📘 第08课：多阶段构建

镜像构建

🏗️ 为什么需要多阶段构建？

传统构建方式中，构建工具（编译器、SDK、源码）会留在最终镜像里，导致镜像臃肿且不安全。多阶段构建让你只保留运行时需要的内容。

📝 多阶段构建语法

# 阶段1：构建阶段 ✅
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# 阶段2：运行阶段 ✅
FROM node:20-alpine AS runtime
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY --from=builder /app/dist ./dist

ENV NODE_ENV=production
USER node
EXPOSE 3000
CMD ["node", "dist/server.js"]

🦀 实战：Go应用多阶段构建

# Go应用：编译型语言，最终镜像可以极小 ✅
FROM golang:1.22-alpine AS builder
WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -o /myapp

# 最终阶段：scratch空镜像或distroless ✅
FROM gcr.io/distroless/static-debian12
COPY --from=builder /myapp /myapp
EXPOSE 8080
ENTRYPOINT ["/myapp"]

# 构建并查看大小 ✅
docker build -t my-go-app .
docker images my-go-app
REPOSITORY   TAG    IMAGE ID       SIZE
my-go-app    latest a1b2c3d4e5f6   2.5MB     ← 极致精简！

🐍 实战：Python应用多阶段构建

# Python多阶段：编译依赖 + 运行时 ✅
FROM python:3.12-slim AS builder
WORKDIR /app
COPY requirements.txt .
RUN pip install --user --no-cache-dir -r requirements.txt

FROM python:3.12-slim
WORKDIR /app
COPY --from=builder /root/.local /root/.local
COPY . .
ENV PATH=/root/.local/bin:$PATH
ENV PYTHONUNBUFFERED=1
EXPOSE 8000
CMD ["gunicorn", "--bind", "0.0.0.0:8000", "app:create_app()"]

📦 实战：React前端多阶段构建

# React/Vue前端：构建 + Nginx托管 ✅
FROM node:20-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=build /app/dist /usr/share/nginx/html
COPY nginx.conf /etc/nginx/conf.d/default.conf
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

🔗 多阶段高级技巧

# 指定构建目标阶段 ✅
docker build --target runtime -t my-app .

# 三个阶段：测试 → 构建 → 运行
FROM node:20-alpine AS test
WORKDIR /app
COPY . .
RUN npm ci && npm test

FROM node:20-alpine AS build
WORKDIR /app
COPY . .
RUN npm ci && npm run build

FROM node:20-alpine AS runtime
COPY --from=build /app/dist ./dist
CMD ["node", "dist/server.js"]

# 从外部镜像复制 ✅
COPY --from=nginx:alpine /etc/nginx/nginx.conf /etc/nginx/

# 使用构建参数选择阶段
ARG TARGET=runtime
FROM node:20-alpine AS ${TARGET}

❓ 常见问题

📚 深度补充：多阶段构建进阶要点

【镜像进阶阶段】生产环境注意事项

常见误区与避坑指南

1. 过度配置：不是所有服务都需要高可用，根据实际需求选择架构复杂度，避免过度工程
2. 忽略日志：日志是排障的关键，确保日志格式统一、级别合理、采集完整
3. 资源超卖：容器资源限制不是摆设，超卖会导致性能下降甚至OOM Kill
4. 安全忽视：默认配置不等于安全配置，生产环境必须加固（非root、只读FS、最小能力）
5. 监控缺失：没有监控等于盲飞，至少要有基础的健康检查和资源监控
6. 手动运维：能自动化的绝不手动，手动操作容易出错且不可追溯
7. 忽略网络策略：默认所有容器互通不安全，应按最小权限原则配置网络

进阶阅读与参考

• Docker官方文档：https://docs.docker.com/
• Docker最佳实践指南：Dev Best Practices
• CIS Docker Benchmark：容器安全基线检查标准
• 12-Factor App方法论：https://12factor.net/
• Google SRE Book：运维可靠性工程实践
• Kubernetes官方文档：https://kubernetes.io/docs/

Docker命令速查卡

# 容器生命周期
docker create/start/stop/restart/rm/pause/unpause
docker logs/top/stats/inspect/exec diff

# 镜像构建
docker build/pull/push/tag/rmi/images/history
docker save/load/import/manifest

# 网络与存储
docker network create/ls/inspect/connect/disconnect/rm/prune
docker volume create/ls/inspect/rm/prune

# Docker Compose
docker compose up/down/ps/logs/build/exec
docker compose config/stop/start/scale/top/cp

# 系统维护
docker system df/prune/info
docker builder prune
docker container/prune/image prune

# K8s常用命令
kubectl get/describe/logs/exec/apply/delete
kubectl rollout status/undo/history
kubectl scale/autoscale/set

本阶段知识脉络

镜像层与存储驱动

OCI标准与镜像规范

实战案例：故障排查流程

# Step 1: 检查容器状态
docker ps -a                          # 查看所有容器
docker inspect <container>            # 查看详细配置

# Step 2: 查看日志
docker logs --tail 100 <container>    # 最近100行日志
docker logs --since 1h <container>    # 最近1小时

# Step 3: 进入容器排查
docker exec -it <container> sh        # 进入容器shell

# Step 4: 检查资源
docker stats --no-stream              # 资源使用概览
docker system df                      # 磁盘使用

# Step 5: 网络排查
docker network ls                     # 网络列表
docker exec <c> ping <target>        # 网络连通性
docker exec <c> nslookup <svc>       # DNS解析

# Step 6: 检查健康状态
docker inspect --format '{{.State.Health}}' <c>
docker inspect --format '{{.State.ExitCode}}' <c>
docker inspect --format '{{.State.OOMKilled}}' <c>

Dockerfile模板：多语言通用

# 通用最佳实践模板
FROM alpine:3.19 AS builder
# ... 构建步骤 ...

FROM alpine:3.19
RUN addgroup -S appgroup && adduser -S appuser -G appgroup
WORKDIR /app
COPY --from=builder /app/output .
USER appuser
HEALTHCHECK --interval=30s --timeout=3s --retries=3 \
  CMD wget -qO- http://localhost:8080/health || exit 1
EXPOSE 8080
CMD ["./app"]

Docker Compose健康检查模板

services:
  app:
    build: .
    healthcheck:
      test: ["CMD", "wget", "-qO-", "http://localhost:8080/health"]
      interval: 30s
      timeout: 5s
      retries: 3
      start_period: 30s
    restart: unless-stopped
    deploy:
      resources:
        limits:
          cpus: '1'
          memory: 512M