Legacy Migration Patterns
├── Lift and Shift
│   ├── Containerization
│   ├── Minimal Changes
│   └── Quick Migration
├── Replatform
│   ├── Cloud-Native Services
│   ├── Managed Databases
│   └── Modern Middleware
├── Refactor
│   ├── Microservices
│   ├── API-First Design
│   └── Event-Driven Architecture
└── Rebuild
    ├── Cloud-Native
    ├── Serverless
    └── Modern Frameworks

# Application Assessment Template
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-assessment
data:
  assessment.yaml: |
    applications:
      - name: "legacy-app-1"
        type: "monolith"
        technology: "Java Spring"
        database: "Oracle"
        dependencies:
          - "Active Directory"
          - "File System"
          - "Message Queue"
        migration_complexity: "medium"
        business_criticality: "high"
        estimated_effort: "8 weeks"
      
      - name: "legacy-app-2"
        type: "web-application"
        technology: "PHP"
        database: "MySQL"
        dependencies:
          - "Apache"
          - "File Upload"
        migration_complexity: "low"
        business_criticality: "medium"
        estimated_effort: "4 weeks"

# Migration Strategy Decision Matrix
apiVersion: v1
kind: ConfigMap
metadata:
  name: migration-strategy
data:
  strategy.yaml: |
    decision_factors:
      business_criticality:
        high: "lift_and_shift"
        medium: "replatform"
        low: "refactor"
      
      technical_debt:
        high: "refactor"
        medium: "replatform"
        low: "lift_and_shift"
      
      time_constraints:
        urgent: "lift_and_shift"
        moderate: "replatform"
        flexible: "refactor"
      
      budget:
        limited: "lift_and_shift"
        moderate: "replatform"
        generous: "refactor"

# Dockerfile für Legacy Java Application
FROM openjdk:11-jre-slim

# Install dependencies
RUN apt-get update && apt-get install -y \
    curl \
    && rm -rf /var/lib/apt/lists/*

# Create app directory
WORKDIR /app

# Copy application JAR
COPY target/legacy-app.jar app.jar

# Copy configuration
COPY config/application.properties /app/config/

# Expose port
EXPOSE 8080

# Health check
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD curl -f http://localhost:8080/health || exit 1

# Run application
CMD ["java", "-jar", "app.jar"]

# Legacy Application Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: legacy-app
  labels:
    app: legacy-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: legacy-app
  template:
    metadata:
      labels:
        app: legacy-app
    spec:
      containers:
        - name: legacy-app
          image: company/legacy-app:latest
          ports:
            - containerPort: 8080
          env:
            - name: SPRING_PROFILES_ACTIVE
              value: 'kubernetes'
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: database-secret
                  key: url
            - name: DATABASE_USERNAME
              valueFrom:
                secretKeyRef:
                  name: database-secret
                  key: username
            - name: DATABASE_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: database-secret
                  key: password
          resources:
            requests:
              memory: '512Mi'
              cpu: '500m'
            limits:
              memory: '1Gi'
              cpu: '1000m'
          livenessProbe:
            httpGet:
              path: /health
              port: 8080
            initialDelaySeconds: 60
            periodSeconds: 10
          readinessProbe:
            httpGet:
              path: /ready
              port: 8080
            initialDelaySeconds: 30
            periodSeconds: 5

# Database Migration Job
apiVersion: batch/v1
kind: Job
metadata:
  name: database-migration
spec:
  template:
    spec:
      containers:
        - name: migration
          image: migration-tool:latest
          command: ['python', 'migrate.py']
          env:
            - name: SOURCE_DB_HOST
              value: 'legacy-db.company.local'
            - name: SOURCE_DB_PORT
              value: '1521'
            - name: SOURCE_DB_NAME
              value: 'LEGACY_DB'
            - name: TARGET_DB_HOST
              value: 'kubernetes-db-service'
            - name: TARGET_DB_PORT
              value: '5432'
            - name: TARGET_DB_NAME
              value: 'kubernetes_db'
          volumeMounts:
            - name: migration-scripts
              mountPath: /scripts
            - name: migration-data
              mountPath: /data
      volumes:
        - name: migration-scripts
          configMap:
            name: migration-scripts
        - name: migration-data
          persistentVolumeClaim:
            claimName: migration-data-pvc
      restartPolicy: Never
  backoffLimit: 3

# Cloud-Native Service Migration
apiVersion: apps/v1
kind: Deployment
metadata:
  name: modernized-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: modernized-app
  template:
    metadata:
      labels:
        app: modernized-app
    spec:
      containers:
        - name: app
          image: company/modernized-app:latest
          env:
            # Replace file system with S3
            - name: S3_BUCKET
              value: 'app-storage'
            - name: S3_ENDPOINT
              value: 'http://minio-service:9000'

            # Replace message queue with Kafka
            - name: KAFKA_BOOTSTRAP_SERVERS
              value: 'kafka-service:9092'
            - name: KAFKA_TOPIC
              value: 'app-events'

            # Replace LDAP with OAuth
            - name: OAUTH_PROVIDER
              value: 'keycloak'
            - name: OAUTH_CLIENT_ID
              valueFrom:
                secretKeyRef:
                  name: oauth-secret
                  key: client-id

# PostgreSQL StatefulSet
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: postgresql
spec:
  serviceName: postgresql
  replicas: 3
  selector:
    matchLabels:
      app: postgresql
  template:
    metadata:
      labels:
        app: postgresql
    spec:
      containers:
        - name: postgresql
          image: postgres:13
          env:
            - name: POSTGRES_DB
              value: 'app_database'
            - name: POSTGRES_USER
              valueFrom:
                secretKeyRef:
                  name: postgresql-secret
                  key: username
            - name: POSTGRES_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: postgresql-secret
                  key: password
          ports:
            - containerPort: 5432
          volumeMounts:
            - name: postgresql-data
              mountPath: /var/lib/postgresql/data
  volumeClaimTemplates:
    - metadata:
        name: postgresql-data
      spec:
        accessModes: ['ReadWriteOnce']
        resources:
          requests:
            storage: 10Gi

# Microservices Architecture
apiVersion: v1
kind: ConfigMap
metadata:
  name: microservices-architecture
data:
  architecture.yaml: |
    services:
      user-service:
        responsibility: "User Management"
        database: "user-db"
        api: "/api/users"
        dependencies: []
      
      order-service:
        responsibility: "Order Processing"
        database: "order-db"
        api: "/api/orders"
        dependencies:
          - "user-service"
          - "inventory-service"
      
      inventory-service:
        responsibility: "Inventory Management"
        database: "inventory-db"
        api: "/api/inventory"
        dependencies: []
      
      payment-service:
        responsibility: "Payment Processing"
        database: "payment-db"
        api: "/api/payments"
        dependencies:
          - "user-service"
          - "order-service"

# Kong API Gateway
apiVersion: apps/v1
kind: Deployment
metadata:
  name: kong-gateway
spec:
  replicas: 3
  selector:
    matchLabels:
      app: kong-gateway
  template:
    metadata:
      labels:
        app: kong-gateway
    spec:
      containers:
        - name: kong
          image: kong:2.8
          env:
            - name: KONG_DATABASE
              value: 'postgres'
            - name: KONG_PG_HOST
              value: 'postgresql-service'
            - name: KONG_PG_DATABASE
              value: 'kong'
          ports:
            - containerPort: 8000
            - containerPort: 8443
            - containerPort: 8001
            - containerPort: 8444

# Istio Service Mesh Configuration
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: app-virtual-service
spec:
  hosts:
    - 'app.company.com'
  gateways:
    - app-gateway
  http:
    - route:
        - destination:
            host: user-service
            port:
              number: 8080
          weight: 50
        - destination:
            host: user-service-v2
            port:
              number: 8080
          weight: 50
---
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: user-service-rule
spec:
  host: user-service
  subsets:
    - name: v1
      labels:
        version: v1
    - name: v2
      labels:
        version: v2

# Migration CI/CD Pipeline
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  name: migration-pipeline
spec:
  entrypoint: migration-workflow
  templates:
    - name: migration-workflow
      steps:
        - - name: analyze
            template: analyze-legacy
        - - name: containerize
            template: containerize-app
        - - name: test
            template: test-migration
        - - name: deploy
            template: deploy-kubernetes
            when: "{{steps.test.outputs.result}} == 'success'"

    - name: analyze-legacy
      container:
        image: analysis-tool:latest
        command: ['python', 'analyze.py']

    - name: containerize-app
      container:
        image: containerization-tool:latest
        command: ['python', 'containerize.py']

    - name: test-migration
      container:
        image: test-tool:latest
        command: ['python', 'test.py']

    - name: deploy-kubernetes
      container:
        image: deployment-tool:latest
        command: ['kubectl', 'apply', '-f', '/manifests']

# Migration Testing Strategy
apiVersion: v1
kind: ConfigMap
metadata:
  name: migration-testing
data:
  testing.yaml: |
    test_phases:
      unit_tests:
        - "Component Tests"
        - "Integration Tests"
        - "API Tests"
      
      functional_tests:
        - "End-to-End Tests"
        - "User Acceptance Tests"
        - "Performance Tests"
      
      migration_tests:
        - "Data Integrity Tests"
        - "Backward Compatibility Tests"
        - "Rollback Tests"

    test_automation:
      tools:
        - "JUnit"
        - "TestNG"
        - "Selenium"
        - "Postman"
        - "JMeter"

# Blue-Green Deployment Strategy
apiVersion: v1
kind: Service
metadata:
  name: app-service
spec:
  selector:
    app: app-blue # Initially points to blue
  ports:
    - port: 80
      targetPort: 8080
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-blue
spec:
  replicas: 3
  selector:
    matchLabels:
      app: app-blue
  template:
    metadata:
      labels:
        app: app-blue
    spec:
      containers:
        - name: app
          image: company/app:blue
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-green
spec:
  replicas: 0 # Initially scaled to 0
  selector:
    matchLabels:
      app: app-green
  template:
    metadata:
      labels:
        app: app-green
    spec:
      containers:
        - name: app
          image: company/app:green

# Canary Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-canary
spec:
  replicas: 1 # Small number for canary
  selector:
    matchLabels:
      app: app-canary
  template:
    metadata:
      labels:
        app: app-canary
    spec:
      containers:
        - name: app
          image: company/app:new-version
          env:
            - name: CANARY_FLAG
              value: 'true'

# Migration Monitoring Dashboard
apiVersion: v1
kind: ConfigMap
metadata:
  name: migration-monitoring
data:
  dashboard.yaml: |
    metrics:
      - name: "Migration Progress"
        query: "migration_progress_percentage"
        alert_threshold: 90
      
      - name: "Application Performance"
        query: "application_response_time"
        alert_threshold: 1000ms
      
      - name: "Error Rate"
        query: "application_error_rate"
        alert_threshold: 5%
      
      - name: "Data Integrity"
        query: "data_integrity_score"
        alert_threshold: 99.9%

    alerts:
      - name: "Migration Stalled"
        condition: "migration_progress < 10% for 1h"
        severity: "critical"
      
      - name: "Performance Degradation"
        condition: "response_time > 2000ms for 5m"
        severity: "warning"
      
      - name: "High Error Rate"
        condition: "error_rate > 10% for 2m"
        severity: "critical"

# Data Validation Job
apiVersion: batch/v1
kind: CronJob
metadata:
  name: data-validation
spec:
  schedule: '*/30 * * * *' # Every 30 minutes
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: validation
              image: validation-tool:latest
              command: ['python', 'validate_data.py']
              env:
                - name: SOURCE_DB
                  value: 'legacy-database'
                - name: TARGET_DB
                  value: 'kubernetes-database'
                - name: VALIDATION_RULES
                  value: '/rules/validation.yaml'
          restartPolicy: OnFailure