Sunday, May 28, 2017

Using fabric8 docker-maven-plugin to automate docker builds

Posted by Unknown at 1:37:00 AM Labels: , , ,
In building the required libraries for a docker container, using a maven project, the libraries have to be copied to a separate location and we have to manually run a docker build. This process is cumbersome since you have to repeat the same process over even if there is a slight modification.

fabric8 docker-maven-plugin is the perfect solution for this requirement. spotify also supports a docker plugin. However fabric8 provides much more functionalities. For example, with fabric8 it's possible to inject values to the docker file with ease.

fabric8 provides a great source of documentation (https://dmp.fabric8.io/). However for a beginner, it could be challenging. My requirement was to configure the plugin in
 such a way that would enable even a user without docker on his/her machine to do a maven build.

The first step was to move the variable names to the POM so that configurations can be separated in order to improve maintainability.


        <fabric8io.docker.version>0.21.0</fabric8io.docker.version>
        <docker.registry>myregistry.malith.com:5000</docker.registry>
        <docker.image.tag>latest</docker.image.tag>
        <docker.repository>projectname:${docker.image.tag}</docker.repository>
        <docker.fileName>Dockerfile</docker.fileName>
        <docker.skip>false</docker.skip>


Next under the <build><plugins> tag add the maven docker plugin.

              <plugin>
                <groupId>io.fabric8</groupId>
                <artifactId>docker-maven-plugin</artifactId>
                <version>${fabric8io.docker.version}</version>
                <configuration>
                    <registry>${docker.registry}</registry>
                    <useColor>true</useColor>
                    <verbose>true</verbose>
                    <skip>${docker.skip}</skip>
                    <images>
                        <image>
                            <name>${docker.registry}/${docker.repository}</name>
                            <build>
                                <dockerFileDir>${project.build.directory}/projectname-${project.version}-docker/projectname</dockerFileDir>
                                <filter>@</filter>
                                <dockerFile>${docker.fileName}</dockerFile>
                                <tags>
                                    <tag>${docker.image.tag}</tag>
                                </tags>
                            </build>
                        </image>
                    </images>
                </configuration>
                <executions>
                    <execution>
                        <id>start</id>
                        <phase>pre-integration-test</phase>
                        <goals>
                            <!-- "build" should be used to create the images with the
                                 artifact -->
                            <goal>build</goal>
                            <goal>start</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>stop</id>
                        <phase>post-integration-test</phase>
                        <goals>
                            <goal>stop</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

Next, I needed to skip the execution of the plugin if the user does not want to build the docker image. Therefore I created a profile, that would set the variable ${docker.skip} to true on the provision of the variable skipDocker.

I added the following section to the pom.


 <profiles>
        <profile>
            <id>docker</id>
            <properties>
                <docker.skip>true</docker.skip>
            </properties>
            <activation>
                <property>
                    <name>skipDocker</name>
                    <value>true</value>
                </property>
            </activation>
        </profile>
    </profiles>

Based on the above code snippet, if skipDocker has been given as a maven directive, it would set docker.skip to true, effectively skipping the execution of the plugin.

Therefore a user can skip building the docker image simply by,


maven clean install -DskipDocker

Fabric8 has a lot of support for docker builds. I have a lot to explore. Hope you've found my findings useful. Don't forget to leave a comment. :-) 

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