YARN-2972. DelegationTokenRenewer thread pool never expands. Contributed by Jason Lowe

(cherry picked from commit 2b4b0e8847048850206f091c6870a02e08cfe836)

hadoop-yarn-project/CHANGES.txt

@@ -106,6 +106,9 @@ Release 2.7.0 - UNRELEASED
     YARN-2762. Fixed RMAdminCLI to trim and check node-label related arguments
     before sending to RM. (Rohith Sharmaks via jianhe)
 
+    YARN-2972. DelegationTokenRenewer thread pool never expands. (Jason Lowe
+    via junping_du)
+
   OPTIMIZATIONS
 
   BUG FIXES

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

@@ -148,7 +148,7 @@ public class DelegationTokenRenewer extends AbstractService {
         .setNameFormat("DelegationTokenRenewer #%d")
         .build();
     ThreadPoolExecutor pool =
-        new ThreadPoolExecutor((5 < nThreads ? 5 : nThreads), nThreads, 3L,
+        new ThreadPoolExecutor(nThreads, nThreads, 3L,
             TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
     pool.setThreadFactory(tf);
     pool.allowCoreThreadTimeOut(true);