Jenkins: In a declarative jenkins pipeline - can I set the agent label dynamically?

Question

Is there a way to set the agent label dynamically and not as plain string?

The job has 2 stages:

1. First stage - Runs on a "master" agent, always. At the end of this stage I will know on which agent should the 2nd stage run.
2. Second stage - should run on the agent decided in the first stage.

My (not working) attempt looks like this:

pipeline {     agent { label 'master' }     stages {         stage('Stage1') {             steps {                 script {                     env.node_name = "my_node_label"                 }                 echo "node_name: ${env.node_name}"             }         }          stage('Stage2') {             agent { label "${env.node_name}" }             steps {                 echo "node_name: ${env.node_name}"             }         }     } } 

The first echo works fine and "my_node_label" is printed. The second stage fails to run on an agent labeled "my_node_label" and the console prints:

There are no nodes with the label ‘null’

Maybe it can help - if I just put "${env}" in the label field I can see that this is a java class as it prints:

There are no nodes with the label ‘org.jenkinsci.plugins.workflow.cps.EnvActionImpl@79c0ce06’

Answer 1

Here is how I made it: mix scripted and declarative pipeline. First I've used scripted syntax to find, for example, the branch I'm on. Then define AGENT_LABEL variable. This var can be used anywhere along the declarative pipeline

def AGENT_LABEL = null  node('master') {   stage('Checkout and set agent'){      checkout scm      ### Or just use any other approach to figure out agent label: read file, etc      if (env.BRANCH_NAME == 'master') {         AGENT_LABEL = "prod"      } else {         AGENT_LABEL = "dev"      }    } }  pipeline {     agent {        label "${AGENT_LABEL}"     }      stages {         stage('Normal build') {            steps {               echo "Running in ${AGENT_LABEL}"               sh "hostname"            }         }           stage ("Docker build") {            agent{              dockerfile {                 dir 'Dockerfiles'                 label "${AGENT_LABEL}"              }             }             steps{                 sh "hostname"             }         }     } }