Starting an independent ApplicationSession and event loop from an existing one

Question

I'd like to be able to spawn an independent event loop/reactor from an existing one. Let's say I have an application in a module standaloneapps:

#in standaloneapps.py
class StandaloneApp(ApplicationSession):
    def runner(self, message):
        print(message)

    @inlineCallbacks
    def start_app(self):
        yield self.subscribe(self.runner, 'com.example.some_topic')

I'd like to be able to start this application from a different one. Example:

from standaloneapps import StandaloneApp

class ApplicationStarter(ApplicationSession):

    @inlineCallbacks
    def onJoin(self, details):
        yield self.subscribe(self.start_app, 'com.example.startapp')

    def start_app(self, message):
        print('subscribing to app')
        new_runner = ApplicationRunner(url="ws://127.0.0.1:8080/ws", 
                                   realm="realm1") 
        runner.run(StandaloneApp)

I can start ApplicationStarter, but as soon as I publish the event 'com.example.startapp' crossbar crashes with exception builtins.Exception: not joined.

Perhaps this seems like an overly complicated setup, but I'm trying to have one application subscribe to an 'app dispatcher' which dynamically starts new applications which may-or-may-not be known ahead of time. I'd like for the new applications to be running on different event loops so as to stay isolated.

Answer 1

Edit: All that was necessary was to add: runner.run(StandaloneApp, start_reactor=False)

to the call to start the second app. This forces it to run in the same loop.