PyZMQ Gevent Websocket Connection Error

Question

I am trying pub/sub pattern using python zmq. I am facing a strange problem on the client side. On the client side I am using pyzmq, gevent-websocket and bottle as wsgi server. Though it works perfectly for one client, the other clients are waiting for the first client to disconnect. While working with one client, if I disconnect and reconnect, I am getting the messages two times or more for each reconnect.

#!/usr/bin/python
from gevent import monkey; monkey.patch_all()
import zmq
import gevent
from bottle import route, run, request, abort, Bottle ,static_file
from gevent import sleep
from gevent.pywsgi import WSGIServer
import geventwebsocket
from geventwebsocket import WebSocketHandler, WebSocketError

host = "127.0.0.1"
port = 8000
mqport = "8082"

context = zmq.Context()
socket = context.socket(zmq.SUB)

app = Bottle()

@app.route('/v1/streams/device/<id>')
def handle_websocket(id):
    socket.setsockopt(zmq.UNSUBSCRIBE, '')
    socket.connect ("tcp://localhost:%s" % mqport)
    socket.setsockopt(zmq.SUBSCRIBE, id)
    wsock = request.environ.get('wsgi.websocket')
    if wsock is None:
        logger.info("Error creating websocket")
    try :
        while True:
            string = socket.recv()
            logger.info("%s" % string)
            id, data = string.split("  ")
            wsock.send("%s" % data)
            sleep(0.1)
    except geventwebsocket.WebSocketError, ex:
        wsock.close()
        sock.close()
server = WSGIServer((host, port), app,
                handler_class=WebSocketHandler)
server.serve_forever()

All the examples I have seen use while loop for receiving the messages. I am not comfortable with this while loop and looking for some call back function like socket.on_message. For experimental purpose I wrote a node.js version of the same without the while loop like this but in my project node is ruled out. The node version is here:

var WebSocketServer = require('websocket').server;

var http = require('http');

global.client = 0;

var server = http.createServer(function(request, response) {

});

server.listen(8000, function() { });

wsServer = new WebSocketServer({

    httpServer: server

});



// WebSocket server

wsServer.on('request', function(request) {

    console.log("connected client :", global.client++)

    var connection = request.accept(null, request.origin); 

    var url = request.resourceURL.href

    var device_id = url.substr(url.lastIndexOf('/') + 1)

    var zeromq = require('zmq');

    var sock = zeromq.socket('sub');

    sock.connect('tcp://127.0.0.1:8082');

    sock.subscribe(device_id);

    sock.on('message', function(data) {
        console.log(data.toString());

        var msg = data.toString();

        var rjson = msg.split("  ") 

        connection.send(rjson.pop());

    });

    connection.on('close', function(connection) {
    });
});

Here I dont use the while Loop.

What I am doing wrong on my python code?

Answer 1

After hitting the wall on several days we find a non-blocking zeromq client called gevent-zeromq.

Lesson is anybody using gevent-websocket with zmq client don't use pyzmq but use gevent-zeromq.

Now the gevent-zeromq is merged with pyzmq. Intead of doing import zmq do from zmq.green import zmq