Jenkins

Jenkins is an open source automation server. It helps automate the parts of software development related to building, testing, and deploying, facilitating continuous integration and continuous delivery. It is a server-based system that runs in servlet containers such as Apache Tomcat. Jenkins is an open source continuous integration/continuous delivery and deployment (CI/CD) automation software DevOps tool written in the Java programming language. It is used to implement CI/CD workflows, called pipelines.

What are the Jenkins Features?

  • Easy Installation. Jenkins is a platform-agnostic, self-contained Java-based program, ready to run with packages for Windows, Mac OS, and Unix-like operating systems.
  • Easy Configuration.
  • Available Plugins.
  • Extensible.
  • Easy Distribution.
  • Free Open Source.

As you can see in the diagram provided above, on the left is the Remote source code repository. The Jenkins server accesses the master environment on the left side and the master environment can push down to multiple other Jenkins Slave environments to distribute the workload.  That lets you run multiple builds, tests, and product environment across the entire architecture. Jenkins Slaves can be running different build versions of the code for different operating systems and the server Master controls how each of the builds operates. Supported on a master-slave architecture, Jenkins comprises many slaves working for a master. This architecture – the Jenkins Distributed Build – can run identical test cases in different environments. Results are collected and combined on the master node for monitoring.

In Jenkins Application:

Jenkins helps to automate and accelerate the software development process. Here are some of the most common applications of Jenkins:

1. Code Coverage Increase

Code coverage is determined by the number of lines of code a component has and how many of them get executed. Jenkins increases code coverage which ultimately promotes a transparent development process among the team members.

2. No Broken Code

Jenkins ensures that the code is good and tested well through continuous integration. The final code is merged only when all the tests are successful. This makes sure that no broken code is shipped into production.

What is Continuous Integration?

Continuous Integration is preferable to a Nightly Build and Integration process, run at day’s end when everyone has gone home (freeing server resources). Nightly integration is limited, occurring only once per day, as opposed to the continuous process of CI. Developers agree that nightly integration is useful in situations where the build process takes such an inordinately large amount of time that it is best conducted when fewer people are accessing the servers. In the next section, we’ll learn the features of Jenkins as a continuation of our discussion on What is Jenkins.

What are the Jenkins Features?

Jenkins offers many attractive features for developers:

  • Easy InstallationJenkins is a platform-agnostic, self-contained Java-based program, ready to run with packages for Windows, Mac OS, and Unix-like operating systems.
  • Easy ConfigurationJenkins is easily set up and configured using its web interface, featuring error checks and a built-in help function.
  • Available PluginsThere are hundreds of plugins available in the Update Center, integrating with every tool in the CI and CD toolchain.
  • ExtensibleJenkins can be extended by means of its plugin architecture, providing nearly endless possibilities for what it can do.
  • Easy DistributionJenkins can easily distribute work across multiple machines for faster builds, tests, and deployments across multiple platforms.
  • Free Open SourceJenkins is an open-source resource backed by heavy community support.

As a part of our learning about what is Jenkins, let us next learn about the Jenkins architecture

These are few questions and answers

1. Name the three different types of pipelines in Jenkins?

The three different types of Jenkins pipelines are:

  • CI/CD pipeline 
  • Scripted pipeline
  • Declarative pipeline

2. What are the features of Jenkins?

Some of the crucial features of Jenkins are the following:

  • It is a free and open-source automation tool
  • Jenkins provides a vast number of plugins
  • It is easy to set up and install on multiple operating systems
  • Provides pipeline support
  • Fast release cycles 
  • Easy upgrades

3. What is Groovy in Jenkins?

  • Apache Groovy is a dynamic object-oriented programming language used as a scripting language for Java platforms. 
  • Groovy is used to orchestrate the Jenkins pipeline and enables different teams to contribute to the work in different languages. 
  • Groovy’s syntax is very similar to that of Java, making it more seamless with the Java interface. 
  • The language has several features like Java compatibility and Development support.

4. How do you install Jenkins?

Follow the steps mentioned below to install Jenkins:

  • Install Java 
  • Install Apache Tomcat Server
  • Download Jenkins war File
  • Deploy Jenkins war File

5. Which commands can be used to begin Jenkins?

Here are the commands used to start Jenkins:

  1. Open the command prompt
  2. After the command prompt opens, browse to the directory where Jenkins war is present
  3. Then run the following command:
  4. sudo systemctl enable jenkins.
  5. sudo systemctl start jenkins.
  6. sudo systemctl status jenkins.
  7. Loaded: loaded (/lib/systemd/system/jenkins

6. What is “Continuous Integration” with reference to Jenkins?

  • Continuous Integration is a development practice where the codes can be integrated into a shared repository. 
  • The practice uses automated verifications for the early detection of code problems. 
  • Continuous Integration triggers the build to find and identify bugs present in the code.
  • It adds consistency to the build process.
  • It’s a means to build things faster and prevents broken code.

7. What is a CI/CD pipeline?

CI/CD Pipeline or Continuous Integration/ Continuous Delivery is considered the DevOps approach’s backbone. The pipeline is responsible for building codes, running tests, and deploying new software versions.

8. What is a Jenkins pipeline?

  • The pipeline represents the continuous delivery and continuous integration of all the jobs in the SDLC and DevOps life cycle. 
  • The Jenkins pipeline is a set of plugins that support implementation and integration of continuous delivery pipelines into Jenkins. It connects this pipeline in a particular format by Jenkins.
  • The Jenkins pipeline solves several problems like the maintenance of thousands of jobs and maintaining deployment with needing to resort to other powerful methods.

9. How can you create a backup and copy files in Jenkins?

  • Jenkins stores all the settings, builds scripts, and logs in the home directory. 
  • Then, if you want to create a backup of this Jenkins set up all you have to do is copy this directory. 
  • The job directory may also be copied to clone a job or rename the directory.

10. What could be the steps to move or copy Jenkins from one server to another?

There are multiple ways to move or copy Jenkins from one server to another:

  • You may move a job from one Jenkins installation to another just by copying the corresponding job directory.
  • You may make a copy of an already existing job by making a clone of the job directory with an uncommon name.
  • You may also just rename a current job by renaming a directory.
oneserver

11. Assume that you have a pipeline. The first job that you performed was successful, but the second one failed.  What would you do now?

You don’t have to worry, and you just have to restart the pipeline from the point where it failed by doing ‘restart from stage.’

12. Explain the process in which Jenkins works?

Here’s the process in which Jenkins works:

  • Jenkins checks changes in repositories regularly, and developers must secure their code regularly. 
  • Once the changes are defined, Jenkins detects them and uses them to prepare a new build.
  • After that, Jenkins will transverse through various stages in its usual pipeline. As one stage completes, the process will move further on to the next stage.
  • If a stage fails, the Jenkins build will stop there, and the software will email the team using it. When completed successfully, the code implements itself in the proper server so that testing begins.
  • After the successful testing phase, Jenkins shares the results with the team.

13. What is Jenkinsfile? 

Jenkins file is a text file that has a definition of a Jenkins pipeline and is checked into the source control repository. It enables code review and iteration on the pipeline. It also permits an audit trail for the pipeline.

Sample of //declarative pipeline
pipeline{
agent any
tools {
maven “maven3.8.4”
}
triggers {
pollSCM ‘* * * * * ‘
}
stages {
stage(‘1.CodeClone’){
steps{
git branch: ‘stage’, credentialsId: ‘GitHubCredentials’, url: ‘https://github.com/AnselemChattme/web-app’
}
}
stage(‘2.mavenBuild’){
steps{
sh “mvn clean package”
}
}
stage(‘3.CodeQuality’) {
steps{
sh “echo reports done”
//sh “mvn sonar:sonar”
}
}
stage(‘4.uploadToNexus’){
steps{
sh “echo artifacts uploaded”
//sh “mvn deploy”
}
}
stage(‘5.Deploy2Tomcat’){
steps{
sshagent([’32d5fb4f-d92f-4a10-9f12-2738eab55fcc’]) {
sh “scp -o StrictHostKeyChecking=no target/*war [email protected]:/opt/tomcat9/webapps/app”
}

}
}
}
post{
always {
mail bcc: ‘[email protected]’, body: ”’Build complete

AnselemChattme”’, cc: ‘[email protected]’, from: ”, replyTo: ”, subject: ‘Build done’, to: ‘v [email protected]
}
failure {
mail bcc: ‘[email protected]’, body: ”’Build complete

AnselemChattme”’, cc: ‘[email protected]’, from: ”, replyTo: ”, subject: ‘Build failed’, to: ‘[email protected]
}
success {
mail bcc: ‘[email protected]’, body: ”’Build complete

AnselemChattme”’, cc: ‘[email protected]’, from: ”, replyTo: ”, subject: ‘Build succeed’, to: ‘[email protected]
}
}
}

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