Asyncio + aiohttp - redis Pub/Sub和websocket在单个处理程序中读/写

Question

我正在玩aiohttp,看看它将如何作为带有websocket连接的移动应用程序的服务器应用程序.

这是一个简单的"Hello world"示例(这里是gist):

import asyncio
import aiohttp
from aiohttp import web


class WebsocketEchoHandler:

    @asyncio.coroutine
    def __call__(self, request):
        ws = web.WebSocketResponse()
        ws.start(request)

        print('Connection opened')
        try:
            while True:
                msg = yield from ws.receive()
                ws.send_str(msg.data + '/answer')
        except:
            pass
        finally:
            print('Connection closed')
        return ws


if __name__ == "__main__":
    app = aiohttp.web.Application()
    app.router.add_route('GET', '/ws', WebsocketEchoHandler())

    loop = asyncio.get_event_loop()
    handler = app.make_handler()

    f = loop.create_server(
        handler,
        '127.0.0.1',
        8080,
    )

    srv = loop.run_until_complete(f)
    print("Server started at {sock[0]}:{sock[1]}".format(
        sock=srv.sockets[0].getsockname()
    ))
    try:
        loop.run_forever()
    except KeyboardInterrupt:
        pass
    finally:
        loop.run_until_complete(handler.finish_connections(1.0))
        srv.close()
        loop.run_until_complete(srv.wait_closed())
        loop.run_until_complete(app.finish())
    loop.close()

问题

现在我想使用下面描述的结构(node server = python aiohttp).更具体地说,使用带有asyncio-redis的Redis Pub/Sub机制来读取和写入我的WebsocketEchoHandler中的 websocket连接和Redis .

WebsocketEchoHandler是一个简单的循环,所以我不确定应该怎么做.使用Tornado和brükva我会使用回调.

额外的(可能是offtopic)问题

由于我已经使用Redis,我应采取以下两种方法中的哪一种:

1. 就像在"经典"网络应用程序中一样,拥有一个控制器/视图,只需使用Redis进行消息传递等.
2. Web应用程序应该只是客户端和Redis之间的一层,也用作任务队列(最简单的Python RQ).每个请求都应该委托给工人.

编辑

图片来自http://goldfirestudios.com/blog/136/Horizo​​ntally-Scaling-Node.js-and-WebSockets-with-Redis

编辑2

我似乎需要澄清一下.

• 上面显示了仅限Websocket的处理程序

• Redis Pub/Sub处理程序可能如下所示:

  class WebsocketEchoHandler:
  
      @asyncio.coroutine
      def __call__(self, request):
          ws = web.WebSocketResponse()
          ws.start(request)
  
          connection = yield from asyncio_redis.Connection.create(host='127.0.0.1', port=6379)
          subscriber = yield from connection.start_subscribe()
          yield from subscriber.subscribe(['ch1', 'ch2'])
  
          print('Connection opened')
          try:
              while True:
                  msg = yield from subscriber.next_published()
                  ws.send_str(msg.value + '/answer')
          except:
              pass
          finally:
              print('Connection closed')
          return ws
  

  该处理程序只订阅Redis通道ch1和ch2,并将从这些通道收到的每条消息发送到websocket.

• 我想要这个处理程序:

  class WebsocketEchoHandler:
  
      @asyncio.coroutine
      def __call__(self, request):
          ws = web.WebSocketResponse()
          ws.start(request)
  
          connection = yield from asyncio_redis.Connection.create(host='127.0.0.1', port=6379)
          subscriber = yield from connection.start_subscribe()
          yield from subscriber.subscribe(['ch1', 'ch2'])
  
          print('Connection opened')
          try:
              while True:
                  # If message recived from redis OR from websocket
                  msg_ws = yield from ws.receive()
                  msg_redis = yield from subscriber.next_published()
                  if msg_ws:
                      # push to redis / do something else
                      self.on_msg_from_ws(msg_ws)
                  if msg_redis:
                      self.on_msg_from_redis(msg_redis)
          except:
              pass
          finally:
              print('Connection closed')
          return ws
  

  但是下面的代码总是按顺序调用,所以读取来自Redis的websocket块:

  msg_ws = yield from ws.receive()
  msg_redis = yield from subscriber.next_published()
  

我希望在事件是从两个来源之一收到的消息的事件上完成阅读.

Answer 1

您应该使用两个while循环 - 一个用于处理来自websocket的消息,另一个用于处理来自redis的消息.你的主要处理程序可以刚刚打完假两个协同程序,一个处理每个循环,然后等待两个人:

class WebsocketEchoHandler:
    @asyncio.coroutine
    def __call__(self, request):
        ws = web.WebSocketResponse()
        ws.start(request)

        connection = yield from asyncio_redis.Connection.create(host='127.0.0.1', port=6379)
        subscriber = yield from connection.start_subscribe()
        yield from subscriber.subscribe(['ch1', 'ch2'])

        print('Connection opened')
        try:
            # Kick off both coroutines in parallel, and then block
            # until both are completed.
            yield from asyncio.gather(self.handle_ws(ws), self.handle_redis(subscriber))
        except Exception as e:  # Don't do except: pass
            import traceback
            traceback.print_exc()
        finally:
            print('Connection closed')
        return ws

    @asyncio.coroutine
    def handle_ws(self, ws):
        while True:
            msg_ws = yield from ws.receive()
            if msg_ws:
                self.on_msg_from_ws(msg_ws)

    @asyncio.coroutine
    def handle_redis(self, subscriber):
        while True:
            msg_redis = yield from subscriber.next_published()
            if msg_redis:
                self.on_msg_from_redis(msg_redis)

通过这种方式,您可以从两个潜在来源中的任何一个进行阅读,而无需关心另一个.