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Semantic versioning for docker tag from Git tag

Posted today at 3:01 pm

Define the version or build number is a very important step in a continuous integration and deployment pipeline.

When we build the docker image, we should add the version number as the tag to the image. And when we need deploy the docker image, we can refer the version number instead using latest tag.

Semantic versioning guideline is a widely used schema to define versions. In practice, how we generate the version number and keep the version number is still a challenge when we design a CI/CD pipeline to build docker images. In this post, I will introduce a method to generate version number from git tags and integrated with Jenkins and docker build.

The idea is to tag the git repo with a naming convention each time when we start a new build on release branch. The build job will check what is the version number of last build and increase the z value of x.y.z by 1. The build job will not change x or y value of the version number. There are 3 major steps in this process,

  1. Check the current branch

We only generate the version number when we build on the release branch. So the first step is check what is current build branch.

String getGitBranch() {
return script.sh(returnStdout: true, script: 'git name-rev --name-only HEAD').trim().minus("remotes/origin/")
}
  1. Check if we already have a release tag on current commit
git describe --tags --exact-match --match release/*
  1. Find the latest tag

If we don’t have a release tag on current commit, we will search for the latest release tag and generate the new version number based on it.

git describe --tags --abbrev=0 --match release/* | grep -o "[^\/]*$"

Let’s put everything together

String getApplicationVersion() {
  def tagPrefix = "release"
  def releaseBranch = "master"
  def currentVersion = ""
  def currentBranch =getGitBranch()
  if (currentBranch == releaseBranch) {
    try {
      def currentRelease = script.sh(returnStdout: true, script: "git describe --tags --exact-match --match ${tagPrefix}/*")
      currentVersion = currentRelease.toString().replaceFirst("${tagPrefix}/", "")
    } catch (error) { //  no release tag for commit
      try {
        def command = "git describe --tags --abbrev=0 --match ${tagPrefix}/* | grep -o \"[^\\/]*\$\" "
        def latestTag = script.sh(returnStdout: true, script: command)
        def versionSplit = latestTag.toString().split("\\.")
        currentVersion = "${versionSplit[0]}.${versionSplit[1]}.${versionSplit[2].toInteger() + 1}"
      } catch (error) { // no release tag for this repo
        currentVersion = "0.0.1"
      }
    }
    try {
        script.sh(returnStdout: true, script: "git tag ${tagPrefix}/${currentVersion}")
        script.sh(returnStdout: true, script: "git push --tag")
    } catch (error) { // cannot push tag
      //send error message
    }
  }
  return currentVersion
}

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Max CaiWritten by Max Cai Github