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Jenkins Tutorial

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  • Last Updated November 21, 2018

Jenkins (Originally Hudson) is most widely used automation server with more than one lakh active sites. It was developed in 2004 by Kohsuke Kawaguchi. Kohsuke worked at Sun Microsystems as a developer, and at that time, he encountered a problem with constant breakage of build. To overcome this problem, he developed Jenkins CI as a process to perform continuous integration. This concept of continuous integration made way to the invention of Jenkins CI project. 

In this article, you will understand the basics of jenkins, how does it work, and where actually is it used. As you go deeper into the concepts of jenkins, you will learn the purpose of continuous integration, continuous delivery, and jenkins pipeline.

What is Jenkins?

Jenkins is an open-source software tool which runs on the basis of Java. It is mainly used for continuous integration and continuous delivery. It is known as one of the popular continuous integration (CI) tools used to build and test many projects. The purpose of using jenkins has advanced to continuous delivery after the release of version 2.0. 

What is Jenkins

Jenkins is easy to use, extensible, and an open-source user friendly tool. It provides continuous integration services for development of applications. Jenkins supports software configuration management tools such as GIT, Star Team, Subversion, etc. Jenkins can also build Apache Maven and Apache Ant based projects. The use of plugins in jenkins makes this tool more attractive, easy to learn and use.

Jenkins provides an easy way to set up a CI or CD environment for most of the languages and source code repositories with the help of pipelines in addition to automating other regular development tasks.  Whereas jenkins does not eliminate the need to generate scripts for individual steps, it provides you a rapid and robust way to integrate your complete chain of build, test and deployment tools.

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Jenkins describes the prominence of continuous integration and continuous delivery as a practice of cultivating devops culture. Let me first explain what continuous integration ia all about.

Continuous Integration

Continuous integration is a well known application development practice. This process comprises of new feature development, developers integrating bug fixes and use of innovative functionality in code repository. The continuous integration tool checks the integration procedure with automated build and test to identify problems with current sources of application and gives quick response.

[Related ArticleContinuous Integration with Jenkins]

Continuous Integration evolved from the extreme programming model which is a part of Agile methodology, but the concepts of CI can be applied to any iterative programming model. Basic Development approaches like the waterfall model can also be benefited from the use of CI practices for the construction stage. CI is commonly paired with CD, wherein the process of delivering executable code to production occurs faster and with automation , for CI/CD.

Continuous Delivery

Continuous Delivery is a discipline of software development where you develop software in such a way that the software can be released to production at any time.

continuous delivery is required when: 

  • The software can be deployable throughout its entire lifecycle.
  • Your team makes sure to keep software deployable when working on new features.
  • Individuals can get quick, automated response on the manufacturing process of their systems every time a person makes a change to them
  • Push-button deployments can be performed with any version of software to any environment on demand.

The process of continuous delivery can be achieved by continuously integrating the software created by the development team, building the executables, and performing computerised tests on those executables to identify bugs. Moreover you push the executables into multiple production environments to make sure the software will work in production. To make this possible you require a deployment pipeline.

Jenkins Pipeline

The features of Jenkins are collectively known as jenkins pipeline. They are configured as plugins which facilitate the implementation of continuous delivery pipelines, which are defined as the automated processes for retrieval of software from source control through deployment to end users.

Pipeline supports building Continuous Delivery pipelines through a scripted Jenkinsfile or a Web UI. The most typical basic pipeline described at a Jenkinsfile consists of 3 phases: Build, Test, and Deploy. The Build phase is normally where the source code is assembled, compiled, and packaged. Jenkinsfile isn't a replacement for a build tool, instead orchestrates the build and controls the resulting output through scripted steps. The Test phase to effective CI/CD processes is enabled by means of a number of Jenkins plugins which ease test execution and results recording, which can be visualized from the Web Dashboard UI.

jenkins pipeline workflow

Lastly, the Deployment phase encompasses anything from releasing build artifacts into management repository for sending code into pre-production environments. Build jobs can be configured to stop some other measure failure. This increases the quality of build and credibility by allowing failing code to advance throughout the deployment process, thus saving time and resources.

Concepts of pipeline:

The below concepts are important aspects of jenkins pipeline:

Pipeline:

A pipeline is a user defined representation of a continuous delivery pipeline. The code declared in the pipeline specifies your entire build process, which basically includes various stages for developing an application, testing it and then delivering it.

Node:

A node is represented as a machine which is a segment of jenkins environment and is useful in executing a pipeline.

Stage:

A stage block specifies an abstract of distinct group of tasks performed through the complete pipeline. (Stages such as build, test and deploy). Which is utilized by many plugins to represent status of jenkins pipeline.

Step:

A step is nothing but a single task which tells jenkins what to do at a certain point of time. Eg: Executing a shell command.

Fundamental Declaration of Pipeline:

The below code is the syntax of declarative pipeline, the pipeline block specifies all the work done throughout the complete pipeline. 

Jenkinsfile (Declarative Pipeline)

pipeline {
    agent any                     
    stages {
        stage('Build') {         
            steps {
                //                        
            }
        }
        stage('Test') {           
            steps {
                //                       
            }
        }
        stage('Deploy') {      
            steps {
                //                        
            }
        }

    }
}

Fundamental declaration of scripted pipeline:

One or more blocks do the core work throughout the entire pipeline in the scripted pipeline syntax.

Jenkinsfile (Scripted Pipeline)

node {                                
    stage('Build') { 
        // 
    }
    stage('Test') { 
        // 
    }
    stage('Deploy') { 
        // 
    }
}

The only difference with the syntax of scripted pipeline is that the stage blocks are optional. However, including stage blocks in scripted pipeline gives clear representation of every stage’s subset of steps in the jenkins UI.

Jenkins Automation

Jenkins is the trending open-source automation server containing more than 1400 plugins, to manage the automation of various development tasks. The continuous integration and continuous delivery of java code (i.e. running tests, building projects, performing static code analysis and deploying ) is the only process which people automate using jenkins. These 1400 plugins cover five areas they are: UI, platforms, administration, build management and source code management.

Continuous Integration common practices

Best practices of Continuous Integration include:

  • Frequent code commits
  • A dedicated integration build machine
  • Developer test categorization
  • Staging builds
  • Continuous feedback mechanisms.

The release of CI can occur at any frequency and this can be estimated depending on the organization that runs it and the project at hand; predominantly, organizations that adopt Continuous integration release more regularly than with software development processes in the past. Every significant change gives rise to a new build. A development team includes CI for various reasons, to receive continuous feedback on the status of software. CI identifies problems early in development, which makes them less complex, less disruptive, and easy to resolve than later in SDLC.

Advantages of Jenkins

  • It is an open-source tool and it is easy to use, install and does not need any additional components and installations.
  • It is available for all the platforms (Such as OSX, Windows or linux) and it is free.
  • Jenkins is easily configurable, it can be easily modified and extended. It generates test reports, deploys code instantly. Jenkins can be configured properly to the needs of CI and CD.
  • It supports a rich plugin ecosystem. The substansial pool of plugins makes jenkins flexible and allows deploying, building and automating across different platforms. 
  • As it is open-source and widely used, there is no lack of support from agile teams through online communities.
  • For early detection of code errors, developers write the tests so that they don’t misuse crucial time on large-scale error-ridden integrations.
  • Problems can be easily detected and rectified which preserves the software in a state where it can be safely released at any time.
  • All the work related to integration is automated. Hence less integration issues occur. This saves money and time over the project lifespan.

Jenkins Certification

Getting certified in Jenkins means you are skilled and possess hands-on experience, which is important to use and implement jenkins. The official jenkins certifications are classified into two categories:

  • Certified Jenkins Engineer
  • Certified CloudBees Jenkins Engineer 

Earning certification as a Jenkins engineer helps you prove a level of jenkins skill and proficiency. For employers, recruiting Jenkins-certified candidate provides assurance of a documented level of expertise for roles that need jenkins skills.

To gain knowledge on the skills you will be tested on and to prepare yourself for the exam, you need to review the following resources:

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About Author

Saikumar Talari

Saikumar Talari is a Technology Enthusiast and has passion towards writing content for various technologies in IT.


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