YARN-4047. ClientRMService getApplications has high scheduler lock contention. Contributed by Jason Lowe

(cherry picked from commit 7a445fcfabcf9c6aae219051f65d3f6cb8feb87c)

Conflicts:
	hadoop-yarn-project/CHANGES.txt

hadoop-yarn-project/CHANGES.txt

@@ -49,6 +49,9 @@ Release 2.7.2 - UNRELEASED
 
     YARN-3999. RM hangs on draing events. (Jian He via xgong)
 
+    YARN-4047. ClientRMService getApplications has high scheduler lock contention
+    (Jason Lowe via jianhe)
+
 Release 2.7.1 - 2015-07-06 
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/ClientRMService.java

@@ -744,13 +744,9 @@ public class ClientRMService extends AbstractService implements
       RMApp application = appsIter.next();
 
       // Check if current application falls under the specified scope
-      boolean allowAccess = checkAccess(callerUGI, application.getUser(),
-          ApplicationAccessType.VIEW_APP, application);
       if (scope == ApplicationsRequestScope.OWN &&
           !callerUGI.getUserName().equals(application.getUser())) {
         continue;
-      } else if (scope == ApplicationsRequestScope.VIEWABLE && !allowAccess) {
-        continue;
       }
 
       if (applicationTypes != null && !applicationTypes.isEmpty()) {
@@ -799,6 +795,13 @@ public class ClientRMService extends AbstractService implements
         }
       }
 
+      // checkAccess can grab the scheduler lock so call it last
+      boolean allowAccess = checkAccess(callerUGI, application.getUser(),
+          ApplicationAccessType.VIEW_APP, application);
+      if (scope == ApplicationsRequestScope.VIEWABLE && !allowAccess) {
+        continue;
+      }
+
       reports.add(application.createAndGetApplicationReport(
           callerUGI.getUserName(), allowAccess));
     }