YARN-7661. NodeManager metrics return wrong value after update node resource. Contributed by Yang Wang

(cherry picked from commit 811fabdebe881248756c0165bf7667bfc22be9bb)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/metrics/NodeManagerMetrics.java

@@ -146,7 +146,7 @@ public class NodeManagerMetrics {
 
   public void addResource(Resource res) {
     availableMB = availableMB + res.getMemorySize();
-    availableGB.incr((int)Math.floor(availableMB/1024d));
+    availableGB.set((int)Math.floor(availableMB/1024d));
     availableVCores.incr(res.getVirtualCores());
   }
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/metrics/TestNodeManagerMetrics.java

@@ -84,6 +84,12 @@ public class TestNodeManagerMetrics {
     // allocatedGB: 3.75GB allocated memory is shown as 4GB
     // availableGB: 4.25GB available memory is shown as 4GB
     checkMetrics(10, 1, 1, 1, 1, 1, 4, 7, 4, 13, 3);
+
+    // Update resource and check available resource again
+    metrics.addResource(total);
+    MetricsRecordBuilder rb = getMetrics("NodeManagerMetrics");
+    assertGauge("AvailableGB", 12, rb);
+    assertGauge("AvailableVCores", 19, rb);
   }
 
   private void checkMetrics(int launched, int completed, int failed, int killed,