Can't get Jacoco coverage to work with app in container

This isn’t a bug, but a question. Please remove if this isn’t the place.

Background I am running a Dropwizard app (using java -jar myjar.jar server config.yml) inside a docker container via this plugin, and I’m running integration tests inside it. In my integration test, I know for sure that code is being exercised, but Jacoco coverage reports for the integration tests aren’t showing coverage.

My Questions How do I know that Jacoco is properly attached to the code running inside the container? Do I have to do anything special to extract the coverage report from the running container? I would think that a simple shared volume would work, as I am using now, but that does not seem to be the case. I have a hunch that I need to add the jacoco agent parameters to the java -jar that’s taking place inside my container, but I’m not sure.

[who]

@rhuss

Thanks for the tip - that worked splendidly!

Here’s what I ended up doing:

1. Configured my integration tests so that they only execute when invoking -P integration-tests
2. Added a step to the pre-integration-test phase that copies the jacoco runtime jar into a volume that’s shared with the docker container
3. Altered my dropwizard startup command to include the following:

-javaagent:./target/dependency/org.jacoco.agent-0.7.9-runtime.jar=destfile=./target/coverage-reports/jacoco-it.exec,append=true

1. Configured my jacoco report to consume jacoco-it.exec over a shared volume.

Thanks again!

To anyone who comes across this issue via Googling for answers: If you are running your Dropwizard integration tests inside a Docker container, you will need to alter your java jar run command to include a properly-configured -javaagent parameter (see http://www.eclemma.org/jacoco/trunk/doc/agent.html). After you do this, you will be able to use a jacoco report step to load the .exec file and convert it to HTML output.

[who]

One more note for pilgrims coming from search engines:

Sometimes, files created inside a shared volume end up being owned by root on the host box. If you run into this, then I recommend doing the following:

1. Change the javagent parameter in your jar execution so that it opens a port inside the container for purposes of using jacoco:dump. Here’s mine, for example:

-javaagent:./target/dependency/org.jacoco.agent-0.7.9-runtime.jar=append=true,output=tcpserver,address=*

1. Add a port mapping for your app, exposing port 6300 to the host:

<port>${docker.app.jacoco}:6300</port>

1. Before your jacoco integration tests report step, execute a jacoco dump:

<execution>
    <id>post-integration-test-dump</id>
    <phase>post-integration-test</phase>
    <goals>
        <goal>dump</goal>
    </goals>
    <configuration>
        <destFile>${project.build.directory}/coverage-reports/jacoco-it.exec</destFile>
        <port>${docker.app.jacoco}</port>
        <dump>true</dump>
    </configuration>
</execution>