docker-gcp-java

Docker image built from Alpine Linux, using GraalVM as JVM and with Stackdriver Debugger and Profiler binaries and scripts embedded.

Download from https://hub.docker.com/r/lustefaniak/docker-gcp-java

Base JVM image used is: lustefaniak/docker-graalvm published to Docker Hub. There are also versions using adoptopenjdk8 and adoptopenjdk11, check available Docker Hub tags.

This image is built from the sources of GoogleCloudPlatform/openjdk-runtime with additional changes.

Main difference is use of GraalVM instead of OpenJDK. Because GoogleCloudPlatform/openjdk-runtime uses Debian as source of JVM, it has some problems around SSL implementation and ALPN setup due to wrong Debian OpenJDK packaging. This image has no such problems.

Usage

To make your application correctly recognized in UI set:

ENV GCP_APP_NAME "app-name"
ENV GCP_APP_VERSION "1.0.0"

Then run your application using provided launcher helper.

ENTRYPOINT ["/docker-entrypoint.bash"]
CMD ["java", "-version"]

You can also launch other script, just make sure it is executable

ENTRYPOINT ["/docker-entrypoint.bash"]
CMD ["/opt/app/bin/path_to_script.sh", "-version"]

Memory allocation

By default launcher calculates available memory using cgroup limits. If for some reason detecting memory does not work you can set available bytes as KUBERNETES_MEMORY_LIMIT environment variable.

To better understand calculations of memory please check setup-env.d/35-java-env.bash.

There are few flags which control calculation of memory. Probably two most important ones are MIN_NON_HEAP_SIZE_MB and HEAP_SIZE_RATIO.

By default HEAP_SIZE_RATIO is set to 80 meaning 80% of available memory.

By default MIN_NON_HEAP_SIZE_MB is set to 400. It is used to workaround non-heap memory issues on small containers, eg. <1024MB.

When calculated NON_HEAP_SIZE_MB < MIN_NON_HEAP_SIZE_MB, it changes to MIN_NON_HEAP_SIZE_MB and HEAP_SIZE_RATIO is adjusted.

If you know your application won't need non-heap memory, you can set HEAP_SIZE_RATIO to 100 (100%), in such case it will automatically alocate for heap HEAP_SIZE_MB = GAE_MEMORY_MB - MIN_NON_HEAP_SIZE_MB

Profiler and debugger

By default both debugger and profiler are disabled, to activate them set env variables in inheriting Dockerfile:

ENV PROFILER_ENABLE true
ENV DBG_ENABLE true

Or run with

-e PROFILER_ENABLE=true -e DBG_ENABLE=true

Heap sampling

Heap sampling is available only for Java 11 and newer. To enable it add environment variables:

-e HEAP_PROFILER_ENABLE=true -e PROFILER_ENABLE=true

Heap dump on OOM

By default it will exit JVM on OOM, to control that you can set JAVA_EXIT_ON_OOM=false.

If you want heap-dump generated on OOM set JAVA_HEAP_DUMP_ON_OOM=true, generated image will be stored to JAVA_HEAP_DUMP_PATH which by default is /var/log/app_engine/heapdump/.

There is also possibility to automatically upload generated heap dump to GCS, to do that configure:

ENV UPLOAD_HEAP_DUMP true
ENV GCS_HEAP_DUMP_PROJECT_ID "project_id"
ENV GCS_HEAP_DUMP_BUCKET "gcs_bucket_name"
ENV GCS_HEAP_DUMP_PATH ""

Uploader needs to be authenticated, for more info check Google documentation