Jenkins Pipeline: Are agents required to utilize Jenkinsfile?

Question

I am investigating the use of Jenkins Pipeline (specifically using Jenkinsfile). The context of my implementation is that I'm deploying a Jenkins instance using Chef. Part of this deployment may include some seed jobs, which will pull job configurations from source control (Jenkinsfile), to automate creation of our build jobs via Chef.

I've investigated the Jenkins documentation for both Pipeline as well as Jenkinsfile, and it seems to me that in order to use Jenkins Pipeline agents are required to be configured and set up in addition to Jenkins Master.

Am I understanding this correctly? Must Jenkins agents exist in order to use Jenkins Pipeline's Jenkinsfile? This specific line in the Jenkinsfile documentation leads me to believe this to be true:

Jenkinsfile (Declarative Pipeline)
pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                echo 'Building..'
            }
        }
        stage('Test') {
            steps {
                echo 'Testing..'
            }
        }
        stage('Deploy') {
            steps {
                echo 'Deploying....'
            }
        }
    }
}

The Declarative Pipeline example above contains the minimum necessary structure to implement a continuous delivery pipeline. The agent directive, which is required, instructs Jenkins to allocate an executor and workspace for the Pipeline.

Thanks in advance for any Jenkins guidance!

Answer 1

The 'agent' part of the pipeline is required however this does not mean that you are required to have an external agent in addition to your master. If all you have is the master this pipeline will execute on the master. If you have additional agents available the pipeline would execute on whichever agent happens to be available when you run the pipeline.