Jenkins

Jenkins is a CI CD (Continuous Integration and Continuous Delivery) tool I have used at work. The team that I was a part of was a subset of QA (Quality Assurance) and the team used Jenkins for test automation.

I was the primary developer responsible for maintaining Jenkins, which involved:

• Creating and maintaining all pipelines
• Maintaining all Groovy code that mainly resided in the shared library
• Monitoring the Jenkins service for outages and providing user support with issues as they came up

There was a separate team that installed Jenkins which I believed was run inside Kubernetes. This made it a challenge to manage the Jenkins plugins, mange any container images, and troubleshoot issues that required us to shell into the pod. For these kinds of activities, the trick was to maintain a good working relationship with the other team and ask for assistance as needed.

Jenkinsfile §

This is the file that contains the code that drives all the pipelines. In general, all of the pipelines I managed were in gitlab and the only important file in the repo was the jenkinsfile. This file was written in Groovy and you can say this was a good example of infrastructure as code.

Pro Tip

Even though the code written in the jenkinsfile is mainly Groovy, you will also find in this file Jenkins plugins that have their own syntax. This is important to note as I myself and other people I have worked with confuse Groovy code with code that references Jenkins plugins.

Where do I find out what plugins I have available in my Jenkins environment?

• {https://YOUR_JENKINS_URL}/pipeline-syntax

What is the basic structure of a jenkinsfile? The stages block defines the individual stages of a pipeline, and each stage contains a steps block that defines the steps to be executed in that stage.

pipeline {
	agent (where to execute, Jenkins agent)
	stages {
		stage("build") {
			steps {}
		}
	}
}

Test/Development Process §

At a high level, all development was done in Eclipse using a common branch for all the pipelines and the shared library. I had access to a Development folder in Jenkins where I had copies of all the production pipelines. I had the ability to point to my git branches in this development area and do all my development and testing here.

I usually had a branch for the pipeline, the shared library, and an application I was attempting to run tests against. At times you may be able to get away with a simple replay and some editing of the jenkinsfile.

Shared Library §

There was a separate gitlab repository that was referred to as the shared library. This repo contained most of the Groovy code for Jenkins and at the top of every pipeline, we imported this library.

@Library('MY_SHARED_LIB@TAG_NAME') _

This repo had to be organized in a very specific manner and I learned this the hard way.

• resources
  • contains any non Groovy file
  • I maintained the Kubernetes pod configuration file here
• src/a/b/c
  • Any folder structure was allowed here
  • We maintained testing code, reporting code, etc
  • Groovy code has to be declared using a class
    • You will need to use the import syntax to access any of these files/functions in the jenkinsfile
• vars
  • DO NOT create sub folders here, this folder is meant to be flat
  • Groovy code can be as simple as a file with a bunch of functions
    • All of these functions will be available in the jenkinsfile without any extra code except the @Library syntax