Declarative Pipelines

(this post if part of the material I cover in my devops course)

Declarative pipelines were created to allow users create pipelines without learning Groovy programming.

Declarative pipeline example

• Create a new pipeline, as we've done in pipelines-primer-1 post
  ...but...
• Choose GitHub + Maven example, which is the same as the one we have covered in scripted-pipelines, but using a declarative syntax.
• Here's the code:

 1pipeline {
 2    agent any
 3
 4    tools {
 5        // Install the Maven version configured as "M3" and add it to the path.
 6        maven "M3"
 7    }
 8
 9    stages {
10        stage('Build') {
11            steps {
12                // Get some code from a GitHub repository
13                git 'https://github.com/jglick/simple-maven-project-with-tests.git'
14
15                // Run Maven on a Unix agent.
16                sh "mvn -Dmaven.test.failure.ignore=true clean package"
17
18                // To run Maven on a Windows agent, use
19                // bat "mvn -Dmaven.test.failure.ignore=true clean package"
20            }
21
22            post {
23                // If Maven was able to run the tests, even if some of the test
24                // failed, record the test results and archive the jar file.
25                success {
26                    junit '**/target/surefire-reports/TEST-*.xml'
27                    archiveArtifacts 'target/*.jar'
28                }
29            }
30        }
31    }
32}

Scripted Pipeline characteristics

• there is a pipeline block at the beginning (which tells us that this pipline uses declarative syntax)
• The agent component defines where we can run our pipeline
• The tools sections is used to auto-install a tool and put it on the PATH.
• There is a stages, stage and step components
• There is no option to ask if this is Linux (as was possible in the scripted version)
  so: if agent is any, then you must make sure that verything is really OK.
  Otherwise, create two version of the pipeline, and use the correct agent and commands in each.
• There is a post section, that defines one or more additional steps that are run upon the completion of a Pipeline’s or stage’s run.
  post can support any of the following post-condition blocks: always, changed, fixed, regression, aborted, failure, success, unstable, unsuccessful, and cleanup.
  We don't see the post in the graphic view of the stages, because it is not one of the stages.