From 7470bbcb74cae360c58840a9f2eadbba21718d3b Mon Sep 17 00:00:00 2001
From: Syed Shameerur Rahman <rhmanns@amazon.com>
Date: Mon, 8 Sep 2025 12:57:22 +0530
Subject: [PATCH] YARN-11838: YARN ConcurrentModificationException When
 Refreshing Node Attributes

---
 .../nodelabels/NodeAttributesManagerImpl.java            | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/nodelabels/NodeAttributesManagerImpl.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/nodelabels/NodeAttributesManagerImpl.java
index 2b7561367033a..c8f7a1f5df787 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/nodelabels/NodeAttributesManagerImpl.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/nodelabels/NodeAttributesManagerImpl.java
@@ -741,7 +741,14 @@ public void refreshNodeAttributesToScheduler(NodeId nodeId) {
     if (host == null || host.attributes == null) {
       return;
     }
-    newNodeToAttributesMap.put(hostName, host.attributes.keySet());
+    // Use read lock and create defensive copy since
+    // other threads might access host.attributes
+    readLock.lock();
+    try {
+      newNodeToAttributesMap.put(hostName, new HashSet<>(host.attributes.keySet()));
+    } finally {
+      readLock.unlock();
+    }
 
     // Notify RM
     if (rmContext != null && rmContext.getDispatcher() != null) {