From 36eb696d429633c9300e62c4d9aa908900f89793 Mon Sep 17 00:00:00 2001
From: Umeshkumar9414 <9414umeshkumar@gmail.com>
Date: Thu, 6 Aug 2026 16:10:32 +0530
Subject: [PATCH] HBASE-30320 TestMemStoreLAB#testLABChunkQueue OOM on fast
 hardware due to unbounded off-pool chunk allocation

Add a memory guard in testLABChunkQueue's allocation threads: before each
copyCellInto call, check heap usage via ManagementFactory and stop allocating
if used memory exceeds 80% of max heap. This prevents OOM on fast hardware
(e.g. Apple Silicon) where threads can allocate ~12.5GB of 256KB chunks in
the 1-second test window, while preserving the time-based test semantics.
---
 .../apache/hadoop/hbase/regionserver/TestMemStoreLAB.java  | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestMemStoreLAB.java b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestMemStoreLAB.java
index dbf8e4cbc891..427e39cfb3fa 100644
--- a/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestMemStoreLAB.java
+++ b/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestMemStoreLAB.java
@@ -329,12 +329,19 @@ public void testForceCopyOfBigCellInto() {
 
   private Thread getChunkQueueTestThread(final MemStoreLABImpl mslab, String threadName,
     ExtendedCell cellToCopyInto) {
+    // Reserve 20% of max heap as safety margin to prevent OOM on fast hardware where threads can
+    // allocate many GB of chunks within the 1-second test window.
+    final long maxMemory = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getMax();
+    final long memoryLimit = (long) (maxMemory * 0.8);
     Thread thread = new Thread() {
       volatile boolean stopped = false;
 
       @Override
       public void run() {
         while (!stopped) {
+          if (ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed() > memoryLimit) {
+            break;
+          }
           // keep triggering chunk retirement
           mslab.copyCellInto(cellToCopyInto);
         }