[Pipeline] @NonCPS causes "sh" to hang with parallel steps

[Jørgen Sølvernes Sandnes]

Hi!

I struggled for a long time trying to figure out why my parallel steps kept hanging when running shell commands (sh). After trying a lot of different things, I found out that the @NonCPS annotation caused this behavior to happen. See the sample Jenkinsfile below. When I commented the @NonCPS line out it started working again. I don't know enough about (Non)CPS stuff to figure out if this is the way it's supposed to work, or if it's a bug of some sort. Are there any experts out there who know? :)

Best regards,

Jørgen

Jenkinsfile: 

#!groovy​
/*
 * Reproduction of the "hanging sh" problem
 */
timestamps {
    node {

        stage ("Running in sequence") {
            echo "Start of stage running in sequence"
            
            sh "pwd"
            
            echo "End of stage running in sequence"
       }
        
        stage ("Running in parallel") {
            echo "Start of stage running in parallel"

            def parallelSteps = [:]
            parallelSteps["step1"] = createParallelStep()

            parallel parallelSteps

            echo "End of stage running in parallel"
        }
    }
}

@NonCPS
def createParallelStep() {
    echo "Creates parallel step"
    return {
        node {
            echo "Running parallel step"
            
            sh "pwd"

            echo "Parallel step complete"

        }
    }
}

[David Karr]

In short, you can't execute "pipeline steps", and "sh" is a pipeline
step, from a @NonCPS method.

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[Jørgen Sølvernes Sandnes]

Thanks! Would it be possible to improve the framework so that an exception would be thrown when attempting to do pipeline steps from a @NonCPS method? (I assume other people than me have spent hours and hours of debugging before realizing what is wrong)

[Ann B]

Very helpful Jorgen!  I have also spent hours on this issue. 

Ann