What Is Jenkins? Working, Uses, Pipelines, and Features

Jenkins is defined as an open-source solution comprising an automation server to enable continuous integration and continuous delivery (CI/CD), automating the various stages of software development such as test, build, and deployment. This article explains how Jenkins works, its key features and use cases, and the functionality of a Jenkins pipeline. 

What Is Jenkins?

Jenkins is an open-source solution comprising an automation server to enable continuous integration and continuous delivery (CI/CD), automating the various stages of software development such as build, test, and deployment. 

Jenkins is a Java-based open-source automation platform with plugins designed for continuous integration. It is used to continually create and test software projects, making it easier for developers and DevOps engineers to integrate changes to the project and for consumers to get a new build. It also enables you to release your software continuously by interacting with various testing and deployment methods. 

Organizations may use Jenkins to automate and speed up the software development process. Jenkins incorporates a variety of development life-cycle operations, such as build, document, test, package, stage, deploy, static analysis, and more. 

Jenkins is a well-known continuous integration tool developed initially by Hudson before it became available on the open-source market. Hudson was created by Kohsuke Kawaguchi in 2004 while working at Sun Microsystems (acquired by Oracle). There was a disagreement between Oracle and the Hudson community about the infrastructure employed after Oracle purchased Sun Microsystems in 2010. 

In 2011, the Hudson community unanimously accepted a referendum to alter the project name from Hudson to Jenkins, resulting in the creation of the first “Jenkins” project. Hudson was later donated to the Eclipse Foundation and is no longer being worked on. Jenkins development is currently administered as an open-source project under the direction of the CD Foundation, a Linux Foundation initiative.

Jenkins is a widely used program with over 300,000 installations worldwide and rising daily. Software firms may speed up their software development process by adopting Jenkins, which can automate test and build at a high pace. It’s a server-based application that necessitates using a web server such as Apache Tomcat. 

See More: DevOps vs. Agile Methodology: Key Differences and Similarities 

What Is Jenkins Used For?

Jenkins software’s popularity stems from its ability to track and monitor repetitive activities that emerge throughout a project’s development. For example, if your team is working on a project, Jenkins will continually test your builds and alert you to any mistakes early in the process. Its top use cases include:

1. Deploying code into production

If all of the tests developed for a feature or release branch are green, Jenkins or another CI system may automatically publish code to staging or production. This is often referred to as continuous deployment. Changes are done before a merging action can also be seen. One may do this in a dynamic staging environment. Then it’s distributed to a central staging system, a pre-production system, or even a production environment when combined.

2. Enabling task automation

Another instance in which one may use Jenkins is to automate workflows and tasks. If a developer is working on several environments, they will need to install or upgrade an item on each of them. If the installation or update requires more than 100 steps to complete, it will be error-prone to do it manually. Instead, you can write down all the steps needed to complete the activity in Jenkins. It will take less time, and you can complete the installation or update without difficulty. 

3. Reducing the time it takes to review a code

Jenkins is a CI system that may communicate with other DevOps tools and notify users when a merge request is ready to merge. This is typically the case when all tests have been passed and all other conditions have been satisfied. Furthermore, the merging request may indicate the difference in code coverage. Jenkins cuts the time it takes to examine a merge request in half. The number of lines of code in a component and how many of them are executed determines code coverage. Jenkins supports a transparent development process among team members by reducing the time it takes to review a code.

See More: DevOps Roadmap: 7-Step Complete Guide

4. Driving continuous integration

Before a change to the software can be released, it must go through a series of complex processes. The Jenkins pipeline enables the interconnection of many events and tasks in a sequence to drive continuous integration. It has a collection of plugins that make integrating and implementing continuous integration and delivery pipelines a breeze. A Jenkins pipeline’s main feature is that each assignment or job relies on another task or job.

On the other hand, continuous delivery pipelines have different states: test, build, release, deploy, and so on. These states are inextricably linked to one another. A CD pipeline is a series of events that allow certain states to function. 

5. Increasing code coverage

Jenkins and other CI servers may verify code to increase test coverage. Code coverage improves as a result of tests. This encourages team members to be open and accountable. The results of the tests are presented on the build pipeline, ensuring that team members adhere to the guidelines. Like code review, comprehensive code coverage guarantees that testing is a transparent process for all team members. 

6. Enhancing coding efficiency 

Jenkins dramatically improves the efficiency of the development process. For example, a command prompt code may be converted into a GUI button click using Jenkins. One may accomplish this by encapsulating the script in a Jenkins task. One may parameterize Jenkins tasks to allow for customization or user input. Hundreds of lines of code can be saved as a result.

Further, it supports manual testing where necessary without switching environments. When code is hosted locally, it does not always work well when pushed to a central system on a private or public cloud. This occurs because things change by the time they push. Continuous integration on Jenkins allows for manual testing that compares code to the current state of a code base in a production-like environment.

7. Simplifying audits

When Jenkins tasks run, they collect console output from stdout and stderr parameters. This makes troubleshooting using Jenkins extremely straightforward. You may assess run timing and find the slowest step utilizing the time stamper plugin, allowing you to tweak the performance of each operation. 

8. Using Slack for synchronization

A major Jenkins use case is its interoperability with Slack. A centralized communication platform is a must-have for large teams, and one of the most popular platforms for this purpose is Slack. Jenkins may be integrated with Slack, allowing communication such as triggered activities, their times, users’ names, and outcomes to be shared with others.

See More: DevOps Engineer: Job Description, Key Skills, and Salary in 2022

How Does Jenkins Work?

Jenkins may be operated as a server on various operating systems, including Windows, macOS, Unix versions, and, most notably, Linux. It also runs on the Oracle JRE or OpenJDK and requires a Java 8 virtual machine or higher. Jenkins is often executed as a Java servlet within a Jetty application server, and other Java application servers, such as Apache Tomcat, can be used to run it. 

Jenkins has recently been modified to operate in a Docker container. Further, it is available as a Web Application Resource (WAR) archive, installation packages for major operating systems, Homebrew packages, Docker images, and source code.

The solution’s source code is predominantly Java, with some Groovy, Ruby, and Antlr files available. One may execute the Jenkins WAR as a standalone or servlet in a Java application server like Tomcat. It generates a web user interface in either instance and takes requests to its REST API. When you initially start Jenkins, it generates an administrator account with a lengthy unique password, which you may input into the installation’s first site to unlock. Keep in mind that read-only Jenkins images are accessible in the Docker Hub online repository. 

Next, the contents of Jenkins are saved locally in a Jenkinsfile as plain text. The Jenkinsfile has a curly bracket syntax that resembles JSON. Pipeline steps are enclosed in curly brackets and specified as commands with arguments. The Jenkins server then reads the Jenkinsfile and runs the tasks, pushing the code from the committed source code to runtime in production.

Jenkinsfiles may be produced using a graphical user interface (GUI) or manually writing code. It automates every stage of the development process, from integration to deployment. Every time a developer pushes a change to the source code repository, it performs a build.

The commits are usually made to a development branch. Before releasing the build into production, Jenkins may deploy it to an environment that allows for any necessary user acceptance testing (UAT). To achieve continuous delivery (CD), these UAT tests may be automated using a tool like Selenium. 

If the tests pass, you can merge the code into the master branch, where a “golden” build can be built and pushed immediately into production without any manual intervention. Amazon, Facebook, and Google are examples of companies that have achieved the 100% continuous delivery milestone and may deploy to production many times daily.

See More: Scrum vs. DevOps: Understanding the Key Differences

What Is a Jenkins Pipeline?

Pipelines are needed to run Jenkins. A pipeline is a set of steps the Jenkins server will execute to complete the CI/CD process’s necessary tasks. In the context of Jenkins, a pipeline refers to a collection of jobs (or events) connected in a specific order. It is a collection of plugins that allow the creation and integration of Continuous Delivery pipelines in Jenkins. 

The ‘Pipeline Domain-Specific Language (DSL)’ syntax also provides a collection of tools for modeling basic and sophisticated delivery pipelines ‘as code.’ Every task in the Jenkins pipeline is reliant on one or more events in some way.

Jenkins Pipelines comprise a powerful technology that includes a set of tools for hosting, monitoring, compiling, and testing code or code modifications across various tools such as:  

• Continuous integration server (Bamboo, Jenkins, TeamCity, CruiseControl, and others)
• Source control software (e.g., SVN, CVS, Mercurial, GIT, ClearCase, Perforce, and others)
• Build tools (Make, Ant, Ivy, Maven, Gradle, and others) 
• Automation testing framework (Appium, Selenium, UFT, TestComplete, and others) 

Jenkins pipeline is a user-created continuous delivery pipeline paradigm. It includes several plugins that aid in the different stages, from version control to user-facing delivery. This is important since, before being released, all software modifications and commits go through a lengthy procedure. The method has three phases: automated building, multi-step testing, and deploying procedures. 

There are two methods to construct a pipeline in Jenkins: directly define the pipeline using the user interface or create a Jenkinsfile using the pipeline as code technique. The pipeline process is described in a text file that employs Groovy-compatible syntax. Before constructing a Jenkins pipeline, here are the key terminologies to understand:

1. Multibranch Pipeline

It builds from various branches are automatically grouped to make branch management easier. Jenkins automatically generates a new project when a new branch is pushed to a source code repository. Other plugins can specify different branches, such as a Git branch, a Subversion branch, a GitHub Pull Request, and so on.

2. Archived Jenkins Pipeline

The file archive is secure; you may clear your workspace and perform subsequent builds. For instance, suppose you create the jar/HTML/js file, which is crucial for deployment. Your file gets replaced or erased after another build.

3. Pipeline speed

This is crucial if your pipeline saves huge files or complex data to variables in the script. Jenkins has a “Speed/Durability” label that allows you to maintain variables in scope for future usage while also allowing you to perform steps. However, if your pipelines spend practically all of their time waiting for a few shell/batch scripts to complete, it won’t help. This isn’t a one-size-fits-all capability.

 See More: What Is DevSecOps? Definition, Pipeline, Framework, and Best Practices for 2022

Key Features of Jenkins

Jenkins is simple to set up and customize. Jenkins has many plugins that give it a lot of versatility. It delivers code instantaneously, generates a report after deployment, highlights errors in code or tests, and detects and resolves various issues in near real-time. It’s also ideal for integration because it’s all done automatically. There is also a fantastic support community. Let us discuss these features in more detail:

1. A variety of plugins

Jenkins plugins are extensions to the Jenkins system. Providing integration points for CI/CD tools, sources and destinations is among the most prevalent plugin applications. They also aid with the expansion of Jenkins’ capabilities as well as the integration of Jenkins with other software. Plugins may be downloaded and installed using the Jenkins Web UI or CLI from the Jenkins Plugin repository. 

Nowadays, the Jenkins community reports that there are around 1,500 plugins available for a variety of applications. The thousands of plug-ins available allow for a great deal of customization. Plugins assist with integrating additional development tools into the Jenkins environment, adding new user interface components to the Jenkins Web UI, Jenkins administration, and enhancing Jenkins for build and source code management.

2. Simple installation and configuration

Jenkins is a self-contained Java software that doesn’t care about the platform it’s running on. It runs on all standard operating systems, including Windows, Unix versions, and Mac OS. Jenkins’ online interface is simple to set up and configure, including error checks and a built-in help feature. It comes as a standard installation as well as an a.war file. It’s simple to set up via the web interface after installing it. 

Jenkins is well-known, with an extensive knowledge base, comprehensive documentation, and a thriving community. It has learning materials that make installing, managing, and troubleshooting Jenkins installations much more accessible. While it is straightforward to set up (with clear instructions), production in Jenkins can be challenging to apply. Jenkinsfiles uses coding in its declarative or scripting languages to create production pipelines.

3. Open-source availability

Jenkins is an open-source project that is entirely free to use. Jenkins has a vibrant development community that meets both in-person and online regularly. This simplifies installation while restricting resources to a single computer, virtual machine, or container. Remember that Jenkins does not support federation between servers, which may cause performance problems.

In addition, a lack of federation might result in a proliferation of remote Jenkins servers that are hard to manage across a big organization. However, it is free to use because it is open-source. The community is quite involved, making it a very effective CI/CD tool.

4. A significant degree of extensibility

Jenkins’ plugin design allows it to be expanded in almost any way, giving it practically limitless capabilities. Jenkins’ community is its backbone, and members have played a vital role in the development (and testing) of almost 1500 plugins accessible in the Update Center. 

Jenkins is built so that it is extensible over any environment and platform for faster development, testing, and deployment. It is more adaptable thanks to its sizeable plug-in library, which allows for creating, deploying, and automating across various platforms. Jenkins, as well as its plugins, are written in Java. Fortunately, Java is a well-known corporate programming language with a large ecosystem. This provides Jenkins with a stable foundation upon which it can be built by utilizing basic design patterns and tools.

5. Server-based security

Jenkins security is concerned with both the server and the user. The server, whether a virtual machine or a bare metal server, is designed to enable the fewest number of processes to interface with it. This is achieved using a standard server operating system and networking security capabilities. Furthermore, using common mechanisms such as multifactor authentication, access to the server via the Jenkins UI is limited to the fewest number of people possible.

Jenkins’ internal user database has security features as well. The Jenkins web UI is used to access these capabilities. The “Security Realm” and the “Authorization Realm” are the two security realms that Jenkins supports.

 See More: What Is DevOps Lifecycle? Definition, Key Components, and Management Best Practices

Takeaway

Jenkins is among the most commonly used developer tools. Companies may use it to automate code build processes, speed up software production, and even enable learning when working with new software and technologies. In 2022, the Jenkins community will continue introducing new upgrades and improvements, such as secure automation, continuous delivery for plugins, better navigation on the plugin site, and much more. This makes it a promising tool for both new and experienced DevOps professionals. 

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