Messaging Package

Purpose

Event-driven messaging patterns for asynchronous communication between services.

Pub/Sub Implementation

Google Cloud Pub/Sub

class PubSubClient {
  async publish(topic: string, message: Message): Promise<string>
  async subscribe(subscription: string, handler: MessageHandler): Promise<void>
  async createTopic(name: string): Promise<void>
  async createSubscription(topic: string, subscription: string): Promise<void>
}

Message Format

interface Message {
  id: string;
  type: string;
  correlationId: string;
  timestamp: string;
  source: string;
  payload: unknown;
  metadata: Record<string, string>;
}

WebSocket Utilities

Connection Management

• Auto-reconnection with backoff
• Heartbeat/ping-pong
• Connection pooling
• Room/channel support

Message Patterns

• Request-response with correlation
• Broadcast to subscribers
• Direct messaging
• Event streaming

Message Processing Patterns

Guaranteed Delivery

• At-least-once delivery
• Idempotency keys
• Deduplication
• Dead letter queues

Batch Processing

class BatchProcessor<T> {
  constructor(
    processor: (items: T[]) => Promise<void>,
    options: { batchSize: number; flushInterval: number }
  )
}

Error Handling

• Retry with exponential backoff
• Circuit breaker for downstream services
• Poison message handling
• Alerting on processing failures

Observability

• Message tracing
• Processing latency metrics
• Queue depth monitoring
• Consumer lag tracking