Google Cloud Platform OpenJDK Docker Image

This repository contains the source for the gcr.io/google_appengine/openjdk docker image. This image can be used as the base image for running Java applications on Google App Engine Flexible Environment and Google Container Engine.

Building the image

To build the image you need git, docker and maven installed:

$ git clone https://github.com/GoogleCloudPlatform/openjdk-runtime.git
$ cd openjdk-runtime
$ mvn clean install

The resulting image is called openjdk

The Default Entry Point

The default entrypoint will print the JDK version:

$ docker run openjdk
openjdk version "1.8.0_66-internal"
OpenJDK Runtime Environment (build 1.8.0_66-internal-b17)
OpenJDK 64-Bit Server VM (build 25.66-b17, mixed mode)

Any arguments passed to the entry point that are not executable are treated as arguments to the java command:

$ docker run openjdk -jar /usr/share/someapplication.jar

Any arguments passed to the entry point that are executable replace the default command, thus a shell could be run with:

> docker run -it --rm openjdk bash
root@c7b35e88ff93:/# 

Entry Point Features

The entry point for the openjdk8 image is docker-entrypoint.bash, which does the processing of the passed command line arguments to look for an executable alternative or arguments to the default command (java).

If the default command (java) is used, then the entry point sources the setup-env.bash, which looks for supported features to be enabled and/or configured. The following table indicates the environment variables that may be used to enable/disable/configure features, any default values if they are not set:

Env Var	Description	Type	Default
DBG_ENABLE	Stackdriver Debugger	boolean	true
SHUTDOWN_AGENT	VM Shutdown Reporter	Java agent	See format_env_shutdown_javaagent.sh
TMPDIR	Temporary Directory	dirname
JAVA_TMP_OPTS	JVM tmpdir args	JVM args	-Djava.io.tmpdir=${TMPDIR}
GAE_MEMORY_MB	Available memory	size	Set by GAE or /proc/meminfo-400M
HEAP_SIZE_MB	Available heap	size	80% of ${GAE_MEMORY_MB}
JAVA_HEAP_OPTS	JVM heap args	JVM args	-Xms${HEAP_SIZE_MB}M -Xmx${HEAP_SIZE_MB}M
JAVA_GC_OPTS	JVM GC args	JVM args	-XX:+UseG1GC plus configuration
JAVA_GC_LOG	JVM GC log file	filename
JAVA_GC_LOG_OPTS	JVM GC args	JVM args	Derived from $JAVA_GC_LOG
JAVA_USER_OPTS	JVM other args	JVM args
JAVA_OPTS	JVM args	JVM args	See below

If not explicitly set, JAVA_OPTS is defaulted to

JAVA_OPTS:=-showversion \
           ${JAVA_TMP_OPTS} \
           ${DBG_AGENT} \
           ${SHUTDOWN_AGENT} \
           ${JAVA_HEAP_OPTS} \
           ${JAVA_GC_OPTS} \
           ${JAVA_GC_LOG_OPTS} \
           ${JAVA_USER_OPTS}

The command line executed is effectively (where $@ are the args passed into the docker entry point):

java $JAVA_OPTS "$@"

Contributing changes

• See CONTRIBUTING.md

Licensing

• See LICENSE.md