Amqp, rabbit mq and socket.io reconnect to a queue even if client is closed

Question

I'm coding a browser notification using rabbitMQ and socket.io. My configuration is working fine except for one case.

When i login to my system with a user it creates a notification-UID-userid queue (For now the queueName is sent by query oaraeter, i will implement more sofisticated method as soon as i will solve the problem)

If i login with another user on another browser it creates another queue notification-UID-seconduserid.

If i logout one of the user the queue will disappear (as it's not durable).

The problem is that when i refresh or load another page on the other session it recreates the second queue even if the paramater queuename isn't sent.

server.js

var amqp = require('amqp');
var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);

var rabbitMqConnection = null;
var _queue = null;
var _consumerTag = null;


io.use(function (socket, next) {
    var handshakeData = socket.handshake;
    // Here i will implement token verification
    console.log(socket.handshake.query.queueName);
    next();
});


// Gets the connection event form client
io.sockets.on('connection', function (socket) {

    var queueName = socket.handshake.query.queueName;

    console.log("Socket Connected");

    // Connects to rabbiMq
    rabbitMqConnection = amqp.createConnection({host: 'localhost', reconnect: false});

    // Update our stored tag when it changes
    rabbitMqConnection.on('tag.change', function (event) {
        if (_consumerTag === event.oldConsumerTag) {
            _consumerTag = event.consumerTag;
            // Consider unsubscribing from the old tag just in case it lingers
            _queue.unsubscribe(event.oldConsumerTag);
        }
    });

    // Listen for ready event
    rabbitMqConnection.on('ready', function () {
        console.log('Connected to rabbitMQ');

        // Listen to the queue
        rabbitMqConnection.queue(queueName, {
                closeChannelOnUnsubscribe: true,
                durable: false,
                autoClose: true
            },
            function (queue) {
                console.log('Connected to ' + queueName);
                _queue = queue;

                // Bind to the exchange
                queue.bind('users.direct', queueName);

                queue.subscribe({ack: false, prefetchCount: 1}, function (message, headers, deliveryInfo, ack) {
                    console.log("Received a message from route " + deliveryInfo.routingKey);
                    socket.emit('notification', message);
                    //ack.acknowledge();
                }).addCallback(function (res) {
                    // Hold on to the consumer tag so we can unsubscribe later
                    _consumerTag = res.consumerTag;
                });
            });
    });


    // Listen for disconnection
    socket.on('disconnect', function () {
        _queue.unsubscribe(_consumerTag);
        rabbitMqConnection.disconnect();
        console.log("Socket Disconnected");
    });

});

http.listen(8080);

client.js

var io = require('socket.io-client');

$(document).ready(function () {

    var socket = io('http://myserver.it:8080/', {
         query:  { queueName: 'notification-UID-' + UID},
        'sync disconnect on unload': true,
        });

    socket.on('notification', function (data) {
        console.log(data);
    });
})

Any idea?

score 2 · Accepted Answer · answered Aug 28 '18 at 09:09

So i solved my problem, it was a variable scope problem that messed things. Let me explain what i'm doing, maybe it could be useful to someone.

Basically i'm trying to create a browser notification system, it means that my application publish (producer side) to an exchange a notification object that contains some info such as subject, link and message.

The exchange is a fanout (users.notification.fanout) that have two binded exchanges: users.direct (direct type) and users.notification.store (fanout type).

When the producer publishes a notification, it does to the users.notification.fanout with routing key "notification-UID-userid" (where userid is the real user id.

The notification object goes to both, users.direct and users.notification.store The last one has a consumer that writes the notification to the DB in case the user is not logged, the first one publishes the notification to the browser.

So how the browser consumer works?

I used the classical combination of socket.io, node server, and amqplib.

Every time a user login, the socket.io creates a queue with name and routing key notification-UID-userid and binds it to users.direct exchange.

In the meanwhile i've added https to my server so things changed a little bit from first version.

You can read comments to know what it does.

So my server.js is

var amqp = require('amqp');
var fs = require('fs');
var app = require('express')();
// Https server, certificates and private key added
var https = require('https').Server({
    key: fs.readFileSync('/home/www/site/privkey.pem'),
    cert: fs.readFileSync('/home/www/site/fullchain.pem')},app);
var io = require('socket.io')(https);

// Used to verify if token is valid
// If not it will discard connection
io.use(function (socket, next) {
    var handshakeData = socket.handshake;
    // Here i will implement token verification
    console.log("Check this token: " + handshakeData.query.token);
    next();
});
// Gets the connection event from client
io.sockets.on('connection', function (socket) {
    // Connection log
    console.log("Socket Connected with ID: " + socket.id);
    // THIS WAS THE PROBLEM
    // Local variables for connections
    // Former i've put these variables outside the connection so at 
    // every client they were "overridden". 
    // RabbitMq Connection (Just for current client)
    var _rabbitMqConnection = null;
    // Queue (just for current client)
    var _queue = null;
    // Consumer tag (just for current client)
    var _consumerTag = null;
    // Queue name and routing key for current user
    var queueName = socket.handshake.query.queueName;
    // Connects to rabbiMq with default data to localhost guest guest
    _rabbitMqConnection = amqp.createConnection();
    // Connection ready
    _rabbitMqConnection.on('ready', function () {
        // Connection log
        console.log('#' + socket.id + ' - Connected to RabbitMQ');
        // Creates the queue (default is transient and autodelete)
        // https://www.npmjs.com/package/amqp#connectionqueuename-options-opencallback
        _rabbitMqConnection.queue(queueName, function (queue) {
            // Connection log
            console.log('#' + socket.id + ' - Connected to ' + queue.name + ' queue');
            // Stores local queue
            _queue = queue;
            // Bind to the exchange (default)
            queue.bind('users.direct', queueName, function () {
                // Binding log
                console.log('#' + socket.id + ' - Binded to users.direct exchange');
                // Consumer definition
                queue.subscribe({ack: false}, function (message, headers, deliveryInfo, messageObject) {
                    // Message log
                    console.log('#' + socket.id + ' - Received a message from route ' + deliveryInfo.routingKey);
                    // Emit the message to the client
                    socket.emit('notification', message);
                }).addCallback(function (res) {
                    // Hold on to the consumer tag so we can unsubscribe later
                    _consumerTag = res.consumerTag;
                    // Consumer tag log
                    console.log('#' + socket.id + ' - Consumer ' + _consumerTag + ' created');
                })
            });

        });
    });
    // Update our stored tag when it changes
    _rabbitMqConnection.on('tag.change', function (event) {
        if (_consumerTag === event.oldConsumerTag) {
            _consumerTag = event.consumerTag;
            // Unsubscribe from the old tag just in case it lingers
            _queue.unsubscribe(event.oldConsumerTag);
        }
    });
    // Listen for disconnection
    socket.on('disconnect', function () {
        _queue.unsubscribe(_consumerTag);
        _rabbitMqConnection.disconnect();
        console.log('#' + socket.id + ' - Socket Disconnected');
    });
});

https.listen(8080);

Then my client.js

var io = require('socket.io-client');

$(document).ready(function () {

    var socket = io('https://myserver.com:8080/', {
        secure: true, // for ssl connections
        query:  { queueName: 'notification-UID-' + UID, token: JWTToken}, // params sent to server, JWTToken for authentication
        'sync disconnect on unload': true // Every time the client unload, socket disconnects
    });

    socket.on('notification', function (data) {
        // Do what you want with your data
        console.log(data);
    });
})

Amqp, rabbit mq and socket.io reconnect to a queue even if client is closed

1 Answers1