blueocean view of dynamic parallel stages rendering issue

Question

I am encountering a strange issue and hope I can get some help. Below is a test jenkins pipeline code which can best demonstrate the issue i am seeing. Stage '1p' executes well with both stage 'a' and 'b' executing in parallel ( stage 'one' and 'two' are sequential stage in 'a' and 'b' ). When Stage '2p' starts, the parallel rendering of stage '1p' (yes, previous stage) flattens out as a single bubble ( parallel view disappears) until '2p' is completed. Once stage '2p' is completed, the state '1p' goes back to parallel stage view. I am not sure if this is a bug or I am missing something. The use case I have is stage '2p' has an input step waiting for QA approval, which could be waiting for several hours and the rest of the pipeline is being rendered as a straight line view, even though there are a lot of stages with parallel execution. Any help is appreciated.

fp = [:]
sp = [:]

pipeline {
 agent any
 stages {
  stage('1p') {
  steps {
   script {
     ['a','b'].each { 
       item -> fp[item] = gen_fp(item) 
      }
      parallel fp
    }
   }
  }
  stage('2p') {
   steps {
    script {
      ['c'].each { item -> 
        sp[item] = gen_fp(item) 
       }
        parallel sp
      }
    }
   }
  }
}
def gen_fp(item) {
 return {
   stage(item) {
    stage('one') { 
      sleep 3 
      echo "one" 
    }
    stage('two') { 
      sleep 3 
      echo "two" 
     }
    }
  }
}

Answer 1

This answer is based on my years working with Blueocean, but please correct me if I'm wrong.

Blueocean makes up the structure of the pipeline as it goes, which is why you don't see any new stages you have added in the pipeline until they start executing. So as far as Blueocean is concerned, it realizes stage('one') and stage('two') run sequentially for a and b, which run in parallel. So it draws up the pipeline in that way. However, when it comes to 2p, stage('one') and stage('two') only runs once for c. So it goes ahead and flattens the stage as well as the previous stage. If you were to create a separate function and call it in 2p, you would notice that the pipeline remains parallel for 1p.

Ultimately, I don't think there is much you can do about this. You can consider this a bug although it is unlikely to be fixed at any point soon.