HDFS-16717. Replace NPE with IOException in DataNode.class (#4699). Contributed by ZanderXu.

Signed-off-by: He Xiaoqiao <hexiaoqiao@apache.org>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java

@@ -889,8 +889,11 @@ private String reconfDfsUsageParameters(String property, String newVal)
     String result = null;
     try {
       LOG.info("Reconfiguring {} to {}", property, newVal);
+      if (data == null) {
+        LOG.debug("FsDatasetSpi has not been initialized.");
+        throw new IOException("FsDatasetSpi has not been initialized");
+      }
       if (property.equals(FS_DU_INTERVAL_KEY)) {
-        Preconditions.checkNotNull(data, "FsDatasetSpi has not been initialized.");
         long interval = (newVal == null ? FS_DU_INTERVAL_DEFAULT :
             Long.parseLong(newVal));
         result = Long.toString(interval);
@@ -902,7 +905,6 @@ private String reconfDfsUsageParameters(String property, String newVal)
           }
         }
       } else if (property.equals(FS_GETSPACEUSED_JITTER_KEY)) {
-        Preconditions.checkNotNull(data, "FsDatasetSpi has not been initialized.");
         long jitter = (newVal == null ? FS_GETSPACEUSED_JITTER_DEFAULT :
             Long.parseLong(newVal));
         result = Long.toString(jitter);
@@ -914,7 +916,6 @@ private String reconfDfsUsageParameters(String property, String newVal)
           }
         }
       } else if (property.equals(FS_GETSPACEUSED_CLASSNAME)) {
-        Preconditions.checkNotNull(data, "FsDatasetSpi has not been initialized.");
         Class<? extends GetSpaceUsed> klass;
         if (newVal == null) {
           if (Shell.WINDOWS) {
@@ -1174,7 +1175,7 @@ private void refreshVolumes(String newVolumes) throws IOException {
               .newFixedThreadPool(changedVolumes.newLocations.size());
           List<Future<IOException>> exceptions = Lists.newArrayList();
 
-          Preconditions.checkNotNull(data, "Storage not yet initialized");
+          checkStorageState("refreshVolumes");
           for (final StorageLocation location : changedVolumes.newLocations) {
             exceptions.add(service.submit(new Callable<IOException>() {
               @Override
@@ -1274,7 +1275,7 @@ private synchronized void removeVolumes(
         clearFailure, Joiner.on(",").join(storageLocations)));
 
     IOException ioe = null;
-    Preconditions.checkNotNull(data, "Storage not yet initialized");
+    checkStorageState("removeVolumes");
     // Remove volumes and block infos from FsDataset.
     data.removeVolumes(storageLocations, clearFailure);
 
@@ -2301,7 +2302,7 @@ public BlockLocalPathInfo getBlockLocalPathInfo(ExtendedBlock block,
       Token<BlockTokenIdentifier> token) throws IOException {
     checkBlockLocalPathAccess();
     checkBlockToken(block, token, BlockTokenIdentifier.AccessMode.READ);
-    Preconditions.checkNotNull(data, "Storage not yet initialized");
+    checkStorageState("getBlockLocalPathInfo");
     BlockLocalPathInfo info = data.getBlockLocalPathInfo(block);
     if (info != null) {
       LOG.trace("getBlockLocalPathInfo successful " +
@@ -2351,7 +2352,7 @@ FileInputStream[] requestShortCircuitFdsForRead(final ExtendedBlock blk,
     FileInputStream fis[] = new FileInputStream[2];
     
     try {
-      Preconditions.checkNotNull(data, "Storage not yet initialized");
+      checkStorageState("requestShortCircuitFdsForRead");
       fis[0] = (FileInputStream)data.getBlockInputStream(blk, 0);
       fis[1] = DatanodeUtil.getMetaDataInputStream(blk, data);
     } catch (ClassCastException e) {
@@ -3382,7 +3383,7 @@ public static void main(String args[]) {
   @Override // InterDatanodeProtocol
   public ReplicaRecoveryInfo initReplicaRecovery(RecoveringBlock rBlock)
       throws IOException {
-    Preconditions.checkNotNull(data, "Storage not yet initialized");
+    checkStorageState("initReplicaRecovery");
     return data.initReplicaRecovery(rBlock);
   }
 
@@ -3393,7 +3394,7 @@ public ReplicaRecoveryInfo initReplicaRecovery(RecoveringBlock rBlock)
   public String updateReplicaUnderRecovery(final ExtendedBlock oldBlock,
       final long recoveryId, final long newBlockId, final long newLength)
       throws IOException {
-    Preconditions.checkNotNull(data, "Storage not yet initialized");
+    checkStorageState("updateReplicaUnderRecovery");
     final Replica r = data.updateReplicaUnderRecovery(oldBlock,
         recoveryId, newBlockId, newLength);
     // Notify the namenode of the updated block info. This is important
@@ -3679,10 +3680,23 @@ public void deleteBlockPool(String blockPoolId, boolean force)
           "The block pool is still running. First do a refreshNamenodes to " +
           "shutdown the block pool service");
     }
-    Preconditions.checkNotNull(data, "Storage not yet initialized");
+    checkStorageState("deleteBlockPool");
     data.deleteBlockPool(blockPoolId, force);
   }
 
+  /**
+   * Check if storage has been initialized.
+   * @param methodName caller name
+   * @throws IOException throw IOException if not yet initialized.
+   */
+  private void checkStorageState(String methodName) throws IOException {
+    if (data == null) {
+      String message = "Storage not yet initialized for " + methodName;
+      LOG.debug(message);
+      throw new IOException(message);
+    }
+  }
+
   @Override // ClientDatanodeProtocol
   public synchronized void shutdownDatanode(boolean forUpgrade) throws IOException {
     checkSuperuserPrivilege();
@@ -4131,7 +4145,7 @@ public String getSlowDisks() {
   @Override
   public List<DatanodeVolumeInfo> getVolumeReport() throws IOException {
     checkSuperuserPrivilege();
-    Preconditions.checkNotNull(data, "Storage not yet initialized");
+    checkStorageState("getVolumeReport");
     Map<String, Object> volumeInfoMap = data.getVolumeInfoMap();
     if (volumeInfoMap == null) {
       LOG.warn("DataNode volume info not available.");