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Tutorial: install Rookout on containerized Java

This short tutorial will walk you through the perfect Rookout deployment for containerized Java applications in three quick steps.

For any follow-up questions, check out the full docs for the Rookout Java Agent or reach out!

Get Your Application

First things first, choose an application. If you don't have one readily available, use our sample application.

Start by:

git clone https://github.com/Rookout/java-tutorial-2022
cd java-tutorial-2022

1. Add the Java Agent

Rookout for Java (and any other JVM-based language) is a simple Java Agent.
Deploy it by downloading the JAR to the image and instructing the JVM to load it.

Open the Dockerfile and add the following two lines just above the ENTRYPOINT command:

RUN curl -L "https://repository.sonatype.org/service/local/artifact/maven/redirect?r=central-proxy&g=com.rookout&a=rook&v=LATEST" -o /app/rook.jar
ENV JAVA_TOOL_OPTIONS "-javaagent:/app/rook.jar"

Note: in multi-stage builds (like ours), make all your changes on the final stage.

2. Start Rookout

Configure the Java Agent to connect to your Rookout account (if you haven't signed up, do that here).

To keep things simple, set the Rookout token as an environment variable.
While you are at it, set up another variable to identify your application instance as a dev environment.

Add these two lines below the lines you have already added:

ENV ROOKOUT_TOKEN [Your Rookout Token]
ENV ROOKOUT_LABELS "env:dev"

Configuration is where you can get fancy. You have got additional options up your sleeve:

  1. Move options from environment variables to secret or configuration managers.
  2. If you are using a Rookout Controller, set up the remote host and port configuration.
  3. Dig deeper into other options available right here.

3. Embed Source Information

Rookout offers the smoothest debugging experience by fetching up-to-date source code for each server.

Set this up for containerized applications by adding a handful of files from your .git folder to the container image.

Edit (or add) your .Dockerignore file and adapt the traditional .git exclude:

# Keep ignoring .git
.git
# Allow specific files with !
!.git/HEAD
!.git/config
!.git/refs

Add a final copy command to the Dockerfile.

COPY .git /.git

Test

One second! if you are not using our demo app, please commit and push your changes to a new branch.

Build and run your Docker image:

docker build . -t rookout-java-todo
docker run -it -p 8080:8080 rookout-java-todo

As your Java application spins up, search for this output at the top:

Interact with your application at http://localhost:8080 and use Rookout to debug it on the fly!

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