How to create a pipeline in Jenkins
Jenkins, an open-source automation server, is a critical component in modern software development, especially in the context of continuous integration and continuous delivery (CI/CD). This guide aims to provide a detailed walkthrough for creating a Jenkins pipeline, emphasizing comprehensive explanations for each step.
Before delving into creating your Jenkins pipeline, ensuring that Jenkins is installed on your system is crucial. If Jenkins still needs to be installed, refer to our detailed article on Jenkins installation guide for step-by-step guidance.
Table of contents
- What is a Pipeline?
- Understanding Jenkins Pipelines
- How to create a Jenkins pipeline
- Try Sample Script menu
- Groovy Sandbox
- Additional considerations
- Common errors in Jenkins pipelines
- Conclusion
What is a pipeline?
In software development, pipelines automate the process of delivering code from development to deployment and beyond. They include stages such as code compilation, testing, artifact generation, deployment, and rollback procedures. Pipelines provide a consistent, efficient, and reliable workflow streamlining software delivery.
Jenkins pipeline is a customizable tool that models, orchestrates, and visualizes the software delivery process. It allows developers to define their pipeline as code, stored alongside application source code for version control and traceability. Two syntaxes are supported for defining pipelines–declarative and scripted.
Declarative Pipelines
Declarative pipelines provide a higher-level abstraction on top of the underlying pipeline syntax. They offer a more structured, readable way to define your pipeline stages, steps, and configuration elements. Declarative pipelines are ideal for straightforward workflows and are well-suited for users new to pipeline syntax.
Scripted Pipelines
Scripted pipelines in Jenkins offer advanced flexibility and power for complex workflows. With the help of this, developers can use Groovy scripts to implement advanced logic and customization in CI/CD processes, addressing unique project requirements. This versatility makes scripted pipelines a preferred choice for intricate control in software development.
Understanding Jenkins pipelines
Stages and steps
A Jenkins pipeline is organized into stages, representing phases in your software delivery process such as build, test, and deploy. Within each stage are individual steps, the most minor work units in a pipeline. Stages provide a logical separation of concerns, allowing for better organization and visualization of your workflow.
Agent and workspace
The agent in a Jenkins pipeline specifies where the pipeline will run, providing flexibility in resource utilization. The workspace is the directory where all the work in a pipeline is done. Understanding the agent and workspace concepts is crucial for efficient pipeline execution.
Parallel execution
Jenkins pipelines empower developers to parallelize the execution of stages, allowing multiple tasks to run concurrently. This capability is invaluable for optimizing build and test times, especially when dealing with large and time-consuming projects. By strategically employing parallelization, teams can significantly reduce pipeline execution time.
Post-conditions and notifications
Beyond the execution of stages, Jenkins pipelines allow for the definition of post-conditions, specifying actions to be taken after the completion of specific stages. Additionally, notifications can be configured to alert relevant stakeholders about the status of the pipeline, ensuring timely awareness of successes or failures.
Artifacts and dependencies
Jenkins pipelines support the management of artifacts and the outputs generated during the pipeline execution. These artifacts can be archived, stored, or even passed between stages, enabling seamless communication and dependency management between different pipeline parts.
Input and approval mechanism
Introducing an interactive aspect, Jenkins pipelines can incorporate user input and approval steps. This is particularly useful for scenarios requiring manual intervention or validation before progressing to the next stage. It adds an extra layer of control and governance to the automated workflow.
Error handling and recovery
Scripted pipelines offer robust error-handling mechanisms. Developers can implement strategies to gracefully handle errors, define fallback scenarios, and even trigger recovery processes. This ensures the resilience of the pipeline in the face of unexpected issues, contributing to a more reliable and fault-tolerant CI/CD workflow.
Understanding these additional aspects of Jenkins pipelines provides a holistic view of their capabilities, enabling teams to tailor their workflows to meet specific project requirements and optimize their software delivery processes.
How to create a Jenkins pipeline
Installing the pipeline plugin
The Pipeline plugin is a cornerstone for Jenkins Pipelines, facilitating the creation and execution of pipeline scripts. Here’s a step-by-step guide to installing the Pipeline plugin:
Navigate to the Jenkins dashboard.
Click on Manage Jenkins in the left-hand menu. Then select Plugins.
If you have already installed the plugin, it is shown under the Installed plugins tab.
If you do not have the plugin previously installed, go to the Available plugins tab and search for Pipeline.
Check the box next to Pipeline and click Install. After that, the plugin will start downloading and be added to the plugin library.
This plugin is essential for defining and executing pipelines.
Creating a new pipeline job
Now that the Pipeline plugin is installed let’s create a new Jenkins job for our pipeline:
From the Jenkins dashboard, click on New Item.
Enter a name for your job (e.g., My FirstPipeline) and select Pipeline as the job type.
Click on OK to create the job.
This step sets up the infrastructure for your pipeline, allowing you to configure and execute it.
Defining your pipeline script
In the Configure page, navigate to the Pipeline section to write the script that defines your pipeline.
For beginners, start with a basic declarative pipeline script:
pipeline {
agent any
stages {
stage('Build') {
steps {
// Your build steps go here
}
}
stage('Test') {
steps {
// Your test steps go here
}
}
stage('Deploy') {
steps {
// Your deployment steps go here
}
}
}
}
Code language: PHP (php)
Explanation
- pipeline: Declares the start of a pipeline block.
- agent any: Specifies that the pipeline can run on any available agent.
- stages: Defines individual stages within the pipeline.
- stage: Represents a stage in the pipeline (e.g., Build, Test, Deploy).
- steps: Contains the specific tasks or commands for each stage.
This script establishes the basic structure of your pipeline.
Adding source code management
Integrating projects stored in a version control system (VCS) with your pipeline ensures the use of the latest code. Add Git integration to your script:
pipeline {
agent any
stages {
stage('SCM Checkout') {
steps {
git 'https://github.com/your/repository.git'
}
}
// ... (other stages)
}
}
Code language: JavaScript (javascript)
Explanation
- stage(‘SCM Checkout’): Represents the stage for checking out code from the version control system.
- git: Specifies the Git repository URL for source code retrieval.
This script ensures that your pipeline fetches the latest code from your repository.
Configuring build and test steps
Define the commands or scripts needed for your project in the Build and Test stages. Consider a Node.js project:
stage('Build') {
steps {
sh 'npm install' // Replace with your build commands
}
}
stage('Test') {
steps {
sh 'npm test' // Replace with your test commands
}
}
Code language: JavaScript (javascript)
Explanation
- sh ‘npm install’: Executes the npm install command for project building.
- sh ‘npm test’: Executes the npm test command for running tests.
Customize these commands to suit your project’s requirements.
Deploying your application
In the Deploy stage, define the steps required to deploy your application. For example, deploying a web application to a remote server might involve copying files over SSH:
stage('Deploy') {
steps {
sh 'scp -r target/* user@server:/path/to/deployment' // Replace with your deployment commands
}
}
Code language: JavaScript (javascript)
Explanation
- sh ‘scp -r target/* user@server:/path/to/deployment’: Uses the Secure Copy Protocol (SCP) to copy files to a remote server.
Adjust the commands based on your deployment strategy and target environment.
Save and run your pipeline
Once you have defined your pipeline script, scroll down to the bottom of the Configure page. You will typically find both Save and Apply buttons.
These buttons serve different purposes:
- Save: This button commits your changes but does not immediately trigger the pipeline. It’s helpful to save your configuration without initiating a new build.
- Apply: This button saves your changes and triggers the pipeline build immediately. It’s beneficial when you want to enact your script changes and observe the pipeline execution.
Once you click, a new page will appear, and then click on Build Now in the Jenkins job dashboard. Jenkins will execute the pipeline, and you can monitor the progress in the Build History section.
Try Sample Script menu
The Try Sample Script dropdown in the Jenkins Pipeline configuration’s Script tab is a convenient feature that provides users with pre-configured sample scripts for various common use cases.
Let’s explore the available options:
Hello World
- This option typically provides a simple, minimalistic pipeline script that prints Hello, World! when executed.
- It is a beginner-friendly introduction to Jenkins Pipelines, allowing users to quickly understand a pipeline script’s basic syntax and structure.
GitHub + Maven
- The GitHub + Maven option is a more complex sample script demonstrating a pipeline integrating with a GitHub repository and involving Maven for building and managing dependencies.
- It showcases a more realistic scenario where code is fetched from a GitHub repository, dependencies are resolved using Maven, and the project undergoes a build process.
Scripted Pipeline
- This option provides a sample scripted pipeline script. Scripted pipelines use Groovy scripts and offer more flexibility in defining complex workflows.
- The scripted pipeline sample will likely include multiple stages, steps, and conditional logic, demonstrating how to structure and organize a more intricate pipeline script.
Groovy Sandbox
In the Jenkins Pipeline configuration, under the Script tab, you may encounter the Groovy Sandbox checkbox. This checkbox is associated with the Groovy Sandbox, a security feature in Jenkins.
Let’s explore its purpose and implications:
Checkbox appearance
The Groovy Sandbox checkbox is usually located below the script editor or input area where you define your pipeline script. Depending on your security needs, it can be enabled or disabled. Its design may vary based on the platform or Jenkins theme, maintaining user-friendly interaction.
Purpose
To ensure maximum security, the Groovy Sandbox must be enabled to restrict any unsafe operations within the script. This will effectively mitigate the risk of any potentially harmful code being executed. It acts as a protective layer, allowing users to confidently manage and deploy pipeline scripts while minimizing the risk of forced consequences.
When to enable the Groovy Sandbox
To strictly stick to security policies, especially when untrusted users can access pipeline configuration, it is recommended to enable the Groovy Sandbox. This is particularly useful in scenarios where you need to control and monitor the actions the pipeline script can perform.
Implications of enabling the Groovy Sandbox
The Groovy Sandbox is designed to improve security by limiting certain operations that might be necessary for specific advanced use cases. If you select the checkbox, the pipeline script will be subject to the limitations of the sandbox. This could result in errors if the script includes any restricted operations.
Disabling the Groovy Sandbox
If you deselect the checkbox, the Groovy Sandbox won’t restrict your pipeline script, giving you more flexibility in executing scripts. This option is useful when you trust the script’s source and need the full capabilities of Groovy without any limitations.
Considerations
Taking the necessary precautions before deciding whether to enable or disable the Groovy Sandbox is crucial. It’s essential to evaluate the security requirements of your Jenkins environment and the kind of pipeline scripts being executed. Always exercise caution when dealing with untrusted sources or allowing unauthenticated users to define pipeline scripts.
The Groovy Sandbox checkbox balances security and flexibility in Jenkins Pipelines. Choose the appropriate setting based on your security considerations and the level of trust in the source of the pipeline scripts.
Additional considerations
Parameterized pipelines
Jenkins pipelines can be parameterized, allowing you to pass parameters to your pipeline script. This is useful for making your pipelines more flexible and reusable.
parameters {
string(name: 'TARGET_ENV', defaultValue: 'production', description: 'Target environment for deployment')
}
pipeline {
agent any
stages {
stage('Deploy') {
steps {
echo "Deploying to ${TARGET_ENV} environment"
// Your deployment steps go here
}
}
}
}
Code language: PHP (php)
Explanation
- parameters: Declares parameters for the pipeline.
- string(name: ‘TARGET_ENV’, defaultValue: ‘production’, description: ‘Target environment for deployment’): Defines a string parameter named TARGET_ENV with a default value of ‘production’.
Pipeline visualization
Jenkins provides a visual representation of your pipeline’s execution. In the pipeline view, you can see the status of each stage, making it easier to identify issues and understand the flow of your pipeline.
Pipeline notifications
Configure email notifications or integrate with messaging platforms like Slack to receive notifications about the status of your pipelines. This ensures your team stays informed about the progress and outcome of builds and deployments.
Common errors in Jenkins pipelines
As you embark on your journey of creating and implementing Jenkins pipelines, it’s essential to be aware of common errors that may arise during the configuration and execution of your pipelines. Understanding and promptly addressing these errors is crucial for maintaining a smooth and reliable CI/CD workflow.
Let’s delve into some of the essential common errors and how to troubleshoot them:
Agent configuration issues
No suitable agent found for this project.
Code language: JavaScript (javascript)
Troubleshooting
This error indicates a problem with specifying the agent in your pipeline script. Ensure the “agent’ directive is correctly defined, and the specified label matches an available agent in your Jenkins environment. Additionally, confirm that the agent has the necessary tools and dependencies installed.
pipeline {
agent {
label 'your_agent_label'
}
// ...
}
Code language: JavaScript (javascript)
Syntax errors in pipeline script
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Code language: CSS (css)
Troubleshooting
Syntax errors in your pipeline script can lead to compilation failures. Review the specific line in the error message and check for syntax issues. Common mistakes include missing parentheses, incorrect indentation, or misused keywords.
Missing plugin dependencies
java.lang.NoSuchMethodError: No such DSL method 'someMethod' found among steps.
Code language: JavaScript (javascript)
Troubleshooting
This error suggests that the pipeline is attempting to use a method that is not available. Ensure that the necessary plugins are installed in Jenkins, and their versions are compatible with the pipeline script. Refer to the plugin documentation for the correct syntax and usage of specific methods.
Issues with workspace and file paths
java.nio.file.NoSuchFileException: /path/to/missing/file.txt
Code language: JavaScript (javascript)
Troubleshooting
File-related errors may occur if the specified paths in your pipeline script do not match the directory structure. Double-check the paths in your file operations, such as file copying or archiving, and ensure that the referenced files exist in the specified locations.
Authentication and permissions
ERROR: Authentication failed. No valid crumb was included in the request.
Code language: HTTP (http)
Troubleshooting
Authentication errors may occur if the pipeline script attempts to perform actions requiring proper credentials. Ensure that the Jenkins user or service account associated with the pipeline has the necessary permissions to execute the specified steps. If using external systems or APIs, validate that authentication credentials are correctly configured.
Final thoughts on creating a Jenkins pipeline
Jenkins pipelines are a potent tool for continuous integration and delivery. It is important to note that this guide is intended as a starting point. As you become more familiar with Jenkins pipelines and CI/CD practices, you will discover additional features, plugins, and best practices to enhance your automation skills further. Happy testing!
Related articles
- Declarative vs Scripted Jenkins pipelines
- Creating pipelines with Jenkins Blue Ocean
- Jenkins-JMeter integration
- Jenkins master-slave architecture
- How to use Jenkins shared libraries
- How to add credentials in Jenkins
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