HADOOP-12897. KerberosAuthenticator.authenticate to include URL on IO failures. Contributed by Ajay Kumar.

hadoop-common-project/hadoop-auth/src/main/java/org/apache/hadoop/security/authentication/client/KerberosAuthenticator.java

@@ -13,6 +13,8 @@
  */
 package org.apache.hadoop.security.authentication.client;
 
+import com.google.common.annotations.VisibleForTesting;
+import java.lang.reflect.Constructor;
 import org.apache.commons.codec.binary.Base64;
 import org.apache.hadoop.security.authentication.server.HttpConstants;
 import org.apache.hadoop.security.authentication.util.AuthToken;
@@ -181,6 +183,7 @@ public class KerberosAuthenticator implements Authenticator {
     if (!token.isSet()) {
       this.url = url;
       base64 = new Base64(0);
+      try {
         HttpURLConnection conn = token.openConnection(url, connConfigurator);
         conn.setRequestMethod(AUTH_HTTP_METHOD);
         conn.connect();
@@ -204,11 +207,34 @@ public class KerberosAuthenticator implements Authenticator {
           Authenticator auth = getFallBackAuthenticator();
           // Make sure that the fall back authenticator have the same
           // ConnectionConfigurator, since the method might be overridden.
-        // Otherwise the fall back authenticator might not have the information
-        // to make the connection (e.g., SSL certificates)
+          // Otherwise the fall back authenticator might not have the
+          // information to make the connection (e.g., SSL certificates)
           auth.setConnectionConfigurator(connConfigurator);
           auth.authenticate(url, token);
         }
+      } catch (IOException ex){
+        throw wrapExceptionWithMessage(ex,
+            "Error while authenticating with endpoint: " + url);
+      } catch (AuthenticationException ex){
+        throw wrapExceptionWithMessage(ex,
+            "Error while authenticating with endpoint: " + url);
+      }
+    }
+  }
+
+  @VisibleForTesting
+   static <T extends Exception> T wrapExceptionWithMessage(
+      T exception, String msg) {
+    Class<? extends Throwable> exceptionClass = exception.getClass();
+    try {
+      Constructor<? extends Throwable> ctor = exceptionClass
+          .getConstructor(String.class);
+      Throwable t = ctor.newInstance(msg);
+      return (T) (t.initCause(exception));
+    } catch (Throwable e) {
+      LOG.debug("Unable to wrap exception of type {}, it has "
+          + "no (String) constructor.", exceptionClass, e);
+      return exception;
     }
   }
 

hadoop-common-project/hadoop-auth/src/test/java/org/apache/hadoop/security/authentication/client/TestKerberosAuthenticator.java

@@ -20,6 +20,9 @@ import static org.apache.hadoop.security.authentication.server.KerberosAuthentic
 import static org.apache.hadoop.security.authentication.server.KerberosAuthenticationHandler.KEYTAB;
 import static org.apache.hadoop.security.authentication.server.KerberosAuthenticationHandler.NAME_RULES;
 
+import java.io.IOException;
+import java.nio.charset.CharacterCodingException;
+import javax.security.sasl.AuthenticationException;
 import org.apache.hadoop.minikdc.KerberosSecurityTestcase;
 import org.apache.hadoop.security.authentication.KerberosTestUtils;
 import org.apache.hadoop.security.authentication.server.AuthenticationFilter;
@@ -218,4 +221,30 @@ public class TestKerberosAuthenticator extends KerberosSecurityTestcase {
     });
   }
 
+  @Test(timeout = 60000)
+  public void testWrapExceptionWithMessage() {
+    IOException ex;
+    ex = new IOException("Induced exception");
+    ex = KerberosAuthenticator.wrapExceptionWithMessage(ex, "Error while "
+        + "authenticating with endpoint: localhost");
+    Assert.assertEquals("Induced exception", ex.getCause().getMessage());
+    Assert.assertEquals("Error while authenticating with endpoint: localhost",
+        ex.getMessage());
+
+    ex = new AuthenticationException("Auth exception");
+    ex = KerberosAuthenticator.wrapExceptionWithMessage(ex, "Error while "
+        + "authenticating with endpoint: localhost");
+    Assert.assertEquals("Auth exception", ex.getCause().getMessage());
+    Assert.assertEquals("Error while authenticating with endpoint: localhost",
+        ex.getMessage());
+
+    // Test for Exception with  no (String) constructor
+    // redirect the LOG to and check log message
+    ex = new CharacterCodingException();
+    Exception ex2 = KerberosAuthenticator.wrapExceptionWithMessage(ex,
+        "Error while authenticating with endpoint: localhost");
+    Assert.assertTrue(ex instanceof CharacterCodingException);
+    Assert.assertTrue(ex.equals(ex2));
+  }
+
 }