spring-boot-microservices

name	spring-boot-microservices
description	Standards for Feign clients and asynchronous messaging with Spring Cloud Stream. Use when implementing Feign HTTP clients or async event messaging in Spring Boot microservices. (triggers: **/*Client.java, **/*Consumer.java, feign-client, spring-cloud-stream, rabbitmq, resilience4j)

Spring Boot Microservices Standards

Priority: P0

Implementation Guidelines

Sync Communication (REST & API Interface)

• Clients: Use Spring Cloud OpenFeign or HTTP Interfaces (Spring 6/Java 21).
• Resilience: Implement Resilience4j with Circuit Breaker, Retry (Exponential Backoff), and RateLimiter. Use fallback methods to return cached or default data on failure. Configure timeout values on all Feign clients.
• Contracts: Share DTO Records via a Maven BOM or API Contract module.
• Tracing: Ensure Micrometers propagation for Distributed Tracing.

Async Communication (Spring Cloud Stream)

• Architecture: Use Message-Driven patterns with Spring Cloud Stream.
• Functions: Define message handlers as java.util.function.Function, Consumer, or Supplier.
• Serialization: Use JSON or Avro for events.
• Reliability: Implement Dead Letter Queues (DLQ) and Idempotent consumers.

Data & Isolation

• DB per Service: NEVER share databases between microservices.
• Shared Libs: Minimize shared logic to shared DTOs/Clients only.
• Discovery: Use Spring Cloud Gateway for routing and auth.

Anti-Patterns

• No Shared DB: Services must communicate via APIs or Events only.
• No Shared Entities: Share DTOs via Maven BOM, never JPA entities.
• No Sync Call Chains: Use async messaging to prevent distributed monolith.

References

• Implementation Examples