[FIXED] How to achive nested parallel in Jenkins declarative pipeline?

Issue

I have declarative pipeline as below and it runs 2* and 3* stages in parallel, pasted the blue ocean diagram below.

pipeline {
    agent { label 'my_node' }
    options {
        timestamps()
        parallelsAlwaysFailFast()
    }
    stages {
        stage('1') {
            steps {
                script {
                    step([$class: 'WsCleanup'])
                }
            }
        }
        stage('2') {
            parallel {
                stage("2.1") {
                    steps {
                        script {
                            sh 'echo hi 2.1'
                        }
                    }
                }
                stage("2p") {
                    steps {
                        script {
                            sh 'echo hi 2p'
                        }
                    }
                }
            }
        }
        stage('3') {
            parallel {
                stage('3.1') {
                    steps {
                        script {
                            sh """
                               echo hi 3.1
                            """
                        }
                    }
                }
                stage('3.2') {
                    steps {
                        script {
                            sh """
                                echo "hi 3.2"
                            """
                        }
                    }
                }
            }
        }
        stage('4') {
            steps {
                script {
                    sh "echo end"
                }
            }
        }
    }
}

But I am looking to run 2p in parallel to 2* and 3*, like shown below, is there a way?

I tried to use paralle under parallel, to start 2p in parallel to 2 and 3, and nested parallel to run 3.1. and 3.2 underneath, but declarative pipeline is not allowing nested parallel.

Solution

You can't do this only with Declarative syntax. But you can achieve this with a combination of Scripted and Declarative syntax. One thing to note is, AFAIK there is no visualization support for nested parallel stages as of now. There is a feature request for this here.

Following is a sample pipeline you can use as a reference for your use case.

pipeline {
    agent any
    options {
        timestamps()
        parallelsAlwaysFailFast()
    }
    stages {
        stage('1') {
            steps {
                script {
                    step([$class: 'WsCleanup'])
                }
            }
        }
        stage('2 AND 3') {
        steps {
            script {
                parallel getWrappedStages()
            }
        }
        }
        stage('4') {
            steps {
                script {
                    sh "echo end"
                }
            }
        }
    }
}

def getWrappedStages() {
    stages = [:]
    stages["Step2.1"] = { stage('2.1') {
        sh """
           echo hi 2.1
        """
        } 
        parallel parallel3xstages()
    }
    stages["Step2.p"] = { stage('2.p') {
        sh """
           echo hi 2.p
        """
        } 
    }
    
    return stages
}

def parallel3xstages() {
  stages = [:]
    stages["Step3.1"] = { stage('3.1') {
        sh """
           echo hi 3.1
        """
        }
    }

    stages["Step3.2"] = { stage('3.2') {
        sh """
           echo hi 3.2
        """
        }
    }
  return stages
}

Answered By - ycr
Answer Checked By - Pedro (JavaFixing Volunteer)