Quart (异步Flask)应用程序中的Autobahn websocket客户端

Question

大家晚上好。我对这个地方并不是很陌生，但最终还是决定注册并寻求帮助。我使用Quart框架(异步Flask)开发了一个web应用程序。现在，随着应用程序变得更大、更复杂，我决定将不同的过程分离到不同的服务器实例，这主要是因为我想保持web服务器的干净，更抽象，没有计算负载。

因此，我计划使用一台web服务器和几台(如果需要)相同的过程服务器。所有的服务器都基于quart框架，目前只是为了开发的简单性。我决定使用Crossbar.io路由器和autobahn将所有服务器连接在一起。

这时问题就出现了。我关注了这篇文章：

Running several ApplicationSessions non-blockingly using autbahn.asyncio.wamp

How can I implement an interactive websocket client with autobahn asyncio?

How I can integrate crossbar client (python3,asyncio) with tkinter

How to send Autobahn/Twisted WAMP message from outside of protocol?

似乎我尝试了所有可能的方法来在我的quart应用程序中实现autobahn websocket客户端。我不知道如何让它成为可能，这样两件事都可以工作，是否Quart应用程序可以工作而autobahn WS客户端不能，或者反之亦然。

简化的我的quart应用程序如下所示：

from quart import Quart, request, current_app
from config import Config
# Autobahn
import asyncio
from autobahn import wamp
from autobahn.asyncio.wamp import ApplicationSession, ApplicationRunner

import concurrent.futures

class Component(ApplicationSession):
    """
    An application component registering RPC endpoints using decorators.
    """

    async def onJoin(self, details):

        # register all methods on this object decorated with "@wamp.register"
        # as a RPC endpoint
        ##
        results = await self.register(self)
        for res in results:
            if isinstance(res, wamp.protocol.Registration):
                # res is an Registration instance
                print("Ok, registered procedure with registration ID {}".format(res.id))
            else:
                # res is an Failure instance
                print("Failed to register procedure: {}".format(res))

    @wamp.register(u'com.mathservice.add2')
    def add2(self, x, y):
        return x + y


def create_app(config_class=Config):

    app = Quart(__name__)
    app.config.from_object(config_class)

    # Blueprint registration
    from app.main import bp as main_bp
    app.register_blueprint(main_bp)

    print ("before autobahn start")
    with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
        runner = ApplicationRunner('ws://127.0.0.1:8080 /ws', 'realm1')
        future = executor.submit(runner.run(Component))
    print ("after autobahn started")

    return app


from app import models

在这种情况下，应用程序被卡在runner循环中，并且整个应用程序无法工作(不能服务于请求)，只有当我通过Ctrl-C中断runner(Autobahn)循环时才有可能。

启动后的命令：

(quart-app) user@car:~/quart-app$ hypercorn --debug --error-log - --access-log - -b 0.0.0.0:8001 tengine:app
Running on 0.0.0.0:8001 over http (CTRL + C to quit)
before autobahn start
Ok, registered procedure with registration ID 4605315769796303

按下ctrl-C后：

...
^Cafter autobahn started
2019-03-29T01:06:52 <Server sockets=[<socket.socket fd=11, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('0.0.0.0', 8001)>]> is serving

如何让quart应用程序与autobahn客户端一起以非阻塞的方式工作？因此，autobahn打开并保持与Crossbar路由器的websocket连接，并在后台静默监听。

Answer 1

经过几个不眠之夜，我终于找到了一个解决这个难题的好方法。

多亏了这篇文章C-Python asyncio: running discord.py in a thread

因此，我像这样重写了我的代码，并能够在其中运行我的Quart应用程序和autobahn客户端，两者都在以非阻塞的方式积极工作。整个__init__.py看起来像这样：

from quart import Quart, request, current_app
from config import Config


def create_app(config_class=Config):

    app = Quart(__name__)
    app.config.from_object(config_class)

    # Blueprint registration
    from app.main import bp as main_bp
    app.register_blueprint(main_bp)

    return app


# Autobahn
import asyncio
from autobahn import wamp
from autobahn.asyncio.wamp import ApplicationSession, ApplicationRunner
import threading


class Component(ApplicationSession):
    """
    An application component registering RPC endpoints using decorators.
    """

    async def onJoin(self, details):

        # register all methods on this object decorated with "@wamp.register"
        # as a RPC endpoint
        ##
        results = await self.register(self)
        for res in results:
            if isinstance(res, wamp.protocol.Registration):
                # res is an Registration instance
                print("Ok, registered procedure with registration ID {}".format(res.id))
            else:
                # res is an Failure instance
                print("Failed to register procedure: {}".format(res))


    def onDisconnect(self):
        print('Autobahn disconnected')

    @wamp.register(u'com.mathservice.add2')
    def add2(self, x, y):
        return x + y


async def start():
    runner = ApplicationRunner('ws://127.0.0.1:8080/ws', 'realm1')
    await runner.run(Component) # use client.start instead of client.run

def run_it_forever(loop):
    loop.run_forever()

asyncio.get_child_watcher() # I still don't know if I need this method. It works without it.
loop = asyncio.get_event_loop()
loop.create_task(start())
print('Starting thread for Autobahn...')
thread = threading.Thread(target=run_it_forever, args=(loop,))
thread.start()
print ("Thread for Autobahn has been started...")


from app import models

在此场景中，我们使用autobahn的runner.run创建任务，并将其附加到当前循环，然后在新线程中永远运行此循环。

我对目前的解决方案相当满意……但是后来发现这个解决方案有一些缺点，这对我来说是至关重要的，例如:如果连接断开，则重新连接(即交叉开关路由器变得不可用)。使用这种方法，如果连接初始化失败或在一段时间后断开，它将不会尝试重新连接。此外，对我来说，如何注册/调用ApplicationSession API并不是很明显，比如在我的quart应用程序中注册/调用RPC。

幸运的是，我发现了autobahn在他们的文档中使用的另一个新组件API：https://autobahn.readthedocs.io/en/latest/wamp/programming.html#registering-procedures https://github.com/crossbario/autobahn-python/blob/master/examples/asyncio/wamp/component/backend.py。

它具有自动重新连接功能，并且很容易使用装饰器@component.register('com.something.do')为RPC注册函数，你只需要在此之前使用import component。

下面是__init__.py解决方案的最终视图：

from quart import Quart, request, current_app
from config import Config

def create_app(config_class=Config):
    ...
    return app

from autobahn.asyncio.component import Component, run
from autobahn.wamp.types import RegisterOptions
import asyncio
import ssl
import threading


component = Component(
    transports=[
        {
            "type": "websocket",
            "url": u"ws://localhost:8080/ws",
            "endpoint": {
                "type": "tcp",
                "host": "localhost",
                "port": 8080,
            },
            "options": {
                "open_handshake_timeout": 100,
            }
        },
    ],
    realm=u"realm1",
)

@component.on_join
def join(session, details):
    print("joined {}".format(details))

async def start():
    await component.start() #used component.start() instead of run([component]) as it's async function

def run_it_forever(loop):
    loop.run_forever()

loop = asyncio.get_event_loop()
#asyncio.get_child_watcher() # I still don't know if I need this method. It works without it.
asyncio.get_child_watcher().attach_loop(loop)
loop.create_task(start())
print('Starting thread for Autobahn...')
thread = threading.Thread(target=run_it_forever, args=(loop,))
thread.start()
print ("Thread for Autobahn has been started...")


from app import models

我希望它能帮助一些人。干杯!