On 17 Oct 2009, at 05:15, Read Roberts wrote:
I have a Python server using twisted which responds to pyAMF calls from Flex/Air applications (following Bruce Eckels 5/1/2008 article "Concurrency with Python, Twisted, and Flex"). The service is basically as follows below. When the client calls a service API, the API needs to make a OS shell call. I see that if I call reactor.stop() after the getProcessOutput call (such as within the doLog and doError functions), the call happens and I see the output. How can can I retrieve the output without calling reactor.stop()? In the example below, the AIR app calls the callback helloWorldTest(), and the deferred.addCallback function is never called.
import os from twisted.spread import pb from twisted.internet.utils import getProcessOutput from twisted.internet import reactor
class FlexInterface(pb.Root): def __init__(self): self.result e
def doLog(self, result): self.result = "%s" % (result) return result
def doError(self, failure): self.result = "%s" % ( failure) return failure
def helloWorldTest(self): deferred = getProcessOutput("echo", ["Hello World"], os.environ) deferred.addErrback(self.doError) deferred.addCallback(self.doLog) while (self.result == None) print "doLog still hasn't been called" return self.result
The while loop will block the event loop, preventing the deferred from ever being called. PyAMF will accept a deferred as a return value for the service function and will not return a response until the deferred's callback is fired. So, you could re-write the method like: def helloWorldTest(self): deferred = getProcessOutput("echo", ["Hello World"], os.environ) deferred.addErrback(self.doError) deferred.addCallback(self.doLog) return deferred If the deferred's callback is called then the return value of doLog will be used as the response value. If the errback is called, the return value of doError will be used as the response, in this case a Failure instance. PyAMF converts Failure instances to remoting/ messaging error objects automagically, so the faultHandler on the flash/air side will be called. hth, Nick