Java 11 application as lightweight docker image

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Java 11 application as lightweight docker image

  1. Java 11 application as lightweight docker image

    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:

  2. Java 11 application as lightweight docker image

    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:

Solution 1

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

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:

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

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

      1. First Docker build stage:

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

        • copy compiled minimal Java distribution from stage 1 to the new image
        • configure path to access Java
        • copy application jar to the image

    So, final Dockerfile looks smth like this

    (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" ]
    

    Note:

    • 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

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

    As an optional improvement of this build workflow:

    • Pre-build an image with downloaded and extracted JDK and use it as a base image for first stage
    • if you know which modules to include every time – pre-build a base image with compiled minimal JRE and included modules
  2. Easy way with vendor’s Open JDK distributions:

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

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" ]

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

Original Author radistao Of This Content

Solution 2

As of 07.2019

(Note: first stage image could be as fat as you wish: one can use debian/ubuntu/whatever and include git/gradle/whatever – this won’t influence the final resulting image size, which is completely based on the last (second) stage)

Using Alpine community repository

FROM alpine:latest as packager

RUN apk --no-cache add openjdk11-jdk openjdk11-jmods

ENV JAVA_MINIMAL="/opt/java-minimal"

# build minimal JRE
RUN /usr/lib/jvm/java-11-openjdk/bin/jlink \
    --verbose \
    --add-modules \
        java.base,java.sql,java.naming,java.desktop,java.management,java.security.jgss,java.instrument \
    --compress 2 --strip-debug --no-header-files --no-man-pages \
    --release-info="add:IMPLEMENTOR=radistao:IMPLEMENTOR_VERSION=radistao_JRE" \
    --output "$JAVA_MINIMAL"

FROM alpine:latest

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

COPY --from=packager "$JAVA_HOME" "$JAVA_HOME"
COPY build/libs/application.jar app.jar

ENTRYPOINT ["java","-jar","/app.jar"]

Using AdoptOpenJDK

FROM adoptopenjdk/openjdk11:x86_64-alpine-jdk-11.0.4_11 as packager

ENV JAVA_MINIMAL="/opt/java-minimal"

# build minimal JRE
RUN jlink \
    --verbose \
    --add-modules \
        java.base,java.sql,java.naming,java.desktop,java.management,java.security.jgss,java.instrument \
    --compress 2 --strip-debug --no-header-files --no-man-pages \
    --output "$JAVA_MINIMAL"

FROM alpine:latest

# magic to make Java binaries work in Alpine
# https://github.com/AdoptOpenJDK/openjdk-docker/blob/master/11/jdk/alpine/Dockerfile.hotspot.releases.slim#L24-L54
RUN apk add --no-cache --virtual .build-deps curl binutils \
    && GLIBC_VER="2.29-r0" \
    && ALPINE_GLIBC_REPO="https://github.com/sgerrand/alpine-pkg-glibc/releases/download" \
    && GCC_LIBS_URL="https://archive.archlinux.org/packages/g/gcc-libs/gcc-libs-9.1.0-2-x86_64.pkg.tar.xz" \
    && GCC_LIBS_SHA256="91dba90f3c20d32fcf7f1dbe91523653018aa0b8d2230b00f822f6722804cf08" \
    && ZLIB_URL="https://archive.archlinux.org/packages/z/zlib/zlib-1%3A1.2.11-3-x86_64.pkg.tar.xz" \
    && ZLIB_SHA256=17aede0b9f8baa789c5aa3f358fbf8c68a5f1228c5e6cba1a5dd34102ef4d4e5 \
    && curl -LfsS https://alpine-pkgs.sgerrand.com/sgerrand.rsa.pub -o /etc/apk/keys/sgerrand.rsa.pub \
    && SGERRAND_RSA_SHA256="823b54589c93b02497f1ba4dc622eaef9c813e6b0f0ebbb2f771e32adf9f4ef2" \
    && echo "${SGERRAND_RSA_SHA256} */etc/apk/keys/sgerrand.rsa.pub" | sha256sum -c - \
    && curl -LfsS ${ALPINE_GLIBC_REPO}/${GLIBC_VER}/glibc-${GLIBC_VER}.apk > /tmp/glibc-${GLIBC_VER}.apk \
    && apk add /tmp/glibc-${GLIBC_VER}.apk \
    && curl -LfsS ${ALPINE_GLIBC_REPO}/${GLIBC_VER}/glibc-bin-${GLIBC_VER}.apk > /tmp/glibc-bin-${GLIBC_VER}.apk \
    && apk add /tmp/glibc-bin-${GLIBC_VER}.apk \
    && curl -Ls ${ALPINE_GLIBC_REPO}/${GLIBC_VER}/glibc-i18n-${GLIBC_VER}.apk > /tmp/glibc-i18n-${GLIBC_VER}.apk \
    && apk add /tmp/glibc-i18n-${GLIBC_VER}.apk \
    && /usr/glibc-compat/bin/localedef --force --inputfile POSIX --charmap UTF-8 "$LANG" || true \
    && echo "export LANG=$LANG" > /etc/profile.d/locale.sh \
    && curl -LfsS ${GCC_LIBS_URL} -o /tmp/gcc-libs.tar.xz \
    && echo "${GCC_LIBS_SHA256} */tmp/gcc-libs.tar.xz" | sha256sum -c - \
    && mkdir /tmp/gcc \
    && tar -xf /tmp/gcc-libs.tar.xz -C /tmp/gcc \
    && mv /tmp/gcc/usr/lib/libgcc* /tmp/gcc/usr/lib/libstdc++* /usr/glibc-compat/lib \
    && strip /usr/glibc-compat/lib/libgcc_s.so.* /usr/glibc-compat/lib/libstdc++.so* \
    && curl -LfsS ${ZLIB_URL} -o /tmp/libz.tar.xz \
    && echo "${ZLIB_SHA256} */tmp/libz.tar.xz" | sha256sum -c - \
    && mkdir /tmp/libz \
    && tar -xf /tmp/libz.tar.xz -C /tmp/libz \
    && mv /tmp/libz/usr/lib/libz.so* /usr/glibc-compat/lib \
    && apk del --purge .build-deps glibc-i18n \
    && rm -rf /tmp/*.apk /tmp/gcc /tmp/gcc-libs.tar.xz /tmp/libz /tmp/libz.tar.xz /var/cache/apk/*

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

COPY --from=packager "$JAVA_HOME" "$JAVA_HOME"
COPY build/libs/application.jar app.jar

ENTRYPOINT ["java","-jar","/app.jar"]

Also read https://blog.gilliard.lol/2018/11/05/alpine-jdk11-images.html

Original Author radistao Of This Content

Solution 3

a list of jdk 11 images by size

openjdk:11.0.6-jre-buster
openjdk:11.0.6-jre
openjdk:11.0.6-jre-slim-buster
openjdk:11.0.6-jre-slim
openjdk:11.0.6-jre-stretch
adoptopenjdk:11.0.6_10-jre-openj9-0.18.1
adoptopenjdk:11.0.6_10-jre-hotspot
adoptopenjdk:11.0.6_10-jre-openj9-0.18.1-bionic
adoptopenjdk:11.0.6_10-jre-hotspot-bionic
adoptopenjdk/openjdk11:jre-11.0.6_10-ubuntu
adoptopenjdk/openjdk11:jre-11.0.6_10
adoptopenjdk/openjdk11:jre-11.0.6_10-ubi-minimal
adoptopenjdk/openjdk11:jre-11.0.6_10-ubi
adoptopenjdk/openjdk11:jre-11.0.6_10-debianslim
adoptopenjdk/openjdk11:jre-11.0.6_10-debian
adoptopenjdk/openjdk11:jre-11.0.6_10-centos
adoptopenjdk/openjdk11:jre-11.0.6_10-alpine
adoptopenjdk/openjdk11:x86_64-alpine-jre-11.0.6_10
adoptopenjdk/openjdk11:x86_64-debian-jre-11.0.6_10
adoptopenjdk/openjdk11:x86_64-debianslim-jre-11.0.6_10
adoptopenjdk/openjdk11:x86_64-ubi-jre-11.0.6_10
adoptopenjdk/openjdk11:x86_64-ubi-minimal-jre-11.0.6_10
adoptopenjdk/openjdk11:x86_64-centos-jre-11.0.6_10
adoptopenjdk/openjdk11:x86_64-ubuntu-jre-11.0.6_10
mcr.microsoft.com/java/jre:11u6-zulu-alpine
mcr.microsoft.com/java/jre:11u6-zulu-centos
mcr.microsoft.com/java/jre:11u6-zulu-debian8
mcr.microsoft.com/java/jre:11u6-zulu-debian9
mcr.microsoft.com/java/jre:11u6-zulu-debian10
mcr.microsoft.com/java/jre:11u6-zulu-ubuntu
azul/zulu-openjdk-alpine:11.0.6-jre

images

Original Author Alisson Gomes Of This Content

Solution 4

Based on the answer by radistao (cool stuff!) I created an Amazon Corretto JDK11 based image. It’s also available on DockerHub.

The minimal maslick/minimalka:jdk11 Corretto image is ~108MB (55MB compressed on Dockerhub).

If you add a simple Springboot jar to it, the resulting image would be ~125MB (71MB compressed on Dockerhub):

FROM maslick/minimalka:jdk11
WORKDIR /app
EXPOSE 8080
COPY my-cool-app.jar ./app.jar
CMD java $JAVA_OPTIONS -jar app.jar
docker build -t my-cool-app:latest .
docker run -d my-cool-app

Original Author maslick Of This Content

Conclusion

So This is all About This Tutorial. Hope This Tutorial Helped You. Thank You.

Also Read,

Siddharth

I am an Information Technology Engineer. I have Completed my MCA And I have 4 Year Plus Experience, I am a web developer with knowledge of multiple back-end platforms Like PHP, Node.js, Python and frontend JavaScript frameworks Like Angular, React, and Vue.

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