Socket.IO MongoDB emitter

The @socket.io/mongo-emitter package allows you to easily communicate with a group of Socket.IO servers from another Node.js process (server-side).

!Emitter diagram

It must be used in conjunction with @socket.io/mongo-adapter.

Supported features:

- broadcasting
- utility methods
- socketsJoin
- socketsLeave
- disconnectSockets
- serverSideEmit

Related packages:

- MongoDB adapter: https://github.com/socketio/socket.io-mongo-adapter/
- Redis adapter: https://github.com/socketio/socket.io-redis-adapter/
- Redis emitter: https://github.com/socketio/socket.io-redis-emitter/
- Postgres adapter: https://github.com/socketio/socket.io-postgres-adapter/
- Postgres emitter: https://github.com/socketio/socket.io-postgres-emitter/

Table of contents

- Installation
- Usage
- API
- Known errors
- License

Installation

``
npm install @socket.io/mongo-emitter mongodb
`

For TypeScript users, you might also need @types/mongodb.

Usage

`js
const { Emitter } = require("@socket.io/mongo-emitter");
const { MongoClient } = require("mongodb");

const DB = "mydb";
const COLLECTION = "socket.io-adapter-events";

const mongoClient = new MongoClient("mongodb://localhost:27017/?replicaSet=rs0", {
useUnifiedTopology: true,
});

const main = async () => {
await mongoClient.connect();

const mongoCollection = mongoClient.db(DB).collection(COLLECTION);
const io = new Emitter(mongoCollection);

setInterval(() => {
io.emit("ping", new Date());
}, 1000);
}

main();
`

API

$3

`js
const io = new Emitter(mongoCollection);
`

The mongoCollection argument is a MongoDB collection object from the mongodb package.

$3

Specifies a specific room that you want to emit to.

`js
io.to("room1").emit("hello");
`

$3

Specifies a specific room that you want to exclude from broadcasting.

`js
io.except("room2").emit("hello");
`

$3

Specifies a specific namespace that you want to emit to.

`js
const customNamespace = io.of("/custom");

customNamespace.emit("hello");
`

$3

Makes the matching socket instances join the specified rooms:

`js
// make all Socket instances join the "room1" room
io.socketsJoin("room1");

// make all Socket instances of the "admin" namespace in the "room1" room join the "room2" room
io.of("/admin").in("room1").socketsJoin("room2");
`

$3

Makes the matching socket instances leave the specified rooms:

`js
// make all Socket instances leave the "room1" room
io.socketsLeave("room1");

// make all Socket instances of the "admin" namespace in the "room1" room leave the "room2" room
io.of("/admin").in("room1").socketsLeave("room2");
`

$3

Makes the matching socket instances disconnect:

`js
// make all Socket instances disconnect
io.disconnectSockets();

// make all Socket instances of the "admin" namespace in the "room1" room disconnect
io.of("/admin").in("room1").disconnectSockets();

// this also works with a single socket ID
io.of("/admin").in(theSocketId).disconnectSockets();
`

$3

Emits an event that will be received by each Socket.IO server of the cluster.

`js
io.serverSideEmit("ping");
`

Known errors

- TypeError: this.mongoCollection.insertOne is not a function

You probably passed a MongoDB client instead of a MongoDB collection to the Emitter` constructor.

License

MIT