山己几

Dockerfile — 多阶段构建

3 min read

核心思想

FROM ... AS builder 创建中间阶段，最终镜像只 COPY --from=builder 取编译产物——编译器、源码、build 缓存全都不带到最终镜像。

# Stage 1: build
FROM golang:1.22-alpine AS builder
# ... 编译 ...
 
# Stage 2: runtime
FROM scratch
COPY --from=builder /app /app

Go 示例：1.2GB → 12MB

普通版（单阶段）：1.2GB（带整个 Go 工具链）

FROM golang:1.22
WORKDIR /src
COPY . .
RUN go build -o app
CMD ["/src/app"]

优化版（多阶段 + scratch）：12MB

# Stage 1: build
FROM golang:1.22-alpine AS builder
WORKDIR /src
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 go build -ldflags="-s -w" -o /app
 
# Stage 2: runtime
FROM scratch
COPY --from=builder /app /app
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
EXPOSE 8080
ENTRYPOINT ["/app"]

-ldflags="-s -w" 去掉调试信息再瘦 30%。

Node 示例：950MB → 180MB

普通版：950MB

FROM node:20
WORKDIR /app
COPY . .
RUN npm install
RUN npm run build
CMD ["node", "dist/server.js"]

优化版：180MB

# Stage 1: build
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build && npm prune --production
 
# Stage 2: runtime
FROM node:20-alpine
WORKDIR /app
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/package.json ./
USER node
EXPOSE 3000
CMD ["node", "dist/server.js"]

关键点：

  • npm ci 比 npm install 严格、可复现
  • npm prune --production 删除 devDependencies
  • 多阶段隔离开发依赖

Java 示例：720MB → 200MB

普通版：720MB

FROM eclipse-temurin:17-jdk
COPY . .
RUN ./mvnw package
CMD ["java", "-jar", "target/app.jar"]

优化版（多阶段 + JRE + Spring Boot layertools）：200MB

# Stage 1: build
FROM eclipse-temurin:17-jdk-alpine AS builder
WORKDIR /build
COPY pom.xml mvnw ./
COPY .mvn .mvn
RUN ./mvnw dependency:go-offline
COPY src src
RUN ./mvnw clean package -DskipTests
RUN java -Djarmode=layertools -jar target/*.jar extract
 
# Stage 2: runtime
FROM eclipse-temurin:17-jre-alpine
WORKDIR /app
COPY --from=builder /build/dependencies/ ./
COPY --from=builder /build/spring-boot-loader/ ./
COPY --from=builder /build/snapshot-dependencies/ ./
COPY --from=builder /build/application/ ./
RUN addgroup -S app && adduser -S app -G app
USER app
EXPOSE 8080
ENTRYPOINT ["java", "org.springframework.boot.loader.launch.JarLauncher"]

关键点：

  • JDK 镜像编译，JRE 镜像运行（JRE 比 JDK 小 100MB+）
  • Spring Boot 的 layertools 把 jar 拆成依赖层 + 应用层，依赖不变时层能复用
  • 进一步瘦：用 jlink 定制 JRE（只含用到的模块），能再砍一半

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