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Continuous Integration is the most important part of DevOps that is used to integrate various DevOps stages. Jenkins is the most famous Continuous Integration tool, I know you are curious to know the reason behind the popularity of Jenkins and I am pretty sure after reading this What is Jenkins blog, all your questions will get answered.
Jenkins is an open source automation tool written in Java with plugins built for Continuous Integration purpose. Jenkins is used to build and test your software projects continuously making it easier for developers to integrate changes to the project, and making it easier for users to obtain a fresh build. It also allows you to continuously deliver your software by integrating with a large number of testing and deployment technologies.
With Jenkins, organizations can accelerate the software development process through automation. Jenkins integrates development life-cycle processes of all kinds, including build, document, test, package, stage, deploy, static analysis and much more.
Jenkins achieves Continuous Integration with the help of plugins. Plugins allows the integration of Various DevOps stages. If you want to integrate a particular tool, you need to install the plugins for that tool. For example: Git, Maven 2 project, Amazon EC2, HTML publisher etc.
The image below depicts that Jenkins is integrating various DevOps stages:
Advantages of Jenkins include:
There are certain things about Jenkins that separates it from other the Continuous Integration tool. Let us take a look on those points.
Jenkins Key Metrics
Following are some facts about Jenkins that makes it better than other Continuous Integration tools:
It is evident from the above points that Jenkins has a very high demand globally. Before we dive into Jenkins it is important to know what is Continuous Integration and why it was introduced.
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.
Let us understand its importance with a use-case.
Continuous Integration in 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 of 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.
Now is the correct time to understand how Jenkins achieves Continuous Integration.
Let us imagine a scenario where the complete source code of the application was built and then deployed on test server for testing. It sounds like a perfect way to develop a software, but, this process has many flaws. I will try to explain them one by one:
It is evident from the above stated problems that not only the software delivery process became slow but the quality of software also went down. This leads to customer dissatisfaction. So to overcome such a chaos there was a dire need for a system to exist where developers can continuously trigger a build and test for every change made in the source code. This is what CI is all about. Jenkins is the most mature CI tool available so let us see how Continuous Integration with Jenkins overcame the above shortcomings.
I will first explain you a generic flow diagram of Continuous Integration with Jenkins so that it becomes self explanatory, how Jenkins overcomes the above shortcomings:
The above diagram is depicting the following functions:
You now know how Jenkins overcomes the traditional SDLC shortcomings. The table below shows the comparison between “Before and After Jenkins”.
|Before Jenkins||After Jenkins|
|The entire source code was built and then tested. Locating and fixing bugs in the event of build and test failure was difficult and time consuming, which in turn slows the software delivery process.||Every commit made in the source code is built and tested. So, instead of checking the entire source code developers only need to focus on a particular commit. This leads to frequent new software releases.|
|Developers have to wait for test results||Developers know the test result of every commit made in the source code on the run.|
|The whole process is manual||You only need to commit changes to the source code and Jenkins will automate the rest of the process for you.|
After “What is Jenkins” my next blog i.e. Jenkins Tutorial focuses on the distributed architecture of Jenkins and also explains how to create a build in Jenkins.
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