Labels for agent selection in Jenkins - Mini Project: Build & Apply

Labels for agent selection

📖 Scenario: You are setting up a Jenkins pipeline to run jobs on specific agents (nodes) based on labels. Labels help Jenkins pick the right machine to run your tasks.

🎯 Goal: Create a Jenkins pipeline script that uses labels to select the correct agent for running a job.

📋 What You'll Learn

Create a pipeline with a label selector for the agent

Define a label variable to specify the agent label

Use the label variable in the agent block

Print a message showing which agent label is used

💡 Why This Matters

🌍 Real World

In real Jenkins setups, labels help direct jobs to the right machines with needed software or resources.

💼 Career

Knowing how to use labels in Jenkins pipelines is essential for DevOps engineers to manage build and deployment environments efficiently.

1

Create a label variable

Create a variable called agentLabel and set it to the string "linux".

Jenkins

# Your code here

Need a hint?

Use def agentLabel = "linux" to create the label variable.

2

Use the label variable in the agent block

Add an agent block to the pipeline that uses the label stored in agentLabel to select the agent.

Jenkins

def agentLabel = "linux"

pipeline {
    agent {
        // Your code here
    }
    stages {
        stage('Example') {
            steps {
                echo "Running on agent"
            }
        }
    }
}

Need a hint?

Use agent { label agentLabel } to select the agent by label.

3

Add a stage to print the agent label

Inside the stages block, add a stage named Print Label with a step that prints the message "Agent label is: ${agentLabel}".

Jenkins

def agentLabel = "linux"

pipeline {
    agent {
        label agentLabel
    }
    stages {
        stage('Example') {
            steps {
                echo "Running on agent with label: ${agentLabel}"
            }
        }
        // Your code here
    }
}

Need a hint?

Add a new stage with stage('Print Label') and use echo to print the label.

4

Print the final output

Run the pipeline and ensure the output includes the line Agent label is: linux.

Jenkins

def agentLabel = "linux"

pipeline {
    agent {
        label agentLabel
    }
    stages {
        stage('Example') {
            steps {
                echo "Running on agent with label: ${agentLabel}"
            }
        }
        stage('Print Label') {
            steps {
                echo "Agent label is: ${agentLabel}"
            }
        }
    }
}

// Run the pipeline and check output

Need a hint?

Look for the output line Agent label is: linux in the console log.