CI/CD as Code Part IV - Stateless Jenkins : Jobs as Code - Advanced

In the previous article of these examples, we created a stateless jenkins container which can be initialised solely by using scripts. In that example, a seed job for jobdsl plugin was also implemented. This job was later on used to create an automated simple jenkins job inline.
In order to create more complex jobs in an automated fashion, we will extend previous seed job implementation further in this example. Our extended seedJob will poll a job definition repository to gather the information on how to create new complex jobs for some other remote repositories.

Summary of the steps:

1. Extend jenkins/init.groovy/1-init-dsl-seed-job.groovy script to enable polling of remote repositories, so that it can check these repositories for new job descriptions.
2. Automate installation of the tools, which will be needed by the builds (e.g. maven, jdk, etc.)
3. Implement some job description scripts in the repository (folder), which will be polled by the seed job initialisation script.
4. Add Jenkinsfile(s) to the target projects which are referenced in the job definition script(s).
5. Run and test the example.

1. Extend jobDsl script

The jobDsl script 1-init-dsl-seed.job.groovy in the previos example is implemented to create a simple "Hello world" job, by passing a dsl job script to the seed jobs scriptText attribute. As we stated earlier, in this step we are going to extend this script to define more advanced jobs via groovy scripts. The new seed job will poll a remote repository and scan the contents for groovy based job descriptions. To achieve this goal, we need to define a scm and pass this to the freestyle job (the seed job):
The rest of the jobdsl initialisation script defines a jobDsl executor ( ExecuteDslScripts)instance and passes jobScriptFile variable to the targets attribute of this instance:
The final form of the script is as follows:

Let's summarize what this script is doing:

1. It will poll the master branch of the repository 'https://github.com/entrofi/oyunbahcesi.git'
2. Check for groovy scripts under the folder "ci_cd/jenkins/configs/jobdsl/" and execute them to create new jenkins jobs. The scripts in this remote repository repository can poll any number of repositories and can define different types of jenkins jobs or views.

2. Installing Tools

Every build jobhas it's own tooling requirements and in order to keep our "stateless CI/CD" goal, we should be able to automate such kind of tool installations. The example projects that we are going to define in the next section are java projects with maven build support. Let's showcase how to install these tools via Jenkins initialization scripts:
The 2-install-tools.groovy script installs two different versions of JDK and maven for us.
Java Installation
Maven Installation

The final form tool installation script can be found here

3. Implementing Job Descriptions

In this section we are going to implement some example job descriptions in the remote repository. Go to jenkins/configs/jobdsl folder, and add a groovy script file called createJobs.groovy:
This groovy script uses jobdsl api to create multibranch jobs for the remote repositories which are defined in the multipbranchJobs array. The the factory section of the implementation checks if the remote repositories have Jenkinsfiles and creates the pipelines for each accordingly.
This snippet demonstrates how to create a multi branch job using jobdsl api; however we are not limited in terms of the variety of the job descriptions. We can define any kind of Jenkins jobs, including build monitors, list views, free style jobs, simple pipeline jobs etc., using this api.

Adding Jenkinsfile to the target projects

The rest is easy, in section two we have defined some target projects which was entrofi/spring/restassured-asciidoctor project for this specific example. Define your project as done in section 2. Add you Jenkinsfile to that project and run your Jenkins instance if everything is working as expected.