From b5633bb34473da068309f90e90129db534add937 Mon Sep 17 00:00:00 2001
From: Mustafa Senoglu <mmustafasenoglu0@gmail.com>
Date: Tue, 21 Jul 2026 15:36:32 +0300
Subject: [PATCH] fix: CacheManager memory leak by reusing
 InheritableThreadLocal

CacheManager.clearCache() was creating a new InheritableThreadLocal
instance on every call without calling .remove() on the previous one.
This caused a progressive memory leak that grows with
iteration_count x thread_count when 'Clear cache each iteration'
is enabled.

The existing TODO comment acknowledged this:
  // TODO: avoid re-creating the thread local every time,
  // reset its contents instead

Fix by initializing threadCache once at field declaration and calling
threadCache.remove() in clearCache() instead of creating a new
instance. The next .get() call will lazily create a fresh cache
via initialValue().

Also added @SuppressWarnings for ErrorProne's ThreadLocalUsage since
InheritableThreadLocal is used intentionally for per-thread caching.

Fixes #6730

Signed-off-by: Mustafa Senoglu <mmustafasenoglu0@gmail.com>
---
 .../protocol/http/control/CacheManager.java   | 21 ++++++++++---------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/protocol/http/src/main/java/org/apache/jmeter/protocol/http/control/CacheManager.java b/src/protocol/http/src/main/java/org/apache/jmeter/protocol/http/control/CacheManager.java
index 8852f6332e4..9ca0f9a2f5e 100644
--- a/src/protocol/http/src/main/java/org/apache/jmeter/protocol/http/control/CacheManager.java
+++ b/src/protocol/http/src/main/java/org/apache/jmeter/protocol/http/control/CacheManager.java
@@ -80,7 +80,16 @@ public class CacheManager extends ConfigTestElement implements TestStateListener
     public static final String MAX_SIZE = "maxSize";  // $NON-NLS-1$
     //-
 
-    private transient InheritableThreadLocal<Cache<String, CacheEntry>> threadCache;
+    @SuppressWarnings("ThreadLocalUsage") // intentionally using InheritableThreadLocal for per-thread cache
+    private final transient InheritableThreadLocal<Cache<String, CacheEntry>> threadCache =
+            new InheritableThreadLocal<Cache<String, CacheEntry>>(){
+                @Override
+                protected Cache<String, CacheEntry> initialValue() {
+                    return Caffeine.newBuilder()
+                            .maximumSize(getMaxSize())
+                            .build();
+                }
+            };
 
     private transient boolean useExpires; // Cached value
 
@@ -602,15 +611,7 @@ public void clear(){
 
     private void clearCache() {
         log.debug("Clear cache");
-        // TODO: avoid re-creating the thread local every time, reset its contents instead
-        threadCache = new InheritableThreadLocal<Cache<String, CacheEntry>>(){
-            @Override
-            protected Cache<String, CacheEntry> initialValue() {
-                return Caffeine.newBuilder()
-                        .maximumSize(getMaxSize())
-                        .build();
-            }
-        };
+        threadCache.remove();
     }
 
     /**