From 0fdc754af8758f62a822c6c5aaa23baa40cf834f Mon Sep 17 00:00:00 2001
From: David Turner <david.turner@elastic.co>
Date: Fri, 23 Dec 2022 14:59:38 +0000
Subject: [PATCH] Release delegate ref in RunOnce (#92507)

Like #92452 but for `RunOnce`.
---
 .../common/util/concurrent/RunOnce.java         | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/server/src/main/java/org/elasticsearch/common/util/concurrent/RunOnce.java b/server/src/main/java/org/elasticsearch/common/util/concurrent/RunOnce.java
index 0b9334a03c448..23d62307cb8cd 100644
--- a/server/src/main/java/org/elasticsearch/common/util/concurrent/RunOnce.java
+++ b/server/src/main/java/org/elasticsearch/common/util/concurrent/RunOnce.java
@@ -8,25 +8,24 @@
 package org.elasticsearch.common.util.concurrent;
 
 import java.util.Objects;
-import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
 
 /**
- * Runnable that can only be run one time.
+ * Runnable that prevents running its delegate more than once.
  */
 public class RunOnce implements Runnable {
 
-    private final Runnable delegate;
-    private final AtomicBoolean hasRun;
+    private final AtomicReference<Runnable> delegateRef;
 
     public RunOnce(final Runnable delegate) {
-        this.delegate = Objects.requireNonNull(delegate);
-        this.hasRun = new AtomicBoolean(false);
+        delegateRef = new AtomicReference<>(Objects.requireNonNull(delegate));
     }
 
     @Override
     public void run() {
-        if (hasRun.compareAndSet(false, true)) {
-            delegate.run();
+        var acquired = delegateRef.getAndSet(null);
+        if (acquired != null) {
+            acquired.run();
         }
     }
 
@@ -34,6 +33,6 @@ public void run() {
      * {@code true} if the {@link RunOnce} has been executed once.
      */
     public boolean hasRun() {
-        return hasRun.get();
+        return delegateRef.get() == null;
     }
 }