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What is the Jenkins Pipeline?

Jenkins Pipeline is a plugin suite that supports integrating and implementing continuous delivery pipelines into Jenkins. The Jenkins Pipeline is also called as a “Pipeline” with a capital “P.” A Continuous Delivery (CD) pipeline is an automated expression for this process to get the software from version control to the user and customer. It involves building the software in a repeatable and reliable manner. It also consists of progressing the built software through multiple testing and deployment (called “build”).

With the Pipeline domain-specific language (DSL) syntax, Jenkins Pipeline provides tools for modeling delivery pipelines right from the simple to the complicated delivery “as code.” The Jenkins Pipeline is defined and written into a text file.

The text file is called a Jenkinsfile, and Jenkins file is committed to a project’s source control repository. Treating the CD pipeline as a part of the application to be reviewed and versioned like any other code is the foundation of “Pipeline as code.”

Creating and committing a Jenkinsfile to source control provides many benefits listed below:

  1. It makes a Pipeline build process for all the pull requests and branches automatically.
  2. Code iteration or review on the Pipeline along with the remaining source code.
  3. Audit trail for the Pipeline.
  4. The source for the Pipeline can be edited and viewed by multiple members of the project.

The syntax for defining a Pipeline is the same – either with the Jenkinsfile or in the web UI. However, determining the Pipeline in Jenkinsfile and checking that into the source control is generally the best and preferred practice. The Jenkins Certification will provide an overview of Jenkins Pipeline in brief. Let us try to understand it in short with this article.

Why Jenkins Pipeline?

Jenkins supports several automation patterns; it is an automation engine. Now, the use of Pipeline in Jenkins adds a robust set of automation tools. Using Pipeline onto Jenkins supports use cases that span from comprehensive CD pipelines to simple continuous integration. By modeling a series of related tasks, there are many advantages of features of Pipeline which the user gets:

  1. Durable: Pipelines can survive both unplanned and planned restarts of Jenkins master.
  2. Code: Pipelines are typically checked and are implemented in code into source control. This gives the team the ability to review, edit, and iterate upon the delivery pipeline.
  3. Pausable: Pipelines can wait for human input or approval and can optionally stop before continuing the Pipeline run.
  4. Extensible: The Pipeline plugin supports multiple options for integration with other plugins and supports a custom extension to its DSL footnote:dsl:[].
  5. Versatile: Pipeline supports CD requirements, which are complex and real-world, including joining or fork, loop, and perform work parallelly.

To form sequential tasks, Jenkins always allows rudimentary forms of changing Freestyle Jobs together. In Jenkins, Pipeline makes this concept a first-class citizen. The Pipeline is extensible by both users with Plugin developers and Pipeline Shared Libraries.

Concepts of Pipeline

The concepts explained below are vital aspects of Jenkins Pipeline. These concepts are tied closely to the syntax of the Pipeline. The Jenkins training will get all your concepts and skills covered.

Pipeline: In the CD pipeline, Pipeline is a user-defined model. The code of Pipeline defines the entire build process, which generally includes stages for testing, building an application, and delivering it. In Declarative Pipeline Syntax, a pipeline block is a crucial part.

Node: A node is nothing but a machine that has the capability of executing a Pipeline and is a part of the Jenkins environment. A node block is a crucial part of Scripted Pipeline Syntax.

Stage: A stage block defines a subset of tasks performed conceptually through the entire Pipeline, which many plugins use to present or visualize Jenkins Pipeline’s progress or status. For example, “Build”, “Deploy”, “Test” stages.

Step: A step is a single task. A step is something that tells Jenkins what to do at that instance of point in time or at that particular “step” in the whole process. For example, use: sh ‘make’ to execute the shell command. When the plugin extends the Pipeline DSL, it generally means that it has implemented the new step.

Pipeline Syntax

Let us see the fundamental differences between the Scripted Pipeline Syntax and Declarative Pipeline Syntax. However, it should be noted that the Stages and Steps explained in the concepts of Pipeline remains the same for Syntaxes. The Jenkins Training will help you develop the required skills in Jenkins.

Declarative Pipeline Syntax: In Declarative Pipeline Syntax, the pipeline block defines all the work done throughout the entire Pipeline.

The fundamental syntax of Declarative Pipeline Syntax is as follows:

  1. On any available agent, execute the Pipeline or any of its stages.
  2. It defines the build stage.
  3. It performs the steps related to the “Build” stage.
  4. It defines the “Test” stage
  5. It performs some steps related to the “Test” stage.
  6. It describes the “Deploy” stage.
  7. It performs few steps related to the “Deploy” stage

Scripted Pipeline Syntax: One or more node blocks do the core work throughout the entire Pipeline in scripted pipeline syntax. It is not necessary for scripted pipeline syntax; however, confining the pipelines work inside a node block does these two things:

  1. as soon as an executive order is free on a node, it schedules the block’s steps to run by adding an item in the Jenkins queue.
  2. Create a workspace where the work can be done on files checked out from the source control. Here, the workspace is nothing but a directory specific to that particular Pipeline.

The fundamental syntax of Scripted Pipeline Syntax is as follows:

  1. On any available agent, execute the Pipeline or any of its stages.
  2. It defines the build stage. In scripted pipeline syntax, the stage blocks are optional. However, implementing them in a scripted Pipeline provides clear visualization and subset of each step of the tasks or involved in Jenkins UI.
  3. It performs a few steps related to the “Build” stage.
  4. It defines the “Test” stage.
  5. It performs a few steps related to the “Test” stage.
  6. It defines the “Deploy” stage.
  7. It performs few steps related to the “Deploy” stage

The Jenkins Training will help you learn server automation, build pipelines and configuration tools, continuous integration, automated testing, distributed systems, and code quality improvement with hands-on practice assignments and projects.