Socket.IO Redis adapter

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

Table of contents

• Supported features
• Installation
• Compatibility table
• Usage
  • With the redis package
  • With the redis package and a Redis cluster
  • With the ioredis package
  • With the ioredis package and a Redis cluster
  • With Redis sharded Pub/Sub
• Options
  • Default adapter
  • Sharded adapter
• License

Supported features

Feature	socket.io version	Support
Socket management	4.0.0	✅ YES (since version 6.1.0)
Inter-server communication	4.1.0	✅ YES (since version 7.0.0)
Broadcast with acknowledgements	4.5.0	✅ YES (since version 7.2.0)
Connection state recovery	4.6.0	❌ NO

Installation

npm install @socket.io/redis-adapter

Compatibility table

Redis Adapter version	Socket.IO server version
4.x	1.x
5.x	2.x
6.0.x	3.x
6.1.x	4.x
7.x and above	4.3.1 and above

Usage

With the redis package

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

const pubClient = createClient({ url: "redis://localhost:6379" });
const subClient = pubClient.duplicate();

await Promise.all([
  pubClient.connect(),
  subClient.connect()
]);

const io = new Server({
  adapter: createAdapter(pubClient, subClient)
});

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-adapter";

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

await Promise.all([
  pubClient.connect(),
  subClient.connect()
]);

const io = new Server({
  adapter: createAdapter(pubClient, subClient)
});

io.listen(3000);

With the ioredis package

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

const pubClient = new Redis();
const subClient = pubClient.duplicate();

const io = new Server({
  adapter: createAdapter(pubClient, subClient)
});

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-adapter";

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

const io = new Server({
  adapter: createAdapter(pubClient, subClient)
});

io.listen(3000);

With Redis sharded Pub/Sub

Sharded Pub/Sub was introduced in Redis 7.0 in order to help scaling the usage of Pub/Sub in cluster mode.

Reference: https://redis.io/docs/interact/pubsub/#sharded-pubsub

A dedicated adapter can be created with the createShardedAdapter() method:

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

const pubClient = createClient({ host: "localhost", port: 6379 });
const subClient = pubClient.duplicate();

await Promise.all([
  pubClient.connect(),
  subClient.connect()
]);

const io = new Server({
  adapter: createShardedAdapter(pubClient, subClient)
});

io.listen(3000);

Minimum requirements:

• Redis 7.0
• redis@4.6.0

Note: it is not currently possible to use the sharded adapter with the ioredis package and a Redis cluster (reference).

Options

Default adapter

Name	Description	Default value
key	The prefix for the Redis Pub/Sub channels.	socket.io
requestsTimeout	After this timeout the adapter will stop waiting from responses to request.	5_000
publishOnSpecificResponseChannel	Whether to publish a response to the channel specific to the requesting node.	false
parser	The parser to use for encoding and decoding messages sent to Redis.	-

Sharded adapter

Name	Description	Default value
channelPrefix	The prefix for the Redis Pub/Sub channels.	socket.io
subscriptionMode	The subscription mode impacts the number of Redis Pub/Sub channels used by the adapter.	dynamic

License

MIT