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Federation Service Architecture

Overview​

The Federation Service acts as a middleware layer between the Gateway and individual microservices, providing federated query capabilities.

Architecture Diagram​

┌─────────────┐
│   Gateway   │
└──────┬──────┘
       │
       ▼
┌─────────────────────┐
│  Federation Service │
│   (Python/FastAPI)   │
└──────┬───────────────┘
       │
       ├──► Service Discovery (Redis)
       │
       ├──► Schema Cache (PostgreSQL)
       │
       └──► Individual Services
              ├──► Gateway (GraphQL)
              ├──► Payment (GraphQL)
              ├──► Authentication (GraphQL)
              └──► Other Services

Components​

API Layer (FastAPI)​

  • GraphQL Endpoint - Federated query execution
  • Schema Management - Introspection and caching
  • Health Monitoring - Service health checks

Service Discovery​

  • Redis-based - Discover services via Redis
  • Static Configuration - Fallback to static service list

Schema Caching​

  • PostgreSQL - Store introspected schemas
  • TTL-based Refresh - Automatic schema refresh
  • Manual Refresh - On-demand schema updates

Query Execution Flow​

  1. Receive Query - Federation service receives federated query
  2. Parse Query - Analyze query to identify required services
  3. Route to Services - Send sub-queries to appropriate services
  4. Combine Results - Merge results from multiple services
  5. Return Response - Send combined result to client

Error Handling​

  • Retry Logic - Automatic retry for failed service calls
  • Circuit Breaker - Prevent cascading failures
  • Fallback - Graceful degradation when services unavailable

Performance​

  • Schema Caching - Reduces introspection overhead
  • Parallel Queries - Execute sub-queries in parallel
  • Connection Pooling - Efficient database and HTTP connections