Docker Maven Plugin

Project Goal:

• Make it easy to build an app on a container, test it and push it to a Docker repository, even if it relies on other containers (e.g. a database)
• Talk "Maven" rather than "Docker" (E.g. "package" rather than "build").
• Keep it simple.

Pre-requisites

Docker installed and Docker daemon running, see the docker getting started guide for e.g. on a mac follow these instructions.

Usage

The best example to look at is the one from the tests which creates a Drop-Wizard app and builds three containers: app (the dropwizard application) data and mysql, and then runs an integration test against the deployed app. Et voila a packaged image!

Typically, you build your app, run your standard unit tests and package it as usual. Then, you build a container with your app deployed onto it, and run integration tests against it. If they pass, deploy your jar into the Maven repository, and optionally, your image into a Docker repository.

To use the plugin, you need to define a docker directory in ${basedir}/src/main which will include a subdirectory for each container that you wish to deploy.

• src/main/docker/ contains one folder per container for e.g. the mysql container would have a folder structure as follows:
  • mysql
    • Dockerfile a standard Docker file.
    • conf.yml configuration:
  • ...
    • Dockerfile a standard Docker file.
    • conf.yml configuration:

# additional data require to create the Docker image
packaging:
  # files to add to the build, usually used with ADD in the Dockerfile
  add:
    - target/example-1.0-SNAPSHOT.jar
    - hello-world.yml
# optional list of port to expose on the host
ports:
  - 8080
# containers that this should be linked to, started before this one and stopped afterwards
links:
  - mysql

Trivial Example

Create a default maven project for e.g.

  mvn archetype:generate -DgroupId=com.example -DartifactId=helloworld -DpackageName=com.example -DarchetypeGroupId=org.apache.maven.archetypes -DarchetypeArtifactId=maven-archetype-quickstart -Dversion=1.0-SNAPSHOT

Add the following to the pom.xml

   <build>
       ...
       <plugins>
           ...
           <plugin>
               <groupId>com.alexecollins.docker</groupId>
               <artifactId>docker-maven-plugin</artifactId>
               <version>0.8.3-SNAPSHOT</version>
           </plugin>
       </plugins>
   </build>

Create your ${basedir}/src/main/docker directory and create a subfolder for your application container

 mkdir -p src/main/docker/app

Define your Dockerfile and conf.yml and place in ${basedir}/src/main/docker/app

   src/main/docker/app
   ├── Dockerfile
   └── conf.yml

You can now invoke functionality from the plugin, information on the plugin can be found by running the following command

 mvn help:describe -DgroupId=com.alexecollins.docker -DartifactId=docker-maven-plugin -Dversion=0.8.3-SNAPSHOT

For e.g. to build containers from their Dockerfile and conf.yml files, run the following command

 mvn docker:package

TODO

• Filter resources to add properties (e.g ${project.version}).
• Set the name of the container.
• Wait for the service on the container to start.
• Add support for pushing tested containers.

Notes to self:

docker ps -a -q | xargs docker rm

References

• http://www.alexecollins.com/tags/docker/