Java 11 application as lightweight docker image

Question

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.

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

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

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

  • 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

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

  • jlink runtime image size (specifically libjvm.so) created from openjdk is huge. Expected it to be much smaller.
  • Solution: https://github.com/docker-library/openjdk/issues/217#issuecomment-436079779

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/

So the question is:

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

Answer 1

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

Answer 2

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