Redis Streams adapter

How it works

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

The main difference with the existing Redis adapter (which use the Redis Pub/Sub mechanism) is that this adapter will properly handle any temporary disconnection to the Redis server and resume the stream without losing any packets.

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

Source code: https://github.com/socketio/socket.io-redis-streams-adapter

Supported features

Feature	socket.io version	Support
Socket management	4.0.0	✅ YES (since version 0.1.0)
Inter-server communication	4.1.0	✅ YES (since version 0.1.0)
Broadcast with acknowledgements	4.5.0	✅ YES (since version 0.1.0)
Connection state recovery	4.6.0	✅ YES (since version 0.1.0)

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

Common questions

Do I still need to enable sticky sessions when using the Redis Streams adapter?

Yes. Failing to do so will result in HTTP 400 responses (you are reaching a server that is not aware of the Socket.IO session).

More information can be found here.

What happens when the Redis server is down?

Unlike the classic Redis adapter, this adapter will properly handle any temporary disconnection to the Redis server and resume the stream without losing any packets.

Latest releases

Version	Release date	Release notes	Diff
0.2.1	March 2024	link	0.2.0...0.2.1
0.2.0	February 2024	link	0.1.0...0.2.0
0.1.0	April 2023	link

Complete changelog