Scripted Pipeline Static Agent

In this guide, we’ll extend an existing Jenkins Scripted Pipeline so that all stages run on a dedicated static agent instead of the controller. You’ll also learn how to inject MongoDB credentials for a Unit Testing stage.

1. Assigning a Static Agent

By default, a Scripted Pipeline executes on the Jenkins controller when no agent label is specified. To delegate it to a static node:

1. Open your Jenkins dashboard and locate the agent you want to use.
2. Copy its label—in this example, Ubuntu-Docker-JDK-17-node20.

Wrap all pipeline stages in a node block with that label:

node('Ubuntu-Docker-JDK-17-node20') {
  // Your pipeline stages go here
}

2. Adding a Unit Test Stage with MongoDB Credentials

We’ll introduce a Unit Testing stage that runs npm test. Since these tests connect to MongoDB, we inject credentials at runtime using Jenkins’ withCredentials.

1. Navigate to Pipeline Syntax in Jenkins.
2. Open the Snippet Generator.
3. Select withCredentials: Username and password (separated).
4. Enter:
   • Credential ID: mongo-db-creds
   • Username Variable: MONGO_USERNAME
   • Password Variable: MONGO_PASSWORD

The generated snippet looks like this:

withCredentials([usernamePassword(
    credentialsId: 'mongo-db-creds',
    usernameVariable: 'MONGO_USERNAME',
    passwordVariable: 'MONGO_PASSWORD'
)]) {
    // your commands
}

3. Complete Jenkinsfile

Below is the full Jenkinsfile that checks out the code, installs dependencies, and runs unit tests with MongoDB credentials:

node('Ubuntu-Docker-JDK-17-node20') {

  stage('Checkout') {
    checkout scm
  }

  stage('Install Dependencies') {
    sh 'npm install'
  }

  stage('Unit Testing') {
    // Define the MongoDB URI
    env.MONGO_URI = 'mongodb+srv://supercluster.d3j...'

    // Inject MongoDB credentials
    withCredentials([usernamePassword(
        credentialsId: 'mongo-db-creds',
        usernameVariable: 'MONGO_USERNAME',
        passwordVariable: 'MONGO_PASSWORD'
    )]) {
      sh 'node -v'
      sh 'npm test'
    }
  }
}

After saving the Jenkinsfile, commit and push it to a new branch:

git checkout -b pipeline/scripted
git add Jenkinsfile
git commit -m "Run scripted pipeline on static agent with MongoDB credentials"
git push origin pipeline/scripted

4. Verifying the Build

Once the branch is pushed, Jenkins automatically triggers the pipeline. In Blue Ocean, you’ll see each stage execute on the specified Ubuntu agent:

Inspect the console output to ensure credentials were injected and tests ran successfully:

Pipeline Stages Summary

Now all stages run on your static Ubuntu agent, and unit tests connect to MongoDB with the provided credentials.

References

• Jenkins Pipeline Syntax
• Snippet Generator
• Blue Ocean Plugin