Building the DevOps Pipeline with Jenkins

Jenkins is an open source tool that provides integration with the tools used in application lifecycle management to automate the entire process, based on feasibility.

The prerequisites for installing Jenkins on a specific system are:

• Jenkins official documentation recommends 256MB of RAM.
• Jenkins official documentation recommends 10GB of drive space; however, I suggest 50GB – 80GB of free space on a disk drive.
• Jenkins official documentation recommends Java 8 or 11.

The commands to run Jenkins are as follows.
You can start Jenkins at the command line by using the Generic Java package (.war):

java -jar jenkins.war

To access the Jenkins dashboard, browse to http://localhost:8080. Change the port to run Jenkins, with the following command:

java -jar jenkins.war --httpPort=9999
Access Jenkins’ dashboard: Browse to http://
localhost:9999

It will redirect the user to unlock the Jenkins page by providing the administrator password, which can be found from the console log when the jenkins command is executed for the first time.

Click on Install Suggested Plugins.

Once all the plugins are installed, create your first admin user (Figure 2) and click on Save and Continue.

Provide the Jenkins URL or keep the default, depending on your needs.

Once the Jenkins setup is complete, click on Start using Jenkins. Verify the Jenkins dashboard. Click on Manage Jenkins.

Go to Manage Jenkins -> Global Tool Configuration.

The Build Pipeline plugin
Using Jenkins and the build pipeline makes us realise the complexities of managing Jenkins over time. It is easier to use the Build Pipeline plugin in Jenkins to create pipelines with upstream and downstream projects (Figure 6).

Execute the pipeline as shown in Figure 7.

Scripted pipelines
Jenkins 2.0 and later versions have built-in support for delivery pipelines. Jenkinsfile contains the script to automate application life cycle management activities. There are two types of pipelines in Jenkins, as of today. This means that Jenkinsfile can contain two different types of styles/syntax and yet it can achieve the same thing.

Scripted pipelines follow the imperative programming model. They are written in the Groovy script in Jenkins. All Groovy blocks/constructs help to manage flow as well as error reporting.

node {
/* Stages and Steps */
}
node {
stage(‘SCA’) {
// steps
}
stage(‘CI’) {
// steps
}
stage(‘CD’) {
// steps
}
}

Figure 7: Build Pipeline plugin

Declarative pipelines
As the name suggests, a declarative pipeline follows a declarative programming model. Declarative pipelines are written in a domain-specific language in Jenkins that is clear and easy to understand.

pipeline {
agent any
stages {
stage(‘SCA’) {
steps {
//

}
}
stage(‘CI’) {
steps {
//
}
}
stage(‘CD’) {
steps {
//
}
}
}
}

Open the Blue Ocean dashboard and click on Create Pipeline. Connect with the required repository; then create stages, select the steps and configure.

Blue Ocean is a new user experience, and it provides an easy way to access unit test results (Figure 10).

Click on Pipeline to get the status of the pipeline. Click on the specific stages to access the logs of these stages.

Click on Artifacts to access the package file and other artifacts (Figure 12).

The following list of open source tools can be integrated in the pipeline to implement DevOps practices.