Chapter 7: Microservices & Spring Cloud

Decomposing complex domains into microservices requires robust distributed engineering: dynamic service discovery, unified reactive edge routing, declarative inter-service RPC, circuit breaker fault tolerance, and asynchronous event streaming.

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🧭 Subtopics & Curriculum

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Distributed Architecture7.1

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7.1 Microservices Architecture Principles

• 1. Monolith vs Microservices
• 2. The Database-per-Service Pattern
  • Why Direct DB Sharing Fails:
• 3. Distributed Transactions & The Saga Pattern

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Dynamic Registry7.2

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7.2 Service Discovery with Netflix Eureka

• 1. Eureka Architecture & Heartbeat Loop
• 2. Setting Up Eureka Server
  • 1. Dependency
  • 2. Main Application Class
  • 3. Server Configuration (application.yml)
• 3. Client Registration & Client-Side Load Balancing
  • Client-Side Load Balancing with Spring Cloud LoadBalancer:

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Edge Gateway7.3

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7.3 API Gateway with Spring Cloud Gateway

• 1. Gateway Architecture & Core Concepts
• 2. Declarative Route Configuration (application.yml)
• 3. Custom Global Authentication Gateway Filter

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Synchronous RPC7.4

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7.4 Inter-Service Communication: OpenFeign & WebClient

• 1. Spring Cloud OpenFeign (Declarative REST Client)
  • 1. Enable Feign Clients
  • 2. Define the Feign Interface
  • 3. Propagating Headers via RequestInterceptor
• 2. Spring WebClient (Non-Blocking & Reactive)
• 3. Comparison: RestTemplate vs OpenFeign vs WebClient

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Fault Tolerance7.5

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7.5 Resilience & Fault Tolerance with Resilience4j

• 1. The Circuit Breaker State Machine
• 2. Using @CircuitBreaker & Fallback Methods
• 3. Configuration in application.yml

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Asynchronous Streaming7.6

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7.6 Event-Driven Messaging with Apache Kafka

• 1. Kafka Architectural Concepts
• 2. Producing Events with KafkaTemplate
• 3. Consuming Events with @KafkaListener
• 4. Idempotency & Dead Letter Queue (DLQ)

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