Websocket (Python 3.5中的ws4py)不能在Docker容器中工作

Question

我有一个简单的web应用程序，使用CherryPy作为RESTful后端，使用ws4py作为websockets。

1) Javascript client sends a POST to Python backend
2) Python replies with a unique id
3) Javascript connects to the websocket and sends the unique id
4) Python associates the websocket client connection to the unique id

Python websocket代码:

class WebSocketHandler(WebSocket):
def __init__(self, *args, **kw):
    WebSocket.__init__(self, *args, **kw)
    print('Connected to websocket server!')
    SUBSCRIBERS.add(self)
def received_message(self, message):
    print('Websocket identified itself?')
    SUBSCRIBERS_WITH_ID[message.data] = self

Python CherryPy代码:

cherrypy.config.update({'server.socket_host': 0.0.0.0,
                        'server.socket_port': 8080})
cherrypy.tools.CORS = cherrypy.Tool('before_handler', CORS)
WebSocketPlugin(cherrypy.engine).subscribe()
cherrypy.tools.websocket = WebSocketTool()
cherrypy.tree.mount(
    DummyAPI(), '/api/dummy', config={
        '/': {
            'request.dispatch': cherrypy.dispatch.MethodDispatcher(),
            'tools.CORS.on': True
        }
    }
)
cherrypy.tree.mount(
    WebSocketAPI(), '/ws', config={
        '/': {
            'tools.websocket.on': True,
            'tools.websocket.handler_cls': WebSocketHandler
        }
    }
)
cherrypy.engine.start()
cherrypy.engine.block()

Javascript代码:

POST到API:

var req = new XMLHttpRequest();
req.onload = function (e) {
    console.log('Response code: ' + req.responseText);
    result_id = req.responseText;
    websocketConnect();
};
req.open('POST', api_url);
req.send();

Websocket部分:

function websocketConnect() {
websocket = new WebSocket(websocket_url);
websocket.onopen = function (evt) { 
      console.log("Connected to WebSocket server.");
      websocket.send(result_id)};

这在我的机器上运行良好，并部署在Amazon EC2上。然而，当我试图在Docker容器中部署它时，websockets不工作。

这是我的Dockerfile:

FROM python
MAINTAINER xxx
RUN pip3.5 install cherrypy ws4py
RUN mkdir /var/www
COPY python /var/www/python
EXPOSE 8080
CMD ["/usr/local/bin/python3.5", "/var/www/python/simplews.py"]

从Docker运行时的输出:

sudo docker run  -v /tmp/dockertmp/:/tmp/ -p 8080:8080 -i 563a51d13f59
[23/Oct/2015:10:09:00] ENGINE Bus STARTING
[23/Oct/2015:10:09:00] ENGINE Starting WebSocket processing
[23/Oct/2015:10:09:00] ENGINE Started monitor thread '_TimeoutMonitor'.
[23/Oct/2015:10:09:00] ENGINE Started monitor thread 'Autoreloader'.
[23/Oct/2015:10:09:01] ENGINE Serving on http://0.0.0.0:8080
[23/Oct/2015:10:09:01] ENGINE Bus STARTED
172.17.42.1 - - [23/Oct/2015:10:09:08] "POST ..."
Connected to websocket server!

它永远不会达到Javascript文件能够通过websocket发送数据的阶段。Chrome调试显示WS状态为"Pending"。

然而，当我退出Docker中的CherryPy应用程序时，websocket消息通过:

enter code here
sudo docker run  -v /tmp/dockertmp/:/tmp/ -p 8080:8080 -i 563a51d13f59
[23/Oct/2015:10:15:30] ENGINE Bus STARTING
[23/Oct/2015:10:15:30] ENGINE Starting WebSocket processing
[23/Oct/2015:10:15:30] ENGINE Started monitor thread '_TimeoutMonitor'.
[23/Oct/2015:10:15:30] ENGINE Started monitor thread 'Autoreloader'.
[23/Oct/2015:10:15:30] ENGINE Serving on http://0.0.0.0:8080
[23/Oct/2015:10:15:30] ENGINE Bus STARTED
172.17.42.1 - - [23/Oct/2015:10:15:33] "POST ..."
Connected to websocket server!
^C[23/Oct/2015:10:15:35] ENGINE Keyboard Interrupt: shutting down bus
[23/Oct/2015:10:15:35] ENGINE Bus STOPPING
[23/Oct/2015:10:15:40] ENGINE HTTP Server     cherrypy._cpwsgi_server.CPWSGIServer(('0.0.0.0', 8080)) shut down
[23/Oct/2015:10:15:40] ENGINE Stopped thread '_TimeoutMonitor'.
[23/Oct/2015:10:15:40] ENGINE Terminating WebSocket processing
[23/Oct/2015:10:15:40] ENGINE Stopped thread 'Autoreloader'.
[23/Oct/2015:10:15:40] ENGINE Bus STOPPED
[23/Oct/2015:10:15:40] ENGINE Bus EXITING
[23/Oct/2015:10:15:40] ENGINE Bus EXITED
[23/Oct/2015:10:15:40] ENGINE Waiting for child threads to terminate...
Websocket identified itself?

在没有Docker的情况下运行时的输出:

python3.5 python/simplews.py 
[23/Oct/2015:06:09:45] ENGINE Bus STARTING
[23/Oct/2015:06:09:45] ENGINE Starting WebSocket processing
[23/Oct/2015:06:09:45] ENGINE Started monitor thread '_TimeoutMonitor'.
[23/Oct/2015:06:09:45] ENGINE Started monitor thread 'Autoreloader'.
[23/Oct/2015:06:09:45] ENGINE Serving on http://0.0.0.0:8080
[23/Oct/2015:06:09:45] ENGINE Bus STARTED
127.0.0.1 - - [23/Oct/2015:06:09:48] "POST ..."
Connected to websocket server!
Websocket identified itself?

在非docker的情况下，websocket立即标识自己。我想不明白。websocket接收线程是否在Docker中卡住?

Docker日志中可疑的部分是当应用程序退出时，websocket接收到的消息最终到达:

[23/Oct/2015:10:15:40] ENGINE Waiting for child threads to terminate...
Websocket identified itself?

Answer 1

将Python多处理模块替换为线程。线程修复了这个问题。我在POST方法处理程序中使用了多处理。

下面是对实际项目进行修复的提交:

https://github.com/sevagh/youtube-audio-dl/commit/9e23ae174f8791206b934608a1d4d702b411d18e