@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

0.2.0 (2022-04-28)

Features

• broadcast and expect multiple acks (055b784)

This feature was added in socket.io@4.5.0:

io.timeout(1000).emit("some-event", (err, responses) => {
  // ...
});

Thanks to this change, it will now work within a Node.js cluster.