HBASE-13314 Fix NPE in HMaster.getClusterStatus()

hbase-client/src/main/java/org/apache/hadoop/hbase/ClusterStatus.java

@@ -118,6 +118,9 @@ public class ClusterStatus extends VersionedWritable {
    * @return the names of region servers on the dead list
    */
   public Collection<ServerName> getDeadServerNames() {
+    if (deadServers == null) {
+      return Collections.<ServerName>emptyList();
+    }
     return Collections.unmodifiableCollection(deadServers);
   }
 
@@ -125,14 +128,14 @@ public class ClusterStatus extends VersionedWritable {
    * @return the number of region servers in the cluster
    */
   public int getServersSize() {
-    return liveServers.size();
+    return liveServers != null ? liveServers.size() : 0;
   }
 
   /**
    * @return the number of dead region servers in the cluster
    */
   public int getDeadServers() {
-    return deadServers.size();
+    return deadServers != null ? deadServers.size() : 0;
   }
 
   /**
@@ -148,9 +151,11 @@ public class ClusterStatus extends VersionedWritable {
    */
   public int getRegionsCount() {
     int count = 0;
+    if (liveServers != null && !liveServers.isEmpty()) {
       for (Map.Entry<ServerName, ServerLoad> e: this.liveServers.entrySet()) {
         count += e.getValue().getNumberOfRegions();
       }
+    }
     return count;
   }
 
@@ -159,9 +164,11 @@ public class ClusterStatus extends VersionedWritable {
    */
   public int getRequestsCount() {
     int count = 0;
+    if (liveServers != null && !liveServers.isEmpty()) {
       for (Map.Entry<ServerName, ServerLoad> e: this.liveServers.entrySet()) {
         count += e.getValue().getNumberOfRequests();
       }
+    }
     return count;
   }
 
@@ -222,6 +229,9 @@ public class ClusterStatus extends VersionedWritable {
   }
 
   public Collection<ServerName> getServers() {
+    if (liveServers == null) {
+      return Collections.<ServerName>emptyList();
+    }
     return Collections.unmodifiableCollection(this.liveServers.keySet());
   }
 
@@ -237,13 +247,16 @@ public class ClusterStatus extends VersionedWritable {
    * @return the number of backup masters in the cluster
    */
   public int getBackupMastersSize() {
-    return this.backupMasters.size();
+    return backupMasters != null ? backupMasters.size() : 0;
   }
 
   /**
    * @return the names of backup masters
    */
   public Collection<ServerName> getBackupMasters() {
+    if (backupMasters == null) {
+      return Collections.<ServerName>emptyList();
+    }
     return Collections.unmodifiableCollection(this.backupMasters);
   }
 
@@ -252,7 +265,7 @@ public class ClusterStatus extends VersionedWritable {
    * @return Server's load or null if not found.
    */
   public ServerLoad getLoad(final ServerName sn) {
-    return this.liveServers.get(sn);
+    return liveServers != null ? liveServers.get(sn) : null;
   }
 
   @InterfaceAudience.Private
@@ -303,28 +316,42 @@ public class ClusterStatus extends VersionedWritable {
   public String toString() {
     StringBuilder sb = new StringBuilder(1024);
     sb.append("Master: " + master);
-    sb.append("\nNumber of backup masters: " + backupMasters.size());
+
+    int backupMastersSize = getBackupMastersSize();
+    sb.append("\nNumber of backup masters: " + backupMastersSize);
+    if (backupMastersSize > 0) {
       for (ServerName serverName: backupMasters) {
         sb.append("\n  " + serverName);
       }
+    }
 
-    sb.append("\nNumber of live region servers: " + liveServers.size());
+    int serversSize = getServersSize();
+    sb.append("\nNumber of live region servers: " + serversSize);
+    if (serversSize > 0) {
       for (ServerName serverName: liveServers.keySet()) {
         sb.append("\n  " + serverName.getServerName());
       }
+    }
 
-    sb.append("\nNumber of dead region servers: " + deadServers.size());
+    int deadServerSize = getDeadServers();
+    sb.append("\nNumber of dead region servers: " + deadServerSize);
+    if (deadServerSize > 0) {
       for (ServerName serverName: deadServers) {
         sb.append("\n  " + serverName);
       }
+    }
 
     sb.append("\nAverage load: " + getAverageLoad());
     sb.append("\nNumber of requests: " + getRequestsCount());
     sb.append("\nNumber of regions: " + getRegionsCount());
-    sb.append("\nNumber of regions in transition: " + intransition.size());
+
+    int ritSize = (intransition != null) ? intransition.size() : 0;
+    sb.append("\nNumber of regions in transition: " + ritSize);
+    if (ritSize > 0) {
       for (RegionState state: intransition.values()) {
         sb.append("\n  " + state.toDescriptiveString());
       }
+    }
     return sb.toString();
   }
 

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

@@ -1721,10 +1721,12 @@ public class HMaster extends HRegionServer implements MasterServices, Server {
         this.zooKeeper.backupMasterAddressesZNode);
     } catch (KeeperException e) {
       LOG.warn(this.zooKeeper.prefix("Unable to list backup servers"), e);
-      backupMasterStrings = new ArrayList<String>(0);
+      backupMasterStrings = null;
     }
-    List<ServerName> backupMasters = new ArrayList<ServerName>(
+
-                                          backupMasterStrings.size());
+    List<ServerName> backupMasters = null;
+    if (backupMasterStrings != null && !backupMasterStrings.isEmpty()) {
+      backupMasters = new ArrayList<ServerName>(backupMasterStrings.size());
       for (String s: backupMasterStrings) {
         try {
           byte [] bytes;
@@ -1754,6 +1756,7 @@ public class HMaster extends HRegionServer implements MasterServices, Server {
         public int compare(ServerName s1, ServerName s2) {
           return s1.getServerName().compareTo(s2.getServerName());
         }});
+    }
 
     String clusterId = fileSystemManager != null ?
       fileSystemManager.getClusterId().toString() : null;