From f715bbef8bafe5a3cfa9a786620d85a83926f29b Mon Sep 17 00:00:00 2001
From: Gary Russell <grussell@pivotal.io>
Date: Fri, 13 Apr 2018 16:22:28 -0400
Subject: [PATCH] GH-646: Avoid sync when no transaction

---
 .../kafka/core/DefaultKafkaProducerFactory.java        | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/spring-kafka/src/main/java/org/springframework/kafka/core/DefaultKafkaProducerFactory.java b/spring-kafka/src/main/java/org/springframework/kafka/core/DefaultKafkaProducerFactory.java
index 7b514a9a..b0000605 100644
--- a/spring-kafka/src/main/java/org/springframework/kafka/core/DefaultKafkaProducerFactory.java
+++ b/spring-kafka/src/main/java/org/springframework/kafka/core/DefaultKafkaProducerFactory.java
@@ -302,9 +302,13 @@ public class DefaultKafkaProducerFactory<K, V> implements ProducerFactory<K, V>,
 		}
 
 		@Override
-		public synchronized void close() {
-			if (this.cache != null && !this.cache.contains(this)) {
-				this.cache.offer(this);
+		public void close() {
+			if (this.cache != null) {
+				synchronized (this) {
+					if (!this.cache.contains(this)) {
+						this.cache.offer(this);
+					}
+				}
 			}
 		}