What is Jenkins Pipeline?

In Jenkins, a pipeline is a group of events or jobs which are interlinked with one another in a sequence.

In simple words, Jenkins Pipeline is a combination of plugins that support the integration and implementation of continuous delivery pipelines using Jenkins. A pipeline has an extensible automation server for creating simple or complex delivery pipelines “as code,” via pipeline DSL (Domain-specific Language)

Jenkins is an open source continuous integration server that provides the ability to continuously perform automated builds and tests. Several tasks can be controlled and monitored by Jenkins, including pulling code from a repository, performing static code analysis, building your project, executing unit tests, automated tests and/or performance tests, and finally, deploying your application. These tasks typically conform a continuous delivery pipeline.

What is Continuous Delivery Pipelines? How it Works?

In a Jenkins pipeline, every job or event has some sort of dependency on at least one or more events.

The picture above represents a continuous delivery pipeline in Jenkins. It contains a group of states called build, deploy, test and release. These events are interlinked with each other. Every state has its events, which work in a sequence called a continuous delivery pipeline.

Pipelines are a suite of Jenkins plugins. Pipelines can be seen as a sequence of stages to perform the tasks just detailed, among others, thus providing continuous releases of your application. The concept “continuous” is relative to your application and/or environment:

Jenkins Pipeline Concepts

Pipeline: The pipeline is a set of instructions given in the form of code for continuous delivery and consists of instructions needed for the entire build process. With pipeline, you can build, test, and deliver the application.

Node: The machine on which Jenkins runs is called a node. A node block is mainly used in scripted pipeline syntax.

Stage: A stage block contains a series of steps in a pipeline. That is, the build, test, and deploy processes all come together in a stage. Generally, a stage block is used to visualize the Jenkins pipeline process.

Step: A step is nothing but a single task that executes a specific process at a defined time. A pipeline involves a series of steps.

Why Use Jenkin’s Pipeline?

Jenkins is an open continuous integration server which has the ability to support the automation of software development processes. You can create multiple automation jobs with the help of use cases, and run them as a Jenkins pipeline.

Here are the reasons why you use should use Jenkins pipeline:

• Jenkins pipeline is implemented as a code which allows multiple users to edit and execute the pipeline process.
• Pipelines are robust. So if your server undergoes an unforeseen restart, the pipeline will be automatically resumed.
• You can pause the pipeline process and make it wait to resume until there is an input from the user.
• Jenkins Pipelines support big projects. You can run multiple jobs, and even use pipelines in a loop.

What is a JenkinsFile?

Jenkins pipelines can be defined using a text file called JenkinsFile. You can implement pipeline as code using JenkinsFile, and this can be defined by using a domain specific language (DSL). With JenkinsFile, you can write the steps needed for running a Jenkins pipeline.

The benefits of using JenkinsFile are:

• You can create pipelines automatically for all branches and execute pull requests with just one JenkinsFile.
• You can review your code on the pipeline
• You can audit your Jenkins pipeline
• This is the singular source for your pipeline and can be modified by multiple users.

JenkinsFile can be defined by either Web UI or with a JenkinsFile.

Declarative versus Scripted pipeline syntax:

There are two types of syntax used for defining your JenkinsFile.

1. Declarative
2. Scripted

Declarative:

Declarative pipeline syntax offers an easy way to create pipelines. It contains a predefined hierarchy to create Jenkins pipelines. It gives you the ability to control all aspects of a pipeline execution in a simple, straight-forward manner.

Scripted:

Scripted Jenkins pipeline runs on the Jenkins master with the help of a lightweight executor. It uses very few resources to translate the pipeline into atomic commands. Both declarative and scripted syntax are different from each other and are defined totally differently.

Install Build Pipeline Plugin in Jenkins

With the build pipeline plugin, you can create a pipeline view of incoming and outgoing jobs, and create triggers which require manual intervention.

1.The settings for the plugin can be found under Manage Jenkins > Manage Plugins.

If you have already installed the plugin, it is shown under the installed tab.

2. If you do not have the plugin previously installed, it shows up under the Available tab.

Once you have successfully installed the build pipeline plugin in your Jenkins, follow these steps to create your Jenkins pipeline.

How to Create Your Jenkins Pipeline

With the introduction of the Pipeline, Jenkins added an embedded Groovy engine, making Groovy the scripting language in the Pipeline´s DSL.

Here are the steps you need to take to setup a Jenkins Pipeline.

1. First, log on to your Jenkins server and select “New Item” from the left panel:

2. Next, enter a name for your pipeline and select “Pipeline” from the options. Click “Ok” to proceed to the next step:

3. You can now start working your Pipeline script:

The red box in the middle is where you can start writing your script, which will be explained now.

References:

https://jenkins.io/doc/book/pipeline/

https://jenkins.io/doc/pipeline/tour/hello-world/