socketio-mongoose-adapter.js

const { createAdapter } = require("@socket.io/mongo-adapter");
const MONGODB_URI = "mongodb://localhost:27017/app";

const params = {
    useNewUrlParser: true,
    useUnifiedTopology: true
};

mongoose.connect(MONGODB_URI, params, async (err, data) => {
    if (err) {
        console.error("<::: Couldn't connect to database", err);
    } else {
        console.log(`:::> Connected to MongoDB database. ${MONGODB_URI}`);

        // Initialize Socket.io Adapter
        const mongooseCollection = mongoose.connection.collection("adapter");
        await mongooseCollection.createIndex(
            { createdAt: 1 },
            { expireAfterSeconds: 3600, background: true }
        )
        io.adapter(createAdapter(mongooseCollection, { addCreatedAtField: true }));
    }
});

// Initialization WebSocket
io.use((socket, next) => {
    return require("./middlewares/auth.middleware")(socket, next);
}).on("connection", (socket) => {
    console.log(`:::> User ${socket.$user.username} connected`);
});