PIPELINE: How to generate env variables on the fly and use them as a Gerrit comment?

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Victor Martinez

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Aug 4, 2017, 4:51:50 AM8/4/17
to Jenkins Users
Hi there,

   I've been struggling a bit in order to accomplish the below use case, first of all this is a long message, It works so far although I've found it a bit 'too much' hacky. That's the reason I want to explain how I did it just in case someone got a similar use case or even, most likely, a better approach.

Use Case

   Using Declarative Pipeline I'd like to inject global env variables using the Gerrit Trigger plugin, then those details will be added as a Gerrit comment. Those env variables will be changed/created on the fly.

   Gerrit Trigger plugin allows to customise the Gerrit comment using the existing env variables plus some default ones, as you can see in the below links
   I've tried to override the value of those env variables or even create a new env variable but those variables weren't expanded correctly or even didn't exist.

From the implementation point of view I used two different DSLs: Pipeline and JobDSL. 

   The JobDSL part is just the Pipeline Job and how it's integrated with Gerrit, while the Pipeline is the declarative pipeline itself.

pipelineJob("gatekeeper") {
  triggers {
    gerritTrigger {
      gerritProjects {
        gerritProject {
          compareType('PLAIN')
          pattern('driver')
          branches {
            branch {
              compareType('PLAIN')
              pattern('trunk')
            }
          }
          disableStrictForbiddenFileVerification(false)
        }
      }
      serverName("gerrit-gpu")
      triggerOnEvents {
        commentAddedContains {
          commentAddedCommentContains('AutomateMe')
        }
      }
      silentMode(false)
    }
  }
  definition {
    cps {
      sandbox()
      script(readFileFromWorkspace('pipeline.groovy'))
    }
  }
}




pipeline {
  agent any
  stage('TestLab') {
      steps {
        script {
          // This is a Long Execution Build in the Test Lab
          def bRun = build job: 'testlab', parameters: [string(name: 'GERRIT_PATCHSET_REVISION', GERRIT_PATCHSET_REVISION)], propagate: false
          sh """
            curl "${bRun.getRawBuild().getAbsoluteUrl()}/artifact/testlab_run.properties/*view*/" --write-out %{http_code} --silent --output /dev/null | grep '200' >/dev/null \
            && curl -s -o ti2_run.properties "${bRun.getRawBuild().getAbsoluteUrl()}/artifact/testlab_run.properties/*view*/" || echo "TESTLAB_URL=null" > testlab_run.properties
          """
        }
      }      
    }
  }
}


How did I inject env variables on the fly using the Declarative Pipeline?

    I was lucky to find: https://issues.jenkins-ci.org/browse/JENKINS-35377 and i coded a declarative pipeline like the below snippet:

import hudson.tasks.test.AbstractTestResultAction
// List of Functions
@NonCPS
def addParameter(build, name, value) {
  // Given a Build it will Inject a Parameter and Value pair
  StringParameterValue p = new StringParameterValue(name, value)
  ParametersAction a = build.getAction(ParametersAction.class)
  if (a) {
    build.replaceAction(a.createUpdated(Collections.singleton(p)));
  } else {
    build.addAction(new ParametersAction(p));
  }
}


pipeline {
  agent any
  parameters {
    string(name: 'TESTLAB_URL', description: 'To expose as a comment in Gerrit')
  }
  stage('TestLab') {
     ...

   post {
    always {
      script {
        def props = readProperties file: 'testlab_run.properties'
        addParameter(currentBuild.rawBuild, "TESTLAB_URL", "${props.
TESTLAB_URL}")
      }
    }
  }   
}


It --worked like a charm--, although I didn't like much the idea of playing with the internal api though. But ... I started to see the below errors:

groovy.lang.MissingPropertyException: No such property: GERRIT_PATCHSET_REVISION for class: WorkflowScript

Null value not allowed as an environment variable: TESTLAB_URL


Those errors where only happing when the pipeline was launched without editing it previously. What do I mean? If i do change the pipeline job, using the Jenkins UI, and save it, then those errors go away only for the next build, while if I don't change anything the next build will fail with the above errors.

How did I solve them?

1st stacktrace error was solved by injecting those env variables which are provided by the Gerrit Trigger as Pipeline parameters:
pipeline {
  agent any
  parameters {
    string(name: 'TESTLAB_URL', description: 'To expose as a comment in Gerrit')
    string(name: 'GERRIT_PATCHSET_REVISION', description: 'To solve MissingPropertyException')
  }
  stage('TestLab') {
      steps {
        script {
          // This is a Long Execution Build in the Test Lab
          def bRun = build job: 'testlab', parameters: [string(name: 'GERRIT_PATCHSET_REVISION', params.GERRIT_PATCHSET_REVISION)], propagate: false


2nd one was by enabling a default value to those parameters

pipeline {
  agent any
  parameters {
    string(name: 'TESTLAB_URL', defaultValue: "empty", description: 'To expose as a comment in Gerrit')
    string(name: 'GERRIT_PATCHSET_REVISION', defaultValue: "empty", description: 'To solve MissingPropertyException')
  }


Final thoughts

This is not an ideal implementation:
  • too complicated
  • too many dependencies
  • non KISS 

Since I couldn't find another way to inject env variables on the fly, I'd like to ask whether you got some ideas, workarounds or even think this is too unstable to keep it running for a while. 

Thanks and sorry for this long message





Victor Martinez

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Aug 4, 2017, 5:52:46 AM8/4/17
to Jenkins Users
Just to clarify, I tried with https://jenkins.io/doc/pipeline/tour/environment/ but I wasn't success unfortunately, since those env variables aren't persistent somehow, see the below snippet:

pipeline {
  agent any
  environment {
      TESTLAB_URL = 'NA'
  }
  stage('TestLab') {
      steps {
        script {
          // This is a Long Execution Build in the Test Lab
          def bRun = build job: 'testlab', parameters: [string(name: 'GERRIT_PATCHSET_REVISION', GERRIT_PATCHSET_REVISION)], propagate: false
          sh """
            curl "${bRun.getRawBuild().getAbsoluteUrl()}/artifact/testlab_run.properties/*view*/" --write-out %{http_code} --silent --output /dev/null | grep '200' >/dev/null \
            && curl -s -o ti2_run.properties "${bRun.getRawBuild().getAbsoluteUrl()}/artifact/testlab_run.properties/*view*/" || echo "TESTLAB_URL=null" > testlab_run.properties
          """
        }
      }      
    }
  }
  post {
    always {
      script {
        def props = readProperties file: 'testlab_run.properties'
        TESTLAB_URL = props. TESTLAB_URL
      }
    }
  }
}


I'm pretty sure I missed something here...

Thanks again

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