Docker：如何在运行 Z05B6053C41A2130AFD6FC3B158BDA4 时打印 jvm memory 信息

Question

I ve a java spring-boot app based, running on Docker.

Within my dockerfile , i'm using Entrypoint .

Obviously, i ve used it like this:

ENTRYPOINT ["java","-Dfile.encoding=utf-8", "-XX:+ExitOnOutOfMemoryError","-Xms256m","-Xmx256m", "-XshowSettings:vm","-jar","/opt/myapp.jar", "--spring.profiles.active=server"]

Like this, when the container starts: it displays this such values when running docker logs :

VM settings:
    Min. Heap Size: 256.00M
    Max. Heap Size: 256.00M
    Ergonomics Machine Class: client
    Using VM: OpenJDK 64-Bit Server VM


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.3.0.RELEASE)

But with a little transformation the the entrypoint format (to inject some en vars):

ENTRYPOINT java -jar /opt/myapp.jar -Dfile.encoding=utf-8 -XX:+ExitOnOutOfMemoryError -Xms=${XMS_VALUE} -Xmx=${XMX_VALUE} -XshowSettings:vm -XX:+PrintFlagsFinal --spring.profiles.active=server

That hides the jvm values, and displays only spring chart:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.3.2.RELEASE)

How may i let it appear again??

Answer 1

The order of JVM options and arguments is important. Usage is:

 java [options] -jar <jarfile> [args...]
           (to execute a jar file)

therefore the JVM options must be placed before the -jar option otherwise they are considered application arguments

ENTRYPOINT java -Dfile.encoding=utf-8 -XX:+ExitOnOutOfMemoryError \
    -Xms${XMS_VALUE} -Xmx${XMX_VALUE} \
    -XshowSettings:vm -XX:+PrintFlagsFinal -XshowSettings:vm \
    -jar /opt/myapp.jar --spring.profiles.active=server

Run it with:

docker run -e XMX_VALUE=256M -e XMS_VALUE=256m <image_name>