A jenkins script to clean up workspaces on slaves

gistfile1.groovy

// Check if a slave has < 10 GB of free space, wipe out workspaces if it does

import hudson.model.*;
import hudson.util.*;
import jenkins.model.*;
import hudson.FilePath.FileCallable;
import hudson.slaves.OfflineCause;
import hudson.node_monitors.*;
import org.jenkinsci.plugins.workflow.job.WorkflowRun
import org.jenkinsci.plugins.workflow.flow.FlowExecution;
import org.jenkinsci.plugins.workflow.graph.FlowGraphWalker;
import org.jenkinsci.plugins.workflow.graph.FlowNode;
import org.jenkinsci.plugins.workflow.graph.StepStartNode;
import org.jenkinsci.plugins.workflow.cps.nodes.StepStartNode;
import org.jenkinsci.plugins.workflow.actions.WorkspaceAction

def MIN_FREE_DISK_SPACE = 10  //GB

boolean shouldSkip(item) {
    jobName = item.getFullDisplayName()
    if ( !item instanceof Job ||
         "${item.class}".contains('Folder') ||
         !item.metaClass.respondsTo(item, "isBuilding")) {
        return true
    }
    if (item.isBuilding()) {
        println(".. job " + jobName + " is currently running, skipped")
        return true
    }
    return false
}

for (node in Jenkins.instance.nodes) {
    computer = node.toComputer()
    if (computer.getChannel() == null) {
       continue
    }
    //this should keep jenkins master out of harms way
    //change prefix to match your env
    name = node.getDisplayName()
    if (!name.startsWith("ub") && !name.startsWith("win")) {
        continue
     }

    rootPath = node.getRootPath()
    size = DiskSpaceMonitor.DESCRIPTOR.get(computer).size
    roundedSize = size / (1024 * 1024 * 1024) as int

    println("node: " + node.getDisplayName() + ", free space: " + roundedSize + "GB")
    if (roundedSize <= MIN_FREE_DISK_SPACE) {
        computer.setTemporarilyOffline(true, new hudson.slaves.OfflineCause.ByCLI("disk cleanup"))
        println "Set " + node.getDisplayName() + " temporarily offline"
        for (item in Jenkins.instance.getAllItems(TopLevelItem)) {
            if (shouldSkip(item)) {
                continue
            }
            jobName = item.getFullDisplayName()

            workspacePath = node.getWorkspaceFor(item)
            if (workspacePath == null) {
                continue
            }

            customWorkspace=""
            if (!"${item.class}".contains('Workflow')) {
                customWorkspace = item.getCustomWorkspace()
                println("Custom workspace " + customWorkspace)
            } else {
                b = item.getLastBuild()
                if(b instanceof WorkflowRun) {
                    exec = b.getExecution();
                    if(exec == null) {
                        continue;
                    }
                    FlowGraphWalker w = new FlowGraphWalker(exec);
                    for (FlowNode n : w) {
                        if (n instanceof StepStartNode) {
                            action = n.getAction(WorkspaceAction);
                            if(action) {
                                if (action.getNode() != node.getNodeName()) {
                                    continue
                                }
                                String workspace = action.getPath().toString();
                                println("WorkspaceAction: " + workspace)
                                customWorkspace = workspace
                                break
                            }
                        }
                    }
                } else {
                    continue
                }
            }
            println("Job " + jobName +", workspace: " + workspacePath + ", custom workspace: " + customWorkspace)
            if (customWorkspace != null && !customWorkspace.isEmpty()) {
                println("Root path: " + node.getRootPath())
                workspacePath = node.getRootPath().child(customWorkspace)
            }
            pathAsString = workspacePath.getRemote()
            println("To delete: " + workspacePath)
            if (workspacePath.exists()) {
                    //uncommend next to actually delete dirs
                    //workspacePath.deleteRecursive()
                    println("Deleted " + name + ":" + pathAsString)
            }
        }
        computer.setTemporarilyOffline(false, null)
        println "Set " + node.getDisplayName() + " back online"
    }
}

Too unreliable, just use https://gist.github.com/EvilBeaver/35ebded526fb53ecb9716889c1de11df instead