Using Redis as PubSub over Socket.io

Question

I am creating a chat application which enable users to do private and group chats. Planning to use following technologies for this app:-

NodeJs + Socket.io + Redis + CouchDB(To store message history) + AngularJS

Per my initial research using Redis as a PubSub service is better approach over using Socket.io as pub-sub .Reason of this is if different users are connected to different server instances, then using socket in this scenario will create problem as message send by user 1 will not pass on to user 2(user 1 connected to server 1 and user 2 connected to server 2).

But if we use Redis, then per my understanding we have to create new channels to enable private chats. And their is a limit to 10k channels in Redis.

My Doubts are

1. Do I need to create new channel every time to enable private chat between two users?
2. If I need to create separate channels, then is there actually a limit of 10K channels?
3. I need a working example of using Redis as pub/sub with socket.io to enable private chats.

Regards, Vikram

Answer 1

After reading below articles/blog post, using Redis for pub/sub over socket.io pub/sub will help in scalability and better performance.

https://github.com/sayar/RedisMVA/blob/master/module6_redis_pubsub/README.md

https://github.com/rajaraodv/redispubsub

Further I am able to create a quick POC on private chat using redis . Here is the code:-

var app = require('http').createServer(handler);
app.listen(8088);
var io = require('socket.io').listen(app);
var redis = require('redis');
var redis2 = require('socket.io-redis');
io.adapter(redis2({ host: 'localhost', port: 6379 }));
var fs = require('fs');

function handler(req,res){
    fs.readFile(__dirname + '/index.html', function(err,data){
        if(err){
            res.writeHead(500);
            return res.end('Error loading index.html');
        }
        res.writeHead(200);
        console.log("Listening on port 8088");
        res.end(data);
    });
}

var store = redis.createClient();   
var pub = redis.createClient();
var sub = redis.createClient();
sub.on("message", function (channel, data) {
        data = JSON.parse(data);
        console.log("Inside Redis_Sub: data from channel " + channel + ": " + (data.sendType));
        if (parseInt("sendToSelf".localeCompare(data.sendType)) === 0) {
             io.emit(data.method, data.data);
        }else if (parseInt("sendToAllConnectedClients".localeCompare(data.sendType)) === 0) {
             io.sockets.emit(data.method, data.data);
        }else if (parseInt("sendToAllClientsInRoom".localeCompare(data.sendType)) === 0) {
            io.sockets.in(channel).emit(data.method, data.data);
        }       

    });

io.sockets.on('connection', function (socket) {

    sub.on("subscribe", function(channel, count) {
        console.log("Subscribed to " + channel + ". Now subscribed to " + count + " channel(s).");
    });

    socket.on("setUsername", function (data) {
        console.log("Got 'setUsername' from client, " + JSON.stringify(data));
        var reply = JSON.stringify({
                method: 'message',
                sendType: 'sendToSelf',
                data: "You are now online"
            });     
    });

    socket.on("createRoom", function (data) {
        console.log("Got 'createRoom' from client , " + JSON.stringify(data));
        sub.subscribe(data.room);
        socket.join(data.room);     

        var reply = JSON.stringify({
                method: 'message', 
                sendType: 'sendToSelf',
                data: "Share this room name with others to Join:" + data.room
            });
        pub.publish(data.room,reply);


    });
    socket.on("joinRooom", function (data) {
        console.log("Got 'joinRooom' from client , " + JSON.stringify(data));
        sub.subscribe(data.room);
        socket.join(data.room);     

    });
    socket.on("sendMessage", function (data) {
        console.log("Got 'sendMessage' from client , " + JSON.stringify(data));
        var reply = JSON.stringify({
                method: 'message', 
                sendType: 'sendToAllClientsInRoom',
                data: data.user + ":" + data.msg 
            });
        pub.publish(data.room,reply);

    });

    socket.on('disconnect', function () {
        sub.quit();
        pub.publish("chatting","User is disconnected :" + socket.id);
    });

  });

HTML Code

<html>
<head>
    <title>Socket and Redis in Node.js</title>
    <script src="/socket.io/socket.io.js"></script>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
</head>
<body>
<div id="username">
    <input type="text" name="usernameTxt" /> 
    <input type="button" name="setUsername" value="Set Username" />
</div>
<div id="createroom" style="display:none;">>
    <input type="text" name="roomNameTxt" /> 
    <input type="button" name="setRooomName" value="Set Room Name" />
    <input type="button" name="joinRooomName" value="Join" />
</div>
<div id="sendChat" style="display:none;">
    <input type="text" name="chatTxt" /> 
    <input type="button" name="sendBtn" value="Send" />
</div>
<br />
<div id="content"></div>
<script>    
    $(document).ready(function() {
        var username = "anonymous";
        var roomname = "anonymous";
        $('input[name=setUsername]').click(function(){
            if($('input[name=usernameTxt]').val() != ""){
                username = $('input[name=usernameTxt]').val();
                //var msg = {type:'setUsername',user:username};
                socket.emit('setUsername',{user:username});
            }
            $('#username').slideUp("slow",function(){
                $('#createroom').slideDown("slow");
            });
        });
        $('input[name=setRooomName]').click(function(){
            if($('input[name=roomNameTxt]').val() != ""){
                roomname = $('input[name=roomNameTxt]').val();
                socket.emit('createRoom',{user:username,room:roomname});
            }
            $('#createroom').slideUp("slow",function(){
                $('#sendChat').slideDown("slow");
            });
        });
        $('input[name=joinRooomName]').click(function(){
            if($('input[name=roomNameTxt]').val() != ""){
                roomname = $('input[name=roomNameTxt]').val();
                socket.emit('joinRooom',{room:roomname});
            }
            $('#createroom').slideUp("slow",function(){
                $('#sendChat').slideDown("slow");
            });
        });

        var socket = new io.connect('http://localhost:8088');
        var content = $('#content');

        socket.on('connect', function() {
            console.log("Connected");
        });

        socket.on('message', function(message){
            //alert('received msg=' + message);
            content.append(message + '<br />');
        }) ;

        socket.on('disconnect', function() {
            console.log('disconnected');
            content.html("<b>Disconnected!</b>");
        });

        $("input[name=sendBtn]").click(function(){
            var msg = {user:username,room:roomname,msg:$("input[name=chatTxt]").val()}
            socket.emit('sendMessage',msg);
            $("input[name=chatTxt]").val("");
        });
    });
</script>
</body>
</html>

Answer 2

That's all code basic redis pub/sub.

 var redis = require("redis"); var pub = redis.createClient(); var sub = redis.createClient(); sub.on("subscribe", function(channel, count) { console.log("Subscribed to " + channel + ". Now subscribed to " + count + " channel(s)."); }); sub.on("message", function(channel, message) { console.log("Message from channel " + channel + ": " + message); }); sub.subscribe("tungns"); setInterval(function() { var no = Math.floor(Math.random() * 100); pub.publish('tungns', 'Generated Chat random no ' + no); }, 5000); 

Answer 3

If you need to get your feet wet and create a simple chat application, then the following development stack works very nicely together:

• Express.js (Node.js)
• Redis
• Socket.IO

The application consists of a chat room that users can join and start up a conversation. Socket.IO is responsible for emitting events when the chatter count/messages are updated and these are refreshed in the UI using jQuery.

For the full article and the source code, check out the following link: https://scalegrid.io/blog/using-redis-with-node-js-and-socket-io/

Answer 4

The socket.io-redis says :

By running socket.io with the socket.io-redis adapter you can run multiple socket.io instances in different processes or servers that can all broadcast and emit events to and from each other. So any of the following commands:

io.emit('hello', 'to all clients');
io.to('room42').emit('hello', "to all clients in 'room42' room");

io.on('connection', (socket) => {
  socket.broadcast.emit('hello', 'to all clients except sender');
  socket.to('room42').emit('hello', "to all clients in 'room42' room except sender");
});

will properly be broadcast to the clients through the Redis Pub/Sub mechanism.

and I guess

io.to(socket.id).emit('hello', "to client which has same socket.id");

would send private message in different processes or servers.

By the way, I am doing a project also need private message. Any other suggestions would like to be raised.