HADOOP-17068. Client fails forever when namenode ipaddr changed. Contributed by Sean Chow.

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

@@ -649,6 +649,7 @@ private synchronized boolean updateAddress() throws IOException {
     
     private synchronized void setupConnection(
         UserGroupInformation ticket) throws IOException {
+      LOG.debug("Setup connection to " + server.toString());
       short ioFailures = 0;
       short timeoutFailures = 0;
       while (true) {
@@ -711,8 +712,16 @@ private synchronized void setupConnection(
         } catch (IOException ie) {
           if (updateAddress()) {
             timeoutFailures = ioFailures = 0;
+            try {
+              // HADOOP-17068: when server changed, ignore the exception.
+              handleConnectionFailure(ioFailures++, ie);
+            } catch (IOException ioe) {
+              LOG.warn("Exception when handle ConnectionFailure: "
+                  + ioe.getMessage());
+            }
+          } else {
+            handleConnectionFailure(ioFailures++, ie);
           }
-          handleConnectionFailure(ioFailures++, ie);
         }
       }
     }
@@ -1277,7 +1286,7 @@ private synchronized void close() {
           cleanupCalls();
         }
       } else {
-        // log the info
+        // Log the newest server information if update address.
         if (LOG.isDebugEnabled()) {
           LOG.debug("closing ipc connection to " + server + ": " +
               closeException.getMessage(),closeException);