svn merge -c 1182641 from trunk for HADOOP-7509.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1189986 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -416,6 +416,9 @@ Release 0.23.0 - Unreleased
     HADOOP-7668. Add a NetUtils method that can tell if an InetAddress 
     belongs to local host. (suresh)
 
+    HADOOP-7509. Improve exception message thrown when Authentication is 
+    required. (Ravi Prakash via suresh)
+
   OPTIMIZATIONS
   
     HADOOP-7333. Performance improvement in PureJavaCrc32. (Eric Caspole

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Server.java

@@ -1171,8 +1171,12 @@ public abstract class Server {
             throw new IOException("Unable to read authentication method");
           }
           if (isSecurityEnabled && authMethod == AuthMethod.SIMPLE) {
-            AccessControlException ae = new AccessControlException(
-                "Authentication is required");
+            AccessControlException ae = new AccessControlException("Authorization ("
+              + CommonConfigurationKeys.HADOOP_SECURITY_AUTHENTICATION
+              + ") is enabled but authentication ("
+              + CommonConfigurationKeys.HADOOP_SECURITY_AUTHORIZATION
+              + ") is configured as simple. Please configure another method "
+              + "like kerberos or digest.");
             setupResponse(authFailedResponse, authFailedCall, Status.FATAL,
                 null, ae.getClass().getName(), ae.getMessage());
             responder.doRespond(authFailedCall);