use putIfAbsent in MomentStatsItemSet.java

broker/src/test/java/org/apache/rocketmq/broker/BrokerStatsManagerTest.java

@@ -41,7 +41,14 @@ public class BrokerStatsManagerTest {
         }
     }
 
-    public AtomicLong test_unit() throws InterruptedException {
+    @Test
+    public void test_getAndCreateMomentStatsItem_multiThread() throws InterruptedException {
+        for (int i = 0; i < 5; i++) {
+            assertEquals(10, test_unit_moment().longValue());
+        }
+    }
+
+    private AtomicLong test_unit() throws InterruptedException {
         brokerStatsManager = new BrokerStatsManager("DefaultCluster");
         executor = new ThreadPoolExecutor(100, 200, 10, TimeUnit.SECONDS,
                 new ArrayBlockingQueue<Runnable>(10000), new ThreadFactoryImpl("testMultiThread"));
@@ -62,6 +69,27 @@ public class BrokerStatsManagerTest {
         return brokerStatsManager.getStatsItem(TOPIC_PUT_NUMS, "topicTest").getValue();
     }
 
+    private AtomicLong test_unit_moment() throws InterruptedException {
+        brokerStatsManager = new BrokerStatsManager("DefaultCluster");
+        executor = new ThreadPoolExecutor(100, 200, 10, TimeUnit.SECONDS,
+                new ArrayBlockingQueue<Runnable>(10000), new ThreadFactoryImpl("testMultiThread"));
+        for (int i = 0; i < 10000; i++) {
+            executor.submit(new Runnable() {
+                @Override
+                public void run() {
+                    brokerStatsManager.getMomentStatsItemSetFallTime().setValue("test",10);
+                }
+            });
+        }
+        while (true) {
+            if (executor.getCompletedTaskCount() == 10000) {
+                break;
+            }
+            Thread.sleep(1000);
+        }
+        return brokerStatsManager.getMomentStatsItemSetFallTime().getAndCreateStatsItem("test").getValue();
+    }
+
     @After
     public void shutdown() {
         executor.shutdown();

common/src/main/java/org/apache/rocketmq/common/stats/MomentStatsItemSet.java

@@ -79,10 +79,10 @@ public class MomentStatsItemSet {
         if (null == statsItem) {
             statsItem =
                 new MomentStatsItem(this.statsName, statsKey, this.scheduledExecutorService, this.log);
-            MomentStatsItem prev = this.statsItemTable.put(statsKey, statsItem);
-
-            if (null == prev) {
+            MomentStatsItem prev = this.statsItemTable.putIfAbsent(statsKey, statsItem);
 
+            if (null != prev) {
+                statsItem = prev;
                 // statsItem.init();
             }
         }