What is Jenkins?

Jenkins is an open-source continuous integration tool or automation server written in Java.

  1. Building projects
  2. Running tests to detect bugs
  3. Static code analysis
  4. Deployment

Jenkins Features:

The following are some facts about Jenkins that makes it better than other Continuous Integration tools:

  1. Adoption: Jenkins is widespread, with more than 147,000 active installations and over 1 million users around the world.
  2. Plugins: Jenkins is interconnected with well over 1,000 plugins that allow it to integrate with most of the development, testing, and deployment tools.

What is Continuous Integration?

Continuous Integration is a development practice in which the developers are required to commit changes to the source code in a shared repository several times a day or more frequently. Every commit made in the repository is then built. This allows the teams to detect the problems early. Apart from this, depending on the Continuous Integration tool, there are several other functions like deploying the build application on the test server, providing the concerned teams with the build and test results, etc.

Continuous Integration Example: Nokia

I am pretty sure you all have used Nokia phones at some point in your life. In a software product development project at Nokia, there was a process called Nightly builds. Nightly builds can be thought of as a predecessor to Continuous Integration. It means that every night an automated system pulls the code added to the shared repository throughout the day and builds that code. The idea is quite similar to Continuous Integration, but since the code that was built at night was quite large, locating and fixing bugs was a real pain. Due to this, Nokia adopted Continuous Integration (CI). As a result, every commit made to the source code in the repository was built. If the build result shows that there is a bug in the code, then the developers only need to check that particular commit. This significantly reduced the time required to release new software.

Continuous Integration With Jenkins

Let us imagine a scenario where the complete source code of the application was built and then deployed on the test server for testing. It sounds like a perfect way to develop software, but, this process has many flaws. I will try to explain them one by one:

  1. Developers have to wait until the complete software is developed for the test results.
  2. There is a high possibility that the test results might show multiple bugs. It was tough for developers to locate those bugs because they have to check the entire source code of the application.
  3. It slows the software delivery process.
  4. Continuous feedback pertaining to things like coding or architectural issues, build failures, test status and file release uploads were missing due to which the quality of software can go down.
  5. The whole process was manual which increases the risk of frequent failure.
  • First, a developer commits the code to the source code repository. Meanwhile, the Jenkins server checks the repository at regular intervals for changes.
  • Soon after a commit occurs, the Jenkins server detects the changes that have occurred in the source code repository. Jenkins will pull those changes and will start preparing a new build.
  • If the build fails, then the concerned team will be notified.
  • If the build is successful, then Jenkins deploys the built-in test server.
  • After testing, Jenkins generates feedback and then notifies the developers about the build and test results.
  • It will continue to check the source code repository for changes made in the source code and the whole process keeps on repeating.

HP Case Study:


  1. Gary’s team consisted of around 400+ developers distributed across countries like the USA, Brazil, and India but only made two software releases per year! This is because LaserJet models had separate code bases which developed enumerable inefficiencies.
  2. Software bugs were detected via manual testing after 6 weeks of writing code. Fixing a bug that incurred within a code weeks ago, was labor-intensive and tiresome for the developers.
  3. This is where the team needed a new approach to remove the bottleneck


The HP team adopted a Continuous Integration/Continuous Deployment (CI/CD) pipeline and test automation.

ETSY Case Study:


  1. Initially, Etsy struggled with the development of its organization because it adopted the monolithic architecture.
  2. Their deployment rate was about two times a week resulting in the isolation of departments. Etsy had to find a way out of this traditional system.


The new chief technology officer(CTO) brought in a team to adopt DevOps practices. As shown in the figure below, the CI/CD pipeline helped in deploying services about 50 to 100 times a day.

The Wrap-Up

I have done my best to give you all a basic idea about Jenkins and How it Works actually in the simplest way I can.



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I am tech enthusiast fascinated towards technology and its various disciplines including Big Data, Hadoop, Web Development, Competative Programming,ML,etc.