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Choose Jenkins Agent

The agent section specifies where the entire Pipeline, or a specific stage, will execute in the Jenkins environment depending on where the agent section is placed. The section must be defined at the upper-level inside the pipeline block, but stage-level usage is optional. For more information, see the official documentation of Jenkins.

Built-in podTemplate

A podTemplate is a template of a Pod that is used to create agents. Users can define a podTemplate to use in the Kubernetes plugin.

As a pipeline runs, every Jenkins agent Pod must have a container named jnlp for communications between the Jenkins controller and Jenkins agent. In addition, users can add containers in the podTemplate to meet their own needs. They can choose to use their own Pod YAML to flexibly control the runtime, and the container can be switched by the container command. Here is an example.

pipeline {
  agent {
    kubernetes {
      //cloud 'kubernetes'
      label 'mypod'
      yaml """
apiVersion: v1
kind: Pod
spec:
  containers:
  - name: maven
    image: maven:3.3.9-jdk-8-alpine
    command: ['cat']
    tty: true
"""
    }
  }
  stages {
    stage('Run maven') {
      steps {
        container('maven') {
          sh 'mvn -version'
        }
      }
    }
  }
}

At the same time, KubeSphere has some built-in podTemplates, so that users can avoid writing YAML files, greatly reducing learning costs.

In the current version, there are 4 types of built-in podTemplates, i.e. base, nodejs, maven and go. KubeSphere also provides an isolated Docker environment in Pods.

You can use the built-in podTemplate by specifying the label for an agent. For example, to use the nodejs podTemplate, you can set the label to nodejs when creating the Pipeline, as shown in the example below.

jenkins-agent

pipeline {
  agent {
    node {
      label 'nodejs'
    }
  }
  
  stages {
    stage('nodejs hello') {
      steps {
        container('nodejs') {
          sh 'yarn -v'
          sh 'node -v'
          sh 'docker version'
          sh 'docker images'
        }
      }
     }
   }
}

podTemplate base

Name	Type / Version
Jenkins Agent Label	base
Container Name	base
OS	centos-7
Docker	18.06.0
Helm	2.11.0
Kubectl	Stable release
Built-in tools	unzip, which, make, wget, zip, bzip2, git

podTemplate nodejs

Name	Type / Version
Jenkins Agent Label	nodejs
Container Name	nodejs
OS	centos-7
Node	9.11.2
Yarn	1.3.2
Docker	18.06.0
Helm	2.11.0
Kubectl	Stable release
Built-in tools	unzip, which, make, wget, zip, bzip2, git

podTemplate maven

Name	Type / Version
Jenkins Agent Label	maven
Container Name	maven
OS	centos-7
Jdk	openjdk-1.8.0
Maven	3.5.3
Docker	18.06.0
Helm	2.11.0
Kubectl	Stable release
Built-in tools	unzip, which, make, wget, zip, bzip2, git

podTemplate go

Name	Type / Version
Jenkins Agent Label	go
Container Name	go
OS	centos-7
Go	1.11
GOPATH	/home/jenkins/go
GOROOT	/usr/local/go
Docker	18.06.0
Helm	2.11.0
Kubectl	Stable release
Built-in tools	unzip, which, make, wget, zip, bzip2, git

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