diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java
index 43c7820e39..6d3791e955 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java
@@ -487,11 +487,10 @@ public void run() {
           ContainerId containerId = entry.getKey();
           ProcessTreeInfo ptInfo = entry.getValue();
           try {
-            String pId = ptInfo.getPID();
-
             // Initialize uninitialized process trees
             initializeProcessTrees(entry);
 
+            String pId = ptInfo.getPID();
             if (pId == null || !isResourceCalculatorAvailable()) {
               continue; // processTree cannot be tracked
             }