rubasace/drone-java-bake-plugin repository overview

⁠Drone Java Bake Plugin

This Drone plugin can be used to generate Docker images from Java compiled applications, as part of the CI process.

⁠Baking the application

Use this plugin on the bake stage of the .drone.yml manifest:

- name: bake
  image: rubasace/drone-java-bake-plugin
  settings:
    container: myorg/test-app:latest

⁠Customizing the bake stage

The bake stage can be customized using the following settings:

An example with a private registry would look similar to this:

- name: bake
  image: rubasace/drone-java-bake-plugin
  settings:
    container: privateregistry.com/myorg/test-app:1.0.0.${CI_BUILD_NUMBER}
    container_uid: 1829
    container_gid: 1829
    registry_user:
      from_secret: registry_user
    registry_pass:
      from_secret: registry_pass
    extra_jib_options:
      - "-s settings.xml"
      - "-X"

Or passing extra_jib_options as a space-separated string:

- name: bake
  image: rubasace/drone-java-bake-plugin
  settings:
    container: privateregistry.com/myorg/test-app:1.0.0.${CI_BUILD_NUMBER}
    container_uid: 1829
    container_gid: 1829
    registry_user:
      from_secret: registry_user
    registry_pass:
      from_secret: registry_pass
    extra_jib_options: -s settings.xml -X

⁠Running the application

This image provides a set of default opinionated JVM flags that are considered best practices by the author, so the container can be run in Kubernetes/Docker (or any other container environment) without further configuration.

The JVM flags that are applied can be checked in the app-entrypoint.sh file⁠ (check how the JDK_JAVA_OPTIONS is set). Alternatively, the applied flags can be checked on the logs at the startup of the application. A line like the following can be found in the logs:

NOTE: Picked up JDK_JAVA_OPTIONS: -XX:+UseContainerSupport -XX:InitialRAMPercentage=75 -XX:MaxRAMPercentage=75 -XX:MaxJavaStackTraceDepth=15

⁠How to customize the JVM options

Sometimes, we might want to tweak the default properties. The default options allow granular tweaking via specific environment variables. You can find all the possible options checking the entrypoint file or in the following table:

For example, we can keep all the defaults but change the -XX:MaxRAMPercentage option to 90 by setting the -XX:MaxRAMPercentage property on our Kubernetes deployment:

image: myorg/myapp:1.0.0
env:
  - name: MAX_RAM_PERCENTAGE
    value: "90"

We can also add extra flags by setting the EXTRA_JAVA_OPTIONS environment variable:

image: myorg/myapp:1.0.0
env:
- name: MAX_RAM_PERCENTAGE
  value: "90"
- name: EXTRA_JAVA_OPTIONS
  value: "-XX:+UnlockDiagnosticVMOptions -XX:+DebugNonSafepoints"

As a last resort, you can provide the JVM standard JDK_JAVA_OPTIONS environment variable indicating the entire set of options:

image: myorg/myapp:1.0.0
env:
- name: JDK_JAVA_OPTIONS
  value: "-XX:+UseContainerSupport -XX:MaxRAMPercentage=75.0 -XX:+UseG1GC -XX:InitiatingHeapOccupancyPercent=40"