From 2509de520f7d1e3187995482ee2ded0cf16050ad Mon Sep 17 00:00:00 2001
From: Mark Vieira <portugee@gmail.com>
Date: Mon, 2 Dec 2024 15:21:37 -0800
Subject: [PATCH] Avoid race condition when listeners are registered
 concurrently

---
 .../test/cluster/util/resource/MutableResource.java             | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/test-clusters/src/main/java/org/elasticsearch/test/cluster/util/resource/MutableResource.java b/test/test-clusters/src/main/java/org/elasticsearch/test/cluster/util/resource/MutableResource.java
index 60863c4ad61db..477ad82e5944a 100644
--- a/test/test-clusters/src/main/java/org/elasticsearch/test/cluster/util/resource/MutableResource.java
+++ b/test/test-clusters/src/main/java/org/elasticsearch/test/cluster/util/resource/MutableResource.java
@@ -47,7 +47,7 @@ public void update(Resource delegate) {
      *
      * @param listener action to be called on update
      */
-    public void addUpdateListener(Consumer<? super Resource> listener) {
+    public synchronized void addUpdateListener(Consumer<? super Resource> listener) {
         listeners.add(listener);
     }
 }