Jenkins Pipeline is a suite of plugins that supports implementing and integrating continuous delivery pipelines into Jenkins. A continuous delivery (CD) pipeline is an automated expression of your process for getting software from version control right through to your users and customers. Jenkins Pipeline provides an extensible set of tools for modeling simple-to-complex delivery pipelines "as code" via the Pipeline domain-specific language (DSL) syntax.
The key features of Jenkins Pipeline are its support for continuous delivery (CD) and its ability to define pipelines as code. This allows teams to manage their pipelines with the same tools they use for their application code. The Jenkins Pipeline plugin supports stages, parallel execution, and can utilize any other Jenkins plugin, making it a powerful tool for creating complex delivery pipelines.
Definition of Jenkins Pipeline
Jenkins Pipeline is a set of plugins which supports Continous Integration (CI) and Continuous Delivery (CD). The pipeline provides a set of tools for modeling, visualizing and diagnosing delivery pipelines. It is a key part of the Jenkins ecosystem and is used in conjunction with other plugins to create a complete CI/CD platform.
The pipeline is defined using a domain-specific language (DSL) that is based on Groovy. This allows for a high degree of customization and flexibility, enabling teams to create pipelines that fit their specific needs. The pipeline can be defined in a Jenkinsfile which can be checked into source control, providing a single source of truth for the pipeline.
Continuous Integration and Continuous Delivery
Continuous Integration (CI) is a development practice where developers integrate code into a shared repository frequently, preferably several times a day. Each integration can then be verified by an automated build and automated tests. While automated testing is not a strict requirement, it is usually implied.
Continuous Delivery (CD) is a software development discipline where you build software in such a way that the software can be released to production at any time. You’re doing continuous delivery when your software is always in a state where it can be released to users at any time and when you’re releasing frequently.
Domain-Specific Language (DSL)
A domain-specific language (DSL) is a computer language specialized to a particular application domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains. There are a wide variety of DSLs, ranging from widely used languages for common domains, such as HTML for web pages, down to languages used by only one or a few pieces of software, such as MUSH soft code.
The pipeline DSL provided by Jenkins is based on Groovy and provides a way to define pipelines as code. This allows for a high degree of customization and flexibility, enabling teams to create pipelines that fit their specific needs.
History of Jenkins Pipeline
Jenkins, originally called Hudson, was created in 2004 by Kohsuke Kawaguchi, a software engineer at Sun Microsystems, as a way to automate the building of his projects. It quickly gained popularity and in 2011, due to a dispute with Oracle (which had acquired Sun), the project was forked and renamed Jenkins.
The Jenkins Pipeline plugin was introduced in 2016 as a way to help teams implement continuous delivery pipelines. The plugin was designed to bring pipeline-as-code to Jenkins, allowing pipelines to be defined in a Jenkinsfile and checked into source control. This provided a single source of truth for the pipeline and allowed teams to manage their pipelines with the same tools they use for their application code.
Creation of Jenkins
Jenkins was created by Kohsuke Kawaguchi in 2004 while he was working at Sun Microsystems. Kawaguchi was frustrated with the existing tools for building his projects and decided to create his own. He initially called it Hudson and released it as an open-source project.
Hudson quickly gained popularity due to its ease of use and extensibility. It was adopted by many large organizations, including NASA, Yahoo, and eBay. In 2011, after Oracle acquired Sun Microsystems, a dispute over the project's governance led to it being forked and renamed Jenkins.
Introduction of Jenkins Pipeline
The Jenkins Pipeline plugin was introduced in 2016 as a response to the growing need for a more flexible and powerful way to implement continuous delivery pipelines. Prior to the introduction of the Pipeline plugin, Jenkins users often used the Freestyle project type, which was limited in its ability to model complex pipelines.
The Pipeline plugin introduced a new way to define pipelines as code using a domain-specific language (DSL) based on Groovy. This allowed for a high degree of customization and flexibility, enabling teams to create pipelines that fit their specific needs. The pipeline could be defined in a Jenkinsfile which could be checked into source control, providing a single source of truth for the pipeline.
Use Cases of Jenkins Pipeline
Jenkins Pipeline is used in a variety of scenarios, ranging from simple continuous integration workflows to complex continuous delivery pipelines. It is used by organizations of all sizes, from small startups to large enterprises, across a wide range of industries.
Some common use cases for Jenkins Pipeline include automating the build, test, and deployment of applications; orchestrating complex workflows across multiple environments; and implementing continuous delivery pipelines.
Automating Build, Test, and Deployment
One of the most common uses of Jenkins Pipeline is to automate the build, test, and deployment of applications. This involves defining a pipeline that starts with the source code, builds the application, runs tests, and then deploys the application to a production environment.
This process can be automated using Jenkins Pipeline by defining each of these steps as stages in the pipeline. Each stage can have its own set of steps, and the pipeline can be configured to stop if any stage fails. This provides a clear and concise way to define and manage the entire process from code to deployment.
Orchestrating Complex Workflows
Jenkins Pipeline can also be used to orchestrate complex workflows that involve multiple stages and environments. This can include workflows that involve deploying to multiple environments, running different sets of tests in each environment, and coordinating deployments across multiple teams.
These complex workflows can be defined using the pipeline DSL, which provides a high degree of flexibility and customization. The pipeline can be visualized using the Jenkins UI, providing a clear view of the entire process and making it easier to diagnose and fix issues.
Implementing Continuous Delivery Pipelines
Another common use case for Jenkins Pipeline is the implementation of continuous delivery pipelines. Continuous delivery is a software development practice where code changes are automatically built, tested, and prepared for a release to production.
Jenkins Pipeline provides a set of tools for implementing continuous delivery pipelines, including support for parallel execution, the ability to pause and resume pipelines, and integration with a wide range of other Jenkins plugins. This makes it a powerful tool for teams looking to implement continuous delivery practices.
Examples of Jenkins Pipeline
Here are some specific examples of how Jenkins Pipeline can be used to automate different parts of the software development process. These examples illustrate the flexibility and power of Jenkins Pipeline and provide a starting point for teams looking to implement their own pipelines.
It's important to note that these examples are just a starting point. Jenkins Pipeline is a highly flexible and customizable tool, and teams can use it to create pipelines that fit their specific needs and workflows.
Example 1: Simple Continuous Integration Pipeline
A simple continuous integration pipeline might involve checking out code from a version control system, building the application, and running unit tests. This can be defined in a Jenkinsfile like this:
pipeline {
agent any
stages {
stage('Build') {
steps {
echo 'Building...'
sh './gradlew build'
}
}
stage('Test') {
steps {
echo 'Testing...'
sh './gradlew test'
}
}
}
}
This pipeline defines two stages: Build and Test. In the Build stage, the application is built using Gradle. In the Test stage, unit tests are run, also using Gradle. If any step fails, the pipeline will stop and the failure will be reported.
Example 2: Continuous Delivery Pipeline with Manual Approval
A more complex continuous delivery pipeline might involve building the application, running tests, deploying to a staging environment, waiting for manual approval, and then deploying to production. This can be defined in a Jenkinsfile like this:
pipeline {
agent any
stages {
stage('Build') {
steps {
echo 'Building...'
sh './gradlew build'
}
}
stage('Test') {
steps {
echo 'Testing...'
sh './gradlew test'
}
}
stage('Deploy to Staging') {
steps {
echo 'Deploying to Staging...'
sh './deploy-to-staging.sh'
}
}
stage('Wait for Approval') {
steps {
input 'Approve deployment?'
}
}
stage('Deploy to Production') {
steps {
echo 'Deploying to Production...'
sh './deploy-to-production.sh'
}
}
}
}
This pipeline defines five stages: Build, Test, Deploy to Staging, Wait for Approval, and Deploy to Production. In the Build stage, the application is built using Gradle. In the Test stage, unit tests are run. In the Deploy to Staging stage, the application is deployed to a staging environment. The pipeline then pauses and waits for manual approval before proceeding to the Deploy to Production stage, where the application is deployed to the production environment.
Conclusion
Jenkins Pipeline is a powerful tool for implementing continuous integration and continuous delivery pipelines. It provides a flexible and customizable way to define pipelines as code, enabling teams to manage their pipelines with the same tools they use for their application code.
Whether you're looking to automate the build, test, and deployment of your applications, orchestrate complex workflows across multiple environments, or implement continuous delivery practices, Jenkins Pipeline provides the tools and features you need to succeed.