How do you implement a custom event-driven microservice?

Question

Accepted Answer

**Event-driven microservice** — communicate via events.

```javascript
const { EventEmitter } = require("events");
const amqp = require("amqplib");

class EventDrivenService {
    constructor(name) {
        this.name = name;
        this.emitter = new EventEmitter();
        this.connection = null;
        this.channel = null;
    }

async connect() {
        this.connection = await amqp.connect("amqp://localhost");
        this.channel = await this.connection.createChannel();
        await this.channel.assertExchange(this.name, "fanout", { durable: true });
    }

async publish(event) {
        this.emitter.emit(event.type, event);
        const msg = Buffer.from(JSON.stringify(event));
        this.channel.publish(this.name, "", msg);
    }

async subscribe(exchange, handler) {
        await this.channel.assertExchange(exchange, "fanout", { durable: true });
        const q = await this.channel.assertQueue("", { exclusive: true });
        await this.channel.bindQueue(q.queue, exchange, "");

this.channel.consume(q.queue, (msg) => {
            const event = JSON.parse(msg.content.toString());
            handler(event);
            this.channel.ack(msg);
        });
    }

on(eventType, handler) {
        this.emitter.on(eventType, handler);
    }
}

// Usage
const orderService = new EventDrivenService("orders");
await orderService.connect();

orderService.on("OrderCreated", async (event) => {
    console.log("Order created:", event.data);
    await sendConfirmation(event.data.userId);
});

await orderService.publish({
    type: "OrderCreated",
    data: { id: 123, userId: "user-1" },
});
```

Node.js: How do you implement a custom event-driven microservice?