Internet Communication - Microservices Architecture

🏗️ System Architecture

This is a distributed microservices application with the following architecture:

┌─────────────────────────────────────────────────┐
│           API Gateway (Spring Cloud)            │
│          JWT Validation & Routing                │
└────────────┬───────────────���────────────────────┘
             │
    ┌────────┴──────────────────────┬──────────────────┬──────────────┐
    │                               │                  │              │
┌───▼───┐  ┌──────────┐  ┌────────▼───┐  ┌──────────▼──┐  ┌───────▼──┐
│ Auth  │  │ Profile  │  │   Order    │  │   Bill      │  │ Discovery│
│Service│  │ Service  │  │  Service   │  │  Service    │  │ Service  │
└───┬───┘  └────┬─────┘  └────┬───────┘  └───────┬─────┘  └──────────┘
    │           │             │                  │
    └───────────┴─────────────┴──────────────────┘
             │
    ┌────────┴──────────────┐
    │                       │
┌───▼──────┐        ┌──────▼────┐
│  MySQL   │        │   Redis   │
│Database  │        │  Cache    │
└──────────┘        └───────────┘

---

🚀 Services Overview

1. Auth Service (auth-service/)

Manages user authentication with hybrid JWT and stateful session control.

Key Features:

• ✅ Hybrid JWT Authentication (stateless + stateful)
• ✅ AES-192 Password Encryption
• ✅ Redis-based Token Session Management
• ✅ Employee Role-Based Access Control
• ✅ Immediate Token Revocation Support

Technology Stack:

• Spring Boot 4.0.1
• Spring Security
• JWT (JSON Web Tokens)
• Redis
• MySQL

Key Files:

• AuthService.md - Hybrid JWT documentation
• TokenService.java - Token generation, validation, logout
• EmployeeService.java - Employee CRUD operations
• AES.java - Password encryption/decryption

---

2. Profile Service (profile-service/)

Manages client and publication profiles with caching and circuit breaker protection.

Key Features:

• ✅ Client Profile Management
• ✅ Publication Management
• ✅ Redis Cache-First Pattern
• ✅ Circuit Breaker (Resilience4j)
• ✅ GST & State Code Management
• ✅ Pagination Support

Technology Stack:

• Spring Boot 3.5.7
• Spring Data JPA
• Redis (Caching)
• MySQL
• Swagger/OpenAPI

Key Files:

• ClientService.md - Cache-first pattern & circuit breaker documentation
• PublicationRepo.java - Publication data access
• GstRepo.java - GST management
• SecurityConfig.java - Role-based access control

---

3. Order Service (order-service/)

Manages orders and release orders (RO) for publications.

Key Features:

• ✅ Estimate Creation & Management
• ✅ Release Order (RO) Generation
• ✅ PDF Report Generation
• ✅ Publication Rate Management
• ✅ Order Status Tracking
• ✅ Service-to-service Communication

Technology Stack:

• Spring Boot 4.0.1
• Spring Data JPA
• Redis
• MySQL
• Thymeleaf (HTML Templates)

Key Templates:

• estimateMultiPageFirstPage.html - Estimate document
• roPage.html - Release order document

---

4. Bill Service (bill-service/)

Manages billing and invoice generation with automatic bill ID generation.

Key Features:

• ✅ Monthly Auto-Reset Bill Counter
• ✅ Financial Year Calculation (April-March cycle)
• ✅ Tax Invoice Generation
• ✅ Publication-wise Billing
• ✅ Discount & GST Calculation
• ✅ Thread-Safe Bill ID Generation

Bill ID Format: MM/COUNT/YY-YY

• Example: 01/1/24-25 (First bill of January 2025)
• Auto-resets to 1 each month
• Financial year: April to March

Technology Stack:

• Spring Boot 4.0.1
• Spring Cloud (Circuit Breaker, Load Balancer)
• Thymeleaf (HTML Templates)
• MySQL

Key Files:

• BillIdGenerator.md - Complete ID generation documentation
• BillService.java - Bill operations
• billSinglePage.html - Single-page invoice
• billMultiPageLastPage.html - Multi-page invoice

---

5. Discovery Service (discovery-service/)

Eureka service registry for microservice discovery.

Key Features:

• ✅ Service Registration & Discovery
• ✅ Health Checks
• ✅ Load Balancing Support

Technology Stack:

• Spring Cloud Netflix Eureka
• Spring Boot 4.0.1

Ports:

• Development: 8086
• Production: Configurable via ${PORT}

---

6. Gateway Service (gateway-service/)

API Gateway with JWT validation and request routing.

Key Features:

• ✅ JWT Token Validation
• ✅ Request Routing to Microservices
• ✅ Custom Gateway Filters
• ✅ Path Blocking
• ✅ Service Discovery Integration

Gateway Routes:

• /api/v1/auth/** → Auth Service
• /api/v1/profile/** → Profile Service
• /api/v1/order/** → Order Service
• /api/v1/billing/** → Bill Service

Technology Stack:

• Spring Cloud Gateway
• Spring Cloud Netflix Eureka Client
• Reactive (WebFlux)

Key Files:

• JwtValidationGatewayFilterFactory.java - Token validation filter
• BlockValidateGatewayFilterFactory.java - Path blocking filter
• application-dev.yml - Development routes configuration

---

📋 Database Schema

Four separate databases for each service:

CREATE DATABASE icProfile;    -- Client & Publication data
CREATE DATABASE icOrder;      -- Orders & Estimates
CREATE DATABASE icBill;       -- Billing & Invoices
CREATE DATABASE icAuth;       -- Employee & Authentication

Shared Sequences Table:

CREATE TABLE `id_sequence` (
  `sequence_name` varchar(30) NOT NULL,
  `current_value` bigint NOT NULL DEFAULT '0',
  PRIMARY KEY (`sequence_name`)
);

Sequences:

• BILLCOUNT - Bill ID counter
• CLIENTID - Client identifier
• EMPLOYEEID - Employee identifier
• ESTIMATEID - Estimate identifier
• PUBLICATIONID - Publication identifier
• REPRESENTATIVEID - Representative identifier
• ROID - Release Order identifier

---

🐳 Docker & Deployment

Running with Docker Compose

docker-compose up -d

---

🔐 Authentication & Security

Hybrid JWT Approach

Stateless JWT:

• Claims: empId, role, jti (JWT ID)
• Fast authentication without database hits

Stateful Server Control:

• Redis stores jti for each employee
• Immediate token revocation capability
• Single active session per employee (configurable)

Benefits:

• ✅ High security (stolen tokens can be revoked)
• ✅ High performance (stateless JWT verification)
• ✅ Admin control (force logout, session management)
• ✅ Device-specific session management

Password Encryption

Algorithm: AES-192 (ECB mode with PKCS5Padding)

• Configured in AES.java
• Secret key length: 24 characters

Role-Based Access Control (RBAC)

Roles:

• USER - Basic user access
• EDITOR - Create/update content
• ADMIN - Full administrative access
• ORDER_SERVICE - Service-to-service calls
• BILLING_SERVICE - Service-to-service calls

---

🔄 Service-to-Service Communication

Communication Pattern

Services communicate through:

• HTTP/REST via Spring WebClient
• Service Discovery via Eureka
• Load Balancing via Spring Cloud LoadBalancer
• Circuit Breaker via Resilience4j

Example: Bill Service to Profile Service

// Fetch client details from Profile Service
profile-service://ic-profile-service/v1/profile/clients/{clientId}

---

📊 Caching Strategy

Redis Cache Implementation

Profile Service:

• Key Format: Entity ID or custom patterns
• TTL: 10 minutes (configurable)
• Fallback: Database query on cache miss

Cache-First Pattern:

1. Check Redis cache
2. If miss, fetch from database
3. Update cache with fresh data
4. Return to client

Circuit Breaker Configuration

Profile Service (Read Operations):

• Name: clientServiceRead
• Failure Rate: 50%
• Sliding Window: 100 calls
• Minimum Calls: 10
• Wait Duration (OPEN): 30 seconds
• Fallback: Return cached data if available

---

📝 API Documentation

Each service provides Swagger/OpenAPI documentation:

• Auth Service: /auth/api-docs
• Profile Service: /profile/api-docs
• Order Service: /order/api-docs
• Bill Service: /billing/api-docs

Gateway routes these to Swagger UI:

• http://localhost:8082/auth/swagger-ui.html
• http://localhost:8082/profile/swagger-ui.html
• etc.

---

🛠️ Development

Prerequisites

• Java 21 (Auth, Bill, Order, Discovery, Gateway services)
• Java 17 (Gateway service)
• Maven 3.9.9
• Docker & Docker Compose
• MySQL 8.0+
• Redis Alpine

Build Individual Services

# Build Auth Service
cd auth-service
mvn clean package

# Build Profile Service
cd profile-service
mvn clean package

# Similar for other services

Build Docker Images

# From each service directory
docker build -t debayan2003/ic-{service-name}:v1 .

Local Development (Without Docker)

1. Start MySQL and Redis locally
2. Create databases using db create.txt script
3. Run each service from IDE or command line:

cd auth-service
mvn spring-boot:run

🔍 Monitoring & Logging

Actuator Endpoints

Each service exposes:

• /actuator/health - Service health status
• /actuator/metrics - Application metrics
• /actuator/** - Full actuator endpoints

Available via Gateway

• http://localhost:8082/auth/actuator/**
• http://localhost:8082/profile/actuator/**
• etc.

Logging

📜 License

This project is managed by Debayan-Guha.