MAPREDUCE-6473. Job submission can take a long time during Cluster initialization. Contributed by Kuhu Shukla

hadoop-mapreduce-project/CHANGES.txt

@@ -468,6 +468,9 @@ Release 2.8.0 - UNRELEASED
     MAPREDUCE-6394. Speed up Task processing loop in HsTasksBlock#render()
     (Ray Chiang via jlowe)
 
+    MAPREDUCE-6473. Job submission can take a long time during Cluster
+    initialization (Kuhu Shukla via jlowe)
+
   BUG FIXES
 
     MAPREDUCE-6314. TestPipeApplication fails on trunk.

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/Cluster.java

@@ -66,6 +66,22 @@ public class Cluster {
 
   private static ServiceLoader<ClientProtocolProvider> frameworkLoader =
       ServiceLoader.load(ClientProtocolProvider.class);
+  private volatile List<ClientProtocolProvider> providerList = null;
+
+  private void initProviderList() {
+    if (providerList == null) {
+      synchronized (frameworkLoader) {
+        if (providerList == null) {
+          List<ClientProtocolProvider> localProviderList =
+              new ArrayList<ClientProtocolProvider>();
+          for (ClientProtocolProvider provider : frameworkLoader) {
+            localProviderList.add(provider);
+          }
+          providerList = localProviderList;
+        }
+      }
+    }
+  }
 
   static {
     ConfigUtil.loadResources();
@@ -85,8 +101,8 @@ public class Cluster {
   private void initialize(InetSocketAddress jobTrackAddr, Configuration conf)
       throws IOException {
 
-    synchronized (frameworkLoader) {
+    initProviderList();
-      for (ClientProtocolProvider provider : frameworkLoader) {
+    for (ClientProtocolProvider provider : providerList) {
       LOG.debug("Trying ClientProtocolProvider : "
           + provider.getClass().getName());
       ClientProtocol clientProtocol = null;
@@ -103,18 +119,15 @@ public class Cluster {
           LOG.debug("Picked " + provider.getClass().getName()
               + " as the ClientProtocolProvider");
           break;
-          }
+        } else {
-          else {
           LOG.debug("Cannot pick " + provider.getClass().getName()
               + " as the ClientProtocolProvider - returned null protocol");
         }
-        } 
+      } catch (Exception e) {
-        catch (Exception e) {
         LOG.info("Failed to use " + provider.getClass().getName()
             + " due to error: ", e);
       }
     }
-    }
 
     if (null == clientProtocolProvider || null == client) {
       throw new IOException(