Example to use socket.io-redis

Question

Hi all and thanks for your time and your help.

I need a simple example for use socket.io-redis, with comments please. I read the documentation, but I did not understand. Thank you,

Stela

Answer 1

The socket.io-redis documentation don't mention you actually need to run a redis server so you might have forgotten that. The socket.io-redis plugin uses the pub/sub client of the redis server to connect multiple socket.io instances.

1. download and install a redis server from https://redis.io

2. add the redis plugin to your socket.io instances:

   var express = require('express');
   var app = express();
   var server = require('http').Server(app);
   var io = require('socket.io')(server);
   var redis = require('socket.io-redis');
   io.adapter(redis({ host: 'localhost', port: 6379 }));
   

   The 6379 is the default redis port, localhost if you run node and redis on the same server.

3. add socket.io and socket.io-redis functions you need

   var your_namespace_socket = io.of('/your-namespace');
   your_namespace_socket.on('connection', function(socket){
   
     socket.on('join', function(room){
       socket.join(room);
   
       //log other socket.io-id's in the room
       your_namespace_socket.adapter.clients([room], (err, clients) => {
         console.log(clients);
       });
     });
   });
   

4. Start the server with socket.io

   server.listen(3000, function(){
      logger.debug('listening on *:3000');
   });
   

Pratt

If I ran multiple sockeio nodejs server in different machine, will this adaptor allow me to join selected users, from different servers, in a single room? – Dewaynedewberry

@Dewaynedewberry yes it will! The room itself is persisted on Redis so when you ask for users, you don't actually ask it from the server (in-memory), but from Redis (persisted across servers). From the package's GitHub page - "Adapter to enable broadcasting of events to multiple separate socket.io server nodes." – Melvinamelvyn

Thanks a lot. Why nobody tell that we need a redis server? Accutally there are a lot of people just starting who never heard about redis that really can't understand this necessity. Again, thanks a lot – Crossbow

@Melvinamelvyn From the Github page - Note: no data is stored in Redis itself. Redis server only acts as a pub/sub server. Each emitted message is published to redis which is broadcast to other socket servers as well. – Ingesta

Answer 2

io.on('connect', socket => {
    socket.on("createNotifications", () => {
        io.sockets.emit("notificationCreated", {
            'id': Date.now(),
            'name': `You just created notification at date`
        });
    });
});

Mickens

please covert this code into socket.io-redis – Mickens

I'm not sure how this answer's OP's question. – Whitelaw