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Jenkins, originally developed as Hudson by Sun Microsystems, has evolved into a robust automation server maintained by a vast community of contributors. Its primary purpose is to automate the repetitive tasks involved in the software development lifecycle, such as building, testing, and deploying applications.
Jenkins CI/CD, originally developed as Hudson by Sun Microsystems, has evolved into a robust automation server maintained by a vast community of contributors. Its primary purpose is to automate the repetitive tasks involved in the software development lifecycle, such as building, testing, and deploying applications.
Introduction to Jenkins CI/CD:
Jenkins CI/CD or jenkins pipelineis a free tool that helps with continuous integration (CI). It's used by many teams to handle different parts of the software delivery process, like building, testing, and packaging. Jenkins gets started when there are changes made to the code in places like GitHub, Bitbucket, or GitLab. It works well with tools like Maven and Gradle for building projects. Jenkins also works with container technologies like Docker and Kubernetes to test and package software, but it's not made specifically for Kubernetes or containers.
Jenkins Pipeline Architecture Overview:
At its core, Jenkins follows a distributed architecture model, enabling scalability and flexibility to accommodate various development environments and workloads. The architecture comprises several key components:
1) Master Node:
The Jenkins master node serves as the central hub responsible for coordinating tasks and managing the build environment. It hosts the Jenkins web interface and schedules build jobs based on triggers or user commands. Through this web interface, we can set up and manage our projects or tasks. However, the actual work of building happens on Nodes or Slaves. By default, Jenkins comes with one of these nodes already set up and running. If we need more, we can add them by providing their IP addresses, along with a username and password, using methods like ssh, or webstart.
2) Nodes (or Slaves):
Agent nodes, also known as slave nodes, are the worker machines responsible for executing build jobs. These nodes can be distributed across different physical or virtual machines to parallelize build processes and optimize resource utilization.
3) Build Jobs:
A build job represents a specific task or set of tasks to be executed by Jenkins. It includes instructions on source code retrieval, build commands, testing procedures, and deployment actions. Jenkins allows users to define build jobs using declarative or scripted pipelines, offering flexibility in workflow design.
4) Plugins:
Jenkins plugins has a vast ecosystem of plugins that extend its functionality to integrate with various tools, technologies, and services. Plugins facilitate seamless integration with version control systems (e.g., Git, SVN), build tools (e.g., Maven, Gradle), testing frameworks, and cloud platforms, among others. You can install/upgrade all available plugins from the Jenkins dashboard.
5) Build Executors:
Executors are the execution agents responsible for running build jobs on agent nodes. Jenkins supports different types of executors, including the built-in Java Virtual Machine (JVM) executor and custom executors for specific use cases.
Workflow Execution in Jenkins:
The typical workflow execution in Jenkins follows these steps:
1) Triggering:
Build job can be triggered manually by a user, periodically at predefined intervals, or automatically in response to events such as code commits or pull requests.
2) Checkout:
Jenkins retrieves the source code from the configured version control repository to the workspace directory on the agent node.
3) Build:
Jenkins executes the build steps defined in the job configuration, which may involve compiling code, running tests, and generating artifacts.
4) Post-build Actions:
After the build completes, Jenkins can perform various post-build actions, such as archiving artifacts, sending notifications, triggering downstream jobs, or deploying the application to target environments.
Scalability and High Availability:
Jenkins provides mechanisms for scaling and ensuring high availability to meet the demands of enterprise-grade jenkins CI/CD pipelines. Administrators can configure Jenkins in a master-slave setup, where multiple master and agent nodes are deployed across a cluster to distribute workloads and mitigate single points of failure. Additionally, Jenkins supports cloud-native architectures, allowing it to run as containers orchestrated by platforms like Kubernetes.
Conclusion:
Jenkins' architecture reflects its versatility and adaptability to diverse software development environments. By understanding the underlying components and workflow execution model, users can harness the full potential of Jenkins to streamline their CI/CD processes, improve development efficiency, and deliver high-quality software at scale. As organizations continue to embrace DevOps practices, Jenkins remains a trusted ally in their journey towards automation and continuous delivery excellence.