YARN-8212. Pending backlog for async allocation threads should be configurable. Contributed by Tao Yang.

(Cherry picked from commit 2d319e37937c1e20c6a7dc4477ef88defd1f8464)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/CapacityScheduler.java

@@ -245,6 +245,7 @@ public class CapacityScheduler extends
       CapacitySchedulerConfiguration.SCHEDULE_ASYNCHRONOUSLY_PREFIX
           + ".scheduling-interval-ms";
   private static final long DEFAULT_ASYNC_SCHEDULER_INTERVAL = 5;
+  private long asyncMaxPendingBacklogs;
 
   public CapacityScheduler() {
     super(CapacityScheduler.class.getName());
@@ -354,6 +355,11 @@ public class CapacityScheduler extends
           asyncSchedulerThreads.add(new AsyncScheduleThread(this));
         }
         resourceCommitterService = new ResourceCommitterService(this);
+        asyncMaxPendingBacklogs = this.conf.getInt(
+            CapacitySchedulerConfiguration.
+                SCHEDULE_ASYNCHRONOUSLY_MAXIMUM_PENDING_BACKLOGS,
+            CapacitySchedulerConfiguration.
+                DEFAULT_SCHEDULE_ASYNCHRONOUSLY_MAXIMUM_PENDING_BACKLOGS);
       }
 
       // Setup how many containers we can allocate for each round
@@ -541,7 +547,8 @@ public class CapacityScheduler extends
             Thread.sleep(100);
           } else {
             // Don't run schedule if we have some pending backlogs already
-            if (cs.getAsyncSchedulingPendingBacklogs() > 100) {
+            if (cs.getAsyncSchedulingPendingBacklogs()
+                > cs.asyncMaxPendingBacklogs) {
               Thread.sleep(1);
             } else{
               schedule(cs);

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/CapacitySchedulerConfiguration.java

@@ -239,6 +239,14 @@ public class CapacitySchedulerConfiguration extends ReservationSchedulerConfigur
   public static final String SCHEDULE_ASYNCHRONOUSLY_MAXIMUM_THREAD =
       SCHEDULE_ASYNCHRONOUSLY_PREFIX + ".maximum-threads";
 
+  @Private
+  public static final String SCHEDULE_ASYNCHRONOUSLY_MAXIMUM_PENDING_BACKLOGS =
+      SCHEDULE_ASYNCHRONOUSLY_PREFIX + ".maximum-pending-backlogs";
+
+  @Private
+  public static final Integer
+      DEFAULT_SCHEDULE_ASYNCHRONOUSLY_MAXIMUM_PENDING_BACKLOGS = 100;
+
   @Private
   public static final boolean DEFAULT_SCHEDULE_ASYNCHRONOUSLY_ENABLE = false;