HADOOP-6687. user object in the subject in UGI should be reused in case of a relogin.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@952454 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -70,6 +70,9 @@ Trunk (unreleased changes)
 
     HADOOP-6649.  login object in UGI should be inside the subject (jnp via boryas)
 
+    HADOOP-6687.   user object in the subject in UGI should be reused in case 
+    of a relogin. (jnp via boryas)
+
 Release 0.21.0 - Unreleased
 
   INCOMPATIBLE CHANGES

src/java/org/apache/hadoop/security/UserGroupInformation.java

@@ -88,6 +88,10 @@ public class UserGroupInformation {
 
     @Override
     public boolean commit() throws LoginException {
+      // if we already have a user, we are done.
+      if (!subject.getPrincipals(User.class).isEmpty()) {
+        return true;
+      }
       Principal user = null;
       // if we are using kerberos, try it out
       if (useKerberos) {

src/test/core/org/apache/hadoop/security/TestUserGroupInformation.java

@@ -302,4 +302,18 @@ public class TestUserGroupInformation {
     //login1 and login2 must be same instances
     Assert.assertTrue(login1 == login2);
   }
+  
+  @Test
+  public void testLoginModuleCommit() throws Exception {
+    UserGroupInformation loginUgi = UserGroupInformation.getLoginUser();
+    User user1 = loginUgi.getSubject().getPrincipals(User.class).iterator()
+        .next();
+    LoginContext login = user1.getLogin();
+    login.logout();
+    login.login();
+    User user2 = loginUgi.getSubject().getPrincipals(User.class).iterator()
+        .next();
+    // user1 and user2 must be same instances.
+    Assert.assertTrue(user1 == user2);
+  }
 }