/socket.io-redis-streams-adapter

The Socket.IO adapter based on Redis Streams, allowing to broadcast events between several Socket.IO servers.

Primary LanguageTypeScriptMIT LicenseMIT

Socket.IO Redis Streams adapter

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

Supported features:

Related packages:

Table of contents

Installation

npm install @socket.io/redis-streams-adapter redis

Usage

With the redis package

import { createClient } from "redis";
import { Server } from "socket.io";
import { createAdapter } from "@socket.io/redis-streams-adapter";

const redisClient = createClient({ url: "redis://localhost:6379" });

await redisClient.connect();

const io = new Server({
  adapter: createAdapter(redisClient)
});

io.listen(3000);

With the redis package and a Redis cluster

import { createCluster } from "redis";
import { Server } from "socket.io";
import { createAdapter } from "@socket.io/redis-streams-adapter";

const redisClient = createCluster({
  rootNodes: [
    {
      url: "redis://localhost:7000",
    },
    {
      url: "redis://localhost:7001",
    },
    {
      url: "redis://localhost:7002",
    },
  ],
});

await redisClient.connect();

const io = new Server({
  adapter: createAdapter(redisClient)
});

io.listen(3000);

With the ioredis package

import { Redis } from "ioredis";
import { Server } from "socket.io";
import { createAdapter } from "@socket.io/redis-streams-adapter";

const redisClient = new Redis();

const io = new Server({
  adapter: createAdapter(redisClient)
});

io.listen(3000);

With the ioredis package and a Redis cluster

import { Cluster } from "ioredis";
import { Server } from "socket.io";
import { createAdapter } from "@socket.io/redis-streams-adapter";

const redisClient = new Cluster([
  {
    host: "localhost",
    port: 7000,
  },
  {
    host: "localhost",
    port: 7001,
  },
  {
    host: "localhost",
    port: 7002,
  },
]);

const io = new Server({
  adapter: createAdapter(redisClient)
});

io.listen(3000);

Options

Name Description Default value
streamName The name of the Redis stream. socket.io
maxLen The maximum size of the stream. Almost exact trimming (~) is used. 10_000
readCount The number of elements to fetch per XREAD call. 100
sessionKeyPrefix The prefix of the key used to store the Socket.IO session, when the connection state recovery feature is enabled. sio:session:
heartbeatInterval The number of ms between two heartbeats. 5_000
heartbeatTimeout The number of ms without heartbeat before we consider a node down. 10_000

How it works

The adapter will use a Redis stream to forward events between the Socket.IO servers.

Notes:

  • a single stream is used for all namespaces
  • the maxLen option allows to limit the size of the stream
  • unlike the adapter based on Redis PUB/SUB mechanism, this adapter will properly handle any temporary disconnection to the Redis server and resume the stream
  • if connection state recovery is enabled, the sessions will be stored in Redis as a classic key/value pair

License

MIT