Java 11 应用程序作为轻量级 docker 镜像 [英] Java 11 application as lightweight docker image

查看：62 发布时间：2021/11/27 8:23:29 java docker alpine java-11

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问题描述

受到问题为什么 Java 11 基础 Docker 镜像如此之大的启发?(openjdk:11-jre-slim) 我发现这个话题在Java世界里还没有解决.

Inspired by question Why is the Java 11 base Docker image so large? (openjdk:11-jre-slim) I found that this topic in Java world is still not settled.

至于 2018 年 12 月 7 日，存在常见问题/陷阱(在上面的票证中讨论):

As for 07 Dec 2018 there are common issues/pitfalls (discussed in the ticket above):

JRE 不作为单独的包"分发.应该使用来自 JDK 的模块

JRE is not distributed as a separate "package". Modules from JDK should be used instead

Oracle OpenJDK 11 不支持 Linux Alpine，所以轻量级图像不容易创建

Oracle OpenJDK 11 doesn't support Linux Alpine, so lightweight images can't be easily created

与此同时，当前稳定的 Debian 版本仍然没有 Java 11 软件包(Ubuntu 在 openjdk-11 软件包下安装了 Java 10)，这就是为什么使用不稳定的 sid 版本的原因基本泊坞窗图像

In the same time current stable Debian versions still doesn't have Java 11 packages (Ubuntu has Java 10 installed under openjdk-11 packages), that's why unstable sid versions are used for base docker images

当前可用的 Oracle openjdk-11 镜像构建未剥离的 libjvm.so 模块，该模块有数百兆字节，必须单独剥离:

currently available Oracle openjdk-11 images build unstripped libjvm.so module, which has hundreds megabyte and must be stripped separately:

由于这些问题，即使 slim Oracle Java 11 基础镜像也很重并且被认为是不稳定的:https://hub.docker.com/_/openjdk/

As a result of these issues even slim Oracle Java 11 base images are quite heavy and considered to be unstable: https://hub.docker.com/_/openjdk/

所以问题是:

什么是优化或推荐的方式来构建和交付 Java 11 应用程序作为 Docker 镜像?

what are optimized or recommended ways to build and deliver Java 11 applications as docker images?

推荐答案

UPD from 07.2019: https://stackoverflow.com/a/57145029/907576

以简单的 spring 启动应用程序(只有一个 REST 端点)为例，到目前为止我能够找出以下解决方案(考虑到应用程序 jar 位于 build/libs/spring-boot-demo.jar ).Docker 构建之前的 jar:

Taking as an example of simple spring boot application (with only one REST endpoint) so far i was able to figure out the following solutions (considering application jar is located at build/libs/spring-boot-demo.jar before Docker build:

绝地路径如果我们想在稳定的超薄 Linux 版本上使用官方 Oracle OpenJDK 发行版(Debian 9 "Stretch" for现在):

Jedi path if we want to use official Oracle OpenJDK distribution on stable slim Linux version (Debian 9 "Stretch" for now):

使用 debian:stretch-slim(最新稳定版)基础镜像
使用 Docker 多阶段构建

use debian:stretch-slim (latest stable) base image
use Docker multi-stage build

第一个 Docker 构建阶段:

First Docker build stage:

在第一个 Docker 构建阶段下载并安装 Oracle OpenJDK 存档
使用 jlink 工具为您的项目(又名 JRE)编译 Java 最小发行版

download and install Oracle OpenJDK archive on the first Docker build stage
compile Java minimal distribution for your project (aka JRE) using jlink tool

第二个 Docker 构建阶段:

Second Docker build stage:

将编译的最小 Java 发行版从阶段 1 复制到新映像
配置访问Java的路径
将应用程序 jar 复制到映像中

所以，最终的 Dockerfile 看起来像这样

So, final Dockerfile looks smth like this

(实现JDK VERSION、URL和HASH值):

(actualize JDK VERSION, URL and HASH value):

# First stage: JDK 11 with modules required for Spring Boot
FROM debian:stretch-slim as packager

# source JDK distribution names
# update from https://jdk.java.net/java-se-ri/11
ENV JDK_VERSION="11.0.1"
ENV JDK_URL="https://download.java.net/java/GA/jdk11/13/GPL/openjdk-${JDK_VERSION}_linux-x64_bin.tar.gz"
ENV JDK_HASH="7a6bb980b9c91c478421f865087ad2d69086a0583aeeb9e69204785e8e97dcfd"
ENV JDK_HASH_FILE="${JDK_ARJ_FILE}.sha2"
ENV JDK_ARJ_FILE="openjdk-${JDK_VERSION}.tar.gz"
# target JDK installation names
ENV OPT="/opt"
ENV JKD_DIR_NAME="jdk-${JDK_VERSION}"
ENV JAVA_HOME="${OPT}/${JKD_DIR_NAME}"
ENV JAVA_MINIMAL="${OPT}/java-minimal"

# downlodad JDK to the local file
ADD "$JDK_URL" "$JDK_ARJ_FILE"

# verify downloaded file hashsum
RUN { 
        echo "Verify downloaded JDK file $JDK_ARJ_FILE:" && 
        echo "$JDK_HASH $JDK_ARJ_FILE" > "$JDK_HASH_FILE" && 
        sha256sum -c "$JDK_HASH_FILE" ; 
    }

# extract JDK and add to PATH
RUN { 
        echo "Unpack downloaded JDK to ${JAVA_HOME}/:" && 
        mkdir -p "$OPT" && 
        tar xf "$JDK_ARJ_FILE" -C "$OPT" ; 
    }
ENV PATH="$PATH:$JAVA_HOME/bin"

RUN { 
        java --version ; 
        echo "jlink version:" && 
        jlink --version ; 
    }

# build modules distribution
RUN jlink 
    --verbose 
    --add-modules 
        java.base,java.sql,java.naming,java.desktop,java.management,java.security.jgss,java.instrument 
        # java.naming - javax/naming/NamingException
        # java.desktop - java/beans/PropertyEditorSupport
        # java.management - javax/management/MBeanServer
        # java.security.jgss - org/ietf/jgss/GSSException
        # java.instrument - java/lang/instrument/IllegalClassFormatException
    --compress 2 
    --strip-debug 
    --no-header-files 
    --no-man-pages 
    --output "$JAVA_MINIMAL"

# Second stage, add only our minimal "JRE" distr and our app
FROM debian:stretch-slim

ENV JAVA_HOME=/opt/java-minimal
ENV PATH="$PATH:$JAVA_HOME/bin"

COPY --from=packager "$JAVA_HOME" "$JAVA_HOME"
COPY "build/libs/spring-boot-demo.jar" "/app.jar"

EXPOSE 8080
CMD [ "-jar", "/app.jar" ]
ENTRYPOINT [ "java" ]

注意:

最小 JRE 示例中包含 5 个 java 模块(java.base,java.sql,java.naming,java.desktop,java.management,java.security.jgss,java.instrument).我发现他们手动"运行应用程序并修复 ClassNotFoundException.等待一些进一步的 Spring Boot 开发人员建议/指南包含哪些 Java 模块以及何时包含，就像删除一些冗余依赖项一样，例如 java.desktop，它似乎仅用于 PropertyEditorSupport
如果您害怕错过某些模块 - 它们非常轻巧，并且所有这些模块一起增加了大约 2 MB 的大小.获取 java.* 和 jdk.* 11 个模块的完整列表:

there are 5 java modules included to the minimal JRE example (java.base,java.sql,java.naming,java.desktop,java.management,java.security.jgss,java.instrument). I found them "manually" running the application and fixing ClassNotFoundException. Waiting for some further Spring Boot developers recommendations/guides which Java modules to include and when, as same as removing some redundant dependencies, like java.desktop, which seems to be used only for PropertyEditorSupport
if you are afraid to miss some modules - they are quite lightweight and all of them together give about 2 MB size increasing. Get a full list of java.* and jdk.* 11 modules:

java --list-modules |grep -E "^java.[^@]*" |cut -d @ -f 1
java --list-modules |grep -E "^jdk.[^@]*" |cut -d @ -f 1

在我的案例中，生成的图像大小为 123 MB，最少有 7 个 Spring Boot 模块，125 MB 包含所有 java.* 模块

The resulting image size in my case was 123 MB with minimal 7 Spring Boot modules and 125 MB with all java.* modules

作为此构建工作流程的可选改进:

使用下载和提取的 JDK 预构建映像，并将其用作第一阶段的基础映像
如果您知道每次要包含哪些模块 - 使用已编译的最小 JRE 和包含的模块预先构建基本映像

使用供应商的 Open JDK 发行版的简单方法:

与 Oracle 相对，Azul 的 Zulu JDK 11 支持 Alpine 端口并有各自的基础 Docker 镜像.

Opposite to Oracle Azul's Zulu JDK 11 supports Alpine port and has respective base Docker image.

因此，如果尊重 Zulu JVM/JDK，则 Docker 构建要简单得多:

Thus, if Zulu JVM/JDK is respected, Docker build is much simpler:

FROM azul/zulu-openjdk-alpine:11 as packager

RUN { 
        java --version ; 
        echo "jlink version:" && 
        jlink --version ; 
    }

ENV JAVA_MINIMAL=/opt/jre

# build modules distribution
RUN jlink 
    --verbose 
    --add-modules 
        java.base,java.sql,java.naming,java.desktop,java.management,java.security.jgss,java.instrument 
        # java.naming - javax/naming/NamingException
        # java.desktop - java/beans/PropertyEditorSupport
        # java.management - javax/management/MBeanServer
        # java.security.jgss - org/ietf/jgss/GSSException
        # java.instrument - java/lang/instrument/IllegalClassFormatException
    --compress 2 
    --strip-debug 
    --no-header-files 
    --no-man-pages 
    --output "$JAVA_MINIMAL"

# Second stage, add only our minimal "JRE" distr and our app
FROM alpine

ENV JAVA_MINIMAL=/opt/jre
ENV PATH="$PATH:$JAVA_MINIMAL/bin"

COPY --from=packager "$JAVA_MINIMAL" "$JAVA_MINIMAL"
COPY "build/libs/spring-boot-demo.jar" "/app.jar"

EXPOSE 8080
CMD [ "-jar", "/app.jar" ]
ENTRYPOINT [ "java" ]

生成的图像为 73 MB，正如预期的那样，带有剥离的 Alpine 分布.

The resulting image is 73 MB, as expected with stripped Alpine distributions.

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Java 11 应用程序作为轻量级 docker 镜像 [英] Java 11 application as lightweight docker image

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Java 11 应用程序作为轻量级 docker 镜像 [英] Java 11 application as lightweight docker image

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