Containers (Docker)

Container, uygulamayı aynı imajla build, test ve deploy edilebilir hale getiren paketleme sınırıdır. Docker kullanmanın amacı makine bağımlılığını azaltmaktır; yanlış kullanılırsa sadece daha taşınabilir bir karmaşa üretir.

Hızlı Karar

İhtiyaç	Yaklaşım	Dikkat
Tekrarlanabilir deploy	Multi-stage Dockerfile	Build ve runtime image ayrılmalı
Küçük ve güvenli imaj	Minimal base image, non-root user	Debug araçları eksik olabilir
Lokal çoklu servis geliştirme	Docker Compose	Prod orkestrasyon yerine geçmez
Hızlı startup	Layer cache ve Spring Boot layering	Büyük image cold start'ı uzatır

Üretim Kontrol Listesi

Problem: Container hangi ortam farkını veya deploy sorununu çözüyor?
Çözüm: Image tag, health check, resource limit, secret injection ve shutdown davranışı tanımlı mı?
Trade-off: Container taşınabilirlik sağlar; image güvenliği ve registry yönetimi ek iş getirir.
Hata durumu: OOMKill, crash loop, port conflict, disk dolması ve signal handling test edilmeli.
Ölçüm: Image size, startup time, memory/CPU limit kullanımı, restart count ve vulnerability count izlenmeli.
Güvenlik/maliyet: Root user, gereksiz paket ve sabit secret yasaklanmalı; büyük image registry ve network maliyeti üretir.

Giriş

Containerlar, uygulamaların ve bağımlılıklarının izole edilmiş ortamlarda çalıştırılması için kullanılan hafif sanallaştırma teknolojisidir. Docker, bu teknolojinin en yaygın kullanılan implementasyonudur.

Docker Mimarisi

Container Yaşam Döngüsü

Docker Temel Kavramlar

1. Docker Architecture

dockerfile

# Multi-stage Dockerfile örneği
FROM openjdk:11-jdk-slim AS build
WORKDIR /app
COPY pom.xml .
COPY src ./src
RUN mvn clean package -DskipTests

FROM openjdk:11-jre-slim
WORKDIR /app
COPY --from=build /app/target/app.jar app.jar
EXPOSE 8080
USER 1000:1000
ENTRYPOINT ["java", "-jar", "app.jar"]

Best practices Dockerfile yazımı:

dockerfile

# Base image optimizasyonu
FROM alpine:3.15 AS base

# Security: Non-root user
RUN addgroup -S appgroup && adduser -S appuser -G appgroup

# Package installation ve cleanup
RUN apk add --no-cache \
    openjdk11-jre \
    && rm -rf /var/cache/apk/*

# Working directory
WORKDIR /app

# Copy application
COPY --chown=appuser:appgroup target/app.jar app.jar

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

# Switch to non-root user
USER appuser

# Startup command
ENTRYPOINT ["java", "-Xmx512m", "-Xms256m", "-jar", "app.jar"]

2. Docker Compose Configuration

Multi-service application örneği:

yaml

version: '3.8'

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "8080:8080"
    environment:
      - SPRING_PROFILES_ACTIVE=docker
      - DATABASE_URL=jdbc:postgresql://db:5432/appdb
    depends_on:
      db:
        condition: service_healthy
    restart: unless-stopped
    networks:
      - app-network
    volumes:
      - app-logs:/var/log/app
    deploy:
      resources:
        limits:
          cpus: '0.5'
          memory: 512M
        reservations:
          cpus: '0.25'
          memory: 256M

  db:
    image: postgres:13-alpine
    environment:
      POSTGRES_DB: appdb
      POSTGRES_USER: ${DB_USER}
      POSTGRES_PASSWORD: ${DB_PASSWORD}
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U ${DB_USER}"]
      interval: 10s
      timeout: 5s
      retries: 5
    networks:
      - app-network
    ports:
      - "5432:5432"

  redis:
    image: redis:7-alpine
    command: redis-server --appendonly yes --requirepass ${REDIS_PASSWORD}
    volumes:
      - redis_data:/data
    networks:
      - app-network
    restart: unless-stopped

  nginx:
    image: nginx:alpine
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
      - ./ssl:/etc/nginx/ssl
    depends_on:
      - app
    networks:
      - app-network
    restart: unless-stopped

volumes:
  postgres_data:
  redis_data:
  app-logs:

networks:
  app-network:
    driver: bridge

Container Runtime Configuration

1. Docker Security Configuration

Security best practices Spring Boot uygulaması için:

java

@Configuration
@EnableWebSecurity
public class DockerSecurityConfig {
    
    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        http
            .headers(headers -> headers
                .frameOptions().deny()
                .contentTypeOptions().and()
                .httpStrictTransportSecurity(hstsConfig -> hstsConfig
                    .maxAgeInSeconds(31536000)
                    .includeSubdomains(true)
                    .preload(true)
                )
            )
            .sessionManagement(session -> session
                .sessionCreationPolicy(SessionCreationPolicy.STATELESS)
            );
        
        return http.build();
    }
}

Container resource monitoring:

java

@Component
public class ContainerMetricsCollector {
    
    private final MeterRegistry meterRegistry;
    
    public ContainerMetricsCollector(MeterRegistry meterRegistry) {
        this.meterRegistry = meterRegistry;
        initializeMetrics();
    }
    
    private void initializeMetrics() {
        // Memory metrics
        Gauge.builder("container.memory.usage")
                .description("Container memory usage")
                .register(meterRegistry, this, ContainerMetricsCollector::getMemoryUsage);
        
        // CPU metrics
        Gauge.builder("container.cpu.usage")
                .description("Container CPU usage")
                .register(meterRegistry, this, ContainerMetricsCollector::getCpuUsage);
        
        // Disk metrics
        Gauge.builder("container.disk.usage")
                .description("Container disk usage")
                .register(meterRegistry, this, ContainerMetricsCollector::getDiskUsage);
    }
    
    private double getMemoryUsage(ContainerMetricsCollector collector) {
        Runtime runtime = Runtime.getRuntime();
        long totalMemory = runtime.totalMemory();
        long freeMemory = runtime.freeMemory();
        return (double) (totalMemory - freeMemory) / totalMemory * 100;
    }
    
    private double getCpuUsage(ContainerMetricsCollector collector) {
        OperatingSystemMXBean osBean = ManagementFactory.getOperatingSystemMXBean();
        if (osBean instanceof com.sun.management.OperatingSystemMXBean) {
            return ((com.sun.management.OperatingSystemMXBean) osBean).getProcessCpuLoad() * 100;
        }
        return 0.0;
    }
    
    private double getDiskUsage(ContainerMetricsCollector collector) {
        File root = new File("/");
        long totalSpace = root.getTotalSpace();
        long usableSpace = root.getUsableSpace();
        return (double) (totalSpace - usableSpace) / totalSpace * 100;
    }
}

2. Container Networking

Network bridge configuration:

bash

#!/bin/bash

# Custom Docker network oluşturma
docker network create --driver bridge \
  --subnet=172.20.0.0/16 \
  --ip-range=172.20.240.0/20 \
  --gateway=172.20.0.1 \
  app-network

# Network security policies
docker network create --driver bridge \
  --opt com.docker.network.bridge.enable_icc=false \
  --opt com.docker.network.bridge.enable_ip_masquerade=true \
  secure-network

Service discovery Docker Compose ile:

java

@Service
public class ServiceDiscoveryService {
    
    @Value("${service.registry.url:http://consul:8500}")
    private String registryUrl;
    
    @Autowired
    private RestTemplate restTemplate;
    
    public List<ServiceInstance> discoverServices(String serviceName) {
        try {
            String url = registryUrl + "/v1/health/service/" + serviceName + "?passing=true";
            ConsulHealthResponse response = restTemplate.getForObject(url, ConsulHealthResponse.class);
            
            return response.getServices().stream()
                    .map(this::mapToServiceInstance)
                    .collect(Collectors.toList());
        } catch (Exception e) {
            log.error("Service discovery failed for service: {}", serviceName, e);
            return Collections.emptyList();
        }
    }
    
    private ServiceInstance mapToServiceInstance(ConsulService consulService) {
        return ServiceInstance.builder()
                .serviceId(consulService.getService().getId())
                .serviceName(consulService.getService().getService())
                .host(consulService.getService().getAddress())
                .port(consulService.getService().getPort())
                .metadata(consulService.getService().getMeta())
                .build();
    }
}

Container Image Management

1. Registry Integration

Docker Registry authentication ve push/pull işlemleri:

java

@Service
public class DockerRegistryService {
    
    @Value("${docker.registry.url}")
    private String registryUrl;
    
    @Value("${docker.registry.username}")
    private String username;
    
    @Value("${docker.registry.password}")
    private String password;
    
    public void pushImage(String imageName, String tag) {
        try {
            ProcessBuilder pb = new ProcessBuilder(
                "docker", "push", registryUrl + "/" + imageName + ":" + tag
            );
            
            Process process = pb.start();
            int exitCode = process.waitFor();
            
            if (exitCode != 0) {
                throw new RuntimeException("Docker push failed with exit code: " + exitCode);
            }
            
            log.info("Successfully pushed image: {}/{}}:{}", registryUrl, imageName, tag);
        } catch (Exception e) {
            log.error("Failed to push image: {}", imageName, e);
            throw new RuntimeException("Image push failed", e);
        }
    }
    
    public boolean pullImage(String imageName, String tag) {
        try {
            ProcessBuilder pb = new ProcessBuilder(
                "docker", "pull", registryUrl + "/" + imageName + ":" + tag
            );
            
            Process process = pb.start();
            int exitCode = process.waitFor();
            
            return exitCode == 0;
        } catch (Exception e) {
            log.error("Failed to pull image: {}:{}", imageName, tag, e);
            return false;
        }
    }
}

Image vulnerability scanning entegrasyonu:

java

@Component
public class ImageSecurityScanner {
    
    @Autowired
    private DockerClient dockerClient;
    
    public SecurityScanResult scanImage(String imageId) {
        try {
            // Trivy scanner kullanarak vulnerability check
            ProcessBuilder pb = new ProcessBuilder(
                "trivy", "image", "--format", "json", "--output", "/tmp/scan-result.json", imageId
            );
            
            Process process = pb.start();
            process.waitFor();
            
            // Scan sonuçlarını parse et
            String scanOutput = Files.readString(Paths.get("/tmp/scan-result.json"));
            ObjectMapper mapper = new ObjectMapper();
            TrivyScanResult trivyResult = mapper.readValue(scanOutput, TrivyScanResult.class);
            
            return mapToSecurityScanResult(trivyResult);
        } catch (Exception e) {
            log.error("Image security scan failed for image: {}", imageId, e);
            throw new SecurityScanException("Security scan failed", e);
        }
    }
    
    private SecurityScanResult mapToSecurityScanResult(TrivyScanResult trivyResult) {
        List<Vulnerability> vulnerabilities = trivyResult.getResults().stream()
                .flatMap(result -> result.getVulnerabilities().stream())
                .map(this::mapVulnerability)
                .collect(Collectors.toList());
        
        return SecurityScanResult.builder()
                .imageId(trivyResult.getArtifactName())
                .scanDate(Instant.now())
                .totalVulnerabilities(vulnerabilities.size())
                .criticalCount(countBySeverity(vulnerabilities, "CRITICAL"))
                .highCount(countBySeverity(vulnerabilities, "HIGH"))
                .mediumCount(countBySeverity(vulnerabilities, "MEDIUM"))
                .lowCount(countBySeverity(vulnerabilities, "LOW"))
                .vulnerabilities(vulnerabilities)
                .build();
    }
}

2. Container Lifecycle Management

Health check implementation:

java

@RestController
@RequestMapping("/actuator")
public class ContainerHealthController {
    
    @Autowired
    private DatabaseHealthIndicator databaseHealth;
    
    @Autowired
    private RedisHealthIndicator redisHealth;
    
    @GetMapping("/health")
    public ResponseEntity<HealthStatus> health() {
        HealthStatus status = HealthStatus.builder()
                .status("UP")
                .timestamp(Instant.now())
                .checks(performHealthChecks())
                .build();
        
        boolean allHealthy = status.getChecks().values().stream()
                .allMatch(check -> "UP".equals(check.getStatus()));
        
        return ResponseEntity.status(allHealthy ? 200 : 503).body(status);
    }
    
    @GetMapping("/health/liveness")
    public ResponseEntity<Map<String, String>> liveness() {
        // Basic liveness check - application is running
        return ResponseEntity.ok(Map.of(
                "status", "UP",
                "timestamp", Instant.now().toString()
        ));
    }
    
    @GetMapping("/health/readiness")
    public ResponseEntity<Map<String, Object>> readiness() {
        Map<String, HealthCheck> checks = performHealthChecks();
        boolean ready = checks.values().stream()
                .allMatch(check -> "UP".equals(check.getStatus()));
        
        return ResponseEntity.status(ready ? 200 : 503)
                .body(Map.of(
                        "status", ready ? "UP" : "DOWN",
                        "checks", checks,
                        "timestamp", Instant.now()
                ));
    }
    
    private Map<String, HealthCheck> performHealthChecks() {
        Map<String, HealthCheck> checks = new HashMap<>();
        
        checks.put("database", databaseHealth.health());
        checks.put("redis", redisHealth.health());
        checks.put("disk", checkDiskSpace());
        checks.put("memory", checkMemoryUsage());
        
        return checks;
    }
    
    private HealthCheck checkDiskSpace() {
        File root = new File("/");
        long usableSpace = root.getUsableSpace();
        long totalSpace = root.getTotalSpace();
        double usagePercent = (double) (totalSpace - usableSpace) / totalSpace * 100;
        
        String status = usagePercent < 90 ? "UP" : "DOWN";
        return HealthCheck.builder()
                .status(status)
                .details(Map.of(
                        "usagePercent", usagePercent,
                        "threshold", 90
                ))
                .build();
    }
}

Container monitoring ve logging:

java

@Component
public class ContainerMonitoringService {
    
    private final MeterRegistry meterRegistry;
    private final Logger structuredLogger = LoggerFactory.getLogger("CONTAINER_METRICS");
    
    @EventListener
    public void handleContainerEvent(ContainerEvent event) {
        structuredLogger.info("Container event: type={}, containerId={}, timestamp={}", 
                event.getType(), event.getContainerId(), event.getTimestamp());
        
        // Metrics recording
        Timer.Sample sample = Timer.start(meterRegistry);
        sample.stop(Timer.builder("container.event.duration")
                .tag("event.type", event.getType())
                .register(meterRegistry));
        
        meterRegistry.counter("container.events.total",
                "type", event.getType(),
                "status", event.getStatus())
                .increment();
    }
    
    @Scheduled(fixedRate = 30000)
    public void collectContainerMetrics() {
        try {
            ContainerStats stats = dockerClient.stats(getCurrentContainerId()).exec();
            
            // Memory metrics
            long memoryUsage = stats.getMemoryStats().getUsage();
            long memoryLimit = stats.getMemoryStats().getLimit();
            double memoryPercent = (double) memoryUsage / memoryLimit * 100;
            
            meterRegistry.gauge("container.memory.usage.bytes", memoryUsage);
            meterRegistry.gauge("container.memory.usage.percent", memoryPercent);
            
            // CPU metrics
            long cpuDelta = stats.getCpuStats().getCpuUsage().getTotalUsage() - 
                           stats.getPreCpuStats().getCpuUsage().getTotalUsage();
            long systemDelta = stats.getCpuStats().getSystemCpuUsage() - 
                              stats.getPreCpuStats().getSystemCpuUsage();
            
            double cpuPercent = (double) cpuDelta / systemDelta * 100;
            meterRegistry.gauge("container.cpu.usage.percent", cpuPercent);
            
            // Network metrics
            Map<String, NetworkStats> networks = stats.getNetworks();
            networks.forEach((interfaceName, networkStats) -> {
                meterRegistry.gauge("container.network.rx.bytes", 
                        Tags.of("interface", interfaceName), networkStats.getRxBytes());
                meterRegistry.gauge("container.network.tx.bytes", 
                        Tags.of("interface", interfaceName), networkStats.getTxBytes());
            });
            
        } catch (Exception e) {
            log.error("Failed to collect container metrics", e);
        }
    }
}

Bu kapsamlı Docker ve Container implementasyonu, production-ready containerized uygulamalar geliştirmek için gereken tüm bileşenleri sağlar.

Containers (Docker) ​

Hızlı Karar ​

Üretim Kontrol Listesi ​

Giriş ​

Docker Mimarisi ​

Container Yaşam Döngüsü ​

Docker Temel Kavramlar ​

1. Docker Architecture ​

2. Docker Compose Configuration ​

Container Runtime Configuration ​

1. Docker Security Configuration ​

2. Container Networking ​

Container Image Management ​

1. Registry Integration ​

2. Container Lifecycle Management ​

Containers (Docker)

Hızlı Karar

Üretim Kontrol Listesi

Giriş

Docker Mimarisi

Container Yaşam Döngüsü

Docker Temel Kavramlar

1. Docker Architecture

2. Docker Compose Configuration

Container Runtime Configuration

1. Docker Security Configuration

2. Container Networking

Container Image Management

1. Registry Integration

2. Container Lifecycle Management