Document mixing Twisted and asyncio in one app

[oberstet]

There are scenarios where one might want to run a mix of native asyncio-only libraries and Twisted-only features in one application - while using Autobahn.

In principle, there are 2 ways:

• run Twisted on top of a asyncio based (Twisted) reactor
• run asyncio on top of a Twisted based (asyncio) loop

The latter doesn't exist as far as we know, but the former does, and it involves interop in 2 dimensions:

• the loop/reactor
• futures vs deferreds

@meejah has an awesome blog post about this here https://meejah.ca/blog/python3-twisted-and-asyncio and @oddjobz wrote the following example - which also uses uvloop and scenic:

#!/usr/bin/env python3

import txaio
import asyncio
import uvloop
from twisted.internet import ssl, asyncioreactor
from autobahn.twisted.component import Component, run
from autobahn.wamp.types import RegisterOptions
from autobahn.twisted.websocket import WampWebSocketClientFactory
from sanic import Sanic
from sanic.response import json

loop = uvloop.new_event_loop()
asyncio.set_event_loop(loop)
asyncioreactor.install(eventloop=loop)
from twisted.internet import reactor
txaio.config.loop = reactor

txaio.start_logging(level='info')
#
#   Ok, this was the bit that gave me a little trouble ...
#
WampWebSocketClientFactory.contextFactory = ssl.ClientContextFactory()

REALM = 'realm1'
TRANSPORT=[{
    'type' : 'websocket',
    'url': 'wss://xbr-fx-1.eu-west-2.crossbar.io/ws',
    'proxy': {
        'host' : '5.83.125.116',
        'port' : 8080
    },
}]

class Crossbar:

    _session = None
    _log = txaio.make_logger()

    @property
    def session(self):
        return self._session

    @property
    def crossbar(self):
        return self._crossbar

    def __init__(self):
        self._counter = 0
        self._crossbar = Component(transports=TRANSPORT, realm=REALM)
        self._crossbar.on("join", self.on_join)

    def on_join(self, session, details):
        self._log.info(f'Connected to Crossbar with authid "{details.authid}" on realm "{details.realm}"')
        self._session = session
        session.register(self.greeting, 'com.example.greeting', options=RegisterOptions(details_arg='details'))

    def greeting(self, name, details=None):
        self._counter += 1
        return {
            'name': name,
            'message': 'Hello, "{}"! (counter={})'.format(name, self._counter)
        }

app = Sanic()

@app.route('/')
async def test(request):
    return json({'hello': 'world'})

crossbar = Crossbar()
server = app.create_server(host="0.0.0.0", port=8087, return_asyncio_server=True)
asyncio.ensure_future(server)
run([crossbar.crossbar])

[meejah]

p.s. that can be RegisterOptions(details=True) now, which is the "preferred" way right?

[meejah]

Also, if we're going to put that example in the docs, the "proxy" stuff should be removed because it's not correct and there's bugs in autobahn using TLS with it, apparently.

[oberstet]

• rgd RegisterOption(details=True): we still need to add that https://github.com/crossbario/autobahn-python/issues/1143
• rgd the example: right, ok.

[oddjobz]

Re; RegisterOptions, yeah I was aware, it was a cut/paste. sorry .. Re; proxy / tls .. would be better (imo) to fix the AB/Component bug and leave the SSL in, minus my hack line ..

[oberstet]

@oddjobz re: RegisterOptions => fixed yesterday .. released on AB v19.3.2

[meejah]

the proxy bug is fixed here https://github.com/crossbario/autobahn-python/pull/1149 (but still, it might be more-clear to leave out the proxy stuff from an example?)