maven-3-git-alpine-docker-image

Docker image that might be used by CI/CD servers to execute the release of project artifacts [by maven-release-plugin].

Motivation

DevOps is a popular field nowadays where engineers spending lots of time automating\enhancing continuous delivery process. Many CI/CD servers have built-in capabilities to develop CD pipelines. For instance Jenkins has a concept of Pipeline as code or defining the deployment pipeline through code rather than configuring a running CI/CD tool, provides tremendous benefits for teams automating infrastructure across their environments.

Docker is very handy tool these days. CI/CD servers might spin up actual docker containers where CI/CD jobs take place.

Say you were given to design\implement CD pipeline for JVM based projects. Maven is a super popular build/automation tool - so why not to take advantage out of it ? There is the maven-release-plugin allowing you to release project with maven, saving a lot of repetitive, manual work.

So you want to:

• utilize maven-release-plugin
• and run release job by Jenkins agent
• where the entire pipeline, or a specific stage, will get executed within docker container.
• how ?

How

There's already available docker image maven:3-alpine that you might use ... but it does NOT have git installed which is required by maven-release-plugin. In order to let maven-release-plugin push changes to your Git server you have to connect your docker container runtime with Git server. This can be done via SSH:

• deploy your public key to GIT server.
• normally private key will be available under ~/.ssh/id_rsa
• build docker image docker build -t git-maven:3-alpine -f Dockerfile . Make sure private key was added to /root/.ssh/id_rsa

Now your newly built docker image is ready to release projects via maven-release-plugin. Appropriate Jenkins Pipeline might look like :

pipeline {
    agent {
        docker {
            image 'git-maven:3-alpine'
            args '-v /root/.m2:/root/.m2 --network=host'
        }
    }
    
    parameters {
        string defaultValue: '', description: 'Release Version.', name: 'releaseVersion', trim: true
        string defaultValue: '', description: 'Next Devevelopment Version.', name: 'developmentVersion', trim: true
    }
    stages {
        stage('Checkout') {
            steps {
               checkout([$class: 'GitSCM', 
						branches: [[name: 'origin/master']], 
						doGenerateSubmoduleConfigurations: false,  extensions: [[$class: 'LocalBranch', localBranch: 'master']], 
						submoduleCfg: [], 
						userRemoteConfigs: [[credentialsId: 'yourCredsId', url: 'https://github.com/[username]/[project]']]])
            }
        }
        stage('Release') {
            steps {
                sh 'mvn release:clean release:prepare release:perform -DreleaseVersion=${releaseVersion} -DdevelopmentVersion=${developmentVersion}'
            }
        }
    }
}

Voilà!