HBASE-20670 NPE in HMaster#isInMaintenanceMode

hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java

@@ -2822,7 +2822,10 @@ public class HMaster extends HRegionServer implements MasterServices {
    * @return true if master is in maintenanceMode
    */
   @Override
-  public boolean isInMaintenanceMode() {
+  public boolean isInMaintenanceMode() throws IOException {
+    if (!isInitialized()) {
+      throw new PleaseHoldException("Master is initializing");
+    }
     return maintenanceModeTracker.isInMaintenanceMode();
   }
 
@@ -3359,9 +3362,13 @@ public class HMaster extends HRegionServer implements MasterServices {
    * @return The state of the load balancer, or false if the load balancer isn't defined.
    */
   public boolean isBalancerOn() {
+    try {
       if (null == loadBalancerTracker || isInMaintenanceMode()) {
         return false;
       }
+    } catch (IOException e) {
+      return false;
+    }
     return loadBalancerTracker.isBalancerOn();
   }
 
@@ -3370,8 +3377,12 @@ public class HMaster extends HRegionServer implements MasterServices {
    * false is returned.
    */
   public boolean isNormalizerOn() {
+    try {
       return (null == regionNormalizerTracker || isInMaintenanceMode()) ?
           false: regionNormalizerTracker.isNormalizerOn();
+    } catch (IOException e) {
+      return false;
+    }
   }
 
   /**
@@ -3382,9 +3393,13 @@ public class HMaster extends HRegionServer implements MasterServices {
    */
   @Override
   public boolean isSplitOrMergeEnabled(MasterSwitchType switchType) {
+    try {
       if (null == splitOrMergeTracker || isInMaintenanceMode()) {
         return false;
       }
+    } catch (IOException e) {
+      return false;
+    }
     return splitOrMergeTracker.isSplitOrMergeEnabled(switchType);
   }
 

hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterRpcServices.java

@@ -1489,7 +1489,11 @@ public class MasterRpcServices extends RSRpcServices
       final RpcController controller,
       final IsInMaintenanceModeRequest request) throws ServiceException {
     IsInMaintenanceModeResponse.Builder response = IsInMaintenanceModeResponse.newBuilder();
+    try {
       response.setInMaintenanceMode(master.isInMaintenanceMode());
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
     return response.build();
   }
 

hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterServices.java

@@ -352,8 +352,9 @@ public interface MasterServices extends Server {
 
   /**
    * @return true if master is in maintanceMode
+   * @throws IOException if the inquiry failed due to an IO problem
    */
-  boolean isInMaintenanceMode();
+  boolean isInMaintenanceMode() throws IOException;
 
   /**
    * Abort a procedure.