🚀 Mikroservisler Projesi - Production-Ready E-Ticaret Sistemi

Bu proje, Clean Architecture, DDD, SAGA, Outbox, CQRS pattern'leri ile Kafka ve Kubernetes kullanarak enterprise-grade mikroservis sistemi geliştirme sürecini öğretir.

📋 Proje Özeti

3 ana mikroservisten oluşan e-ticaret domain'i:

• Order Service (Port: 8081) - Sipariş yönetimi
• Inventory Service (Port: 8082) - Stok yönetimi
• Payment Service (Port: 8083) - Ödeme işlemleri

Infrastructure:

• PostgreSQL (Port: 5432) - Database per service pattern
• Apache Kafka (Port: 9092) - Event-driven communication
• pgAdmin (Port: 5050) - Database management UI

🎯 Öğrenme Hedefleri

Bu proje ile şunları öğreneceksiniz:

🏗️ Architecture Patterns

• ✅ Clean Architecture - Dependency inversion ve katman separasyonu
• ✅ Hexagonal Architecture - Ports & adapters pattern
• ✅ Domain Driven Design - Strategic ve tactical patterns
• ✅ SAGA Pattern - Distributed transaction management
• ✅ Outbox Pattern - Reliable event publishing
• ✅ CQRS Pattern - Command/Query responsibility segregation

⚡ Technology Stack

• ✅ Spring Boot 3.x - Modern Java microservices
• ✅ Apache Kafka - Event streaming platform
• ✅ PostgreSQL - ACID compliant database
• ✅ Docker & Docker Compose - Containerization
• ✅ Kubernetes - Container orchestration
• ✅ Google Cloud GKE - Production deployment

🎓 Advanced Concepts

• ✅ Event Sourcing - Temporal data management
• ✅ Exactly-Once Semantics - Reliable message processing
• ✅ Change Data Capture - Database event streaming
• ✅ Observability - Metrics, tracing, logging
• ✅ Production Readiness - Security, scaling, monitoring

🚀 Hızlı Başlangıç

Ön Koşullar

# 1. Java Development Kit 17+
java -version

# 2. Maven 3.8+
mvn -version

# 3. Docker & Docker Compose
docker --version
docker-compose --version

# 4. PowerShell (Windows) veya Bash (Linux/Mac)
$PSVersionTable.PSVersion  # PowerShell

Sistem Başlatma

# 1. Repository clone et
git clone <repo-url>
cd microservices-quickstart

# 2. Tüm sistemi başlat
.\scripts\start.ps1

# 3. Smoke test çalıştır
.\scripts\smoke-test.ps1

# 4. Sistemi durdur
.\scripts\stop.ps1

Manuel Başlatma (Alternatif)

# Infrastructure başlat
docker-compose up -d postgres pgadmin zookeeper kafka

# Servisleri build et
mvn clean compile -f order-service/pom.xml
mvn clean compile -f inventory-service/pom.xml
mvn clean compile -f payment-service/pom.xml

# Mikroservisleri başlat
docker-compose up -d order-service inventory-service payment-service

📡 API Endpoints

Order Service (Port: 8081)

# Sipariş oluştur
POST http://localhost:8081/orders
{
  "customerId": "CUST-001",
  "items": [
    {
      "productId": "PROD-123",
      "quantity": 2,
      "unitPrice": 99.99
    }
  ]
}

# Siparişleri listele
GET http://localhost:8081/orders

# Sipariş detayı
GET http://localhost:8081/orders/{orderId}

# Müşteri siparişleri
GET http://localhost:8081/orders/customer/{customerId}

Inventory Service (Port: 8082)

# Stok durumu sorgula
GET http://localhost:8082/inventory/{productId}

# Stok rezervasyonu
POST http://localhost:8082/inventory/reserve
{
  "productId": "PROD-123",
  "quantity": 2,
  "orderId": "order-123",
  "reservationId": "res-456"
}

# Rezervasyon serbest bırak
POST http://localhost:8082/inventory/release
{
  "productId": "PROD-123",
  "quantity": 2,
  "orderId": "order-123",
  "reservationId": "res-456"
}

# Tüm stokları listele
GET http://localhost:8082/inventory

Payment Service (Port: 8083)

# Ödeme işlemi
POST http://localhost:8083/payments
{
  "orderId": "order-123",
  "amount": 199.98,
  "paymentMethod": "CREDIT_CARD",
  "cardToken": "tok_123456"
}

# Ödeme durumu
GET http://localhost:8083/payments/{paymentId}

# Sipariş ödemeleri
GET http://localhost:8083/payments/order/{orderId}

# İade işlemi
POST http://localhost:8083/payments/{paymentId}/refund
{
  "amount": 199.98,
  "reason": "Customer request"
}

🔍 Health Checks

# Servis durumları
curl http://localhost:8081/actuator/health  # Order Service
curl http://localhost:8082/actuator/health  # Inventory Service
curl http://localhost:8083/actuator/health  # Payment Service

# Database bağlantıları
curl http://localhost:8081/actuator/health/db
curl http://localhost:8082/actuator/health/db
curl http://localhost:8083/actuator/health/db

🗄️ Database Erişimi

pgAdmin Web UI

• URL: http://localhost:5050
• Login: admin@admin.com / admin
• Server: postgres:5432
• Database: order_db, inventory_db, payment_db

Direct PostgreSQL

# Order database
docker exec -it microservices-quickstart-postgres-1 psql -U admin -d order_db

# Inventory database
docker exec -it microservices-quickstart-postgres-1 psql -U admin -d inventory_db

# Payment database
docker exec -it microservices-quickstart-postgres-1 psql -U admin -d payment_db

📊 Monitoring & Logs

Container Durumları

# Tüm container'ları göster
docker-compose ps

# Spesifik servis logları
docker-compose logs -f order-service
docker-compose logs -f inventory-service
docker-compose logs -f payment-service

# Infrastructure logları
docker-compose logs -f postgres
docker-compose logs -f kafka

Kafka Topics

# Topic'leri listele
docker exec -it microservices-quickstart-kafka-1 kafka-topics --list --bootstrap-server localhost:9092

# Event'leri consume et
docker exec -it microservices-quickstart-kafka-1 kafka-console-consumer --topic orders --bootstrap-server localhost:9092 --from-beginning

🧪 Test Scenarios

Scenario 1: Temel CRUD Operations

# PowerShell test script
.\scripts\smoke-test.ps1

Scenario 2: Event-Driven Workflow Test

# 1. Sipariş oluştur (OrderCreated event publish edilir)
POST http://localhost:8081/orders
{
  "customerId": "CUST-EVENT-001",
  "items": [{"productId": "PROD-123", "quantity": 1, "unitPrice": 99.99}]
}

# 2. Kafka consumer loglarını kontrol et
docker-compose logs inventory-service | grep "OrderCreated"

# 3. Stok durumunu kontrol et (otomatik rezervasyon olmuş olmalı)
GET http://localhost:8082/inventory/PROD-123

# 4. Ödeme işlemi (PaymentCompleted event publish edilir)
POST http://localhost:8083/payments
{
  "orderId": "created-order-id",
  "amount": 99.99,
  "paymentMethod": "CREDIT_CARD"
}

# 5. Final sipariş durumunu kontrol et
GET http://localhost:8081/orders/{orderId}

🏗️ Mimari Yaklaşım

Current State (QuickStart)

• ✅ Layered Architecture - Controller → Service → Repository
• ✅ Event-Driven Communication - Kafka ile async messaging
• ✅ Database per Service - PostgreSQL ile data isolation
• ✅ Containerization - Docker Compose ile orchestration

Target State (Advanced Patterns)

• 🎯 Clean Architecture - Dependency inversion, use cases
• 🎯 Hexagonal Architecture - Ports & adapters
• 🎯 DDD Implementation - Aggregates, value objects, domain events
• 🎯 SAGA Orchestration - Distributed transaction coordination
• 🎯 Outbox Pattern - Reliable event publishing
• 🎯 CQRS Implementation - Command/Query segregation
• 🎯 Event Sourcing - Kafka as event store
• 🎯 Kubernetes Deployment - Production-ready orchestration

📚 Öğrenme Yolu

Temel Seviye (Hafta 1-2)

1. QuickStart Lab - Sistem kurulumu ve temel API testleri
2. Clean Architecture - Katman separasyonu ve dependency inversion
3. Hexagonal Architecture - Ports & adapters pattern

Orta Seviye (Hafta 3-5)

4. Domain Driven Design - Strategic ve tactical patterns
5. SAGA Pattern - Distributed transaction management
6. Outbox Pattern - Reliable event publishing
7. CQRS Pattern - Command/Query responsibility segregation

İleri Seviye (Hafta 6-8)

8. Kafka Advanced - Advanced programming patterns
9. Event Sourcing - Kafka as event store
10. Kubernetes - Container orchestration
11. GKE Production - Production deployment

🐛 Troubleshooting

Yaygın Problemler

Port Conflict

# Port kullanımını kontrol et
netstat -an | findstr :5432
netstat -an | findstr :9092

# Çakışan servisleri durdur
Stop-Service postgresql-x64-13  # Windows
sudo service postgresql stop     # Linux

Memory Issues

# Docker memory kullanımını kontrol et
docker stats

# Kullanılmayan container'ları temizle
docker system prune -a

Build Failures

# Maven cache temizle
mvn dependency:purge-local-repository

# Build dependency'lerini güncelle
mvn clean compile -U

Log Analysis

# Error logları filtrele
docker-compose logs order-service | grep -i error
docker-compose logs inventory-service | grep -i error
docker-compose logs payment-service | grep -i error

# Kafka connection sorunları
docker-compose logs kafka | grep -i "connection"

🚀 Production Hazırlığı

Performance Tuning

• JVM heap size optimization
• Kafka partition configuration
• Database connection pooling
• Caching strategies

Security Implementation

• JWT token authentication
• Kafka SASL/TLS encryption
• Database connection encryption
• API rate limiting

Observability Stack

• Prometheus metrics collection
• Grafana dashboards
• Distributed tracing (Jaeger)
• Centralized logging (ELK Stack)

Deployment Pipeline

• GitHub Actions CI/CD
• Docker image registry
• Kubernetes manifests
• Helm charts
• Environment-specific configurations

🤝 Katkıda Bulunma

1. Fork yapın
2. Feature branch oluşturun (git checkout -b feature/amazing-feature)
3. Changes'inizi commit edin (git commit -m 'Add amazing feature')
4. Branch'inizi push edin (git push origin feature/amazing-feature)
5. Pull Request oluşturun

📞 Destek

• Documentation: documentation/ klasöründeki detaylı kılavuzlar
• API Examples: Postman collection ve curl örnekleri
• Troubleshooting: Her bölümdeki sorun giderme rehberleri
• GitHub Issues: Sorun bildirimi ve öneriler için

📊 Proje Durumu

✅ Tamamlanan Bölümler (%70 Complete)

• QuickStart Lab - Tam hazır ve çalışır durumda
• Order Service - Clean Architecture + DDD + Outbox + CQRS tam implement
• Comprehensive Documentation - SAGA, Outbox, CQRS, Kafka Advanced, Event Sourcing
• Inventory Service Domain Layer - Entities, Value Objects, Domain Events

🔄 Devam Eden Bölümler

• Inventory & Payment Services - Application ve Infrastructure layers
• SAGA Orchestrator - Concrete implementation
• Advanced Kafka - Exactly-once semantics
• Kubernetes & GKE - Production deployment

📋 Detaylı durum raporu: PROJECT-STATUS.md

🎯 Final Hedef

Bu proje sonunda elde edeceğiniz skills:

• ✅ Enterprise Microservices Architecture tasarlama
• ✅ Event-Driven Systems geliştirme
• ✅ Distributed Patterns implementation
• ✅ Production-Ready Applications deployment
• ✅ Cloud-Native Development yaklaşımları
• ✅ Advanced Kafka Programming patterns
• ✅ Kubernetes Operations ve monitoring

🚀 Hızlı Başlangıç

Proje zaten solid bir foundation'a sahip. Hemen başlamak için:

# 1. Environment'ı başlat
cd microservices-quickstart
docker-compose up -d

# 2. Mevcut implementasyonu test et
./scripts/smoke-test.ps1

# 3. Durum raporunu incele
cat PROJECT-STATUS.md

# 4. Kaldığınız yerden devam edin
# Priority: Inventory Service Application Layer

Happy Coding! 🚀✨