What is Jenkins and How Does it Work?

Introduction to Jenkins

Jenkins is a game-changing automation tool that has revolutionized the way software development is carried out. It serves as the backbone of Continuous Integration and Continuous Delivery (CI/CD) practices, ensuring faster and more reliable software delivery.

At its core, Jenkins is a powerful open-source automation server that enables developers to automate various tasks throughout the software development lifecycle. From building and testing code to deploying applications, Jenkins handles these repetitive tasks with ease, freeing up valuable time for developers to focus on more critical aspects of their work.

Jenkins acts as a bridge between various tools and processes involved in software development. It integrates seamlessly with version control systems, such as Git and Subversion, and allows developers to trigger automated builds and tests whenever new code is committed. This capability ensures that any changes made to the codebase are immediately validated, preventing integration issues that can arise in large development teams.

One of the key advantages of Jenkins is its extensibility. With a vast array of plugins available, developers can customize and enhance Jenkins to fit their specific project requirements. These plugins enable integrations with various tools, such as cloud platforms, testing frameworks, and deployment services, making Jenkins a versatile and adaptable tool for any development environment.

History

Jenkins has a fascinating history that reflects the evolution of Continuous Integration (CI) practices. Originally known as Hudson, Jenkins was developed by Kohsuke Kawaguchi while working at Sun Microsystems. However, due to a trademark dispute in 2011, the project was renamed Jenkins and forked to create a separate entity.

In a significant move, Jenkins was eventually donated to the Eclipse Foundation, where it continued to thrive as an open-source project. However, its journey did not end there. Today, Jenkins development is managed under the governance of the CD Foundation, an organization operating within the Linux Foundation.

The concept of Continuous Integration has evolved significantly over time. Initially, a daily build was considered standard practice. However, modern CI dictates that each team member submits their work, referred to as a "commit," on a daily or even more frequent basis. With each significant change, a build is triggered, providing continuous feedback on the software's status.

By embracing Continuous Integration effectively, development teams reap various benefits. One of the significant advantages is the early detection of deficiencies during the development process. This results in smaller, less complex defects that are easier to address, leading to improved software quality.

Jenkins has played a pivotal role in driving the CI movement forward, supporting agile development methodologies and enabling teams to deliver software with enhanced efficiency and reliability. Its historical journey and its present role as a prominent CI/CD automation tool have solidified Jenkins' position as a critical asset for software development teams worldwide. That is what is Jenkins.

How Does Jenkins Work?

When wondering what is Jenkins, you might wonder how does it work as well. Jenkins operates as a versatile server, compatible with various platforms, including Windows, MacOS, Unix variants, and especially Linux. To run Jenkins, a Java 8 VM and above are required, and it can be executed using the Oracle JRE or OpenJDK. Typically, Jenkins functions as a Java servlet within an application server like Jetty or Apache Tomcat. Moreover, recent advancements have adapted Jenkins to run in Docker containers, with read-only Jenkins images accessible on the Docker Hub online repository.

At the core of Jenkins' functionality lies the concept of pipelines. These pipelines consist of a sequence of steps that the Jenkins server follows to execute the essential tasks of the CI/CD process. The pipeline configuration is stored in a plain text file known as the Jenkinsfile. Using a curly bracket syntax akin to JSON, the Jenkinsfile outlines the steps, each declared as commands with specific parameters enclosed in curly brackets. Once the Jenkins server reads the Jenkinsfile, it carries out the defined commands, efficiently moving the code through the pipeline, from committed source code to production runtime.

The beauty of Jenkins lies in its flexibility. Developers can create Jenkinsfiles either through a graphical user interface (GUI) or by writing code directly, allowing teams to tailor the CI/CD process to their unique project requirements. Jenkins empowers development teams by automating the entire software delivery pipeline, from building and testing to deployment, simplifying and accelerating the development lifecycle.

How To Install Jenkins?

Installing Jenkins is a straightforward process, and it is available for various operating systems, including Unix flavors like Ubuntu, Gentoo, and FreeBSD, as well as Mac OS. If you prefer a containerized approach, Jenkins can be easily deployed in a Docker Container. To initiate the installation, you can visit the official Jenkins website here and download the required Jenkins installer.

One of the installation options is the Jenkins installer provided as a generic Java Package (.war). If you plan to use Jenkins in conjunction with Selenium for performing cross-browser testing, we recommend opting for the .war file. Using this approach allows you to observe the test scenarios executing on browsers in the non-headless mode, providing valuable insights into the test execution process.

How To Configure Jenkins?

Configuring Jenkins involves setting up user management, assigning roles to users, and configuring Master and Agents. To manage users, navigate to "Manage Jenkins" and then "Configure Global Security." You can create users and assign roles to them using the "Matrix-based security" authorization strategy.

For a more role-based authorization approach, install the "Role-based Authorization Strategy" plugin. Change the Authorization strategy to "Role-Based Strategy," and then go to "Manage Jenkins" to access "Manage and Assign Roles." Here, you can create global roles, such as "developer," and assign specific permissions to them.

You can then proceed to assign Project Roles, Item roles, or Node roles, depending on your project's needs. For instance, you can specify that the "developer" role has access to build jobs that start with a specific pattern using Regex.

By configuring Jenkins effectively, you can ensure that access is granted appropriately and that teams can collaborate efficiently in the development process.

Plugins

We can't answer what is Jenkins without talking about plugins. Jenkins plugins are powerful enhancements that extend its capabilities and allow seamless integration with other software. With over 1500 plugins available from the Jenkins Plugin repository, developers can easily download and incorporate them through the Web UI or CLI.

These plugins enrich the Jenkins environment, integrate developer tools, improve the Web UI, aid in administration, and enhance build and source code management. They also serve as crucial integration points for various CI/CD sources and destinations, including version control systems, container runtimes, virtual machine hypervisors, and cloud platforms.

Written in Java and utilizing unique design patterns, these plugins provide versatile functionality and UI representation in the Jenkins Web UI. With Jenkins plugins, developers can customize their workflows, making Jenkins an adaptable and powerful automation tool.

Security

What is Jenkins security stance? It surely takes security seriously, ensuring protection at both the server and user levels. For server security, access to the server is carefully configured, limiting communication to essential processes through standard OS and networking security measures.

User access to the Jenkins UI is strictly controlled, employing multifactor authentication and other standard techniques to restrict entry to authorized personnel only. The HTTP server serving the UI reinforces security measures, further fortifying the access control.

Jenkins provides robust security features for its internal user database, managed through the Jenkins Web UI. With two security realms, the Security Realm allows administrators to control user access, while the Authorization Realm defines specific permissions for each user. By diligently addressing security concerns, Jenkins establishes a safe and trusted automation environment for development teams, protecting against potential threats and ensuring the confidentiality and integrity of critical data.

Advantages of Jenkins

• Jenkins is highly extensible through plugins, allowing seamless integration with various IT environments.
• It offers rich scripting and declarative languages for customized pipelines, adapting well to complex hybrid and multi-cloud systems.
• Jenkins has a well-established history, leading to widespread adoption and a supportive community.
• Its extensive documentation and knowledge base make installation, management, and troubleshooting easier.
• Jenkins is built on the robust foundation of Java, leveraging its broad ecosystem and design patterns.

Disadvantages of Jenkins

• Implementing production Jenkins, especially for complex pipelines, may require skilled development efforts.
• Jenkins follows a single-server architecture, limiting resource scalability, and may lead to performance issues.
• Lack of federation across servers can result in difficulties managing multiple Jenkins instances in large enterprises.
• Jenkins relies on older Java architectures, hindering compatibility with newer technologies like Spring Boot or GraalVM.
• Developing complex pipelines with Jenkinsfiles may be challenging, requiring proficient coding, debugging, and maintenance skills.