How to specify docker agent parametrically?

Question

In Jenkins pipeline code we can set environment variables and use them later as parameters when executing different stages:

pipeline {
  agent any
  environment {
    MY_VAR = 'hello'
  }
  stage('Greetings') {
    steps {
      echo "Say $MY_VAR first"
      sh "./make-all-greetings"
      echo "This worked as expected!"          
    }
  }
}

This trick, however, doesn't seem to work when specifying a docker image as an agent:

pipeline {
  agent any
  environment {
    MY_VAR = 'hello'
    DOCKER_IMAGE = 'python:3'
  }
  stage('Greetings') {
    steps {
      echo "Say $MY_VAR first"
      sh "./make-all-greetings"
      echo "This worked as expected!"
    }
  }
  stage('Build in docker') {
    agent {
      image "$DOCKER_IMAGE"
      reuseNode true
    }
    steps {
      echo "Who cares... Pipeline breaks"
    }
  }
}

It fails miserably with:

groovy.lang.MissingPropertyException: No such property: DOCKER_IMAGE for class: groovy.lang.Binding
  at groovy.lang.Binding.getVariable(Binding.java:63)
  at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onGetProperty(SandboxInterceptor.java:242)
  at org.kohsuke.groovy.sandbox.impl.Checker$6.call(Checker.java:284)
  ...

UPDATE:

Declaring image "${env.DOCKER_IMAGE}" does help with not breaking things immediately but the agent declaration section doesn't seem to see the same environment steps do:

[job-name] Running shell script
+ docker inspect -f . null

Error: No such object: null
[Pipeline] sh
[job-name] Running shell script
+ docker pull null
Using default tag: latest
Error response from daemon: pull access denied for null, repository does not exist or may require 'docker login'

Is what I'm trying to do illegal?
If so, why?
What are my options for parametric selection of docker agent?

@Vasan, yes, I have. It does not work either. Seems to return the environment variable as null and then fails when trying to find a docker container named "null". It seems like declaring agents happens on a different scope separate from everything else. — AlexanderF, Jan 25 '18 at 17:39

score 0 · Answer 1 · answered Apr 20 '18 at 03:03

Got it... Not sure I'm happy about it, but got it to work, just I wonder why it has to be so hard...

try :

pipeline {
  agent any
  environment {
    MY_VAR = 'hello'
    DOCKER_IMAGE = 'python:3'
  }
  stage('Greetings') {
    steps {
      echo "Say $MY_VAR first"
      sh "./make-all-greetings"
      echo "This worked as expected!"
    }
  }
  stage('Build in docker') {
    agent {
      image '$DOCKER_IMAGE'
      reuseNode true
    }
    steps {
      echo "Who cares... Pipeline breaks"
    }
  }
}

Yes it's counter intuitive but the quotes made the trick.

How to specify docker agent parametrically?

1 Answers1