What is Jenkins? Jenkins Tutorial Guide to Beginners

Introduction

Through continuous integration, various stages of DevOps can be integrated. Jenkins is a tool that can be used to integrate these stages of DevOps, it is quite popular these days. This Jenkins Tutorial step by step guide will cover the introduction part and some other details like features or benefits of using Jenkins. Jenkins was only an open-source continuous integration tool at the time of its launch but now after version update of Jenkins, it has become continuous integration and a continuous delivery tool that can organize the application deployment phase too. The objective of this Jenkins guide for beginners is to cover maximum facts about the tool and how it supports the continuous integration or continuous deployment for various IT projects.

What is Jenkins?

Let's start with an introduction to one of the most popular DevOps tools that are popular as Jenkins. Jenkins wiki is an open-source tool that has many plug-ins and it is written in Java. The Jenkins wiki tool was launched to build and test software projects in an easy way.

Developers can easily integrate application changes with this tool to help the user to obtain a fresh build. The software can be tested and delivered continuously with the help of various integration and deployment technologies.

Through automation, software developers can accelerate the process of software development. Jenkins mainly integrates all the stages of the software development lifecycle that are documentation, packaging, testing, deployment, static analysis, and other ones.

Jenkins plugins help the developers in providing continuous integration and various stages can be integrated through Jenkins. To integrate any specific tool like Git, Amazon EC2, Manen 2 project, HTML publisher, etc. you can download the appropriate plugin and integrate the tool. It is a basically advantageous tool and the reason for the advantages of Jenkins is:

• Jenkins is an open-source tool that has wide community support
• Installation of Jenkins is quite easier
• A vast number of plugins are available; even if any plugin doesn’t exist then you can develop it and add it to the community.
• Due to Java's written code, it is portable to major platforms.

Jenkins Continuous Integration

So far, we have discussed that Jenkins is a continuous integration tool, now let's take a quick look at this most used DevOps concept. In the case of continuous integration, there is a shared repository in which developers can perform multiple changes even throughout the day and save them right there. As soon as the changes are committed, it gets stored in the repository and the team can easily detect if they found any problem due to that change.

Apart from the changes, there are several other operations like deployment of the application, testing it on the server, and providing it to the relevant teams after building and testing the results. All these steps can be performed as and when required by the DevOps team easily in a quick manner.

Learn the Key Metrics of Jenkins

There are several continuous integration tools in the market that makes the DevOps task easier and efficient. For the following metrics Jenkins is considered as best of them:

• Adoption: Jenkins has been adopted widely by DevOps professionals and so far, the tool has 147,000 active installations along with more than a million users across the globe.
• Plugins: Jenkins is popular due to the availability of many plugins around 100 to ease integration with most used tools for development, testing, and deployment.

Jenkins is a highly demanded tool globally and it can provide continuous integration just due to the availability of various plugins for several tools.

How the Tool Supports Continuous Integration?

In the case of the software development lifecycle, the application has to be built and deployed on the test server for the testing purpose by the team members. It is quite a popular and easy looking process for application development, but at the same time, this process has several flaws that need to be resolved. The so-called and mostly noticed flaws are like:

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• To submit the supplication to test server developers have to wait for complete application development
• The test result can show multiple or number of bugs after the testing process and developers may need to check the entire source code to locate the bug.
• The software delivery process gets slow.
• Many feedbacks like any coding or architectural related issue or any missed release update message or file release upload or any build failure can be missed.
• The risk of frequent failure is increased due to a completely manual process.

In short, we can say that as a result not only the delivery process gets slow but even the quality of the application can also be degraded due to all of these reasons. As a result, customer dissatisfaction may result. So, a platform that can overcome all of such shortcomings of the process as required by the developers that can provide the facility of continuous development and testing of the application, so that every change made to the source code can be triggered and altered. This process is known as CI and Jenkin tool is the one that can provide all of such CI features.

Jenkins Architecture Guide

Let's see how Jenkins helps the developers and testers? Following diagram shows the continuous integration with Jenkins:

Above diagram shows the complete process of continuous integration that takes place in Jenkins:

• Firstly, developers make and commit any changes in the source code of the application that are stored in the Git repository. On the other side, Jenkin server keeps on checking any changes done and committed in the repository
• After any changes are done by developers they are detected by Jenkin server in the source code repository. After tracking the changes Jenkin pulls the changes and starts preparing a new built of the application.
• On failing of the build, the concerned team is notified about it
• Successful builds are deployed on test servers by Jenkins.
• The result of build formation and testing is sent to the developers as notification
• This complete cycle of changes and sending feedback keeps on repeating.

Now as we have understood working of Jenkins now let’s see what changes it has made from the earlier way of releasing and deploying an application. In the following scenario that is for before and after Jenkins:

Before Jenkins:

• When Jenkins was not there, the entire source code was built and tested. The process of locating and fixing of bugs was quite long and difficult that many times even slows down the complete process of software delivery.
• Developers keep on waiting for the test result
• The complete deployment process was manual

After Jenkins:

• Every change or committed change of source code is tested as soon as it takes place. Developers now need not check the entire source code to locate any particular bug and frequent build releases are launched now
• The test result of every change or commit to the source code is informed to developers
• As soon as the changes are committed, the Jenkin server can execute the rest of the processes.

Learn Distributed Architecture of Jenkins:

For a distributed environment, Jenkins uses master-slave architecture to manage the builds. Here TCP/IP protocol is used to manage communication between master and slave units. Jenkins master and slave have the following responsibilities:

Jenkins Master

Main Jenkin server is the master that has the following responsibilities:

• To schedule job builds
• To dispatch builds to slaves for execution
• To monitor slaves online and offline as and when required
• To record and present the build results
• Master instance can also execute build jobs directly

Jenkins Slave

Jenkin Slave is a Java executable instance that is basically a remote machine. Jenkin slave has the following characteristics:

• To hear the requests of Jenkin master instance
• Slaves can run on a variety of OS
• Slaves have to do the job as per direction that is given to them
• Any project can also be executed on a particular machine or slave machine. Jenkin can also pick the next available Slave machine for execution

What are the Features of Jenkins?

Jenkin is a continuous integration tool provides following features for the application deployment:

• Code pipelines
• Better UX and UI
• Improved plugins and security

Through a DSL Jenkins has introduced a version builder that can help you to build, test and deploy various code pipelines. These pipeline scripts are easy to write, manage and execute. Parallel builds can be executed through these pipelines. You must have control over how and what you are going to build.

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As Jenkins provide better UI/UX so that user can easily visualize the flow and can easily configure passwords as and when required. You can also get a great view of Jenkin pipelines. Visual editor can be used to check and view these pipelines. The plugins are more safe and secure as well.

Jenkins Architecture with Example

Let us understand the Jenkins architecture with the help of an example. In the following diagram, there is one master and three Jenkins slaves. Let us see how they are connected.

Moving ahead, let us see how you can use Jenkins for testing in different environments like Ubuntu, Windows, or MAC, etc. The following diagram represents the same.

The following things are taken care of in the given diagram:

• Jenkins will keep checking the GIT repository at regular intervals for any changes in the source code.
• Each build in Jenkins needs a different testing environment that cannot be established using a single server. For this purpose, Jenkins utilizes different slaves as needed.
• Jenkins Master will send the request to these slaves for testing and generating test reports too.

Jenkins Build Pipelines

Jenkins pipelines are used to check which task is executing currently. Usually, multiple changes are made by different developers and it is necessary to know which changes have been tested and which changes are in the queue. There are three options available when building a project using Jenkins. These are:

• Freestyle Project: To provide maximum flexibility, this option is used for general-purpose builds.
• Multiconfiguration Job: If you want to run the same job in different testing environments then a multiconfiguration job option is used.
• Monitor the external Job: To keep an eye on the non-interactive processes, this option is used.

How to download and install Jenkins?

Jenkins can be installed at both Unix and the Windows platform. Here, we will focus on the installation of Jenkins on Windows. 

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Prerequisites:

Before you start with the Jenkins installation, there are some prerequisites to follow for the tool in your system.

• A basic 256 MB of RAM is necessary to install Jenkins in your system.
• You need a minimum of 1GB hard disk space for Jenkins Wiki.
• Jenkins runs over Java, so the latest version of Java should be installed on your PC.
• Jenkins supports two types of versions, Long-term support release, and the weekly release. You can choose any one of them as needed.

Step by step guide to Download and install Jenkins:

The following steps can help you to download Jenkins successfully.

• Download the Jenkins tool and select the Windows option from the list. 
• Go to the download location in your local system and unzip the download package.
• Now, the setup screen will appear in front of you, Click Next from the screen. 
• In the next step, decide on the location where you want to store the Jenkins instance then click Next. 
• Now, the installation window is ready, Click Install option and move ahead. 
• Once the installation is complete, click the Finish option and you are done. 

 Jenkins and GitHub Integration

• In the first step, you should start with the GitHub plug-in installation. Once the installation is done, go to the “Manage Plugins” option from the Jenkins dashboard.
• Using Jenkins URL, log in to the dashboard and create a new Jenkins job.
• Now, enter the item name, select the job type then click Finish. 
• As soon as you click OK, you will be redirected to the project from where you have to add all project details. 
• Here, you can see the Git option under the source code management. You can see this option only if the Git plugin has been installed successfully. 
• Choose the Git option and enter the Git repository URL to extract code from GitHub. 
• Choose Add repository and you can see that Git is properly installed and integrated with Jenkins.

Getting Started with Jenkins – Create your first build with the Freestyle Project

• From the Jenkins Dashboard, select the option “New Item”.
• Enter the name and choose the option “Freestyle project”.
• In the next step, you have to specify the job configuration. From the configuration page, choose the “add build setup” option then select “Execute shell” option. 
• Save the project and it will take you to the Project overview page where you have to give the basic project details. 
• Click the “build now” option on the left to start the build.
• Now go back to the Jenkins Dashboard where you can see quick details of all projects created so far. You can select your particular ones and start work.

Final Words

DevOps has made the software development and deployment process quicker and easier, but for this, you may need certain tools. Jenkins is one of the most used DevOps tools that can ease the operations by providing multiple plugins and an effective interface. Better UI tools like Jenkins are there to make the DevOps process easier. As it is an open-source tool so it can be used by anyone.

This Jenkins Tutorial For beginners presents a sound idea of the tool and how it can be used by industries for CI/CD. Also, you can create your first project using this Jenkins Tutorial step by step guide. To know more about DevOps and the related tools, you should join the DevOps certification program at JanBask Training and explore your learning with the brightest minds.