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 | :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 |

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
• [email protected]

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