Skip to content

EVENT_DRIVEN_ARCHITECTURE.md

Latest commit

 

History

History
165 lines (123 loc) · 3.92 KB

EVENT_DRIVEN_ARCHITECTURE.md

File metadata and controls

165 lines (123 loc) · 3.92 KB

Event-Driven Architecture

Overview

Fully decoupled microservices using event-driven communication with RabbitMQ message broker and event sourcing.

Architecture Components

1. Event Bus (In-Memory)

  • Fast synchronous event processing
  • Development and testing
  • Located: databases/event-patterns/EventBus.ts

2. Message Broker (RabbitMQ)

  • Asynchronous event processing
  • Persistent message queues
  • Production-ready with retry logic
  • Located: databases/event-patterns/MessageBroker.ts

3. Event Store

  • Event sourcing for audit trails
  • State reconstruction capability
  • Located: databases/event-patterns/EventStore.ts

4. Async Event Processor

  • Retry logic with exponential backoff
  • Dead letter queue for failed events
  • Located: databases/event-patterns/AsyncEventProcessor.ts

Event Flow

Service A → Publish Event → [EventBus + MessageBroker]
                                    ↓
                            Event Handlers
                                    ↓
                    [Notification, Billing, Analytics Services]

Domain Events

Payment Events

  • payment.success - Payment completed successfully
  • payment.failed - Payment failed

Billing Events

  • bill.created - New bill generated
  • bill.paid - Bill marked as paid

User Events

  • user.created - New user registered
  • user.updated - User profile updated

Notification Events

  • notification.sent - Notification delivered

Document Events

  • document.uploaded - Document uploaded

Event Handlers

Notification Handlers

  • Listen: payment.success, payment.failed, bill.created
  • Action: Send email/SMS notifications

Billing Handlers

  • Listen: payment.success, payment.failed
  • Action: Update bill status

Analytics Handlers

  • Listen: All events (*)
  • Action: Track for analytics and reporting

Setup

1. Start Message Broker

npm run messaging:start

2. Access RabbitMQ Management UI

3. Initialize Event Handlers

Event handlers auto-initialize when services start.

Usage

Publishing Events

import EventBus from './databases/event-patterns/EventBus';
import MessageBroker from './databases/event-patterns/MessageBroker';
import { createPaymentSuccessEvent } from './databases/event-patterns/events';

const event = createPaymentSuccessEvent(paymentId, billId, userId, amount);

// In-memory (fast)
EventBus.publish(event);

// Persistent queue (reliable)
await MessageBroker.publish(event);

Subscribing to Events

import EventBus from './databases/event-patterns/EventBus';

EventBus.subscribe('payment.success', async (event) => {
  // Handle event
  console.log('Payment successful:', event.payload);
});

Event Sourcing

import EventStore from './databases/event-patterns/EventStore';
import { analyticsClient } from './databases/clients';

const eventStore = new EventStore({ client: analyticsClient });

// Append event
await eventStore.append(event);

// Get all events for aggregate
const events = await eventStore.getEvents(aggregateId);

// Replay events
await eventStore.replay(aggregateId, async (event) => {
  // Reconstruct state
});

Benefits Achieved

✅ Decoupled Services - Services don't directly depend on each other ✅ Async Processing - Non-blocking event handling ✅ Fault Tolerance - Retry logic and dead letter queues ✅ Audit Trail - Complete event history via event sourcing ✅ Scalability - Independent event consumers ✅ Real-time Sync - Automatic data propagation across services

Monitoring

RabbitMQ Metrics

  • Queue depth
  • Message rates
  • Consumer count
  • Failed deliveries

Event Metrics

  • Events published per type
  • Processing latency
  • Retry counts
  • DLQ size

Configuration

RABBITMQ_URL=amqp://localhost
RABBITMQ_USER=admin
RABBITMQ_PASS=admin
REDIS_URL=redis://localhost:6379