Phase 1: Foundation

1. Understand the Why of Microservices:
   • Why microservices vs monolith? (Scalability, fault isolation, deployment independence)
   • Core principles: autonomy, decentralized data, bounded contexts.
2. Domain-Driven Design (DDD):
   • Learn strategic patterns: Bounded Contexts, Aggregate Roots.
   • Break down a monolith into domain-driven microservices.

Phase 2: Building Blocks

1. Spring Boot Basics:
   • Create REST APIs.
   • Understand project structure, dependency injection, and application properties.

Phase 3: Service Coordination and Management

1. Spring Cloud Ecosystem

• Inter-Service Communication:

  • REST: Start with HTTP-based synchronous calls.
  • Messaging: Introduce RabbitMQ or Kafka for async communication. ( again can be kept for later)
    • Focus: Event-driven architecture, Event Sourcing, and CQRS.
  • Take a look at a the page below, (as of now just learn Step one only)

  Microservices Inter-Service Communication Roadmap

• Service Discovery:

  • Use Eureka or Consul to allow microservices to find and communicate with each other. Eureka works well with Spring Boot, and you can integrate it via spring-cloud-starter-netflix-eureka-server for the service registry.
  • Implement Spring Cloud Eureka Client in your microservices so they can register themselves with the service discovery tool.

• API Gateway:

  • Use Spring Cloud Gateway or Zuul for routing requests from clients to the appropriate services.
  • Focus on load balancing and security (e.g., OAuth2 authentication). The API Gateway is a key component for managing routing between services and can handle things like request throttling, load balancing, and even rate limiting.

• Centralized Configuration:

  • Implement Spring Cloud Config Server to manage application configurations across your microservices. It ensures that all services pull configuration from a central repository, which can be stored in Git or other systems like HashiCorp Vault.
  • This allows for consistent configuration management and ensures scalability as your system grows.

• Circuit Breakers:

  • Implement Resilience4j to handle fault tolerance. For example, if a downstream service fails, the circuit breaker ensures that your service doesn't continually try to call the failing service and instead falls back to a predefined behavior (such as returning default values).
  • You’ll also want to focus on timeout management, retry mechanisms, and bulkheads for isolating faults.

2. Data Management

• Database per Service:
  • Design your microservices with their own databases, following the polyglot persistence pattern. Each service should own its own data, and use the right database type for each service (e.g., relational DB for the User service, NoSQL for the Product catalog).
• Eventual Consistency:
  • Learn about Sagas and the Outbox pattern for managing distributed transactions. Use event-driven patterns to ensure that when a service updates its state, it triggers events that other services can react to asynchronously.
  • For example, when an Order service creates an order, it can send an event that triggers the Payment service to process the payment.

Phase 4: Securing Microservices