Socket.IO Redis adapter

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

Table of contents

• Supported features
• Security notice
• 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
    • With redis
    • With ioredis
• Options
  • Default adapter
  • Sharded adapter
• License

Supported features

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

Security notice

The Redis adapter assumes that Redis is part of the trusted internal infrastructure.

Messages exchanged through Redis Pub/Sub are not signed, encrypted, or authenticated by the adapter. Anyone able to publish to the adapter channels may be able to inject packets or control messages. Redis should therefore not be exposed to untrusted networks or shared with untrusted clients.

Please use Redis ACLs, authentication, TLS, firewall rules, private networking, and dedicated credentials/channel permissions where appropriate.

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:

With redis

Minimum requirements:

• Redis 7.0
• redis@4.6.0

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);

With ioredis

Minimum requirements:

• Redis 7.0
• ioredis@5.9.0

Please note that the shardedSubscribers option is required to enable sharded Pub/Sub.

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

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

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

io.listen(3000);

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