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

$3

`js
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);
`

$3

`js
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);
`

$3

`js
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);
`

$3

`js
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);
`

$3

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:

`js
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

$3

| 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. | - |

$3

| 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