Case Study and Industry Use Cases: What is Jenkins, Why to Use It, How It Works and Where To use it ?

Jenkins is a self-contained, open source automation server which can be used to automate all sorts of tasks related to building, testing, and delivering or deploying software.

Jenkins is one of the leading open-source automation server which provides hundreds of plugins to support building, deploying and automating any project which in turns helps in continuous integration and build automation. The basic functionality of Jenkins is to execute a predefined list of tasks i.e. as soon as there is a change in repository, triggers a pipeline that executes different jobs and performs the tasks.

The image below depicts that Jenkins is integrating various DevOps stages:

Architecture Of Jenkins

Before we dive into how does Jenkins work, we must understand the architecture of Jenkins. These are the series of steps that outlines the interaction between different elements in Jenkins:

• Developers do the necessary modifications in the source code and commit the changes to the repository. A new version of that file will be created in the version control system that is used for maintaining the repository of source code.
• The repository is continuously checked by Jenkins CI server for any changes (either in the form of code or libraries) and changes are pulled by the server.
• In the next step, we ensure that the build with the ‘pulled changes’ is going through or not. The Build server performs a build with the code and an executable is generated if the build process is successful. In case of a build failure, an automated email with a link to build logs and other build artifacts is sent to the developer.
• In case of a successful build, the built application (or executable) is deployed to the test server. This step helps in realizing continuous testing where the newly built executable goes through a series of automated tests. Developers are alerted in case the changes have caused any breakage in functionality.
• If there are no build, integration, and testing issues with the checked-in code, the changes and tested application are automatically deployed to the Prod/Production server.

Why Pipeline?

Jenkins is, fundamentally, an automation engine which supports a number of automation patterns. Pipeline adds a powerful set of automation tools onto Jenkins, supporting use cases that span from simple continuous integration to comprehensive CD pipelines.

By modeling a series of related tasks, users can take advantage of the many features of Pipeline:

• Code: Pipelines are implemented in code and typically checked into source control, giving teams the ability to edit, review, and iterate upon their delivery pipeline.
• Durable: Pipelines can survive both planned and unplanned restarts of the Jenkins controller.
• Pausable: Pipelines can optionally stop and wait for human input or approval before continuing the Pipeline run.
• Versatile: Pipelines support complex real-world CD requirements, including the ability to fork/join, loop, and perform work in parallel.
• Extensible: The Pipeline plugin supports custom extensions to its DSL footnote:dsl:[] and multiple options for integration with other plugins.

While Jenkins has always allowed rudimentary forms of chaining Freestyle Jobs together to perform sequential tasks, Pipeline makes this concept a first-class citizen in Jenkins.

Building on the core Jenkins value of extensibility, Pipeline is also extensible both by users with Pipeline Shared Libraries and by plugin developers.

Advantages of Jenkins include:

• It is open source and it is user-friendly, easy to install and does not require additional installations or components.
• It is free of cost and easy to install.
• Rich Plugin ecosystem. The extensive pool of plugins makes Jenkins flexible and allows building, deploying and automating across various platforms.
• It has 1500+ plugins to ease your work. If a plugin does not exist, you can code it and share it with the community.
• It is built with Java and hence, it is portable to all the major platforms.