OpenShift 4.6 Automation and Integration: Jenkins

Introduction

A Jenkinsfile is a text file using Groovy syntax, which is very similar to Java and JavaScript.

https://www.jenkins.io/doc/book/pipeline/syntax/

https://www.jenkins.io/doc/book/pipeline/syntax/#scripted-pipeline

There are Two Possible Styles for Writing a Jenkinsfile:

Declarative Pipeline

Pipelines that start with a pipeline directive and define declarative scripts using a special-purpose domain-specific language (DSL) that is a subset of Groovy.

pipeline {
    /* insert Declarative Pipeline here */
}

Scripted Pipeline

Pipelines that start with a node directive and define imperative scripts using the full Groovy programming language.

node {
    stage('Example') {
        if (env.BRANCH_NAME == 'master') {
            echo 'I only execute on the master branch'
        } else {
            echo 'I execute elsewhere'
        }
    }
}

Declarative Pipeline Example

pipeline {
    agent any
    triggers {
        cron('H */4 * * 1-5')
    } 
    stages {
        stage('Example Build') {
            agent { docker 'maven:3.8.1-adoptopenjdk-11' } 
            steps {
                echo 'Hello, Maven'
                sh 'mvn --version'
            }
        }
        stage('Example Test') {
            agent { docker 'openjdk:8-jre' } 
            steps {
                echo 'Hello, JDK'
                sh 'java -version'
            }
        }
    }
}

The Two Most Common Project Types are:

Pipeline

Runs a pipeline taking as input a single branch from a version control system repository.

Multibranch pipeline

Automatically creates new projects when new branches are detected in a version control system repository. All these projects share the same pipeline definition that must be flexible enough to avoid conflicts between builds in different branches.

Jenkins agent images

https://access.redhat.com/documentation/en-us/openshift_container_platform/4.6/html-single/images/index#images-other-jenkins-agent

Jenkins images are available through the Red Hat Registry:

$ docker pull registry.redhat.io/openshift4/ose-jenkins:<v4.5.0>

$ docker pull registry.redhat.io/openshift4/jenkins-agent-nodejs-10-rhel7:<v4.5.0>

$ docker pull registry.redhat.io/openshift4/jenkins-agent-nodejs-12-rhel7:<v4.5.0>

$ docker pull registry.redhat.io/openshift4/ose-jenkins-agent-maven:<v4.5.0>

$ docker pull registry.redhat.io/openshift4/ose-jenkins-agent-base:<v4.5.0>

Installng Jenkins on OCP

$ oc get templates -A | grep jenkins
openshift   jenkins-ephemeral                               Jenkins service, without persistent storage....
openshift   jenkins-ephemeral-monitored                     Jenkins service, without persistent storage. ...
openshift   jenkins-persistent                              Jenkins service, with persistent storage....
openshift   jenkins-persistent-monitored                    Jenkins service, with persistent storage. ...

$ oc describe -n openshift template jenkins-persistent

$ oc new-project gitops-deploy

$ oc new-app --template jenkins-persistent -p JENKINS_IMAGE_STREAM_TAG=jenkins:v4.8

$ oc adm policy add-cluster-role-to-user self-provisioner -z jenkins -n gitops-deploy