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What is Jenkins? Features & How it Works [CI/CD Integration]
Table of Contents
When we talk about continuous integration or continuous delivery (CI/CD) tools, there’s one tool that tops that list: Jenkins. It is the most famous open-source CI/CD tool used to support DevOps with several other cloud-native tools.
Jenkins is an open-source automation server. With this incredible server, it is possible to escalate the software development process by automation. Throughout the life cycle, it helps you manage software delivery processes. Various life cycle stages consist of building, testing, documenting, packaging, staging, deployment, and much more.
This article will assist you in understanding the Jenkins ecosystem in detail.
What is Jenkins?
Kohsuke Kawaguchi created Jenkins in 2004. The sole objective of Jenkins is to perform continuous integration. Jenkins is the most popularly chosen solution for continuous delivery across the globe.
Jenkins is a continuous integration tool written in Java that allows continuous development, test, and deployment of newly created codes.
Jenkins was written originally by the community as a build and release tool. It is a server-based application and requires a web server like Apache Tomcat. Jenkins allows users to build and test projects continuously making it easier for developers to integrate changes to the project, and making it easier for users to obtain a fresh build.
Now, let us analyze the concept of continuous integration!
What is Continuous Integration?
Continuous integration is a procedure to integrate all the code changes done by several developers in one project. A code is repeatedly tested after a commit to guarantee the code is error and bug-free.
As there are several team members in the development team, there are chances of bugs in multiple commits. With CI, it is easier to detect these bugs early before pushing the changes in production. The integration of every piece of code into one executable form takes place, known as a build. If this build is green, then the executed code is ready for deployment. Otherwise, the team has to settle the bug and repeat the entire process from scratch.
This is a continuous process; therefore, the name, continuous integration or continuous deployment.
Furthermore, the backbone of this tool is the Jenkins community. This incredible community supports the project and plays a significant role in its success. Jenkins has grown exponentially since its development. At present, there are millions of downloads and active users of Jenkins.
But the real question is, how does Jenkins achieve continuous integration? It uses plug-ins to integrate several DevOps stages. If you wish to integrate, all you need is to install the plug-ins, and you are good to go!
What is Jenkins Used For?
As a continuous integration tool, Jenkins helps development teams identify errors in the early stages of a project, as well as automate the integration process of new code. CI/CD is a significant part of the DevOps process and plays an important role in everything from startups to the largest tech companies like Netflix.
The actual involvement of Jenkins in the development process is as follows:
- Developers begin committing code to the repository, which Jenkins checks regularly
- If there is a change in the code, Jenkins compiles the code
- If there is a failed build, the developer gets notified
- If the build is successful, the code is deployed to production
The large number of plugins are also quite useful, as they offer a lot of customizability. As a whole, it’s quite flexible and can work in different environments. Jenkins also allows you to schedule tests based on particular events, and you can set the frequency of these tests. You don’t have to run the test manually.
Features of Jenkins
Jenkins has some features that really sell it as a CI/CD tool. These are some of them:
- Easy to set up
- Supports most environments
- Easy distribution
The availability of thousands of plug-ins allows for a large degree of customizability. The developers have the opportunity to integrate these plug-ins with development and testing tools, and tailor the architecture to serve a lot of possibilities.
Easy to Set Up
There are executable packages that quickly install Jenkins on Windows, Mac and Unix operating systems, as it is just a self-contained Java program. You can get it set up in under 10 minutes.
Supports Most Environments
Jenkins supports most environments, including cloud-based architecture. This makes it handy as teams begin to use different environments. All major cloud platforms are supported, including Amazon, Azure, Google, and IBM Cloud.
Jenkins is open-source and free to use. Jenkins has an enthusiastic developer community that frequently holds meetings, both in-person and online.
It’s easy to distribute Jenkins across work machines, which makes building, testing, and deployment faster.
After understanding the basics, let us analyze the workings of Jenkins in detail.
How Does Jenkins Work?
Initially, a developer commits the code to the source code. Now, the Jenkins server keeps a regular check at the repository. As soon as the commit occurs, the Jenkins server discovers the changes and pulls them. Further, it prepares a new build.
If in between the tests, the build does not pass, the developer is instantly notified to take suitable action. Now, Jenkins gets ready for the deployment of the build to an environment that allows any User Acceptance Testing (UAT) before the release into the production pipeline.
The above-performed UAT tests are automated with the help of a tool known as Selenium to achieve continuous delivery. The code is appended to the master branch to create a golden build if the test is passed. It is then directly deployed into the production pipeline.
After testing, Jenkins notifies the developers regarding the test results and build.
Now, the whole cycle goes on repeatedly.
In Jenkins, you can easily figure out which commit was the reason behind the failure of the build. However, if all the unit tests pass, the build pipeline will move forward to the next stage.
Jenkins runs parallel builds across several machines to decrease the total time consumed to complete the other activities.
Moreover, several multinational companies such as Google and Amazon have achieved the continuous delivery milestone. It helps them to deploy to production several times a day.
Jenkins’ continuous integration pipeline is an incredibly powerful tool that inhabits several tools for different purposes such as hosting, monitoring, testing the code, and compilation.
Here is a list of such tools:
- Continuous integration server: Jenkins, TeamCity, etc
- Source control tool: CVS, GIT, SVN, etc
- Automation testing framework: Appium, Selenium, UFT, etc
- Build tool: ANT, Ivy, Make, Gradle
What is the Jenkins Pipeline?
The interconnection of several tasks and events in a sequence is known as the Jenkins Pipeline. It is a pool of plugins that helps the continuous delivery pipelines with easy integration and implementation.
The primary feature of a Jenkins pipeline is that every task or job is dependent on some other task or job. However, there are different states in the case of continuous delivery pipelines: build, test, deploy, release, etc. These states are interconnected with each other.
A CD pipeline is a sequence of events in which these states work. It is an automated expression required by the processes to get version control software. Every change made to the software has to pass via multiple complex processes before the release.
This step reliably guarantees software development as it includes multiple testing and deployment stages.
How to Implement the Pipelines
To define the Jenkins pipeline, JenkinsFile is used. It is a text file. It is used for the implementation of pipelines in code. This process is explained using DSL.
There are two syntaxes used to define the JenkinsFile.
- Scripted pipeline syntax: it runs on Jenkins master and uses its resources to convert pipelines into atomic commands.
- Declarative pipeline syntax: it is simple to create pipelines with this syntax. There are easy ways to control several aspects related to the execution of the pipelines.
Some of the advantages of JenkinsFile include:
- It is easier to review the code on the pipeline.
- You can conduct an audit on the Jenkins pipeline.
- It helps to execute full requests for the pipelines created for several branches.
With the help of continuous integration abilities, Jenkins automates the software development process.
You can have various users in the Jenkins pipeline for editing and executing several processes.
You can pause Jenkins pipeline processes till you get any user output.
Architecture of Jenkins
Jenkins adheres to a master-slave architecture technique to manage distributed builds. Let us dig deeper and form a better understanding.
When we talk about the single Jenkins server, there are some impediments:
- You may want to test your builds on several environments, but it is not possible to execute that on a single Jenkins server.
- A single server is unable to bear the load of heavier projects.
Therefore, Jenkins came up with a distributed architecture known as master-slave architecture.
- Jenkins Master
- Jenkins Slave
This is the primary Jenkins server. It handles a plethora of tasks and executes them directly. A few of them are mentioned below:
- Scheduling build jobs.
- Record and present build results.
- Delivering build to slaves to execute.
- Monitor slaves both online and offline.
Jenkins slaves run on the remote server. The Jenkins master orders the slave to execute several tasks. Here are some key characteristics of the Jenkins slave:
- The Jenkins slave has to obey the orders of the Jenkins master and execute the build jobs given by the master.
- Slaves can run on several operating systems.
- It is possible to configure a project to run on a specific slave machine.
Moving forward, let us now talk about the advantages associated with Jenkins.
Advantages of Jenkins
There are abundant advantages of this open-source tool. We have curated a list presenting the most impressive benefits of Jenkins:
- Jenkins is user-friendly and easy to install. You do not require extra installations or tools with it.
- It is platform-independent. You can find Jenkins on several platforms and operating systems such as Windows, Linux, OS X, etc.
- Configuration of Jenkins is extremely easy. You can modify or extend it. Moreover, the deployment of code and the generation of test reports are done quickly. For continuous delivery and continuous integration, you can configure Jenkins according to your requirements.
- It consists of a rich plugin ecosystem. The massive collection of plug-ins makes Jenkins more flexible and permits building, deploying, and automating across several platforms.
- It is free of cost.
- With Jenkins, you receive incredible support. As you have seen, it is the most popular open-source server available; therefore, you receive agile teams to resolve your queries all across the globe.
- Along the journey, there are multiple issues faced by the users. Such obstacles are solved immediately, which helps to keep the software in a position where you can release it any time with utmost safety.
- The integration work is mostly automated. Therefore, there are fewer integration problems. This further helps to save money and time in the journey of every project.
- The developers can detect errors in the code as soon as possible. This saves them from large-scale error-coated integrations.
Moreover, in collaboration with Docker, Jenkins escalates the progress of the development team working on different projects. It also provides the software infrastructure with Agile development throughout the journey.
Disadvantages of Jenkins
There are several flaws associated with Jenkins as well. We have curated a list of some of them:
- The management of Jenkins is a hard nut to crack. It runs on a server and requires skills as a server administrator to monitor all the activities associated with it.
- In some aspects, it lacks user-friendliness when compared to current UI trends.
- The process to install and configure Jenkins is pretty tedious.
- The continuous integration pipeline breaks whenever changes occur in the settings. The integration halts and needs interference by the developer.
As you have seen, Jenkins is an extremely popular application across the globe. Millions of installations have taken place, and the number is soaring higher day by day.
With Jenkins, software companies have the opportunity to escalate the software development process. It is possible to automate, build, and test processes at a rapid rate. It gives you the liberty to track repeated tasks that occur in the development of a project.
In a nutshell, if you wish to escalate your organization’s progress in the field of software development, then Jenkins is the best pick for you!
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