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Minimal Play 2.8.0 running on openjdk13/alpine-slim docker image.
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README.md

Play 2.8.0 using JDK 13 on Slim Alpine Docker

Here's a minimal Play 2.8.0 running on a trimmed down Java 13 image using an Alpine.

JLink Attempt

I made an attempt to create a custom JLink image to trim it down further, but didn't succeed. See the deps directory for details.

Setup

The first thing you should do is install SDKMAN and jenv, which will let you be specific about what JDK version you want.

Install SDKMAN and jenv

SDKMAN is the best way to pick out different versions of Java and have them all co-exist.

jenv is the best way to set different JDKs for different projects.

You can install multiple JDKs and have them available. Here, we'll use the OpenJDK 13.0.1 image.

$ sdk install java 13.0.1.hs-adpt

After that, you can see the JDK available in $HOME/.sdkman/candidates/java/13.0.1-zulu.

Now that you've got the JDK available, let's tell jenv about it:

$ jenv add $HOME/jenv add $HOME/.sdkman/candidates/java/13.0.1.hs-adpt

And then we'll set it as the default for this project.

$ jenv local 13.0

This will create a .java-version file in your directory that picks up and points you to the JDK.

$ java --version 
openjdk 13.0.1 2019-10-15
OpenJDK Runtime Environment AdoptOpenJDK (build 13.0.1+9)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 13.0.1+9, mixed mode, sharing)

Now you're running JDK 13 for your project.

Publishing

Publish a local docker image with

sbt docker:publishLocal

Running

Run the local image with

docker run \
  -p 9000:9000 \
  --rm \
  --env "PLAY_APPLICATION_SECRET=very-long-secret-for-entropy" \
  slimmest-play-example:latest

Or run ./run-docker.

Then go to http://localhost:9000.

Monitoring and Control Plane

Diagnostics and control of the JVM is managed through Jolokia running as an agent. You can control the JVM and see how the GC is running by running Hawt in another console window:

java -jar hawt/hawtio-app-2.8.0.jar

Or by running ./run-hawt.

Once hawt is up and running, add the connection as "http://localhost:8778/jolokia" and from there you can see GC and dump JFR logs.

Logging

Logs are exported from /opt/docker/logs

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