From 7521efa02aa0564f935048c999828f8c8e331648 Mon Sep 17 00:00:00 2001
From: Nick Bulleid <nickb@carallon.com>
Date: Thu, 8 Jul 2021 11:48:44 +0100
Subject: [PATCH] Add PauseAction when throttling pipelines

---
 .../ThrottleQueueTaskDispatcher.java          | 50 +++++++++++++++----
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/src/main/java/hudson/plugins/throttleconcurrents/ThrottleQueueTaskDispatcher.java b/src/main/java/hudson/plugins/throttleconcurrents/ThrottleQueueTaskDispatcher.java
index e04d6322..262c01a3 100644
--- a/src/main/java/hudson/plugins/throttleconcurrents/ThrottleQueueTaskDispatcher.java
+++ b/src/main/java/hudson/plugins/throttleconcurrents/ThrottleQueueTaskDispatcher.java
@@ -41,6 +41,7 @@
 import org.jenkinsci.plugins.workflow.graph.StepNode;
 import org.jenkinsci.plugins.workflow.graphanalysis.LinearBlockHoppingScanner;
 import org.jenkinsci.plugins.workflow.steps.StepDescriptor;
+import org.jenkinsci.plugins.workflow.support.actions.PauseAction;
 import org.jenkinsci.plugins.workflow.support.concurrent.Timeout;
 import org.jenkinsci.plugins.workflow.support.steps.ExecutorStepExecution.PlaceholderTask;
 
@@ -58,14 +59,17 @@ public class ThrottleQueueTaskDispatcher extends QueueTaskDispatcher {
     @Deprecated
     @Override
     public @CheckForNull CauseOfBlockage canTake(Node node, Task task) {
+        CauseOfBlockage cause = null;
         if (Jenkins.getAuthentication().equals(ACL.SYSTEM)) {
-            return canTakeImpl(node, task);
-        }
-
-        // Throttle-concurrent-builds requires READ permissions for all projects.
-        try (ACLContext ctx = ACL.as(ACL.SYSTEM)) {
-            return canTakeImpl(node, task);
+            cause = canTakeImpl(node, task);
+        } else {
+            // Throttle-concurrent-builds requires READ permissions for all projects.
+            try (ACLContext ctx = ACL.as(ACL.SYSTEM)) {
+                cause = canTakeImpl(node, task);
+            }
         }
+        updatePauseAction(task, cause);
+        return cause;
     }
 
     private CauseOfBlockage canTakeImpl(Node node, Task task) {
@@ -214,14 +218,17 @@ private boolean shouldBeThrottled(@NonNull Task task, @CheckForNull ThrottleJobP
     }
 
     private CauseOfBlockage canRun(Task task, ThrottleJobProperty tjp, List<String> pipelineCategories) {
+        CauseOfBlockage cause = null;
         if (Jenkins.getAuthentication().equals(ACL.SYSTEM)) {
-            return canRunImpl(task, tjp, pipelineCategories);
-        }
-
+            cause = canRunImpl(task, tjp, pipelineCategories);
+        } else {
         // Throttle-concurrent-builds requires READ permissions for all projects.
-        try (ACLContext ctx = ACL.as(ACL.SYSTEM)) {
-            return canRunImpl(task, tjp, pipelineCategories);
+            try (ACLContext ctx = ACL.as(ACL.SYSTEM)) {
+                cause = canRunImpl(task, tjp, pipelineCategories);
+            }
         }
+        updatePauseAction(task, cause);
+        return cause;
     }
 
     private CauseOfBlockage canRunImpl(Task task, ThrottleJobProperty tjp, List<String> pipelineCategories) {
@@ -682,5 +689,26 @@ private int getMaxConcurrentPerNodeBasedOnMatchingLabels(
         return maxConcurrentPerNodeLabeledIfMatch;
     }
 
+    private void updatePauseAction(Task task, CauseOfBlockage cause) {
+        if (task instanceof PlaceholderTask) {
+            PlaceholderTask placeholderTask = (PlaceholderTask)task;
+            try {
+                FlowNode flowNode = placeholderTask.getNode();
+                if (cause != null) {
+                    if (flowNode.getAction(PauseAction.class) == null) {
+                        flowNode.addAction(new PauseAction(cause.getShortDescription()));
+                    }
+                } else {
+                    PauseAction.endCurrentPause(flowNode);
+                }
+            } catch (IOException|InterruptedException e) {
+                LOGGER.log(
+                        Level.WARNING,
+                        "Error setting pause action on pipeline {0}: {1}",
+                        new Object[] {task.getDisplayName(), e});
+            }
+        }
+    }
+
     private static final Logger LOGGER = Logger.getLogger(ThrottleQueueTaskDispatcher.class.getName());
 }