Socket.IO cluster adapter

The @socket.io/cluster-adapter package allows broadcasting packets between multiple Socket.IO servers.

It can be used in conjunction with @socket.io/sticky to broadcast packets between the workers of the same Node.js cluster.

Supported features:

• broadcasting
• utility methods
  • socketsJoin
  • socketsLeave
  • disconnectSockets
  • fetchSockets
  • serverSideEmit

Related packages:

• Postgres adapter: https://github.com/socketio/socket.io-postgres-adapter/
• Redis adapter: https://github.com/socketio/socket.io-redis-adapter/
• MongoDB adapter: https://github.com/socketio/socket.io-mongo-adapter/

Table of contents

• Installation
• Usage
• License

Installation

npm install @socket.io/cluster-adapter

Usage

1const cluster = require("cluster");
2const http = require("http");
3const { Server } = require("socket.io");
4const numCPUs = require("os").cpus().length;
5const { setupMaster, setupWorker } = require("@socket.io/sticky");
6const { createAdapter, setupPrimary } = require("@socket.io/cluster-adapter");
7
8if (cluster.isMaster) {
9  console.log(`Master ${process.pid} is running`);
10
11  const httpServer = http.createServer();
12
13  // setup sticky sessions
14  setupMaster(httpServer, {
15    loadBalancingMethod: "least-connection",
16  });
17
18  // setup connections between the workers
19  setupPrimary();
20
21  // needed for packets containing buffers (you can ignore it if you only send plaintext objects)
22  // Node.js < 16.0.0
23  cluster.setupMaster({
24    serialization: "advanced",
25  });
26  // Node.js > 16.0.0
27  // cluster.setupPrimary({
28  //   serialization: "advanced",
29  // });
30
31  httpServer.listen(3000);
32
33  for (let i = 0; i < numCPUs; i++) {
34    cluster.fork();
35  }
36
37  cluster.on("exit", (worker) => {
38    console.log(`Worker ${worker.process.pid} died`);
39    cluster.fork();
40  });
41} else {
42  console.log(`Worker ${process.pid} started`);
43
44  const httpServer = http.createServer();
45  const io = new Server(httpServer);
46
47  // use the cluster adapter
48  io.adapter(createAdapter());
49
50  // setup connection with the primary process
51  setupWorker(io);
52
53  io.on("connection", (socket) => {
54    /* ... */
55  });
56}

License

MIT