introduction
Jenkins is a platform for building aContinuous integration/continuous delivery(CI/CD) Vicinity. The system offers many different tools, languages, and automation tasks to help create pipelines when developing and deploying programs.
Although Jenkins has to script some automation steps, the program offers a fast and robust method for systematizationSoftware development lifecycle.
Read on to learn more about Jenkins and why it's one of the leading DevOps tools today.
Jenkins-Definition
Jenkins is an automation server written in Java that helps build, test, and continuously deploy software. The open source system is currently one of the leading automation servers.
In general, Jenkins provides support for:
- Various version control tools such asGit.
- Ant build andApache Maven-based projects.
- Running bash scriptsand Windows batch files.
A brief history of Jenkins
The Jenkins project started in 2004 under the Hudson name. Developer Kohsuke Kawaguchi, who worked at Sun Systems, wanted to create a method for continuous integration. The idea was to test the code before committing to avoid breaking builds.
The idea proved successful and quickly spread to the rest of his team. As a result, Kohsuke Kawaguch created the Jenkins project and released the program as open source. Usage spread across the world with a current estimate of1.6 million users.
What is Jenkins used for?
Although Jenkins started out as a continuous integration tool, current usage covers the whole thingSoftware Delivery Pipeline, including delivery.
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The program runs web containers and plugins, such asApache tomcat, and helps manage lifecycle and access rights requirements. Over 1700 plugins for Jenkins enrich the software integration, automation and deployment processes and provide a customizable environment.
Jenkins Core-Terminologie
Jenkins encompasses different DevOps terminologies in different pipeline creation and management options. Below is a list of some common terms and their definitions.
Jenkins-Pipeline
The Jenkins pipeline is a user-created model for the continuous delivery pipeline. The pipeline includes various plugins that help define procedural steps from version control to users.
All software changes and commits go through a complex process before release. The method includesthree steps:
- Automatedbuilding.
- multi-levelto test.
- ProvideProcedure.
Jenkins has themtwo ways to create a pipeline:
- Define the pipeline directly from the user interface.
- Use thePipeline als Codemethodology and create aJenkinsfile. The text file uses Groovy-compatible syntax to define the pipeline process.
DieJenkinsfileSyntax is eitherdeclarativeorwritten.
A reasondeclarative JenkinsfilePipeline is easier to understand. An example looks like this:
Pipeline { agent any stages { stage ('build') { steps { echo 'build...' } } stage ('test') { steps { echo 'test...' } } stage ('deploy') { steps { echo 'Deploying...' } } }}The code has the following elements:
- The obligatory
Management { }block calls the Jenkins pipeline plugin. - The keyword
Agentdefines where the pipeline runs whereanyindicates that the pipeline will run on each available agent. - Die
Stages { }Block represents the order in which the pipeline runs. - The code contains three stages:
To build,TestandInsert, each with their ownSteps { }. - Die
Steps { }Tell Jenkins what to do at a given point.
Diewrittenequivalent ofJenkinsfilelooks like this:
node { stage('Build') { echo 'Building…' } stage('Test') { echo 'Testing...' } stage('Deploy') { echo 'Deploying...' }}Checking a Jenkins file into a source control tool allows the entire team to edit, review, and adjust the steps in the deployment pipeline.
Continuous integration
Continuous integration is a software development practice where each applied change invokes an automated build test. The process ensures that the code integrates into a working executable form without errors.
Continuous integration is an essential aspect in multi-developer environments. Every developer makes changes to code, and every change has potential problems.
A continuous integration tool like Jenkins helps test, identify, and fix issues before making changes to production.
Automated testing
Automated testingfor Jenkins sets the test execution and saves the results. The idea is to ensure code works in different scenarios. Creation of automated tests for different environments, e.g. B. severalJava versionsor operating systems helps to anticipate and prevent problems in later versions.
The automated test phases fit seamlessly into the CI pipeline in Jenkins. Various plugins help run unit, integration, functional and regression tests and save the results for later viewing and analysis.
Controller (formerly Master)
The Jenkins architecture is designed for distributed builds. A node is the central control unit and organizer known as the controller.
The controller is the central process where the Jenkins configurations reside. Formerly known as the master, the Jenkins controller manages agents and their connections, helps load plugins, and coordinates project flow.
Agent (Formerly Slave)
The agents connect to the Jenkins controller to run projects. Agents require a Java installation on a physical or virtual machine, such asBare-Metal-CloudsCases,Docker-Images, orKubernetes-Cluster.
Agents in Jenkins contribute to better performance byload balancingbuilds and creates a secure environment separate from the controller.
node
A node is a generic term for agents and controllers, regardless of their actual role. Any machine with the ability to create projects and pipelines is a Jenkins node, and the controller is referred to as thebuilt-in knot.
The integrated node monitors the health of all connected nodes and takes them offline when values exceed a threshold.
Project (formerly Job)
A Jenkins project or job is a user-created automation process with a specific goal. Jenkins offers various build jobs by default, and more are available through plugins.
Below is a table with a brief description of some project types.
| Project | description |
|---|---|
| freestyle | An unrestricted build task with multiple operations. |
| Pipeline | A multi-stage project with multiple build agents. |
| multi configuration | A project with multiple test environments and different configurations. |
| Pipeline with multiple branches | A project that creates a series of pipeline projects according to branches in a version control system. |
To build
In Jenkins, builds represent the single execution of a job with the current configuration. A build creates software from various sources defined in the project procedure. Depending on the project, the build mechanisms include:
- collect dependencies.
- Compile or transform code.
- archive materials.
- To test.
- Deployment in different environments.
Therefore a build is a run of a defined project with different steps.
Note:Learn how you can use to make software development and delivery more efficientJenkins Shared Libraries.
How does Jenkins work?
Jenkins takes the development steps for youintegration into deploymentthat automate every step of the way.
Every time a developer publishes a commit to the source code repository, Jenkins triggers a build. Typically, the commits post a development branch.
The build steps include testing the code to ensure the build doesn't break. When an error occurs, Jenkins notifies the developer to take appropriate action. If all tests pass, the pipeline continues with the integration steps.
Integration takes longer and requires testing the code with multiple system configurations. Jenkins runs parallel integration tests on different nodes, reducing the time it takes to test and integrate code.
Further down the pipeline, Jenkins automates user acceptance testing, which is a pre-deployment requirement. If all tests pass, the code will be merged into the main branch, making the code available to users.
Jenkins features
The main features of Jenkins are:
- easy installation. The Java-based program is autonomous and platform-independent.
- Easy to configure. The user-friendly web interface makes configuration a simple process. For initial setup information, see ourJenkins-Tutorial.
- Customizable with massive plugin availability. There are currently over 1700 plugins available to extend Jenkins' functionality. Import additional external or custom plugins for any missing functionality.
- Open Source. Jenkins is completely open source and free to use, making it a cheap technology to implement.
Note:See our articleJenkins vs. Kubernetesto find out the main differences.
Pros and cons of Jenkins
Jenkins comes with certain advantages and disadvantages. Below is a detailed overview of the pros and cons of working with Jenkins.
Jenkins Benefits
Some advantages of Jenkins are:
- Faster development cycle. Builds and tests on every commit create a fast-paced environment to debug. New features and releases reach end users faster and with fewer errors.
- Less time to integrate code. Before Jenkins, code integration was a manual process and code debugging was complex. In order to reach a working version, various commits would have to be run and problems analyzed. When using Jenkins, the integration after each commit ensures that the program functionality is always available and ready to use.
- Quick feedback for developers. Whenever a build breaks, the developers stay informed. The feedback system helps the development team to quickly address the issues instead of debugging numerous commits.
- Automated pipeline workflow. Automated tests for each commit are integrated directly into the pipeline.
Disadvantages of Jenkins
Here are some disadvantages of working with Jenkins:
- Expensive. Although Jenkins is free, the program requires a stable and robust infrastructure.
- constant maintenance. Maintaining a Jenkins server is time consuming. Adding stages to a pipeline, updating the server with new features, and tracking plugin updates all require an adminstart anewand manage the server manually.
- Developer-centric. The platform is feature-oriented and not very user-friendly for non-developers. Some developer experience is a must when working with Jenkins.
How to install Jenkins
Jenkins works on different operating systems and environments. The installation is available in many forms such as:
- Installation packages for the most important operating systems, such aswindow,Ubuntu,Debian,CentOS, etc.
- A WAR archive file.
- A Docker image.
- On oneKubernetes-Cluster.
- create source code.
Jenkins runs as a standalone package or on a Java application server. The user interface is web-based and has aREST-APIin both cases.
Note:Check out our step-by-step guide if you want to learnhow to configure docker in jenkins.
Conclusion
Currently, Jenkins is one of the bestCI/CD-Toolsand is essential for DevOps and agile teams. For more DevOps topics, see our list ofbest DevOps tools.