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Lab 2: First Steps

In this lab we create our first Jenkins pipelines. Jenkins has the ability to automatically create Jobs based on Git repositories containing a Jenkinsfile:

  • Multibranch: Jenkins automatically manages jobs based on Jenkinsfiles in branches of a single Git repository.
  • Organization Folder: Jenkins automatically manages jobs for Jenkinsfiles in a set of Git repositories. (Currently GitHub and Bitbucket), including pull requests and forks.

In these labs we use the former method so that each participant can configure its labs independently. A Jenkinsfile provides a single source of truth for a build job https://en.wikipedia.org/wiki/Single_source_of_truth.

Lab 2.1: Declarative "Hello, World!"

  1. Create a new GitHub repository with a suitable name, e.g. jenkins-techlab.
  2. Create a new branch in the repository named lab-2.1
  3. Create a file named Jenkinsfile with the following content in the root directory of the lab-2.1 branch.
pipeline {
    agent any
    stages {
        stage('Greeting') {
            steps {
                echo 'Hello, World!'
            }
        }
    }
}
  1. On Jenkins, create a new "Multibranch Pipeline" item named techlab in your previously created folder
  2. Add a Git branch source (not Github, because then you need credentials)
  3. Set "Project Repository" to the URL of your new GitHub repository (use the https URL for anonymous access)
  4. Set the trigger "Periodically if not otherwise run" to "2 minutes"
  5. Click Save

If everything is configured correctly this will immediately scan your repository, create a job named "lab-2.1" below the multibranch pipeline and start a build of the "lab-2.1" job.

The multibranch pipeline scan trigger will also trigger builds of any jobs whose Jenkinsfile changes.

You can only view but not edit the configuration of a job generated from a Jenkinsfile. The Jenkinsfile is the single source of truth https://en.wikipedia.org/wiki/Single_source_of_truth for these jobs, the only thing that is configured directly in Jenkins is how to access the repositories. The next lab shows how to configure job properties like log rotation and build triggers in a Jenkinsfile.

Note:

  • Declarative pipelines require Jenkins Pipeline 2.5 or later
  • agent any indicates that any of the available executors can be used and allocates a workspace. agent is the equivalent of node in scripted pipelines.
  • agent and stages are mandatory in declarative Pipelines.

Lab 2.2: Scripted "Hello, World!"

Jenkinsfile also supports a scripted syntax. This can be considered a legacy feature and it is recommended to use the declarative syntax.

With the scripted syntax the above example would look like this:

node {
    stage('Greeting') {
        echo 'Hello, World!'
    }
}

In the following labs we will use the declarative syntax. If you are interested in the scripted syntax (or maybe have to maintain older projects) you can find scripted versions of most labs under /labs/scripted.

Note:

  • Stages are optional but recommended in scripted pipelines
  • node is technically optional in scripted pipelines but required by any steps which depend on a workspace, e.g. checkout or sh. So any non-trivial pipeline will require it.

End of Lab 2

Build Options/Properties →

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