🌐 Microservices

Microservices is an architectural style that structures an application as a collection of small, loosely coupled services, which can be developed, deployed, and scaled independently. Each service in a microservices architecture focuses on a specific business capability and can be built and deployed independently.

❓ Why Microservices?

Microservices offer several advantages, particularly for complex, large-scale applications:

🚀 Scalability: Each service can be scaled independently to meet specific demands.
🛡️ Resilience: Failure in one service doesn’t necessarily affect the entire application.
⚡ Faster Development: Development teams can work on different services independently, accelerating time-to-market.
🎨 Flexibility: Microservices allow using different technologies and programming languages for each service.
🧹 Easier Maintenance: Each service is smaller and focused on specific functionality, making it easier to understand, maintain, and modify.

🧩 Microservices Components

1️⃣ Service

A service is a core component of the microservices architecture. It performs a specific business function and is typically responsible for a single module or domain of the application. Each service is designed to be:

🛠️ Autonomous: Can be deployed, updated, or scaled independently.
📦 Self-contained: Has its own database, business logic, and API.
🌐 Communicating over the network: Communicates with other services via APIs, usually REST or messaging queues.

2️⃣ API Gateway

The API Gateway is a crucial component in a microservices architecture. It serves as a single entry point for all client requests and is responsible for routing requests to the appropriate service.

Responsibilities include:

🔀 Request Routing: Directs requests to the appropriate microservice.
⚖️ Load Balancing: Balances the load across multiple instances of a microservice.
🔒 Authentication and Authorization: Handles security concerns such as API authentication, rate limiting, etc.
🧩 Aggregation: Combines responses from multiple services into a single response for the client.

3️⃣ Service Registry and Discovery

In a microservices architecture, services need to discover each other to communicate. A Service Registry (e.g., Eureka, Consul) keeps track of the available services and their locations.

🔍 Dynamic discovery: Services register themselves at startup and remove themselves on shutdown.
⚖️ Load balancing: Service discovery helps the system balance load among instances of the same service.

4️⃣ Database per Service

Each microservice has its own database or persistence layer, which can be a different database type based on the service’s needs (SQL, NoSQL, etc.).

Benefits include:

🔒 Data encapsulation: Each service owns its own data and is decoupled from other services’ databases.
🎨 Technology independence: Each service can choose the best database for its use case.

5️⃣ Communication Between Services

Services in a microservices architecture communicate with each other via lightweight communication mechanisms, typically HTTP, REST APIs, or messaging queues (e.g., Kafka, RabbitMQ).

🌐 Synchronous Communication: Direct API calls using HTTP/REST.
📩 Asynchronous Communication: Message brokers and queues for decoupling services and handling long-running tasks.

🌍 Microservices in Fullstack Applications

Backend (Spring Boot + Microservices)

🛠️ Service: Individual Spring Boot applications that focus on specific business functions.
🔀 API Gateway: Often implemented using tools like Spring Cloud Gateway or Zuul.
🔍 Service Registry: Managed using tools like Eureka or Consul.
🗂️ Database: Each service can have its own database (SQL/NoSQL) depending on its requirements.
📡 Communication: REST API calls, messaging systems like Kafka or RabbitMQ.

Frontend (Angular)

🧩 Model: Angular services for communicating with microservices APIs.
🎨 View: Angular components and templates that interact with the backend.
🧠 Controller: Component classes managing interactions with backend APIs and frontend logic.

📂 Folder Structure Example

microservices-app/
├── backend/
│   ├── service-a/
│   │   ├── src/
│   │   ├── Dockerfile
│   │   ├── application.yml
│   ├── service-b/
│   │   ├── src/
│   │   ├── Dockerfile
│   │   ├── application.yml
│   ├── api-gateway/
│   │   ├── src/
│   │   └── application.yml
│   ├── service-registry/
│   │   ├── src/
│   │   └── application.yml
│   └── docker-compose.yml
├── frontend/
│   ├── src/app/
│   │   ├── components/
│   │   ├── services/
│   ├── app.module.ts
│   └── main.ts
└── docker-compose.yml