[FIXED] Jenkins - How to run a stage/function before pipeline starts?

Issue

We are using a Jenkins multibranch pipeline with BitBucket to build pull request branches as part of our code review process.

We wanted to abort any queued or in-progress builds so that we only run and keep the latest build - I created a function for this:

def call(){
    def jobName = env.JOB_NAME
    def buildNumber = env.BUILD_NUMBER.toInteger()
    def currentJob = Jenkins.instance.getItemByFullName(jobName)
    
    for (def build : currentJob.builds){
        def exec = build.getExecutor()
        if(build.isBuilding() && build.number.toInteger() != buildNumber && exec != null){
            exec.interrupt(
                Result.ABORTED,
                new CauseOfInterruption.UserInterruption("Job aborted by #${currentBuild.number}")
            )
            println("Job aborted previously running build #${build.number}")
        }
    }
}

Now in my pipeline, I want to run this function when the build is triggered by the creation or push to a PR branch.

It seems the only way I can do this is to set the agent to none and then set it to the correct node for each of the subsequent stages. This results in missing environment variables etc. since the 'environment' section runs on the master.

If I use agent { label 'mybuildnode' } then it won't run the stage until the agent is free from the currently in-progress/running build.

Is there a way I can get the 'cancelpreviousbuilds()' function to run before the agent is allocated as part of my pipeline?

This is roughly what I have currently but doesn't work because of environment variable issues - I had to do the skipDefaultCheckout so I could do it manually as part of my build:

pipeline {
    agent none
    environment {
        VER = '1.2'
        FULLVER = "${VER}.${BUILD_NUMBER}.0"
        PROJECTPATH = "<project path>"
        TOOLVER = "2017"
    }   
    options {
        skipDefaultCheckout true
    }
    stages {
        stage('Check Builds') {
            when {
                branch 'PR-*'
            }
            steps {
                // abort any queued/in-progress builds for PR branches
                cancelpreviousbuilds()
            }
        }
        stage('Checkout') {
    
            agent {
                label 'buildnode'
            }       
            steps {         
                checkout scm        
            }
        }
    }
}

It works and aborts the build successfully but I get errors related to missing environment variables because I had to start the pipeline with agent none and then set each stage to agent label 'buildnode' to.

I would prefer that my entire pipeline ran on the correct agent so that workspaces / environment variables were set correctly but I need a way to trigger the cancelpreviousbuilds() function without requiring the buildnode agent to be allocated first.

Solution

You can try combining the declarative pipeline and the scripted pipeline, which is possible.

Example (note I haven't tested it):

// this is scripted pipeline
node('master') { // use whatever node name or label you want
    stage('Cancel older builds') {
        cancel_old_builds()
    }
}

// this is declarative pipeline
pipeline {
    agent { label 'buildnode' }
    ...
}

As a small side comment, you seem to use: build.number.toInteger() != buildNumber which would abort not only older builds but also newer ones. In our CI setup, we've decided that it's best to abort the current build if a newer build has already been scheduled.

Answered By - MaratC
Answer Checked By - Timothy Miller (JavaFixing Admin)