Socket.IO Redis Streams adapter

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

Supported features:

• broadcasting
• utility methods
  • socketsJoin
  • socketsLeave
  • disconnectSockets
  • fetchSockets
  • serverSideEmit
• connection state recovery

Related packages:

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

Table of contents

• Installation
• Usage
• Options
• How it works
• License

Installation

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

Usage

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);

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 | | 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