From 53994882c4f065f3b6576af3c201178eebf1fa3f Mon Sep 17 00:00:00 2001
From: waterWang <waterWang@users.noreply.github.com>
Date: Sun, 2 Aug 2026 18:22:30 +0800
Subject: [PATCH] fix: synchronize GraalVM JavaScript context access in
 JavaScriptTieredBrokerSelectorStrategy (#18253)

---
 .../router/JavaScriptTieredBrokerSelectorStrategy.java      | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/services/src/main/java/org/apache/druid/server/router/JavaScriptTieredBrokerSelectorStrategy.java b/services/src/main/java/org/apache/druid/server/router/JavaScriptTieredBrokerSelectorStrategy.java
index b6a1995a64b0..aff305314d16 100644
--- a/services/src/main/java/org/apache/druid/server/router/JavaScriptTieredBrokerSelectorStrategy.java
+++ b/services/src/main/java/org/apache/druid/server/router/JavaScriptTieredBrokerSelectorStrategy.java
@@ -53,9 +53,11 @@ public JavaScriptTieredBrokerSelectorStrategy(
   }
 
   @Override
-  public Optional<String> getBrokerServiceName(TieredBrokerConfig config, Query query)
+  public synchronized Optional<String> getBrokerServiceName(TieredBrokerConfig config, Query query)
   {
-    fnSelector = fnSelector == null ? JavaScriptUtil.compileSelectorFunction(SelectorFunction.class, function) : fnSelector;
+    if (fnSelector == null) {
+      fnSelector = JavaScriptUtil.compileSelectorFunction(SelectorFunction.class, function);
+    }
     return Optional.fromNullable(fnSelector.apply(config, query));
   }