容器化部署

为什么用容器

容器技术解决了软件开发中最经典的痛点——"在我本地是好的"。容器将应用与其运行时依赖（JDK 版本、库文件、配置）打包在一起，确保在任何环境（开发机、CI/CD、生产服务器）中行为一致。

• 环境一致性：消除"在我机器上能跑"问题，开发、测试、生产使用相同镜像
• 快速扩缩容：启动一个容器通常只需秒级，而非分钟级（传统 VM）
• 资源隔离：容器间 CPU/内存隔离，单个服务崩溃不影响其他服务
• 不可变基础设施：每次部署都是创建新容器而非修改旧容器，回滚简单可靠

核心概念名词解释

完整部署架构

多阶段 Dockerfile

# ===== 阶段 1: 构建阶段（使用完整 JDK）=====
FROM eclipse-temurin:21-jdk-alpine AS builder

WORKDIR /app

# 先复制 pom.xml 利用 Docker 层缓存（依赖不变时跳过下载）
COPY pom.xml .
COPY mvnw .
COPY .mvn .mvn

# 下载依赖（利用缓存层）
RUN ./mvnw dependency:go-offline -B

# 复制源代码并构建
COPY src src
RUN ./mvnw package -DskipTests -B

# ===== 阶段 2: 运行阶段（只用 JRE，体积更小）=====
FROM eclipse-temurin:21-jre-alpine

# 安全：不以 root 用户运行
RUN addgroup -g 1001 spring && adduser -u 1001 -G spring -s /bin/sh -D spring
USER spring

WORKDIR /app

# 从构建阶段复制 JAR（利用 Spring Boot 分层 JAR 优化）
ARG JAR_FILE=target/*.jar
COPY --from=builder /app/${JAR_FILE} app.jar

# JVM 内存配置：容器感知，避免 OOM
ENV JAVA_OPTS="-XX:+UseContainerSupport -XX:MaxRAMPercentage=75.0 -XX:+UseZGC"

EXPOSE 8080

HEALTHCHECK --interval=30s --timeout=3s --start-period=40s --retries=3 \
    CMD wget -qO- http://localhost:8080/actuator/health || exit 1

ENTRYPOINT ["sh", "-c", "java $JAVA_OPTS -jar app.jar"]

docker-compose.yml — 本地开发环境

version: '3.9'

services:
  app:
    build: .
    ports:
      - "8080:8080"
    environment:
      - SPRING_PROFILES_ACTIVE=dev
      - DB_HOST=postgres
      - DB_PASSWORD=dev_password
      - REDIS_HOST=redis
      - RABBITMQ_HOST=rabbitmq
    depends_on:
      postgres:
        condition: service_healthy
      redis:
        condition: service_healthy

  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: demo
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: dev_password
    ports:
      - "5432:5432"
    volumes:
      - postgres_data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 5s

  rabbitmq:
    image: rabbitmq:3.13-management-alpine
    ports:
      - "5672:5672"
      - "15672:15672"  # 管理界面
    environment:
      RABBITMQ_DEFAULT_USER: admin
      RABBITMQ_DEFAULT_PASS: admin

volumes:
  postgres_data:

Spring Boot Actuator 与 Kubernetes 探针

# application.yml
management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics,prometheus
  endpoint:
    health:
      show-details: when-authorized
      probes:
        enabled: true   # 开启 /health/liveness 和 /health/readiness
  health:
    livenessstate:
      enabled: true
    readinessstate:
      enabled: true

# kubernetes/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-demo
spec:
  replicas: 3
  selector:
    matchLabels:
      app: spring-demo
  template:
    metadata:
      labels:
        app: spring-demo
    spec:
      containers:
      - name: app
        image: your-registry/spring-demo:1.0.0
        resources:
          requests:
            memory: "512Mi"
            cpu: "250m"
          limits:
            memory: "1Gi"
            cpu: "1000m"
        livenessProbe:
          httpGet:
            path: /actuator/health/liveness
            port: 8080
          initialDelaySeconds: 45  # JVM 启动需要时间
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /actuator/health/readiness
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 5
        envFrom:
        - configMapRef:
            name: spring-demo-config
        - secretRef:
            name: spring-demo-secrets