Service Communication & Integration

6. Service Communication & Integration

This document details how components interact with each other and the outside world, including protocols, API gateway patterns, messaging systems, and security boundaries.

Communication Protocols

HTTP/HTTPS (Primary Protocol)

Usage: Synchronous service-to-service communication and external API access Implementation: RESTful APIs with JSON payloads

Standards:

  • RESTful resource design (GET, POST, PUT, DELETE)
  • JSON API specification for consistent responses
  • HTTP status codes for error handling
  • Content negotiation and versioning

Security:

  • TLS 1.3 encryption for all communications
  • API key authentication for service access
  • JWT tokens for user authentication
  • Request signing for webhook verification

HTTP Platform API (Client–Platform Communication)

Usage: Client-to-platform communication for commands, queries, and event-driven responses Implementation: HTTP POST to Platform API (

/api/query
, 
/api/command
) with JSON payloads

Key Features:

  • Request/response over HTTP; no long-lived connection required
  • Same API shape for all clients (auth, admin, marketing)
  • Timeout and retry handling
  • Integrates with Redis Streams for backend routing

Use Cases:

  • Auth flows (sign-in, sign-up, onboarding)
  • Admin operations (user/tenant management)
  • Marketing actions (contact form, newsletter, tracking)

Message Queues (Asynchronous Communication)

Usage: Decoupled asynchronous processing and event-driven workflows Implementation: Redis Streams for real-time, Kafka for high-throughput

Patterns:

  • Publisher/Subscriber for event distribution
  • Work queues for background job processing
  • Dead letter queues for failed message handling
  • Message retry with exponential backoff

API Gateway Integration Patterns

Request Routing and Load Balancing

Dynamic Routing

// API Gateway routing logic
const routeRequest = (request: NextRequest) => {
  const { pathname } = request.nextUrl;

  // Service-specific routing
  if (pathname.startsWith('/api/users')) {
    return proxyToService('user-service', request);
  }

  if (pathname.startsWith('/api/payments')) {
    return proxyToService('payment-service', request);
  }

  // Default routing or 404
  return NextResponse.json({ error: 'Not found' }, { status: 404 });
};

Routing Benefits:

  • Centralized request management
  • Service abstraction from clients
  • Dynamic service discovery
  • A/B testing and canary deployments

Load Balancing Strategies

  • Round Robin: Equal distribution across service instances
  • Least Connections: Route to least busy instance
  • Weighted Distribution: Custom weights for service capacity
  • Health-Based: Route only to healthy instances

Authentication and Authorization

Multi-Layer Authentication

  1. API Gateway Level: JWT validation, API key verification
  2. Service Level: Service-specific authorization checks
  3. Database Level: Row-level security for tenant isolation

Authentication Flow

Security Features:

  • Stateless JWT authentication
  • Refresh token rotation for security
  • API key management for service access
  • Request rate limiting per user/tenant

Rate Limiting and Throttling

Multi-Level Rate Limiting

  • Global Limits: System-wide request throttling
  • Per-Tenant Limits: Tenant-specific usage quotas
  • Per-User Limits: Individual user request limits
  • Per-Endpoint Limits: Specific endpoint restrictions

Implementation Strategy

// Redis-based rate limiting
const rateLimit = async (key: string, limit: number, windowMs: number) => {
  const redisKey = `ratelimit:${key}`;
  const current = await redis.incr(redisKey);

  if (current === 1) {
    await redis.expire(redisKey, windowMs / 1000);
  }

  if (current > limit) {
    throw new RateLimitError('Too many requests');
  }
};

Service Mesh Integration

Service Discovery

Implementation: Dynamic service registration and health monitoring

Discovery Mechanisms:

  • DNS-based service discovery
  • Service registry with health checks
  • Load balancer integration
  • Circuit breaker pattern implementation

Circuit Breaker Pattern

Implementation Strategy

class CircuitBreaker {
  private failures = 0;
  private lastFailureTime = 0;
  private state: 'CLOSED' | 'OPEN' | 'HALF_OPEN' = 'CLOSED';

  async execute<T>(operation: () => Promise<T>): Promise<T> {
    if (this.state === 'OPEN') {
      if (Date.now() - this.lastFailureTime > 60000) { // 1 minute
        this.state = 'HALF_OPEN';
      } else {
        throw new Error('Circuit breaker is OPEN');
      }
    }

    try {
      const result = await operation();
      this.onSuccess();
      return result;
    } catch (error) {
      this.onFailure();
      throw error;
    }
  }

  private onSuccess() {
    this.failures = 0;
    this.state = 'CLOSED';
  }

  private onFailure() {
    this.failures++;
    this.lastFailureTime = Date.now();

    if (this.failures >= 5) { // Threshold
      this.state = 'OPEN';
    }
  }
}

Benefits:

  • Prevents cascade failures
  • Fast failure for unavailable services
  • Automatic recovery testing
  • Improved system resilience

Traffic Management

A/B Testing and Canary Deployments

  • Traffic splitting for feature testing
  • Gradual rollout strategies
  • Performance comparison capabilities
  • Rollback mechanisms for failed deployments

Traffic Shaping

  • Request prioritization by user type
  • Resource allocation based on tenant tier
  • Dynamic traffic routing based on load
  • Geographic traffic distribution

Event-Driven Integration

Event Publishing and Consumption

Event Schema Definition

interface BaseEvent {
  id: string;
  type: string;
  timestamp: Date;
  source: string;
  tenantId: string;
  userId?: string;
  correlationId: string;
}

interface UserCreatedEvent extends BaseEvent {
  type: 'user.created';
  data: {
    userId: string;
    email: string;
    tenantId: string;
    roles: string[];
  };
}

Event Standards:

  • Structured event schemas with versioning
  • Correlation IDs for request tracing
  • Tenant isolation in all events
  • Standardized timestamp formats

Event Streaming Architecture

Publisher Pattern

class EventPublisher {
  async publish(event: BaseEvent): Promise<void> {
    // Add metadata
    const enrichedEvent = {
      ...event,
      id: uuidv4(),
      timestamp: new Date(),
      source: this.serviceName,
    };

    // Publish to stream
    await this.redis.xadd(
      'events',
      '*',
      'event', JSON.stringify(enrichedEvent)
    );

    // Publish to monitoring
    await this.monitoring.recordEvent(enrichedEvent);
  }
}

Consumer Pattern

class EventConsumer {
  async startConsuming(): Promise<void> {
    while (true) {
      const events = await this.redis.xreadgroup(
        'events',
        this.consumerGroup,
        '0',
        100
      );

      for (const event of events) {
        await this.processEvent(event);
      }
    }
  }

  private async processEvent(event: any): Promise<void> {
    try {
      // Validate event schema
      const validatedEvent = this.validateEvent(event);

      // Process based on event type
      await this.eventHandlers[validatedEvent.type]?.(validatedEvent);

      // Acknowledge successful processing
      await this.redis.xack('events', this.consumerGroup, event.id);
    } catch (error) {
      // Handle processing errors
      await this.handleError(event, error);
    }
  }
}

Event Sourcing and CQRS

Event Sourcing Implementation

class EventSourcedAggregate {
  private events: DomainEvent[] = [];
  private state: AggregateState;

  async applyEvent(event: DomainEvent): Promise<void> {
    // Apply event to state
    this.state = this.reducer(this.state, event);

    // Store event for audit trail
    this.events.push(event);
    await this.eventStore.save(event);
  }

  // Rebuild state from events
  static async fromEvents(events: DomainEvent[]): Promise<EventSourcedAggregate> {
    const aggregate = new EventSourcedAggregate();
    for (const event of events) {
      await aggregate.applyEvent(event);
    }
    return aggregate;
  }
}

CQRS Benefits:

  • Optimized read and write operations
  • Event-driven consistency across read models
  • Scalable query processing
  • Audit trail for compliance

External API Integrations

Third-Party Service Integration

Payment Provider Integration (Stripe)

class StripeIntegration {
  async createPaymentIntent(amount: number, currency: string): Promise<string> {
    const paymentIntent = await this.stripe.paymentIntents.create({
      amount: amount * 100, // Convert to cents
      currency,
      metadata: {
        tenantId: this.tenantId,
        userId: this.userId,
      },
    });

    return paymentIntent.client_secret;
  }

  async handleWebhook(event: Stripe.Event): Promise<void> {
    switch (event.type) {
      case 'payment_intent.succeeded':
        await this.processSuccessfulPayment(event.data.object);
        break;
      case 'payment_intent.payment_failed':
        await this.processFailedPayment(event.data.object);
        break;
    }
  }
}

Integration Patterns:

  • Webhook verification for security
  • Idempotent event processing
  • Retry logic for transient failures
  • Comprehensive error handling

Email Provider Integration (SendGrid)

class SendGridIntegration {
  async sendEmail(templateId: string, to: string, data: any): Promise<void> {
    const email = {
      to,
      from: this.fromEmail,
      templateId,
      dynamicTemplateData: data,
      trackingSettings: {
        clickTracking: { enable: true },
        openTracking: { enable: true },
      },
    };

    await this.sendgrid.send(email);
  }

  async getEmailAnalytics(emailId: string): Promise<EmailAnalytics> {
    const [response] = await this.sendgrid.request({
      url: `/v3/messages/${emailId}`,
      method: 'GET',
    });

    return this.parseAnalytics(response.body);
  }
}

Email Features:

  • Template-based email generation
  • Delivery tracking and analytics
  • Bounce handling and suppression
  • A/B testing capabilities

Webhook Integration

Incoming Webhook Handling

class WebhookHandler {
  async handleWebhook(payload: any, signature: string): Promise<void> {
    // Verify webhook signature
    if (!this.verifySignature(payload, signature)) {
      throw new Error('Invalid webhook signature');
    }

    // Process based on event type
    const eventType = payload.type;
    await this.webhookHandlers[eventType]?.(payload.data);

    // Publish to internal event system
    await this.eventPublisher.publish({
      type: 'webhook.received',
      source: 'external',
      data: payload,
    });
  }
}

Webhook Security:

  • Signature verification for authenticity
  • Duplicate event detection and handling
  • Rate limiting for webhook endpoints
  • Comprehensive logging for debugging

Security Communication Patterns

Inter-Service Authentication

mTLS (Mutual TLS)

Usage: Secure service-to-service communication Implementation: Certificate-based authentication

Certificate Management:

  • Automated certificate provisioning
  • Certificate rotation and renewal
  • Service identity verification
  • Encrypted communication channels

Service Tokens

Usage: Lightweight service authentication Implementation: Shared secret or public key tokens

Token Usage:

  • Service-to-service API authentication
  • Temporary access tokens with expiration
  • Scoped permissions per service
  • Token revocation capabilities

API Security

API Gateway Security

  • JWT token validation and renewal
  • API key management and rotation
  • Request signature verification
  • CORS configuration for browser clients

Service-Level Security

  • Input validation and sanitization
  • SQL injection prevention
  • XSS protection measures
  • Rate limiting per service

Monitoring and Observability

Distributed Tracing

Implementation: OpenTelemetry for trace collection and propagation

Tracing Flow:

  1. Request enters API Gateway with trace context
  2. Context propagated to downstream services
  3. Spans collected for performance analysis
  4. Traces correlated for end-to-end visibility

Metrics Collection

Implementation: Prometheus metrics with custom business metrics

Key Metrics:

  • Request latency and throughput
  • Error rates and failure modes
  • Resource utilization (CPU, memory, disk)
  • Business-specific KPIs (users, payments, emails)

Logging Strategy

Implementation: Structured logging with correlation IDs

Log Levels:

  • ERROR: System failures and exceptions
  • WARN: Deprecated features and potential issues
  • INFO: Important business events
  • DEBUG: Detailed debugging information

Integration Testing Patterns

Service Integration Testing

describe('Service Integration', () => {
  it('should handle complete user registration flow', async () => {
    // Test API Gateway routing
    const response = await request(app)
      .post('/api/users')
      .send(userData);

    // Test service interaction
    expect(response.status).toBe(201);

    // Test event publishing
    await expectEventPublished('user.created');

    // Test email sending
    await expectEmailSent('welcome-email');
  });
});

Testing Benefits:

  • End-to-end workflow validation
  • Event-driven interaction testing
  • External service integration verification
  • Performance and reliability testing

This comprehensive communication and integration framework ensures reliable, secure, and scalable interactions between all components in the ProgNetwork ecosystem.