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08_tools.md

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Lab 8: Tools

Jobs usually require specific versions of build tools for build automation, compilation, testing etc. As soon as you have more than a handful number of tools and versions it becomes impractical to install every version of every tool on all slaves. That's why Jenkins provides a mechanism to provide the necessary tools for a build on the slaves it runs on. This lab shows how jobs can declare the tools they need.

Lab 8.1: Default Tools

Declarative pipelines provide a tools section to declare which tools a job requires. Jenkins per default supports the installation of the following tools:

  • JDK
  • Maven
  • git
  • Gradle
  • Ant
  • Docker

Before a tool can be used in a job it needs to be added to the global tool configuration.

Add a JDK:

  1. Go to Manage Jenkins > Global Tool Configuration
  2. Under JDK click Add JDK
  3. Under name enter jdk8
  4. Check Install automatically
  5. Under Add Installer select Extract *.zip/*.tar.gz
  1. At the bottom of the page click Apply

Add Maven:

  1. Go to Manage Jenkins > Global Tool Configuration
  2. Under Maven click Add Maven
  3. Under name enter maven35
  4. Check Install automatically
  5. Under Install from Apache select 3.5.0
  6. At the bottom of the page click Save

Now we can use Java and Maven in our jobs.

Create a new branch named lab-8.1 from branch lab-3.1 and change the contents of the Jenkinsfile to:

pipeline {
    agent any // with hosted env use agent { label env.JOB_NAME.split('/')[0] }
    options {
        buildDiscarder(logRotator(numToKeepStr: '5'))
        timeout(time: 10, unit: 'MINUTES')
        timestamps()  // Requires the "Timestamper Plugin"
    }
    tools {
        jdk 'jdk8'
        maven 'maven35'
    }
    stages {
        stage('Build') {
            steps {

                sh 'java -version'

                sh 'javac -version'

                sh 'mvn --version'
            }
        }
    }
}

Inside the tool{} directive we define which tools are needed and in what version. The installed tools will be available because their bin directories are added to the PATH environment variable.

The configured tools are downloaded when the job runs, directly onto the slaves it runs on. Note that tool installers are run for every build and therefore have to be efficient in case the tools are already installed.

However we often need to use other tools not supported by default Jenkins (like rvm or nvm). In this case we have two options; the custom tool plugin and docker agents.

Lab 8.2: Custom Tools (Plugin)

The custom tools plugin enables the installation of any tool to the agent node. We will use it to configure the nvm tools we will use in lab-16.

  1. Under Manage Jenkins > Global Tool Configuration click Add Custom Tool
  2. Under name enter nvm
  3. Check Install automatically
  4. Under Add Installer select Run shell command

The custom tool plugin does not support the tool{} directive but we can use the tool() step inside an environment{} directive to install the tool. The tool step returns the home directory of the installed tool.

environment {
    NVM_HOME = tool('nvm')
}

A full example can be found in lab-16.

Custom Tools (Docker Agent)

Jenkis can also use a container image as a build environment. In this case all the required tools are present in the image and the source files are mounted in the image.

agent {
    docker {
        image 'ruby:2.7.1'
    }
}

We will use this method in lab-15

End of Lab 8

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