Practical Experience of Containerizing Java Applications: Docker, JVM Tuning, Multi‑Stage Builds, and Operational Tips

Java Vs Docker

Low‑version Java does not automatically detect Docker memory/CPU limits, requiring explicit JVM options.

Memory Limits

Docker uses cgroups; without limits containers compete for resources. Example command:

docker run -m 1024M --cpuset-cpus="1,3"

Pre‑Docker‑8u131 Java cannot see limits; need -Xmx and enable OutOfMemoryException .

CPU Limits

JVM may see host CPUs instead of Docker‑set CPUs, affecting thread pools and parallel GC.

Log Collection

Logs inside containers disappear on container removal; use bind mounts, volumes, filebeat, or nxlog to persist.

Technical Preparation

Choose appropriate JDK version and JVM flags:

Before 8u131 set -Xmx , ParallelGCThreads , CICompilerCount .

8u131+ recognize CPU limits; need -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap .

8u191 adds InitialRAMPercentage , MinRAMPercentage , MaxRAMPercentage .

Java 11 enables -XX:UseContainerSupport by default.

-Xmx=2G -XX:ParallelGCThreads=cpus -XX:CICompilerCount=cpus

-XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap

-XX:UseContainerSupport

Image Build

Base image selection avoids distroless/Alpine due to missing tools. Example Dockerfile:

FROM xxxx.autohome.com.cn/project/centos7-jdk8:full-nxlog
ADD skywalking-agent/6.4.0/ /skywalking-agent/
ADD arthas-3.1.4/ /arthas/
RUN echo 'Asia/Shanghai' > /etc/timezone && chown -R root:root "/var/run/nxlog"
MAINTAINER [email protected]

Build and push commands:

docker build -t xxxx.autohome.com.cn/project/centos7-jdk8:v1
docker push xxx.autohome.com.cn/project/centos7-jdk8:v1

Multi‑Stage Build

Standard Maven build example:

FROM maven:3.5-jdk-8 AS build
COPY src /usr/src/app/src
COPY pom.xml /usr/src/app
RUN mvn -f /usr/src/app/pom.xml clean package

FROM openjdk:8-jre
ARG DEPENDENCY=/usr/src/app/target/dependency
COPY --from=build ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY --from=build ${DEPENDENCY}/META-INF /app/META-INF
COPY --from=build ${DEPENDENCY}/BOOT-INF/classes /app
ENTRYPOINT ["java","-cp","app:app/lib/*","hello.Application"]

Health Checks

Kubernetes Liveness and Readiness probes ensure container health; set appropriate probe logic based on service state.

Graceful Shutdown

Use preStop hook, enable Spring Boot shutdown endpoint, and run Java as PID 1 with exec‑form CMD:

CMD ["java","$JAVA_OPTS","-jar","/app.jar"]

Additional tips on timezone, language settings, log conflicts, and downloading files from containers are provided.