What is Jenkins? Working with CI/CD Pipeline and Features

Ever wondered how software gets updated so quickly? Jenkins is the answer. But What is Jenkins, exactly? Let us explain. Jenkins is an open-source automation server that accelerates development by automating the building, testing, and deployment of code. 

With Jenkins, DevOps teams can keep their code in a constant state of readiness for release. It’s highly customisable too thanks to a vast array of plugins that cater to any team’s unique needs. Think of Jenkins as your tireless assistant, always on the job! 

Dive into this blog to uncover the question “What is Jenkins?”, how it works, what its diverse features are, and what many advantages it offers. Discover why Jenkins is an essential tool in any development pipeline. 

Table of Contents 

1) Understanding What is Jenkins? 

2) How Jenkins Works? 

3) Jenkins Core Concepts 

4) What is the use of Jenkins in DevOps? 

5) What is Jenkins DevOps Pipeline? 

6) DevOps CI CD with Jenkins 

7) Key Features of Jenkins 

8) Advantages and Disadvantages of Jenkins 

9) Conclusion 

Understanding What is Jenkins? 

Jenkins is an Open-source Continuous Integration (CI) server. It handles various stages of software delivery, such as building, documenting, automated testing, packaging, and static code analysis. Many development teams use Jenkins as a popular DevOps tool.
 

Jenkins automation starts with code changes in repositories like GitHub, Bitbucket, and GitLab. It integrates with build tools like Maven and Gradle. Although Jenkins supports Docker and Kubernetes for testing and packaging, it is not natively designed for these container technologies. 
 

 

How Jenkins Works? 

Jenkins runs on various platforms like Windows, macOS, Unix variants, and especially Linux. It requires Java 8 or above, using the Oracle Java Runtime Environment or OpenJDK. Jenkins typically operates as a Java Servlet within a Jetty application server but can also run on other servers like Apache Tomcat. 

Once installed, Jenkins helps developers with a repeatable workflow that builds, tests, deploys, and releases new software. This workflow, known as a pipeline, is customised for each project and used repeatedly. A Jenkins pipeline automates tasks such as code testing, staged deployment to test environments, and final deployment to production. 

Jenkins is especially useful for deploying software to Microservices Architectures. It integrates with Docker for containerisation and Kubernetes for container orchestration. One key goal of microservices is frequent updates. Jenkins supports this by providing the necessary automation for faster and more numerous service updates. 

Jenkins Core Concepts 

Now that you understand what is Jenkins and how it works, let’s explore the key concepts of Jenkins. 

1) Jenkins Controller (Formerly Master) 

The Jenkins Controller acts as the central node in a distributed build setup. It manages other nodes, known as Jenkins Agents, and can also execute builds, though it is less scalable. The controller handles the central configuration, manages agent connections, loads plugins, and coordinates project workflows. 

2) Jenkins Agent (Formerly Slave) 

A Jenkins Agent connects to the Jenkins Controller to run build jobs. You need to install Java on a physical machine, Virtual Machine, cloud instance, Docker image, or Kubernetes cluster to use an agent. Multiple agents can balance build load, improve performance, and create a secure environment independent of the controller. 

3) Jenkins Node 

A Jenkins node refers to both Agents and Controllers. It is a machine used to build projects and pipelines. Jenkins monitors the health of all nodes and takes a node offline if its metrics drop below a threshold. 

4) Jenkins Project (Formerly Job) 

A Jenkins project or task is an automated process created by users. Jenkins offers a variety of build tasks for Continuous Integration, with more available through a large ecosystem of plugins. 

5) Jenkins Plugins 

Plugins are community-developed modules that add features to Jenkins. You can install or upgrade plugins from the Jenkins dashboard. 

6) Jenkins Pipeline 

A Jenkins Pipeline is a user-created model for defining step-by-step actions in a software pipeline. It includes automated builds, multi-step testing, deployment procedures, and security scanning. Pipelines can be created in the user interface or as a "Jenkinsfile" using a Groovy-compatible text format, which can be either declarative or scripted. 

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What is the use of Jenkins in DevOps? 

Jenkins is popular because it tracks and monitors repetitive tasks during a project's development. For example, it tests builds and alerts your team to mistakes early on. Here are some top use cases: 

1) Deploying Code to Production 

If all tests pass, Jenkins can automatically publish code to staging or production environments, a process known as continuous deployment. Changes are tested in a dynamic staging environment before being distributed to a central staging system, pre-production, or production. 

2) Automating Tasks 

Jenkins automates workflows and tasks. Developers working on multiple environments can use Jenkins to automate installations or updates, which can otherwise be error-prone and time-consuming. 

3) Speeding up Code Review Processes 

Jenkins integrates with other DevOps tools and notifies users when a merge request is ready. It also shows code coverage differences, cutting the time needed for code reviews and ensuring a transparent development process. 

4) Facilitating Continuous Integration 

Jenkins pipelines connect events and tasks to drive Continuous Integration. It uses plugins to simplify the integration and implementation of CI/CD Pipelines, where each task relies on another. 

5) Boosting Code Coverage 

Jenkins can verify code to increase test coverage, encouraging team transparency and accountability. Test results are shown on the build pipeline, ensuring adherence to guidelines. 

6) Improving Coding Efficiency 

Jenkins improves development efficiency by converting command prompt codes into Graphical User Interface (GUI) button clicks. It supports manual testing without switching environments, comparing code to the current state of a code base in a production-like environment. 

7) Streamlining Audits 

Jenkins collects console output from tasks, making troubleshooting straightforward. The time stamper plugin helps identify and tweak slow operations. 

8) Synchronising Through Slack 

Jenkins integrates with Slack, a popular communication platform for large teams. It shares triggered activities, times, usernames, and outcomes with team members. 

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What is Jenkins DevOps Pipeline? 

Pipelines are essential for Jenkins. They are sequences of steps that complete CI/CD tasks. A Jenkins pipeline uses plugins to create Continuous Delivery pipelines and models basic and complex delivery pipelines 'as code.' 

Jenkins Pipelines include tools for hosting, monitoring, compiling, and testing code across various systems like CI servers (e.g., Bamboo, TeamCity), source control software (e.g., Git, SVN), build tools (e.g., Maven, Gradle), and automation testing frameworks (e.g., Selenium, UFT). 

Jenkins pipelines involve three phases: automated building, multi-step testing, and deployment. You can create a pipeline using the user interface or a Jenkinsfile with Groovy-compatible syntax. Before constructing a Jenkins pipeline, here are the key terminologies to understand: 

a.    Multibranch Pipeline: Automatically, groups are built from various branches, simplifying management. 

b.    Archived Pipeline: Secures file archives, ensuring essential files remain even after new builds. 

c.    Pipeline Speed: Maintains variables for future use while performing steps, though it may not help if waiting for scripts. 

DevOps CI CD with Jenkins 

Jenkins uses the CI/CD Pipeline methodology to streamline DevOps tasks. The pipeline has two parts: 

Continuous Integration (CI) 

a) Developers regularly add new code to improve the project. 

b) CI detects bugs before integrating new code into the codebase. 

Continuous Delivery and Deployment (CD) 

a) CD automates building and packaging code for deployment to test, staging, and production environments. 

b) Continuous deployment automates the software delivery process, ensuring that the code reaches its destination. 

Automation in Jenkins reduces errors by encoding best practices into the software. It ensures a desired state and increases release velocity, reducing stress on development and operations teams by eliminating the need for overnight rollouts. 

Jenkins integrates with Docker and Kubernetes to build and orchestrate containers into apps, streamlining development through continuous building, testing, and deployment. This workflow enhances developers' efficiency. 

Key Features of Jenkins 

Jenkins is simple to set up and customise, offering many versatile plugins. It instantly delivers code, generates deployment reports, highlights errors, and resolves issues in near real-time. Its automatic integration and supportive community make it ideal for DevOps teams. Let's dive into its features: 

 

1) Wide Range of Plugins 

Jenkins plugins extend its capabilities and integrate CI/CD tools. The community offers around 1,500 plugins for various applications, which can be downloaded and installed from the Jenkins Web UI or Command Line Interface (CLI). 

2) Easy Installation and Setup 

Jenkins, a self-contained Java software, runs on all major operating systems. Its online interface is easy to set up and configure, with built-in error checks and help features. Comprehensive documentation and a thriving community support learning and troubleshooting. 

3) Open-source Accessibility 

Jenkins is free and open-source, with a vibrant community contributing to its development. While it doesn't support server federation, which can lead to performance issues, its open-source nature makes it a highly effective CI/CD tool. 

4) High Level of Extensibility 

Jenkins' plugin design allows extensive customisation. The community has developed nearly 1,500 plugins, making Jenkins adaptable to any environment. Written in Java, Jenkins benefits from a stable foundation and a large ecosystem. 

5) Server-side Security 

Jenkins ensures security for both the server and the user. Servers use standard OS and networking security features, while the Jenkins UI employs common mechanisms like multifactor authentication. The internal user database offers additional security features accessed through the web UI. 

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Advantages and Disadvantages of Jenkins 

Like all software, there are pros and cons to Jenkins as well. Some of them are mentioned below. 

Advantages 

a) Extendable with Plugins 

Jenkins is adaptable to changing IT environments due to its extensive plugin support. Plugins and scripting languages allow highly customised pipelines, fitting well into complex systems. 

b) Flexibility and Longevity 

Jenkins has been widely deployed due to its flexibility and long history. It is well-understood, with a broad knowledge base, extensive documentation, and abundant community resources. This makes installation, management, and troubleshooting easier. 

c) Java-Based 

Jenkins and its plugins are built on Java, a proven enterprise development language with a broad ecosystem. This provides a stable foundation, allowing extension using common design patterns and frameworks. 

Disadvantages 

a) Complex Implementation 

While easy to install, production Jenkins can be challenging to implement. Developing production pipelines with Jenkinsfiles requires coding, which can be difficult to debug and maintain, especially for complex pipelines. 

b) Single-Server Architecture 

Jenkins' single-server architecture caps resources to a single computer, VM, or container, leading to performance issues and difficult management across large enterprises due to the lack of server federation. 

c) Older Java Technologies 

Jenkins relies on older Java architectures like servlets and Maven. Even with Docker, Jenkins maintains a monolithic architecture and is not designed for newer technologies like Spring Boot or GraalVM. 

Conclusion 

We hope you read and understood What is Jenkins in this blog. Jenkins is an Open-source Automation Server that streamlines DevOps tasks through CI/CD Pipelines. It offers flexibility with numerous plugins and a supportive community. Jenkins simplifies code integration, testing, and deployment, making it a valuable tool for efficient Software Development. 

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