Issue
When using @Grab then using import for third party libraries, or using ConfigSlurper, or Eval in Pipeline code, you may encounter a Java Metaspace leak. This issue arises because each time the Pipeline is executed, the Pipeline code to clean up classes was only cleaning up Groovy classes, not Java classes. Over time, these accumulate in the Java Metaspace, causing a memory leak.
An example of the Pipeline code that can cause this issue from https://github.com/jenkinsci/pipeline-groovy-lib-plugin/pull/199 is:
@Grab(group='org.codehaus.groovy.modules.http-builder', module='http-builder', version='0.7.1') import groovyx.net.http.RESTClient
Another example related to ConfigSlurper from https://github.com/jenkinsci/workflow-cps-plugin/pull/122 is:
new ConfigSlurper().parse(...)
Another example that causes Metaspace leaks is using Eval in Pipeline code:
Eval.me("...")
Resolution
The ideal resolution is to avoid using @Grab, ConfigSlurper, or Eval in Pipeline code.
Instead use sh or bat steps to call external scripts, as per Using third-party libraries.
The fix for @Grab has been released in version 4209.v83c4e257f1e9 of the Pipeline: Groovy plugin, and will be included in a future CloudBees CI version.