@socket.io/sticky

    1.0.1 • Public • Published

    Sticky sessions for Socket.IO

    A simple and performant way to use Socket.IO within a cluster.

    Unlike other packages like sticky-session, the routing is based on the session ID (the sid query parameter).

    Cluster diagram

    See also:

    Table of contents

    Installation

    npm install @socket.io/sticky
    

    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();
    
      setupMaster(httpServer, {
        loadBalancingMethod: "least-connection", // either "random", "round-robin" or "least-connection"
      });
    
      setupPrimary();
    
      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);
      io.adapter(createAdapter());
      setupWorker(io);
    
      io.on("connection", (socket) => {
        /* ... */
      });
    }

    How it works

    The first HTTP request (without sid query parameter) is forwarded to a random worker (based on the loadBalancingMethod option).

    The underlying Engine.IO server creates a new session and emits a connection event with the session ID. The worker sends this session ID to the master, which stores the relationship between the worker ID and the session ID.

    For subsequent requests, the sid query parameter is extracted by the master process, which then forwards the handle to the right worker.

    Notes

    • this package is not needed if you only use WebSockets (which might be a sensible choice as of 2021)
    // client-side
    const socket = io({
      transports: ["websocket"] // HTTP long-polling is disabled
    });
    • in a multi-server setup, you will need to use another adapter, like the Redis adapter

    Cluster diagram with Redis

    • this module is not compatible with an HTTPS server

    For more information, please see this issue.

    License

    MIT

    Install

    npm i @socket.io/sticky

    DownloadsWeekly Downloads

    572

    Version

    1.0.1

    License

    MIT

    Unpacked Size

    9.17 kB

    Total Files

    5

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