@socket.io/cluster-adapter

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

const cluster = require("cluster");
const http = require("http");
const { Server } = require("socket.io");
const numCPUs = require("os").cpus().length;
const { setupMaster, setupWorker } = require("@socket.io/sticky");
const { createAdapter, setupPrimary } = require("@socket.io/cluster-adapter");

if (cluster.isMaster) {
  console.log(`Master ${process.pid} is running`);

  const httpServer = http.createServer();

  // setup sticky sessions
  setupMaster(httpServer, {
    loadBalancingMethod: "least-connection",
  });

  // setup connections between the workers
  setupPrimary();

  // needed for packets containing buffers (you can ignore it if you only send plaintext objects)
  // Node.js < 16.0.0
  cluster.setupMaster({
    serialization: "advanced",
  });
  // Node.js > 16.0.0
  // cluster.setupPrimary({
  //   serialization: "advanced",
  // });

  httpServer.listen(3000);

  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }

  cluster.on("exit", (worker) => {
    console.log(`Worker ${worker.process.pid} died`);
    cluster.fork();
  });
} else {
  console.log(`Worker ${process.pid} started`);

  const httpServer = http.createServer();
  const io = new Server(httpServer);

  // use the cluster adapter
  io.adapter(createAdapter());

  // setup connection with the primary process
  setupWorker(io);

  io.on("connection", (socket) => {
    /* ... */
  });
}

License

MIT

Changelog

0.2.2 (2023-03-24)

The socket.io-adapter package was added to the list of peerDependencies, in order to fix sync issues with the version imported by the socket.io package (see 15fd56e).

Support for connection state recovery (see here) will be added in the next release.