In the course of testing pipeline error handling and skipping of stages etc I stumbled over the fact that in concurrent pipelines runs with the "milestone" step the following happened:

• Based upon org.jenkinsci.plugins.workflow.steps.FlowInterruptedException#actualInterruption it wrongly pretends that the build was aborted/interrupted due to user action (user aborting the build via UI):

  ...
  Superseded by ACME-Pipeline#9067
  ...
  [DEBUG] isActualInterruption: true             // !!!!!!!
  Skipping stage 'deploy-PRODUCTION-dry-run' due to cancelled build (due to overtaking: [org.jenkinsci.plugins.pipeline.milestone.CancelledCause@3b62f126])...
  ...
  Finished: NOT_BUILT
  

   
  Based upon about this basic pipeline code:

  try {
    ...
  } catch (FlowInterruptedException e) {
    Util.debugLog(script, true, "isActualInterruption: ${e.isActualInterruption()}")
    if (PipelineUtils.isCancelledDueToOvertakingBuild(e.getCauses())) {
      ...
  }
  

  and PipelineUtils.isCancelledDueToOvertakingBuild(...) (corrected 06.11.2021)

    /**
     * Returns true when the caught org.jenkinsci.plugins.workflow.steps.FlowInterruptedException signals that the build
     * interruption was not caused by a user wanting to abort the build; this is typically due to "milestone" step
     * aborting the build due to overtaking builds.
     */
    static boolean isCancelledDueToOvertakingBuild(FlowInterruptedException fie) {
      boolean isCancelledDueToOvertakingBuild = !fie.isActualInterruption()
      return isCancelledDueToOvertakingBuild
    }
  

   

org.jenkinsci.plugins.workflow.steps.FlowInterruptedException states:

    /**
     * If true, this exception represents an actual build interruption, rather than a general error with a result and
     * no stack trace.
     * Used by steps like {@code RetryStep} to decide whether to handle or rethrow a {@link FlowInterruptedException}.
     * Non-null, except momentarily during deserialization before {@link #readResolve} sets the field to {@code true}
     * for old instances serialized before this field was added.
     */
    private Boolean actualInterruption = true;

and

actualInterruption – true if this is an actual build interruption (e.g. the user wants to abort the build)

If my understanding (cf. above assumptions) is correct, then the solution is really trivial: https://github.com/jenkinsci/pipeline-milestone-step-plugin/pull/29