Twisted July 2004

twisted@python.org

49 participants
50 discussions

[Twisted-Python] Writing a plug-in for an online game that uses UDP
by Ibrahim Mubarak 27 Jul '04

27 Jul '04

Hi, I am currently writing a server prototype for an online game called "If I Were U" (GPL). It will be using UDP and a MySQL db. I was successful in writing the code as a plug-in. I love the idea of being able to seperate in different files the levels of abstraction. But I am not sure of how to go about the following: I have an iiwuServer class derived from DatagramProtocol. I defined the datagramReceived method. This method calls one of my other classes's methods which returns a deferred object (this is where the connection to the db happens). I am trying to set the callback function for this deferred object and I want it to be a method of iiwuServer as I need to access the transport member object which in its turn writes out a datagram to the client. And I am not sure how to set up the callbackArgs for it (the "self" argument for methods is where I am confused). What am I doing wrong? Also, if you have a couple of minutes, can u look at my other three code segments (found after the iiwuServer) and tell me if you see anything that should be changed. Don't worry, the code is not that long. The thing is that in the documentation, each part (UDP, plug-in, deferred, etc...) are very well explained. But when I tried to put all that together, I got a little confused as I did not see any examples of UDP plug-ins or more complex deferred callback functions. All these segments are actually files in a folder called UDPServer. If you prefer that I send you the directory tarred and zipped, let me know. All that is left out is the empty __init__.py file in the folder. Thanks a lot, Ib http://www.iiwu.org Here is the code for the protocol (file name: iiwuserverprotocol.py): ////////CODE START\\\\\\\\ ############################ ##This is where the UDP packets are recieved and then sent to the server logic ############################ from twisted.internet.protocol import DatagramProtocol from UDPServer import iiwuserverlogic class iiwuServer(DatagramProtocol): iiwuservice = iiwuserverlogic.LoginService() def sendingOutput(self, result, host, port): """ A callback for the deferred object returned """ self.transport.write(str(result) + "\n" + str(self) + "\n", (host, port)) return def datagramReceived(self, data, (host, port)): msg = data.split() if len(msg) != 1 and len(msg) != 3: self.sendingOutput("error" , host, port) return if msg[0] == "log" and len(msg) == 3: user = msg[1] pswd = msg[2] self.iiwuservice.logUser(user, pswd, host, port).addCallback(self.sendingOutput(self, host, port)) return if msg[0] == "get": self.iiwuservice.loggedUsers().addCallback(self.sendingOutput(self, host, port)) return return \\\\\\\\CODE END//////// Here is the code for the server's logic (file name: iiwuserverlogic.py): ////////CODE START\\\\\\\\ ############################## ##This is where all the logic of the server lies ############################## from twisted.python import components from twisted.enterprise import adbapi class IService(components.Interface): """ An object that recieves messages. """ class LoginService: """ Respond to different messages """ __implements__ = IService def __init__(self): """ Setting up the db connection pool """ self.dbpool = adbapi.ConnectionPool("MySQLdb", 'database_name', 'login', 'password') return def mysqlQuery(self, q): """ Run a MySql query and return the result """ result = self.dbpool.runQuery(q) return result #Returning a Deferred object def logUser(self, name, pswd, ip, port): """ Connects to the DB and logs the user, returning nothing """ query = "INSERT INTO users (name, pswd, ip, port) VALUES (%s, %s, %s, %s)" % (name, pswd, ip, port) return self.mysqlQuery(query) def loggedUsers(self): """ Connects to the DB and returns a list of the users logged in """ query = "SELECT * FROM users" return self.mysqlQuery(query) \\\\\\\\CODE END//////// Here is the code for the tap construction (file name: servertap.py): ////////CODE START\\\\\\\\ from twisted.application import internet # services that run TCP/SSL/etc. from UDPServer import iiwuserverprotocol # Protocol from UDPServer import iiwuserverlogic # Server code from twisted.python import usage # twisted command-line processing class Options(usage.Options): """ Defining options when building the application """ optParameters = [["port", "p", 8007, "Port number to listen on for iiwuServer protocol."]] def makeService(config): """ Return a service that will be attached to the application. """ protocol = iiwuserverprotocol.iiwuServer() port = int(config["port"]) # UCP port to listen on # Finally, set up our protocol when events arrive on the specified port return internet.UDPServer(port, protocol) \\\\\\\\CODE END//////// Finally, here is the plugins.tml file: ////////CODE START\\\\\\\\ register("IIWU Server TAP Builder", "UDPServer.servertap", description=""" IIWU TAP builder module. """ , type="tap", tapname="iiwuserv") \\\\\\\\CODE END//////// __________________________________ Do you Yahoo!? New and Improved Yahoo! Mail - 100MB free storage! http://promotions.yahoo.com/new_mail

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[Twisted-Python] reconnecting ConnectionPools
by Christopher Armstrong 26 Jul '04

26 Jul '04

In my client's app we've been having problems with database connections going down; so far if that happens we need to restart the server to reconnect to the DB. I looked at adbapi's implementation and noticed that it wasn't doing anything special to notice lost connections. Then I realized DBAPI2 doesn't actually specify a way to tell whether your connection has gone down. I've been trying to think of a way to at least work around this on a per-app basis -- mine is using psycopg. It just raises either a ProgrammingError or an OperationalError on cursor.execute. The brightest idea we've come up with is to reconnect after N (~ 3) consecutive errors. Any other ideas? -- Twisted | Christopher Armstrong: International Man of Twistery Radix | Release Manager, Twisted Project ---------+ http://radix.twistedmatrix.com/

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[Twisted-Python] proxy question
by paolo veronelli 24 Jul '04

24 Jul '04

I'm behind a proxy.How should I use twisted.web.client.getPage as a wget clone? Thnx Paolino -- ....lotta dura per la verdura

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[Twisted-Python] Notes on switching twisted to new zope.interface code
by Itamar Shtull-Trauring 23 Jul '04

23 Jul '04

1. Switch classes from: class C: __implements__ = IFoo, to: class C: zope.interface.implements(IFoo) and if you have third party subclasses that may depend on C having __implements__, also add: twisted.python.components.backwardsCompatImplements(C) 2. Using zope.interface APIs directly is better, e.g. IFoo.providedBy(o) rather than components.implements(o, IFoo). But! If the object is third party, it may be using __implements__, and if the class never got processed by t.p.c it will not be hooked up to zope.interface at all. So, you may want to do: t.p.componets.fixClassImplements(o.__class__) this will make sure that __implements__ declarations get converted to new style implements declarations. 3. Basically all of t.p.c is deprecated except for registerAdapter and the other APIs that talk to registry. Componentized is not, in theory, but hopefully will be replaced soon. -- Itamar Shtull-Trauring http://itamarst.org

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[Twisted-Python] Re:
by Radix 23 Jul '04

23 Jul '04

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Re: [Twisted-Python] reactor.callLater always requires args object?
by Sergio Trejo 22 Jul '04

22 Jul '04

Much thanks orbitz and radix. Went down the wrong path on something subtle. I thought I had read in an example document, "d.callback" to the reactor.callLater() whereas it turns out to be "callback" and not "d.callback". I should have stopped and slept instead of going on sleepless fumes! Cheers, Sergio >From: Christopher Armstrong <radix(a)twistedmatrix.com> >Reply-To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >Subject: Re: [Twisted-Python] reactor.callLater always requires args >object? >Date: Wed, 21 Jul 2004 14:55:00 -0400 > >Sergio Trejo wrote: >>There's sure to be a good reason why, perhaps something utterly obvious to >>most but as a newbie I'm still trying to grok as much as possible where >>needed. Thanks for any clarification. > >*Deferreds* need a result, not callLater. As orbitz mentioned, >reactor.callLater(3, checkForSanity) would work fine. d.callback, as well >as all callbacks added to a Deferred with d.addCallback, always require at >least one argument. > >-- > Twisted | Christopher Armstrong: International Man of Twistery > Radix | Release Manager, Twisted Project >---------+ http://radix.twistedmatrix.com/ ><< signature.asc >> >_______________________________________________ >Twisted-Python mailing list >Twisted-Python(a)twistedmatrix.com >http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python _________________________________________________________________ Tired of spam? Get advanced junk mail protection with MSN 8. http://join.msn.com/?page=features/junkmail

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[Twisted-Python] reactor.callLater always requires args object?
by Sergio Trejo 21 Jul '04

21 Jul '04

I'm trying to be a good soldier by heeding the warning issued by the Twisted gods warning strongly *not* to use defer.Deferred's setTimeout() and instead using reactor.callLater I've looked at the API for twisted.internet.defer.Deferred.callback and twisted.internet.default.SelectReactor.callLater (which refers one to see twisted.internet.interfaces.IReactorTime.callLater which I have also read). I don't understand why at least one args object must always be supplied to reactor.callLater, as in: reactor.callLater(3, d.callback, "an unused arg") even though the callback function: d.addCallback(checkForSanity) receives no args: def checkForSanity(): print "this is a sanity test" In order to get the reactor.callLater to perform the callback, I had to pass in at least one arg: def checkForSanity(ignoreMe): print "this is a sanity test" d = defer.Deferred() d.addCallback(checkForSanity) reactor.callLater(3, d.callback, "ignore me") There's sure to be a good reason why, perhaps something utterly obvious to most but as a newbie I'm still trying to grok as much as possible where needed. Thanks for any clarification. Serg _________________________________________________________________ MSN 8 with e-mail virus protection service: 2 months FREE* http://join.msn.com/?page=features/virus

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Re: [Twisted-Python] Twisted gets mad freaky love from IEEE InternetComputing
by Sergio Trejo 21 Jul '04

21 Jul '04

>From: Stephen Waterbury <golux(a)comcast.net> >Reply-To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >Subject: Re: [Twisted-Python] Twisted gets mad freaky love from IEEE >InternetComputing >Date: Tue, 20 Jul 2004 22:41:27 -0400 > >Daniel Burr wrote: >>A very nice section on Twisted appears in this article about dynamic >>languages and distributed systems. > >Particularly impressive since the author works for IONA, one of >the main CORBA vendors. How refreshing! Apparently IONA is >immune to the virulent open source paranoia that afflicts a >certain monolithic operating system vendor whose president >happens to be the richest earthling. ;) Whose copyright holders of such an operating system announced a huge stock buyback to try and ooh and ahhh its shareholders to thus try to give people the warm fuzzy feelings that closed source still rules (which of course it doesn't). > >Steve > >_______________________________________________ >Twisted-Python mailing list >Twisted-Python(a)twistedmatrix.com >http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python _________________________________________________________________ Tired of spam? Get advanced junk mail protection with MSN 8. http://join.msn.com/?page=features/junkmail

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[Twisted-Python] Twisted gets mad freaky love from IEEE Internet Computing
by Daniel Burr 21 Jul '04

21 Jul '04

A very nice section on Twisted appears in this article about dynamic languages and distributed systems. PEAK gets a nice mention as well. Read it at: http://dsonline.computer.org/0407/d/w4towp.htm Naz

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Re: [Twisted-Python] PB - Dual Use Objects?
by Sergio Trejo 18 Jul '04

18 Jul '04

Radix -- this was an excellent suggestion - it works quite well. Thanks for your trips. Its been interesting delving into the aspects of Avatars, the Mind, Realms and Portals. Good stuff. Sergio >From: Christopher Armstrong <radix(a)twistedmatrix.com> >Reply-To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >To: Twisted discussion stuff <twisted-python(a)twistedmatrix.com> >Subject: Re: [Twisted-Python] PB - Dual Use Objects? >Date: Fri, 16 Jul 2004 12:45:32 -0400 > >Sergio Trejo wrote: >>I'm curious, for those who use PB for their projects, do they make their >>objects at each end of the wire dual use (meaning, both objects run a PB >>Server and PB Client Factory such that each object can remotely call the >>other), or do most people stick to a typical client-server model wherby >>the PB Server Factory object just waits for requests from the Client and >>does not attempt to initiate any messages to the client? >> >>I ask because as a newbie to Twisted, I also started reading the >>twisted.flow HowTo and it looks like there are some really interesting >>things that could be done with PB. I have an app in mind whereby a PB >>Client (A) triggers a PB Server, and then the PB Server expects incoming >>data from another PB Client (B) but the data that comes in from B is >>useful to pass back to A (all in a deferred manner however). Therefore the >>PB Server acts as an intermediary. But this could get really hairy if I >>turned the PB Server into a server handling multiple requests from PB >>Clients of type A and PB Clients of type B (could look like a spaghetti >>bowl f the Server is required to route data from the Bs to the As) so >>maybe better to stick with a typical client-server model. > >No, this is very simple. First of all, you need the Bs to pass a "mind" >object to pb.login(). It'll probably be a Referenceable subclass instance. >You'll get this mind object passed to your Realm's requestAvatar method, so >you can save it wherever relevant there. Let's pretend this object has a >messageFromAnA remote method. > >Then the As connect, and do middleman.callRemote('doSomethingToAB'): > >def remote_doSomethingToAB(self): > return self.mind.callRemote('messageFromAnA') > >callRemote will return a Deferred that fires with the result from B's >messageFromAnA method, and PB will pass this result off as the result to A, >so A is getting the result that B returned. > >-- > Twisted | Christopher Armstrong: International Man of Twistery > Radix | Release Manager, Twisted Project >---------+ http://radix.twistedmatrix.com/ ><< signature.asc >> >_______________________________________________ >Twisted-Python mailing list >Twisted-Python(a)twistedmatrix.com >http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python _________________________________________________________________ STOP MORE SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail

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Twisted July 2004