented in C, but none of these hypothetical accelerated serializers have actually been written yet. This would allow C serialization of basic types (lists, tuples) while retaining standard python serialization of user-defined complex types, as opposed to the oldpb/cBanana approach that uses C for only the lowest level (turning string/number tokens into bytes). In theory, it should be possible to make newpb run faster than oldpb. It will take some good use-cases and benchmarking before this actually happens, though. cheers, -Brian

2 1

Re: [Twisted-Python] Re: Traceback from pb-Server
by Brian Warner 06 Sep '05

06 Sep '05

> Popp> If the pythonscript named taskDescription.fileName isn't there > Popp> self.serverErrorCB is called - thats ok. But it prints: > Popp> reason [Failure instance: Traceback from remote host -- Traceback unavailable] > > Popp> But I need to know why the call failed. Can anyone please > Popp> help me to get the traceback or the exception message that > Popp> the server prints (exceptions.ImportError: No module named > Popp> fitfunc2). Also, you may want to enable the 'unsafeTracebacks' flag. In general, when PB calls a method that raises an exception, the traceback is recorded to the log on the "near" side of the connection, but very little information is sent to the "far" side of the connection. (this is intended as a security feature.. tracebacks frequently contain copies of the code that failed, and you might not want to expose that.. Failure instances can contain copies of stack frames, local variables, all kinds of juicy stuff). The 'unsafeTracebacks' flag tells PB to convey more information over the wire. The remote side (the one which callRemote'ed the failing method) still gets a Failure object, all asynchronous exceptions in Twisted are reported this way, but it gets a Failure object with more attributes than it would get if unsafeTracebacks==False. The "Traceback unavailable" message is specifically a result of unsafeTracebacks==False. But, in practice, I usually try to debug these sorts of failures on the target side, closer to the code that raised the exception. You're always going to get more information on that end of the wire. hope that helps, -Brian

1 0

[Twisted-Python] Traceback from pb-Server
by Stephan Popp 06 Sep '05

06 Sep '05

Hi, Please excuse my bad english, I hope you will understand what I mean, otherwise feel free to ask. I'm trying to get error messages from my server. I'm using twisted 2.0.0 with python 2.4. The server looks like this: from twisted.spread import pb from twisted.internet import reactor, threads class ServerObject(pb.Root): #...some other methods, which aren't involved... def remote_fitness(self, task, taskDescription, serverID): return threads.deferToThread(self.calc, task, serverID, taskDescription) def calc(self, task, serverID, taskDescription): exec('from %s import %s as func' % (taskDescription.fileName,taskDescription.functionName)) #problem: file specified in fileName needn't to be in working directory of server func(task) #calulates something return task if __name__ == '__main__': factory = pb.PBServerFactory(ServerObject()) reactor.listenTCP(8800, factory) reactor.run() The client calls, after connection is made. def1 = root.call_remote("fitness", task, taskDescription, serverID) def1.addCallback(self.serverCB) def1.addErrback(self.serverErrorCB) def serverErrorCB(self, reason): print reason If the pythonscript named taskDescription.fileName isn't there self.serverErrorCB is called - thats ok. But it prints: reason [Failure instance: Traceback from remote host -- Traceback unavailable] But I need to know why the call failed. Can anyone please help me to get the traceback or the exception message that the server prints (exceptions.ImportError: No module named fitfunc2).

6 6

[Twisted-Python] some bugs(?)
by Antony Kummel 06 Sep '05

06 Sep '05

Hi, I encountered what seem to be some bugs: 1. In twisted/scripts/trial.py, line 276: the module's contents are not executed if the lines are terminated with "\r\n". I suggest using "r" instead of "rb" when reading the file. Additionally, I would compile() the source before executing it in order to associate it with its filename. This will make debugging (at least with winpdb) much easier (currently the filename is "<string>", which prevents winpdb from finding the source). 2. In twisted/plugin.py, line 135: paths are skipped if they don't exist, but there is also the possibility that they're misspelled. This gives rise to WindowsError 123, which I think should also be ignored, or at least an informative message should be provided. It took me a very long time to find out my PYTHONPATH was missing a ";". Cheers, Antony Kummel __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

2 2

[Twisted-Python] database connection through ssh tunnel using twisted
by Yves Glodt 05 Sep '05

05 Sep '05

Hello, (I am new to twisted, so please excuse me if my question is not appropriate...) I am using the python module kinterbasdb [1] for connecting to a Firebird DB, and I wonder if it's possible, using twisted, to pass this connection through a ssh tunnel, which should be created on the fly by twisted (without running a /usr/bin/ssh commandline)... best regards and thanks in advance, Yves [1]: http://kinterbasdb.sourceforge.net/dist_docs/usage.html#tutorial_connect

1 2

[Twisted-Python] time
by Antony Kummel 05 Sep '05

05 Sep '05

Hi, I noticed that the convention in Twisted is to measure time with python.runtime.seconds. This in turn uses time.time which is sensitive to the system clock, meaning that it may return decreasing values if the user sets the system clock to an earlier time between calls. This would likely break many things, no? Why not use time.clock or some combination between them? Antony Kummel ______________________________________________________ Click here to donate to the Hurricane Katrina relief effort. http://store.yahoo.com/redcross-donate3/

4 5

[Twisted-Python] application
by Antony Kummel 05 Sep '05

05 Sep '05

Hi, I am beginning to use twisted.application, mktap and twistd in my project, and I have some questions about their use: 1. It seems that mktap is aimed primarily to create applications containing just one service (since to append a service to an application you need a separate invocation of mktap). I am thinking to use it mostly to combine services and I wonder if I'm misunderstanding something or if I should use MultiService or what. Specifically, I want to have numerous services that are (modified) PB client/servers, and when several such services are at the same process, I want them all to use the same ServerFactory. What I did was to make one mktap plugin for the "base server", and several plugins for the services themselves. These services require that the application also contains a "base server", and they bind to it automatically. This requires creating an application with only the "base server", and then adding to it the different subsidiary services. Any ideas on how to do this optimally? 2. Tap conventions: it is not very clear how to make the best use of mktap in terms of code organization. It seems that to make plugins I need to have a twisted/plugins folder in my application's root directory. In twisted, this folder contains files named twisted_*.py, I'm not sure why this naming convention. The files in this directory point to tap construction modules. These modules seem to be either in twisted/tap or in twisted/*something*, in which case they are called either tap.py or *something*_tap.py. Additionally, the services these modules use come from a variety of places in which I couldn't find coherence. So, my question is, where should I put the mktap plugins, the tap construction modules, and the service implementations so that it makes sense? Am I missing anything? 2. I understand that application is meant to hold the services' configuration. However, there are many kinds of configurations, and I'm struggling to make a distinction between options that are suitable for the mktap command line, for xml-serialized applications, and for other mechanisms, such as a human-readable configuration file suitable for an innocent end-user. For example, an ini file could be used to specify the skin of a GUI application, and debugging options, but what is more suitable for the mktap command line? Maybe only options that somehow affect the basic "type" of the service? Thanks, Antony Kummel ______________________________________________________ Click here to donate to the Hurricane Katrina relief effort. http://store.yahoo.com/redcross-donate3/

2 1

[Twisted-Python] OK to remove doctest support from Trial?
by Jonathan Lange 05 Sep '05

05 Sep '05

Does anyone care deeply about Trial supporting doctests? I would like to remove the support. It's almost unused in Twisted, clutters the trial code and is slowing down refactoring. My grep skills indicate that there's only one set of doctests in Twisted (in t.web2.test.test_stream). A patch is attached to replace these with unit tests. (I'll apply it if the web2 maintainers approve). cheers, jml

2 2