YARN-9765. SLS runner crashes when run with metrics turned off. Contributed by Abhishek Modi.

(cherry picked from commit 10ec31d20ee1b6a0b1da915acb6b6ec33f2cd415)

hadoop-tools/hadoop-sls/src/main/java/org/apache/hadoop/yarn/sls/SLSRunner.java

@@ -82,6 +82,7 @@ import org.apache.hadoop.yarn.sls.conf.SLSConfiguration;
 import org.apache.hadoop.yarn.sls.nodemanager.NMSimulator;
 import org.apache.hadoop.yarn.sls.resourcemanager.MockAMLauncher;
 import org.apache.hadoop.yarn.sls.scheduler.SLSCapacityScheduler;
+import org.apache.hadoop.yarn.sls.scheduler.SchedulerMetrics;
 import org.apache.hadoop.yarn.sls.scheduler.TaskRunner;
 import org.apache.hadoop.yarn.sls.scheduler.SLSFairScheduler;
 import org.apache.hadoop.yarn.sls.scheduler.ContainerSimulator;
@@ -768,7 +769,10 @@ public class SLSRunner extends Configured implements Tool {
     }
 
     queueAppNumMap.put(queueName, appNum);
-    wrapper.getSchedulerMetrics().trackQueue(queueName);
+    SchedulerMetrics metrics = wrapper.getSchedulerMetrics();
+    if (metrics != null) {
+      metrics.trackQueue(queueName);
+    }
   }
 
   private void runNewAM(String jobType, String user,