Docker Compose JUnit Rule Spark demo

Demonstrating Docker Compose JUnit Rule in a Spark project.

Challenge

You got a Java-microservice, which you want to run using Docker(-compose). You want to integration-test this (your application running in Docker), using your build-tool Apache Maven and your test-framework JUnit. You are using Git.

This testing shall be capable of parallel builds (on different git-branches) at the same time. You want to test exact the git-commit-id you are working on, or your CI-system has checked out.

Demo setup

For this demo, Spark is used, "A micro framework for creating web applications[...]". The application is very simple, it serves /hello as a "Hello World"-endpoint, see App.java.

Demo usage

Required

• Git
• Maven
• Docker, including Docker-compose

# Builds a docker-image for this git-commit-id, integration-tests against a related container
docker-compose-rule-spark-demo $ mvn verify
...
[INFO] DOCKER> [schulte.markus/docker-compose-rule-spark-demo:8379f8a]: Built image sha256:6d570
...
[INFO] Running schulte.markus.dockercomposerulesparkdemo.AppIT
...
[INFO] BUILD SUCCESS

Solution

1. Create a docker-image (service), containing the current state of the application, tagged with the git-commit-id
2. Integration-test the service, running in a related docker-container

In this documentation, 8379f8a is the current git-commit-id

1. Create docker-images, tagged with git-commit-id

• First of all, you need to create an executable jar for your Spark-application. You can do so by using maven-shade-plugin, see pom.xml. This way, you wil have a target/docker-compose-rule-spark-demo.jar, which you can run via java -jar target/docker-compose-rule-spark-demo.jar.

docker-compose-rule-spark-demo $ mvn package
...
[INFO] --- maven-shade-plugin:3.0.0:shade (default) @ docker-compose-rule-spark-demo ---
[INFO] Including com.sparkjava:spark-core:jar:2.6.0 in the shaded jar.
...
[INFO] Replacing original artifact with shaded artifact.
[INFO] Replacing /home/markus-tarent/workspace/docker-compose-rule-spark-demo/target/docker-compose-rule-spark-demo.jar with /home/markus-tarent/workspace/docker-compose-rule-spark-demo/target/docker-compose-rule-spark-demo-shaded.jar

docker-compose-rule-spark-demo $ ls target/ | grep .jar
docker-compose-rule-spark-demo.jar # Executable jar
original-docker-compose-rule-spark-demo.jar

• Now you need to have information about your git-commit-id both while maven-building as well as useable in your later integration-test. For this purpose, you can use Maven git commit id plugin, see pom.xml. The way this Maven-plugin is used, you will have maven-variables while building, containing information about git (${git.commit.id} for example), as well as a target/classes/git.properties-file, containing needed information, useable at runtime.

docker-compose-rule-spark-demo $ mvn compile
...
[INFO] --- git-commit-id-plugin:2.1.9:revision (default) @ docker-compose-rule-spark-demo ---
...

docker-compose-rule-spark-demo $ cat target/classes/git.properties | grep commit.id
git.commit.id.abbrev=8379f8a
git.commit.id=8379f8ae469a71d10c63b875abe643724efd4092
git.commit.id.describe=8379f8a

• Have a Dockerfile for building a docker-image for your service.
• Now, build your docker-image as part of maven package-phase. For this purpose fabric8io/docker-maven-plugin is used, see pom.xml. The way this Maven-plugin is used, a docker-image will be created while maven package-phase, tagged with the current git-commit-id. Note the required .maven-dockerignore.

docker-compose-rule-spark-demo $ mvn package
...
[INFO] --- docker-maven-plugin:0.21.0:build (default) @ docker-compose-rule-spark-demo ---
[INFO] Building tar: /home/markus-tarent/workspace/docker-compose-rule-spark-demo/target/docker/schulte.markus/docker-compose-rule-spark-demo/8379f8a/tmp/docker-build.tar
[INFO] DOCKER> [schulte.markus/docker-compose-rule-spark-demo:8379f8a]: Created docker-build.tar in 107 milliseconds
[INFO] DOCKER> [schulte.markus/docker-compose-rule-spark-demo:8379f8a]: Built image sha256:ee9c7
[INFO] DOCKER> [schulte.markus/docker-compose-rule-spark-demo:8379f8a]: Removed old image sha256:6d570
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS

docker-compose-rule-spark-demo $ docker images schulte.markus/docker-compose-rule-spark-demo
REPOSITORY                                      TAG                 IMAGE ID            CREATED              SIZE
schulte.markus/docker-compose-rule-spark-demo   8379f8a             f534f2fa3d3e        About a minute ago   83.9MB

2. Integration-test

• AppIT will be your integration-test, using JUnit. Don't forget to configure your Maven Failsafe Plugin for running while maven verify-phase (see pom.xml).
• First you have to get information about your git-commit-id. This is extracted from target/classes/git.properties, using GitHelper.
• Now, you can finally use Docker Compose JUnit Rule in your test. This starts the correct spark-hello-world-service, defined in your src/test/resources/docker-compose.yml. The correct version (git-commit-id) is given to the docker-compose.yml, by passing in an environment variable.

docker-compose-rule-spark-demo $ mvn verify
...
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running schulte.markus.dockercomposerulesparkdemo.AppIT
...
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 3.419 s - in schulte.markus.dockercomposerulesparkdemo.AppIT
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] 
[INFO] --- maven-failsafe-plugin:2.20:verify (default) @ docker-compose-rule-spark-demo ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS

docker-compose-rule-spark-demo $ docker ps #While AppIT had run
3b953a1958f9        schulte.markus/docker-compose-rule-spark-demo:8379f8a   "java -jar /app.jar"   Less than a second ago   Up Less than a second   0.0.0.0:32771->4567/tcp   bdc647fb_spark-hello-world-service_1