socket.io-multi-redis

The socket.io-multi-redis package allows broadcasting packets between multiple Socket.IO servers.

socket.io-multi-redis Uses Custom Scaling Solution.

By running socket.io with the socket.io-multi-redis adapter you can run multiple socket.io instances in different processes or servers that can all broadcast and emit events to and from each other with any number of redis server connections.

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-multi-redis

Compatibility table

Redis Adapter version	Socket.IO server version
2.x	2.x
3.x	4.3.x and above

Usage

With the redis package

import { createClient } from "redis";
import { Server } from "socket.io";
import { createAdapter } from "socket.io-multi-redis";

const pubClient1 = createClient({ url: "redis://localhost:6379" });
const subClient1 = pubClient.duplicate();

const pubClient2 = createClient({ url: "redis://localhost:6380" });
const subClient2 = pubClient.duplicate();

const pubClient3 = createClient({ url: "redis://localhost:6381" });
const subClient3 = pubClient.duplicate();

await Promise.all([
  pubClient1.connect(),subClient1.connect(),
  pubClient2.connect(),subClient2.connect(),
  pubClient3.connect(),subClient3.connect()
]);

const io = new Server({
  adapter: createAdapter(
    [pubClient1, pubClient2, pubClient3],
    [subClient1, subClient2, subClient3],
  )
});

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-multi-redis";

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-multi-redis";

const pubClient1 = new Redis();
const subClient1 = pubClient.duplicate();

const pubClient2 = new Redis();
const subClient2 = pubClient.duplicate();

const pubClient3 = new Redis();
const subClient3 = pubClient.duplicate();

const io = new Server({
  adapter: createAdapter(
    [pubClient1, pubClient2, pubClient3],
    [subClient1, subClient2, subClient3],
  )
});

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-multi-redis";

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-multi-redis";

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