要查看其工作原理，请使用GString 对象执行println 并同时返回agentName 的变量。您可以从输出中看到，此行在任何其他管道代码之前进行了很好的评估。
agentName = "Windows"
agentLabel = "${println 'Right Now the Agent Name is ' + agentName; return agentName}"
pipeline {
agent none
stages {
stage('Prep') {
steps {
script {
agentName = "Linux"
}
}
}
stage('Checking') {
steps {
script {
println agentLabel
println agentName
}
}
}
stage('Final') {
agent { label agentLabel }
steps {
script {
println agentLabel
println agentName
}
}
}
}
}
控制台输出（注意我在这个实例上实际上并没有标记为 Windows 的节点，所以我在找不到它后中止了它）：
Started by user Admin
[Pipeline] echo
Right Now the Agent Name is Windows
[Pipeline] stage
[Pipeline] { (Prep)
[Pipeline] script
[Pipeline] {
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] stage
[Pipeline] { (Checking)
[Pipeline] script
[Pipeline] {
[Pipeline] echo
Windows
[Pipeline] echo
Linux
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] stage
[Pipeline] { (Final)
[Pipeline] node
Still waiting to schedule task
There are no nodes with the label ‘Windows’
Aborted by Admin
[Pipeline] // node
[Pipeline] }
[Pipeline] // stage
[Pipeline] End of Pipeline
ERROR: Queue task was cancelled
Finished: ABORTED
注意Right Now the Agent Name is Windows 行是如何出现在输出的早期的。这解释了为什么您的值为 null。该语句在您的脚本修改变量之前很久就被评估。
以后我可能会尝试使用懒惰的GString 来获取变量。
agentLabel = "${-> println 'Right Now the Agent Name is ' + agentName; return agentName}"
不幸的是，这会引发错误，因为它需要一个字符串类型。显然，它可以将非惰性 GString 强制转换为 String ，但不能强制惰性版本。因此，当我强制强制转换为 String 时，它当然会在那个时候评估变量（这也是在管道代码实际运行之前）。
agent { label agentLabel as String }
您可以通过回退到旧的节点分配方法来解决问题：
agentName = "Windows"
agentLabel = "${-> println 'Right Now the Agent Name is ' + agentName; return agentName}"
pipeline {
agent none
stages {
stage('Prep') {
steps {
script {
agentName = "Linux"
}
}
}
stage('Checking') {
steps {
script {
println agentLabel
println agentName
}
}
}
stage('Final') {
steps {
node( agentLabel as String ) { // Evaluate the node label later
echo "TEST"
}
script {
println agentLabel
println agentName
}
}
}
}
}
您可以从此控制台输出中看到，它现在正确地找到了 Linux 节点并完成了管道。 agentName == Windows 时的早期评估永远不会发生：
Started by user Admin
[Pipeline] stage
[Pipeline] { (Prep)
[Pipeline] script
[Pipeline] {
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] stage
[Pipeline] { (Checking)
[Pipeline] script
[Pipeline] {
[Pipeline] echo
Right Now the Agent Name is Linux
[Pipeline] echo
Linux
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] stage
[Pipeline] { (Final)
[Pipeline] echo
Right Now the Agent Name is Linux
[Pipeline] node
Running on Slave 1 in /home/jenkinsslave/jenkins/workspace/test
[Pipeline] {
[Pipeline] echo
TEST
[Pipeline] }
[Pipeline] // node
[Pipeline] script
[Pipeline] {
[Pipeline] echo
Right Now the Agent Name is Linux
[Pipeline] echo
Linux
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] End of Pipeline
Finished: SUCCESS
如果没有懒惰的GString 并稍后键入强制，这可能会起作用，但我没有尝试过。