How to Use Parallel Stages in Jenkins Pipeline

In Jenkins Pipeline, you use the parallel step inside a stage to run multiple stages at the same time. Define each parallel branch as a separate block inside parallel, and Jenkins will execute them concurrently.

Syntax

The parallel step runs multiple branches simultaneously inside a stage. Each branch is a named block with its own steps.

• stage: Defines a pipeline stage.
• parallel: Runs multiple branches at the same time.
• branch name: Label for each parallel task.
• steps: Commands or actions to run in each branch.

groovy

stage('Parallel Stage') {
    parallel(
        branch1: {
            // steps for branch1
        },
        branch2: {
            // steps for branch2
        }
    )
}

Example

This example shows a Jenkins Declarative Pipeline with a stage that runs two tasks in parallel: one prints a message and the other waits 3 seconds before printing.

groovy

pipeline {
    agent any
    stages {
        stage('Parallel Stage') {
            parallel {
                branch1 {
                    echo 'Running branch 1'
                }
                branch2 {
                    sleep 3
                    echo 'Running branch 2 after 3 seconds'
                }
            }
        }
    }
}

Output

[Pipeline] stage
[Pipeline] { (Parallel Stage)
[Pipeline] parallel
[Pipeline] { (branch1)
[Pipeline] echo
Running branch 1
[Pipeline] }
[Pipeline] { (branch2)
[Pipeline] sleep
Sleeping for 3 sec
[Pipeline] echo
Running branch 2 after 3 seconds
[Pipeline] }
[Pipeline] }
[Pipeline] }
[Pipeline] // stage

Common Pitfalls

Common mistakes when using parallel stages include:

• Not wrapping parallel branches inside a stage, causing syntax errors.
• Using the wrong syntax for parallel branches (e.g., missing branch names).
• Trying to use parallel outside of a stage block.
• Not handling shared resources properly, which can cause conflicts when branches run simultaneously.

groovy

/* Wrong: parallel used outside stage */
parallel(
    branch1: { echo 'Task 1' },
    branch2: { echo 'Task 2' }
)

/* Right: parallel inside a stage */
stage('Parallel Stage') {
    parallel(
        branch1: { echo 'Task 1' },
        branch2: { echo 'Task 2' }
    )
}

Quick Reference

Tips for using parallel stages in Jenkins Pipeline:

• Always define parallel inside a stage.
• Name each parallel branch clearly for easy identification.
• Use echo, sh, or other steps inside branches.
• Be mindful of shared workspace or resources to avoid conflicts.
• Use parallel stages to speed up builds by running independent tasks simultaneously.

Key Takeaways

Use the parallel step inside a stage to run multiple branches concurrently.

Each parallel branch must have a unique name and its own steps.

Parallel stages speed up pipelines by running tasks at the same time.

Always place parallel inside a stage block to avoid syntax errors.

Be careful with shared resources when running parallel branches to prevent conflicts.