Dockerfile Maven

This is a Maven plugin and extension which help to seamlessly integrate Docker with Maven.

The design goals are:

• Don't try to do anything fancy. Dockerfiles are how you build Docker projects; that's what this plugin uses. They are mandatory.
• Make the Docker build process integrate with the Maven build process. If you bind the default phases, when you type mvn package, you get a Docker image. When you type mvn deploy, your image gets pushed.
• Make the goals remember what you are doing. You can type mvn dockerfile:build and later mvn dockerfile:tag and later mvn dockerfile:push without problems. This also eliminates the need for something like mvn dockerfile:build -DalsoPush; instead you can just say mvn dockerfile:build dockerfile:push.
• Integrate with the Maven build reactor. You can depend on the Docker image of one project in another project, and Maven will build the projects in the correct order. This is useful when you want to run integration tests involving multiple services.

This project adheres to the Open Code of Conduct. By participating, you are expected to honor this code.

Set-up

This plugin requires Java 7 or later, and Apache Maven 3 or later. To run the integration tests or to use the plugin in practice, a working Docker set-up is needed.

Example

For more examples, see the integration test directory.

In particular, the advanced test showcases a full service consisting of two micro-services that are integration tested using helios-testing.

This configures the actual plugin to build your image with mvn package and push it with mvn deploy. Of course you can also say mvn dockerfile:build explicitly.

<plugin>
  <groupId>com.spotify</groupId>
  <artifactId>dockerfile-maven-plugin</artifactId>
  <version>${version}</version>
  <executions>
    <execution>
      <id>default</id>
      <goals>
        <goal>build</goal>
        <goal>push</goal>
      </goals>
    </execution>
  </executions>
  <configuration>
    <repository>spotify/foobar</repository>
    <tag>${project.version}</tag>
  </configuration>
</plugin>

A corresponding Dockerfile could look like:

FROM dockerfile/java:oracle-java8
MAINTAINER David Flemström <[email protected]>

ENTRYPOINT ["/usr/bin/java", "-jar", "/usr/share/myservice/myservice.jar"]

# Add Maven dependencies (not shaded into the artifact; Docker-cached)
ADD target/lib           /usr/share/myservice/lib
# Add the service itself
ADD target/myservice.jar /usr/share/myservice/myservice.jar

What does it give me?

There are many advantages to using this plugin for your builds.

Faster build times

This plugin lets you leverage Docker cache more consistently, vastly speeding up your builds by letting you cache Maven dependencies in your image. It also encourages avoiding the maven-shade-plugin, which also greatly speeds up builds.

Consistent build lifecycle

You no longer have to say something like:

mvn package
mvn docker:build
mvn verify
mvn docker:push
mvn deploy

Instead, it is simply enough to say:

mvn deploy

With the basic configuration, this will make sure that the image is built and pushed at the correct times.

Depend on Docker images of other services

You can depend on the Docker information of another project, because this plugin attaches project metadata when it builds Docker images. Simply add this information to any project:

<dependency>
  <groupId>com.spotify</groupId>
  <artifactId>foobar</artifactId>
  <version>1.0-SNAPSHOT</version>
  <type>docker-info</type>
</dependency>

Now, you can read information about the Docker image of the project that you depended on:

String imageName = getResource("META-INF/docker/com.spotify/foobar/image-name");

This is great for an integration test where you want the latest version of another project's Docker image.

Note that you have to register a Maven extension in your POM (or a parent POM) in order for the docker-info type to be supported:

<build>
  <extensions>
    <extension>
      <groupId>com.spotify</groupId>
      <artifactId>dockerfile-maven-extension</artifactId>
      <version>${version}</version>
    </extension>
  </extensions>
</build>

Use other Docker tools that rely on Dockerfiles

Your project(s) look like so:

a/
  Dockerfile
  pom.xml
b/
  Dockerfile
  pom.xml

You can now use these projects with Fig or docker-compose or some other system that works with Dockerfiles. For example, a docker-compose.yml might look like:

service-a:
  build: a/
  ports:
  - '80'

service-b:
  build: b/
  links:
  - service-a

Now, docker-compose up and docker-compose build will work as expected.

Authentication and private Docker registry support

Since version 1.3.0, the plugin will automatically use any configuration in your ~/.dockercfg or ~/.docker/config.json file when pulling, pushing, or building images to private registries.

Additionally the plugin will enable support for Google Container Registry if it is able to successfully load Google's "Application Default Credentials". The plugin will also load Google credentials from the file pointed to by the environment variable DOCKER_GOOGLE_CREDENTIALS if it is defined. Since GCR authentication requires retrieving short-lived access codes for the given credentials, support for this registry is baked into the underlying docker-client rather than having to first populate the docker config file before running the plugin.