@socket.io/redis-streams-adapter NPM

Socket.IO Redis Streams adapter

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

Table of contents

Supported features

Feature	`socket.io` version	Support
Socket management	`4.0.0`	:white_check_mark: YES (since version `0.1.0`)
Inter-server communication	`4.1.0`	:white_check_mark: YES (since version `0.1.0`)
Broadcast with acknowledgements	`4.5.0`	:white_check_mark: YES (since version `0.1.0`)
Connection state recovery	`4.6.0`	:white_check_mark: YES (since version `0.1.0`)

Installation

npm install @socket.io/redis-streams-adapter redis

Usage

With the `redis` package

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

const redisClient = createClient({ url: "redis://localhost:6379" });

await redisClient.connect();

const io = new Server({
  adapter: createAdapter(redisClient)
});

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-streams-adapter";

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

await redisClient.connect();

const io = new Server({
  adapter: createAdapter(redisClient)
});

io.listen(3000);

With the `ioredis` package

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

const redisClient = new Redis();

const io = new Server({
  adapter: createAdapter(redisClient)
});

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-streams-adapter";

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

const io = new Server({
  adapter: createAdapter(redisClient)
});

io.listen(3000);

Options

Name	Description	Default value
`streamName`	The name of the Redis stream.	`socket.io`
`maxLen`	The maximum size of the stream. Almost exact trimming (~) is used.	`10_000`
`readCount`	The number of elements to fetch per XREAD call.	`100`
`sessionKeyPrefix`	The prefix of the key used to store the Socket.IO session, when the connection state recovery feature is enabled.	`sio:session:`
`heartbeatInterval`	The number of ms between two heartbeats.	`5_000`
`heartbeatTimeout`	The number of ms without heartbeat before we consider a node down.	`10_000`

How it works

The adapter will use a Redis stream to forward events between the Socket.IO servers.

Notes:

a single stream is used for all namespaces
the maxLen option allows to limit the size of the stream
unlike the adapter based on Redis PUB/SUB mechanism, this adapter will properly handle any temporary disconnection to the Redis server and resume the stream
if connection state recovery is enabled, the sessions will be stored in Redis as a classic key/value pair