HDFS-11196. Ozone: Improve logging and error handling in the container layer. Contributed by Anu Engineer.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/scm/container/common/helpers/StorageContainerException.java

@@ -0,0 +1,104 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.apache.hadoop.scm.container.common.helpers;
+
+import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos;
+
+import java.io.IOException;
+
+/**
+ * Exceptions thrown from the Storage Container.
+ */
+public class StorageContainerException extends IOException {
+  private ContainerProtos.Result result;
+
+  /**
+   * Constructs an {@code IOException} with {@code null}
+   * as its error detail message.
+   */
+  public StorageContainerException(ContainerProtos.Result result) {
+    this.result = result;
+  }
+
+  /**
+   * Constructs an {@code IOException} with the specified detail message.
+   *
+   * @param message The detail message (which is saved for later retrieval by
+   * the {@link #getMessage()} method)
+   * @param result - The result code
+   */
+  public StorageContainerException(String message,
+      ContainerProtos.Result result) {
+    super(message);
+    this.result = result;
+  }
+
+  /**
+   * Constructs an {@code IOException} with the specified detail message
+   * and cause.
+   * <p>
+   * <p> Note that the detail message associated with {@code cause} is
+   * <i>not</i> automatically incorporated into this exception's detail
+   * message.
+   *
+   * @param message The detail message (which is saved for later retrieval by
+   * the {@link #getMessage()} method)
+   *
+   * @param cause The cause (which is saved for later retrieval by the {@link
+   * #getCause()} method).  (A null value is permitted, and indicates that the
+   * cause is nonexistent or unknown.)
+   *
+   * @param result - The result code
+   * @since 1.6
+   */
+  public StorageContainerException(String message, Throwable cause,
+      ContainerProtos.Result result) {
+    super(message, cause);
+    this.result = result;
+  }
+
+  /**
+   * Constructs an {@code IOException} with the specified cause and a
+   * detail message of {@code (cause==null ? null : cause.toString())}
+   * (which typically contains the class and detail message of {@code cause}).
+   * This constructor is useful for IO exceptions that are little more
+   * than wrappers for other throwables.
+   *
+   * @param cause The cause (which is saved for later retrieval by the {@link
+   * #getCause()} method).  (A null value is permitted, and indicates that the
+   * cause is nonexistent or unknown.)
+   * @param result - The result code
+   * @since 1.6
+   */
+  public StorageContainerException(Throwable cause, ContainerProtos.Result
+      result) {
+    super(cause);
+    this.result = result;
+  }
+
+  /**
+   * Returns Result.
+   *
+   * @return Result.
+   */
+  public ContainerProtos.Result getResult() {
+    return result;
+  }
+
+
+}

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/scm/storage/ContainerProtocolCalls.java

@@ -18,13 +18,7 @@
 
 package org.apache.hadoop.scm.storage;
 
-import static java.net.HttpURLConnection.HTTP_BAD_REQUEST;
-import static java.net.HttpURLConnection.HTTP_INTERNAL_ERROR;
-
-import java.io.IOException;
-
 import com.google.protobuf.ByteString;
-
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos.ChunkInfo;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
@@ -35,9 +29,15 @@ import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
     .GetKeyRequestProto;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
     .GetKeyResponseProto;
+import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .GetSmallFileRequestProto;
+import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .GetSmallFileResponseProto;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos.KeyData;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
     .PutKeyRequestProto;
+import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .PutSmallFileRequestProto;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
     .ReadChunkRequestProto;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
@@ -45,13 +45,10 @@ import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos.Type;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
     .WriteChunkRequestProto;
-import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
-    .PutSmallFileRequestProto;
-import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
-    .GetSmallFileResponseProto;
-import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
-    .GetSmallFileRequestProto;
 import org.apache.hadoop.scm.XceiverClient;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
+
+import java.io.IOException;
 
 /**
  * Implementation of all container protocol calls performed by Container
@@ -87,7 +84,7 @@ public final class ContainerProtocolCalls {
         .setGetKey(readKeyRequest)
         .build();
     ContainerCommandResponseProto response = xceiverClient.sendCommand(request);
-    validateContainerResponse(response, traceID);
+    validateContainerResponse(response);
     return response.getGetKey();
   }
 
@@ -112,7 +109,7 @@ public final class ContainerProtocolCalls {
         .setPutKey(createKeyRequest)
         .build();
     ContainerCommandResponseProto response = xceiverClient.sendCommand(request);
-    validateContainerResponse(response, traceID);
+    validateContainerResponse(response);
   }
 
   /**
@@ -140,7 +137,7 @@ public final class ContainerProtocolCalls {
         .setReadChunk(readChunkRequest)
         .build();
     ContainerCommandResponseProto response = xceiverClient.sendCommand(request);
-    validateContainerResponse(response, traceID);
+    validateContainerResponse(response);
     return response.getReadChunk();
   }
 
@@ -170,7 +167,7 @@ public final class ContainerProtocolCalls {
         .setWriteChunk(writeChunkRequest)
         .build();
     ContainerCommandResponseProto response = xceiverClient.sendCommand(request);
-    validateContainerResponse(response, traceID);
+    validateContainerResponse(response);
   }
 
   /**
@@ -218,7 +215,7 @@ public final class ContainerProtocolCalls {
         .setPutSmallFile(putSmallFileRequest)
         .build();
     ContainerCommandResponseProto response = client.sendCommand(request);
-    validateContainerResponse(response, traceID);
+    validateContainerResponse(response);
   }
 
   /**
@@ -245,7 +242,7 @@ public final class ContainerProtocolCalls {
     request.setTraceID(traceID);
     ContainerCommandResponseProto response = client.sendCommand(
         request.build());
-    validateContainerResponse(response, traceID);
+    validateContainerResponse(response);
   }
 
   /**
@@ -280,7 +277,7 @@ public final class ContainerProtocolCalls {
         .setGetSmallFile(getSmallFileRequest)
         .build();
     ContainerCommandResponseProto response = client.sendCommand(request);
-    validateContainerResponse(response, traceID);
+    validateContainerResponse(response);
     return response.getGetSmallFile();
   }
 
@@ -289,28 +286,15 @@ public final class ContainerProtocolCalls {
    * return code is mapped to a corresponding exception and thrown.
    *
    * @param response container protocol call response
-   * @param traceID container protocol call args
    * @throws IOException if the container protocol call failed
    */
   private static void validateContainerResponse(
-      ContainerCommandResponseProto response, String traceID
+      ContainerCommandResponseProto response
-  ) throws IOException {
+  ) throws StorageContainerException {
-    // TODO : throw the right type of exception
+    if (response.getResult() == ContainerProtos.Result.SUCCESS) {
-    switch (response.getResult()) {
+      return;
-    case SUCCESS:
-      break;
-    case MALFORMED_REQUEST:
-      throw new IOException(HTTP_BAD_REQUEST +
-          ":Bad container request: " + traceID);
-    case UNSUPPORTED_REQUEST:
-      throw new IOException(HTTP_INTERNAL_ERROR +
-          "Unsupported container request: " + traceID);
-    case CONTAINER_INTERNAL_ERROR:
-      throw new IOException(HTTP_INTERNAL_ERROR +
-          "Container internal error:" + traceID);
-    default:
-      throw new IOException(HTTP_INTERNAL_ERROR +
-          "Unrecognized container response:" + traceID);
     }
+    throw new StorageContainerException(
+        response.getMessage(), response.getResult());
   }
 }

hadoop-hdfs-project/hadoop-hdfs-client/src/main/proto/DatanodeContainerProtocol.proto

@@ -99,6 +99,23 @@ enum Result {
   UNSUPPORTED_REQUEST = 2;
   MALFORMED_REQUEST = 3;
   CONTAINER_INTERNAL_ERROR = 4;
+  INVALID_CONFIG = 5;
+  INVALID_FILE_HASH_FOUND = 6;
+  CONTAINER_EXISTS = 7;
+  NO_SUCH_ALGORITHM = 8;
+  CONTAINER_NOT_FOUND = 9;
+  IO_EXCEPTION = 10;
+  UNABLE_TO_READ_METADATA_DB = 11;
+  NO_SUCH_KEY = 12;
+  OVERWRITE_FLAG_REQUIRED = 13;
+  UNABLE_TO_FIND_DATA_DIR = 14;
+  INVALID_WRITE_SIZE = 15;
+  CHECKSUM_MISMATCH = 16;
+  UNABLE_TO_FIND_CHUNK = 17;
+  PROTOC_DECODING_ERROR = 18;
+  INVALID_ARGUMENT = 19;
+  PUT_SMALL_FILE_ERROR = 20;
+  GET_SMALL_FILE_ERROR = 21;
 }
 
 message ContainerCommandRequestProto {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/helpers/ChunkUtils.java

@@ -24,6 +24,7 @@ import org.apache.commons.codec.digest.DigestUtils;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.ozone.OzoneConsts;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.ozone.container.common.impl.ChunkManagerImpl;
 import org.apache.hadoop.scm.container.common.helpers.Pipeline;
 import org.slf4j.Logger;
@@ -39,6 +40,23 @@ import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.concurrent.ExecutionException;
 
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.CHECKSUM_MISMATCH;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.CONTAINER_INTERNAL_ERROR;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.CONTAINER_NOT_FOUND;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.INVALID_WRITE_SIZE;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.IO_EXCEPTION;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.OVERWRITE_FLAG_REQUIRED;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.UNABLE_TO_FIND_CHUNK;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.UNABLE_TO_FIND_DATA_DIR;
+
 /**
  * Set of utility functions used by the chunk Manager.
  */
@@ -90,10 +108,10 @@ public final class ChunkUtils {
    * @param data - container data.
    * @param info - chunk info.
    * @return File
-   * @throws IOException
+   * @throws StorageContainerException
    */
   public static File validateChunk(Pipeline pipeline, ContainerData data,
-                                   ChunkInfo info) throws IOException {
+      ChunkInfo info) throws StorageContainerException {
 
     Logger log = LoggerFactory.getLogger(ChunkManagerImpl.class);
 
@@ -102,8 +120,9 @@ public final class ChunkUtils {
       if (!ChunkUtils.isOverWritePermitted(info)) {
         log.error("Rejecting write chunk request. Chunk overwrite " +
             "without explicit request. {}", info.toString());
-        throw new IOException("Rejecting write chunk request. OverWrite " +
+        throw new StorageContainerException("Rejecting write chunk request. " +
-            "flag required." + info.toString());
+            "OverWrite flag required." + info.toString(),
+            OVERWRITE_FLAG_REQUIRED);
       }
     }
     return chunkFile;
@@ -116,22 +135,24 @@ public final class ChunkUtils {
    * @param data - Container Data
    * @param info - Chunk info
    * @return - File.
-   * @throws IOException
+   * @throws StorageContainerException
    */
   public static File getChunkFile(Pipeline pipeline, ContainerData data,
-                                  ChunkInfo info) throws IOException {
+      ChunkInfo info) throws StorageContainerException {
 
     Logger log = LoggerFactory.getLogger(ChunkManagerImpl.class);
     if (data == null) {
       log.error("Invalid container Name: {}", pipeline.getContainerName());
-      throw new IOException("Unable to find the container Name: " +
+      throw new StorageContainerException("Unable to find the container Name:" +
-          pipeline.getContainerName());
+          " " +
+          pipeline.getContainerName(), CONTAINER_NOT_FOUND);
     }
 
     File dataDir = ContainerUtils.getDataDirectory(data).toFile();
     if (!dataDir.exists()) {
       log.error("Unable to find the data directory: {}", dataDir);
-      throw new IOException("Unable to find the data directory: " + dataDir);
+      throw new StorageContainerException("Unable to find the data directory:" +
+          " " + dataDir, UNABLE_TO_FIND_DATA_DIR);
     }
 
     return dataDir.toPath().resolve(info.getChunkName()).toFile();
@@ -143,11 +164,12 @@ public final class ChunkUtils {
    *
    * @param chunkFile - File to write data to.
    * @param chunkInfo - Data stream to write.
-   * @throws IOException
+   * @param data - The data buffer.
+   * @throws StorageContainerException
    */
   public static void writeData(File chunkFile, ChunkInfo chunkInfo,
-                               byte[] data)
+      byte[] data) throws
-      throws IOException, ExecutionException, InterruptedException,
+      StorageContainerException, ExecutionException, InterruptedException,
       NoSuchAlgorithmException {
 
     Logger log = LoggerFactory.getLogger(ChunkManagerImpl.class);
@@ -156,7 +178,7 @@ public final class ChunkUtils {
               "specified. DataLen: %d Byte Array: %d",
           chunkInfo.getLen(), data.length);
       log.error(err);
-      throw new IOException(err);
+      throw new StorageContainerException(err, INVALID_WRITE_SIZE);
     }
 
     AsynchronousFileChannel file = null;
@@ -175,15 +197,24 @@ public final class ChunkUtils {
         verifyChecksum(chunkInfo, data, log);
       }
       int size = file.write(ByteBuffer.wrap(data), chunkInfo.getOffset()).get();
-      if(size != data.length) {
+      if (size != data.length) {
-        log.error("Invalid write size found. Size:{}  Expected: {} " , size,
+        log.error("Invalid write size found. Size:{}  Expected: {} ", size,
             data.length);
-        throw new IOException("Invalid write size found. Size: " + size
+        throw new StorageContainerException("Invalid write size found. " +
-            + " Expected: " + data.length);
+            "Size: " + size + " Expected: " + data.length, INVALID_WRITE_SIZE);
       }
+    } catch (IOException e) {
+      throw new StorageContainerException(e, IO_EXCEPTION);
+
     } finally {
       if (lock != null) {
+        try {
           lock.release();
+        } catch (IOException e) {
+          log.error("Unable to release lock ??, Fatal Error.");
+          throw new StorageContainerException(e, CONTAINER_INTERNAL_ERROR);
+
+        }
       }
       if (file != null) {
         IOUtils.closeStream(file);
@@ -198,19 +229,19 @@ public final class ChunkUtils {
    * @param data - data buffer
    * @param log - log
    * @throws NoSuchAlgorithmException
-   * @throws IOException
+   * @throws StorageContainerException
    */
   private static void verifyChecksum(ChunkInfo chunkInfo, byte[] data, Logger
-      log) throws NoSuchAlgorithmException, IOException {
+      log) throws NoSuchAlgorithmException, StorageContainerException {
     MessageDigest sha = MessageDigest.getInstance(OzoneConsts.FILE_HASH);
     sha.update(data);
     if (!Hex.encodeHexString(sha.digest()).equals(
         chunkInfo.getChecksum())) {
       log.error("Checksum mismatch. Provided: {} , computed: {}",
           chunkInfo.getChecksum(), DigestUtils.sha256Hex(sha.digest()));
-      throw new IOException("Checksum mismatch. Provided: " +
+      throw new StorageContainerException("Checksum mismatch. Provided: " +
           chunkInfo.getChecksum() + " , computed: " +
-          DigestUtils.sha256Hex(sha.digest()));
+          DigestUtils.sha256Hex(sha.digest()), CHECKSUM_MISMATCH);
     }
   }
 
@@ -219,21 +250,24 @@ public final class ChunkUtils {
    *
    * @param chunkFile - file where data lives.
    * @param data - chunk definition.
+   *
    * @return ByteBuffer
-   * @throws IOException
+   *
+   * @throws StorageContainerException
    * @throws ExecutionException
    * @throws InterruptedException
    */
   public static ByteBuffer readData(File chunkFile, ChunkInfo data) throws
-      IOException, ExecutionException, InterruptedException,
+      StorageContainerException, ExecutionException, InterruptedException,
       NoSuchAlgorithmException {
     Logger log = LoggerFactory.getLogger(ChunkManagerImpl.class);
 
     if (!chunkFile.exists()) {
       log.error("Unable to find the chunk file. chunk info : {}",
           data.toString());
-      throw new IOException("Unable to find the chunk file. chunk info " +
+      throw new StorageContainerException("Unable to find the chunk file. " +
-          data.toString());
+          "chunk info " +
+          data.toString(), UNABLE_TO_FIND_CHUNK);
     }
 
     AsynchronousFileChannel file = null;
@@ -252,9 +286,15 @@ public final class ChunkUtils {
       }
 
       return buf;
+    } catch (IOException e) {
+      throw new StorageContainerException(e, IO_EXCEPTION);
     } finally {
       if (lock != null) {
+        try {
           lock.release();
+        } catch (IOException e) {
+          log.error("I/O error is lock release.");
+        }
       }
       if (file != null) {
         IOUtils.closeStream(file);
@@ -276,6 +316,7 @@ public final class ChunkUtils {
 
   /**
    * Gets a response to the read chunk calls.
+   *
    * @param msg - Msg
    * @param data - Data
    * @param info - Info

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/helpers/ContainerUtils.java

@@ -25,6 +25,7 @@ import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos;
 import org.apache.hadoop.ozone.OzoneConsts;
 import org.apache.hadoop.ozone.container.common.impl.ContainerManagerImpl;
 import org.apache.hadoop.utils.LevelDBStore;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -34,6 +35,10 @@ import java.nio.file.Path;
 import java.nio.file.Paths;
 
 import static org.apache.commons.io.FilenameUtils.removeExtension;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.INVALID_ARGUMENT;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.UNABLE_TO_FIND_DATA_DIR;
 import static org.apache.hadoop.ozone.OzoneConsts.CONTAINER_EXTENSION;
 import static org.apache.hadoop.ozone.OzoneConsts.CONTAINER_META;
 
@@ -42,6 +47,10 @@ import static org.apache.hadoop.ozone.OzoneConsts.CONTAINER_META;
  */
 public final class ContainerUtils {
 
+  private ContainerUtils() {
+    //never constructed.
+  }
+
   /**
    * Returns a CreateContainer Response. This call is used by create and delete
    * containers which have null success responses.
@@ -98,6 +107,37 @@ public final class ContainerUtils {
             .setMessage(message);
   }
 
+  /**
+   * Logs the error and returns a response to the caller.
+   *
+   * @param log - Logger
+   * @param ex - Exception
+   * @param msg - Request Object
+   * @return Response
+   */
+  public static ContainerProtos.ContainerCommandResponseProto logAndReturnError(
+      Logger log, StorageContainerException ex,
+      ContainerProtos.ContainerCommandRequestProto msg) {
+    log.info("Trace ID: {} : Message: {} : Result: {}", msg.getTraceID(),
+        ex.getMessage(), ex.getResult().getValueDescriptor().getName());
+    return getContainerResponse(msg, ex.getResult(), ex.getMessage()).build();
+  }
+
+  /**
+   * Logs the error and returns a response to the caller.
+   *
+   * @param log - Logger
+   * @param ex - Exception
+   * @param msg - Request Object
+   * @return Response
+   */
+  public static ContainerProtos.ContainerCommandResponseProto logAndReturnError(
+      Logger log, RuntimeException ex,
+      ContainerProtos.ContainerCommandRequestProto msg) {
+    log.info("Trace ID: {} : Message: {} ", msg.getTraceID(), ex.getMessage());
+    return getContainerResponse(msg, INVALID_ARGUMENT, ex.getMessage()).build();
+  }
+
   /**
    * We found a command type but no associated payload for the command. Hence
    * return malformed Command as response.
@@ -133,7 +173,6 @@ public final class ContainerUtils {
     Preconditions.checkNotNull(containerFile);
     return Paths.get(containerFile.getParent()).resolve(
         removeExtension(containerFile.getName())).toString();
-
   }
 
   /**
@@ -239,6 +278,7 @@ public final class ContainerUtils {
 
   /**
    * Returns container file location.
+   *
    * @param containerData - Data
    * @param location - Root path
    * @return Path
@@ -252,6 +292,7 @@ public final class ContainerUtils {
 
   /**
    * Container metadata directory -- here is where the level DB lives.
+   *
    * @param cData - cData.
    * @return Path to the parent directory where the DB lives.
    */
@@ -264,20 +305,23 @@ public final class ContainerUtils {
 
   /**
    * Returns the path where data or chunks live for a given container.
+   *
    * @param cData - cData container
    * @return - Path
+   * @throws StorageContainerException
    */
-  public static Path getDataDirectory(ContainerData cData) throws IOException {
+  public static Path getDataDirectory(ContainerData cData)
+      throws StorageContainerException {
     Path path = getMetadataDirectory(cData);
     Preconditions.checkNotNull(path);
-    path = path.getParent();
+    Path parentPath = path.getParent();
-    if(path == null) {
+    if (parentPath == null) {
-      throw new IOException("Unable to get Data directory. null path found");
+      throw new StorageContainerException("Unable to get Data directory."
+          + path, UNABLE_TO_FIND_DATA_DIR);
     }
-    return path.resolve(OzoneConsts.CONTAINER_DATA_PATH);
+    return parentPath.resolve(OzoneConsts.CONTAINER_DATA_PATH);
   }
 
-
   /**
    * remove Container if it is empty.
    * <p/>
@@ -323,8 +367,4 @@ public final class ContainerUtils {
     FileUtils.forceDelete(containerPath.toFile());
     FileUtils.forceDelete(metaPath.toFile());
   }
-
-  private ContainerUtils() {
-    //never constructed.
-  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/helpers/KeyUtils.java

@@ -19,6 +19,7 @@ package org.apache.hadoop.ozone.container.common.helpers;
 
 import com.google.common.base.Preconditions;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.ozone.container.common.impl.KeyManagerImpl;
 import org.apache.hadoop.ozone.container.common.utils.ContainerCache;
 import org.apache.hadoop.utils.LevelDBStore;
@@ -29,6 +30,9 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.charset.Charset;
 
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.UNABLE_TO_READ_METADATA_DB;
+
 /**
  * Utils functions to help key functions.
  */
@@ -60,18 +64,25 @@ public final class KeyUtils {
    * @param container - container.
    * @param cache     - cache
    * @return LevelDB handle.
-   * @throws IOException
+   * @throws StorageContainerException
    */
   public static LevelDBStore getDB(ContainerData container,
-                                   ContainerCache cache) throws IOException {
+                                   ContainerCache cache)
+      throws StorageContainerException {
     Preconditions.checkNotNull(container);
     Preconditions.checkNotNull(cache);
+    try {
       LevelDBStore db = cache.getDB(container.getContainerName());
       if (db == null) {
         db = getDB(container.getDBPath());
         cache.putDB(container.getContainerName(), db);
       }
       return db;
+    } catch (IOException ex) {
+      String message = "Unable to open DB. DB Name: %s, Path: %s. ex: %s"
+          .format(container.getContainerName(), container.getDBPath(), ex);
+      throw new StorageContainerException(message, UNABLE_TO_READ_METADATA_DB);
+    }
   }
 
   /**
@@ -107,8 +118,8 @@ public final class KeyUtils {
 
 
   public static ContainerProtos.ContainerCommandResponseProto
-      getKeyDataResponse(ContainerProtos.ContainerCommandRequestProto msg
+      getKeyDataResponse(ContainerProtos.ContainerCommandRequestProto msg,
-                       , KeyData data) {
+      KeyData data) {
     ContainerProtos.GetKeyResponseProto.Builder getKey = ContainerProtos
         .GetKeyResponseProto.newBuilder();
     getKey.setKeyData(data.getProtoBufMessage());

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/impl/ChunkManagerImpl.java

@@ -19,19 +19,24 @@ package org.apache.hadoop.ozone.container.common.impl;
 
 import com.google.common.base.Preconditions;
 import org.apache.hadoop.fs.FileUtil;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.ozone.container.common.helpers.ChunkInfo;
 import org.apache.hadoop.ozone.container.common.helpers.ChunkUtils;
-import org.apache.hadoop.scm.container.common.helpers.Pipeline;
 import org.apache.hadoop.ozone.container.common.interfaces.ChunkManager;
 import org.apache.hadoop.ozone.container.common.interfaces.ContainerManager;
+import org.apache.hadoop.scm.container.common.helpers.Pipeline;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.File;
-import java.io.IOException;
 import java.security.NoSuchAlgorithmException;
 import java.util.concurrent.ExecutionException;
 
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.CONTAINER_INTERNAL_ERROR;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.UNSUPPORTED_REQUEST;
+
 /**
  * An implementation of ChunkManager that is used by default in ozone.
  */
@@ -56,32 +61,34 @@ public class ChunkManagerImpl implements ChunkManager {
    * @param pipeline - Name and the set of machines that make this container.
    * @param keyName - Name of the Key.
    * @param info - ChunkInfo.
-   * @throws IOException
+   * @throws StorageContainerException
    */
   @Override
   public void writeChunk(Pipeline pipeline, String keyName, ChunkInfo info,
       byte[] data)
-      throws IOException {
+      throws StorageContainerException {
 
     // we don't want container manager to go away while we are writing chunks.
     containerManager.readLock();
 
     // TODO : Take keyManager Write lock here.
     try {
-      Preconditions.checkNotNull(pipeline);
+      Preconditions.checkNotNull(pipeline, "Pipeline cannot be null");
-      Preconditions.checkNotNull(pipeline.getContainerName());
+      Preconditions.checkNotNull(pipeline.getContainerName(),
+          "Container name cannot be null");
       File chunkFile = ChunkUtils.validateChunk(pipeline,
           containerManager.readContainer(pipeline.getContainerName()), info);
       ChunkUtils.writeData(chunkFile, info, data);
 
-    } catch (ExecutionException |
+    } catch (ExecutionException | NoSuchAlgorithmException e) {
-        NoSuchAlgorithmException e) {
       LOG.error("write data failed. error: {}", e);
-      throw new IOException("Internal error: ", e);
+      throw new StorageContainerException("Internal error: ", e,
+          CONTAINER_INTERNAL_ERROR);
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
       LOG.error("write data failed. error: {}", e);
-      throw new IOException("Internal error: ", e);
+      throw new StorageContainerException("Internal error: ", e,
+          CONTAINER_INTERNAL_ERROR);
     } finally {
       containerManager.readUnlock();
     }
@@ -94,13 +101,13 @@ public class ChunkManagerImpl implements ChunkManager {
    * @param keyName - Name of the Key
    * @param info - ChunkInfo.
    * @return byte array
-   * @throws IOException TODO: Right now we do not support partial reads and
+   * @throws StorageContainerException
-   *                     writes of chunks. TODO: Explore if we need to do that
+   * TODO: Right now we do not support partial reads and writes of chunks.
-   *                     for ozone.
+   * TODO: Explore if we need to do that for ozone.
    */
   @Override
   public byte[] readChunk(Pipeline pipeline, String keyName, ChunkInfo info)
-      throws IOException {
+      throws StorageContainerException {
     containerManager.readLock();
     try {
       File chunkFile = ChunkUtils.getChunkFile(pipeline, containerManager
@@ -108,11 +115,13 @@ public class ChunkManagerImpl implements ChunkManager {
       return ChunkUtils.readData(chunkFile, info).array();
     } catch (ExecutionException | NoSuchAlgorithmException e) {
       LOG.error("read data failed. error: {}", e);
-      throw new IOException("Internal error: ", e);
+      throw new StorageContainerException("Internal error: ",
+          e, CONTAINER_INTERNAL_ERROR);
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
       LOG.error("read data failed. error: {}", e);
-      throw new IOException("Internal error: ", e);
+      throw new StorageContainerException("Internal error: ",
+          e, CONTAINER_INTERNAL_ERROR);
     } finally {
       containerManager.readUnlock();
     }
@@ -124,11 +133,11 @@ public class ChunkManagerImpl implements ChunkManager {
    * @param pipeline - Pipeline.
    * @param keyName - Key Name
    * @param info - Chunk Info
-   * @throws IOException
+   * @throws StorageContainerException
    */
   @Override
   public void deleteChunk(Pipeline pipeline, String keyName, ChunkInfo info)
-      throws IOException {
+      throws StorageContainerException {
 
     containerManager.readLock();
     try {
@@ -139,8 +148,9 @@ public class ChunkManagerImpl implements ChunkManager {
       } else {
         LOG.error("Not Supported Operation. Trying to delete a " +
             "chunk that is in shared file. chunk info : " + info.toString());
-        throw new IOException("Not Supported Operation. Trying to delete a " +
+        throw new StorageContainerException("Not Supported Operation. " +
-            "chunk that is in shared file. chunk info : " + info.toString());
+            "Trying to delete a chunk that is in shared file. chunk info : "
+            + info.toString(), UNSUPPORTED_REQUEST);
       }
     } finally {
       containerManager.readUnlock();

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/impl/Dispatcher.java

@@ -30,14 +30,15 @@ import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos.Type;
 import org.apache.hadoop.ozone.container.common.helpers.ChunkInfo;
 import org.apache.hadoop.ozone.container.common.helpers.ChunkUtils;
 import org.apache.hadoop.ozone.container.common.helpers.ContainerData;
+import org.apache.hadoop.ozone.container.common.helpers.ContainerMetrics;
 import org.apache.hadoop.ozone.container.common.helpers.ContainerUtils;
 import org.apache.hadoop.ozone.container.common.helpers.FileUtils;
 import org.apache.hadoop.ozone.container.common.helpers.KeyData;
 import org.apache.hadoop.ozone.container.common.helpers.KeyUtils;
-import org.apache.hadoop.ozone.container.common.helpers.ContainerMetrics;
 import org.apache.hadoop.ozone.container.common.interfaces.ContainerDispatcher;
 import org.apache.hadoop.ozone.container.common.interfaces.ContainerManager;
 import org.apache.hadoop.scm.container.common.helpers.Pipeline;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -45,6 +46,11 @@ import java.io.IOException;
 import java.util.LinkedList;
 import java.util.List;
 
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.PUT_SMALL_FILE_ERROR;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.GET_SMALL_FILE_ERROR;
+
 /**
  * Ozone Container dispatcher takes a call from the netty server and routes it
  * to the right handler function.
@@ -55,6 +61,7 @@ public class Dispatcher implements ContainerDispatcher {
   private final ContainerManager containerManager;
   private ContainerMetrics metrics;
   private Configuration conf;
+
   /**
    * Constructs an OzoneContainer that receives calls from
    * XceiverServerHandler.
@@ -79,9 +86,10 @@ public class Dispatcher implements ContainerDispatcher {
 
   @Override
   public ContainerCommandResponseProto dispatch(
-      ContainerCommandRequestProto msg) throws IOException {
+      ContainerCommandRequestProto msg) {
     long startNanos = System.nanoTime();
     ContainerCommandResponseProto resp = null;
+    try {
       Preconditions.checkNotNull(msg);
       Type cmdType = msg.getCmdType();
       metrics.incContainerOpcMetrics(cmdType);
@@ -118,20 +126,27 @@ public class Dispatcher implements ContainerDispatcher {
       }
 
       return ContainerUtils.unsupportedRequest(msg);
+    } catch (StorageContainerException e) {
+      // This useful since the trace ID will allow us to correlate failures.
+      return ContainerUtils.logAndReturnError(LOG, e, msg);
+    } catch (IllegalStateException | NullPointerException e) {
+      return ContainerUtils.logAndReturnError(LOG, e, msg);
+    }
   }
 
   public ContainerMetrics getContainerMetrics() {
     return metrics;
   }
+
   /**
    * Handles the all Container related functionality.
    *
    * @param msg - command
    * @return - response
-   * @throws IOException
+   * @throws StorageContainerException
    */
   private ContainerCommandResponseProto containerProcessHandler(
-      ContainerCommandRequestProto msg) throws IOException {
+      ContainerCommandRequestProto msg) throws StorageContainerException {
     try {
 
       switch (msg.getCmdType()) {
@@ -175,10 +190,10 @@ public class Dispatcher implements ContainerDispatcher {
    *
    * @param msg - command
    * @return - response
-   * @throws IOException
+   * @throws StorageContainerException
    */
   private ContainerCommandResponseProto keyProcessHandler(
-      ContainerCommandRequestProto msg) throws IOException {
+      ContainerCommandRequestProto msg) throws StorageContainerException {
     try {
       switch (msg.getCmdType()) {
       case PutKey:
@@ -217,10 +232,10 @@ public class Dispatcher implements ContainerDispatcher {
    *
    * @param msg - command
    * @return - response
-   * @throws IOException
+   * @throws StorageContainerException
    */
   private ContainerCommandResponseProto chunkProcessHandler(
-      ContainerCommandRequestProto msg) throws IOException {
+      ContainerCommandRequestProto msg) throws StorageContainerException {
     try {
       switch (msg.getCmdType()) {
       case WriteChunk:
@@ -254,7 +269,7 @@ public class Dispatcher implements ContainerDispatcher {
   }
 
   private ContainerCommandResponseProto smallFileHandler(
-      ContainerCommandRequestProto msg) throws IOException {
+      ContainerCommandRequestProto msg) throws StorageContainerException {
     switch (msg.getCmdType()) {
     case PutSmallFile:
       return handlePutSmallFile(msg);
@@ -494,7 +509,6 @@ public class Dispatcher implements ContainerDispatcher {
     String keyName = msg.getDeleteKey().getName();
     Preconditions.checkNotNull(keyName);
     Preconditions.checkState(!keyName.isEmpty());
-
     this.containerManager.getKeyManager().deleteKey(pipeline, keyName);
     return KeyUtils.getKeyResponse(msg);
   }
@@ -504,19 +518,22 @@ public class Dispatcher implements ContainerDispatcher {
    *
    * @param msg - Message.
    * @return ContainerCommandResponseProto
-   * @throws IOException
+   * @throws StorageContainerException
    */
   private ContainerCommandResponseProto handlePutSmallFile(
-      ContainerCommandRequestProto msg) throws IOException {
+      ContainerCommandRequestProto msg) throws StorageContainerException {
 
     if (!msg.hasPutSmallFile()) {
       LOG.debug("Malformed put small file request. trace ID: {}",
           msg.getTraceID());
       return ContainerUtils.malformedRequest(msg);
     }
+    try {
 
       Pipeline pipeline =
-        Pipeline.getFromProtoBuf(msg.getPutSmallFile().getKey().getPipeline());
+          Pipeline.getFromProtoBuf(msg.getPutSmallFile()
+              .getKey().getPipeline());
+
       Preconditions.checkNotNull(pipeline);
       KeyData keyData = KeyData.getFromProtoBuf(msg.getPutSmallFile().getKey()
           .getKeyData());
@@ -532,6 +549,10 @@ public class Dispatcher implements ContainerDispatcher {
       keyData.setChunks(chunks);
       this.containerManager.getKeyManager().putKey(pipeline, keyData);
       return FileUtils.getPutFileResponse(msg);
+    } catch (IOException e) {
+      throw new StorageContainerException("Put Small File Failed.", e,
+          PUT_SMALL_FILE_ERROR);
+    }
   }
 
   /**
@@ -540,17 +561,21 @@ public class Dispatcher implements ContainerDispatcher {
    *
    * @param msg - ContainerCommandRequestProto
    * @return ContainerCommandResponseProto
+   * @throws StorageContainerException
    */
   private ContainerCommandResponseProto handleGetSmallFile(
-      ContainerCommandRequestProto msg) throws IOException {
+      ContainerCommandRequestProto msg) throws StorageContainerException {
     ByteString dataBuf = ByteString.EMPTY;
     if (!msg.hasGetSmallFile()) {
       LOG.debug("Malformed get small file request. trace ID: {}",
           msg.getTraceID());
       return ContainerUtils.malformedRequest(msg);
     }
+    try {
       Pipeline pipeline =
-        Pipeline.getFromProtoBuf(msg.getGetSmallFile().getKey().getPipeline());
+          Pipeline.getFromProtoBuf(msg.getGetSmallFile()
+              .getKey().getPipeline());
+
       long bytes = 0;
       Preconditions.checkNotNull(pipeline);
       KeyData keyData = KeyData.getFromProtoBuf(msg.getGetSmallFile()
@@ -560,7 +585,8 @@ public class Dispatcher implements ContainerDispatcher {
       for (ContainerProtos.ChunkInfo chunk : data.getChunks()) {
         bytes += chunk.getSerializedSize();
         ByteString current =
-          ByteString.copyFrom(this.containerManager.getChunkManager().readChunk(
+            ByteString.copyFrom(this.containerManager.getChunkManager()
+                .readChunk(
                     pipeline, keyData.getKeyName(), ChunkInfo.getFromProtoBuf(
                         chunk)));
         dataBuf = dataBuf.concat(current);
@@ -569,6 +595,10 @@ public class Dispatcher implements ContainerDispatcher {
       metrics.incContainerBytesStats(Type.GetSmallFile, bytes);
       return FileUtils.getGetSmallFileResponse(msg, dataBuf.toByteArray(),
           ChunkInfo.getFromProtoBuf(c));
-  }
+    } catch (IOException e) {
+      throw new StorageContainerException("Unable to decode protobuf", e,
+          GET_SMALL_FILE_ERROR);
 
+    }
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/impl/KeyManagerImpl.java

@@ -25,19 +25,31 @@ import org.apache.hadoop.ozone.OzoneConfigKeys;
 import org.apache.hadoop.ozone.container.common.helpers.ContainerData;
 import org.apache.hadoop.ozone.container.common.helpers.KeyData;
 import org.apache.hadoop.ozone.container.common.helpers.KeyUtils;
-import org.apache.hadoop.scm.container.common.helpers.Pipeline;
 import org.apache.hadoop.ozone.container.common.interfaces.ContainerManager;
 import org.apache.hadoop.ozone.container.common.interfaces.KeyManager;
 import org.apache.hadoop.ozone.container.common.utils.ContainerCache;
+import org.apache.hadoop.scm.container.common.helpers.Pipeline;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.utils.LevelDBStore;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
 import java.util.List;
 
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.IO_EXCEPTION;
+import static org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos
+    .Result.NO_SUCH_KEY;
+
+
 /**
  * Key Manager impl.
  */
 public class KeyManagerImpl implements KeyManager {
+  static final Logger LOG =
+      LoggerFactory.getLogger(KeyManagerImpl.class);
+
   private static final float LOAD_FACTOR = 0.75f;
   private final ContainerManager containerManager;
   private final ContainerCache containerCache;
@@ -48,8 +60,9 @@ public class KeyManagerImpl implements KeyManager {
    * @param containerManager - Container Manager.
    */
   public KeyManagerImpl(ContainerManager containerManager, Configuration conf) {
-    Preconditions.checkNotNull(containerManager);
+    Preconditions.checkNotNull(containerManager, "Container manager cannot be" +
-    Preconditions.checkNotNull(conf);
+        " null");
+    Preconditions.checkNotNull(conf, "Config cannot be null");
     int cacheSize = conf.getInt(OzoneConfigKeys.OZONE_KEY_CACHE,
         OzoneConfigKeys.OZONE_KEY_CACHE_DEFAULT);
     this.containerManager = containerManager;
@@ -60,17 +73,22 @@ public class KeyManagerImpl implements KeyManager {
    * {@inheritDoc}
    */
   @Override
-  public void putKey(Pipeline pipeline, KeyData data) throws IOException {
+  public void putKey(Pipeline pipeline, KeyData data)
+      throws StorageContainerException {
     containerManager.readLock();
     try {
       // We are not locking the key manager since LevelDb serializes all actions
       // against a single DB. We rely on DB level locking to avoid conflicts.
-      Preconditions.checkNotNull(pipeline);
+      Preconditions.checkNotNull(pipeline, "Pipeline cannot be null");
-      Preconditions.checkNotNull(pipeline.getContainerName());
+      Preconditions.checkNotNull(pipeline.getContainerName(),
+          "Container name cannot be null");
       ContainerData cData = containerManager.readContainer(
           pipeline.getContainerName());
       LevelDBStore db = KeyUtils.getDB(cData, containerCache);
-      Preconditions.checkNotNull(db);
+
+      // This is a post condition that acts as a hint to the user.
+      // Should never fail.
+      Preconditions.checkNotNull(db, "DB cannot be null here");
       db.put(data.getKeyName().getBytes(KeyUtils.ENCODING), data
           .getProtoBufMessage().toByteArray());
     } finally {
@@ -83,22 +101,30 @@ public class KeyManagerImpl implements KeyManager {
    * {@inheritDoc}
    */
   @Override
-  public KeyData getKey(KeyData data) throws IOException {
+  public KeyData getKey(KeyData data) throws StorageContainerException {
     containerManager.readLock();
     try {
-      Preconditions.checkNotNull(data);
+      Preconditions.checkNotNull(data, "Key data cannot be null");
-      Preconditions.checkNotNull(data.getContainerName());
+      Preconditions.checkNotNull(data.getContainerName(),
+          "Container name cannot be null");
       ContainerData cData = containerManager.readContainer(data
           .getContainerName());
       LevelDBStore db = KeyUtils.getDB(cData, containerCache);
-      Preconditions.checkNotNull(db);
+
+      // This is a post condition that acts as a hint to the user.
+      // Should never fail.
+      Preconditions.checkNotNull(db, "DB cannot be null here");
+
       byte[] kData = db.get(data.getKeyName().getBytes(KeyUtils.ENCODING));
-      if(kData == null) {
+      if (kData == null) {
-        throw new IOException("Unable to find the key.");
+        throw new StorageContainerException("Unable to find the key.",
+            NO_SUCH_KEY);
       }
       ContainerProtos.KeyData keyData =
           ContainerProtos.KeyData.parseFrom(kData);
       return KeyData.getFromProtoBuf(keyData);
+    } catch (IOException ex) {
+      throw new StorageContainerException(ex, IO_EXCEPTION);
     } finally {
       containerManager.readUnlock();
     }
@@ -108,24 +134,29 @@ public class KeyManagerImpl implements KeyManager {
    * {@inheritDoc}
    */
   @Override
-  public void deleteKey(Pipeline pipeline, String keyName) throws IOException {
+  public void deleteKey(Pipeline pipeline, String keyName)
+      throws StorageContainerException {
     containerManager.readLock();
     try {
-      Preconditions.checkNotNull(pipeline);
+      Preconditions.checkNotNull(pipeline, "Pipeline cannot be null");
-      Preconditions.checkNotNull(pipeline.getContainerName());
+      Preconditions.checkNotNull(pipeline.getContainerName(),
+          "Container name cannot be null");
       ContainerData cData = containerManager.readContainer(pipeline
           .getContainerName());
       LevelDBStore db = KeyUtils.getDB(cData, containerCache);
-      Preconditions.checkNotNull(db);
 
+      // This is a post condition that acts as a hint to the user.
+      // Should never fail.
+      Preconditions.checkNotNull(db, "DB cannot be null here");
       // Note : There is a race condition here, since get and delete
       // are not atomic. Leaving it here since the impact is refusing
       // to delete a key which might have just gotten inserted after
       // the get check.
 
       byte[] kData = db.get(keyName.getBytes(KeyUtils.ENCODING));
-      if(kData == null) {
+      if (kData == null) {
-        throw new IOException("Unable to find the key.");
+        throw new StorageContainerException("Unable to find the key.",
+            NO_SUCH_KEY);
       }
       db.delete(keyName.getBytes(KeyUtils.ENCODING));
     } finally {
@@ -139,7 +170,7 @@ public class KeyManagerImpl implements KeyManager {
   @Override
   public List<KeyData> listKey(Pipeline pipeline, String prefix, String
       prevKey, int count) {
-    // TODO :
+    // TODO : Implement listKey function.
     return null;
   }
 
@@ -148,7 +179,8 @@ public class KeyManagerImpl implements KeyManager {
    */
   @Override
   public void shutdown() {
-    Preconditions.checkState(this.containerManager.hasWriteLock());
+    Preconditions.checkState(this.containerManager.hasWriteLock(), "asserts " +
+        "that we are holding the container manager lock when shutting down.");
     KeyUtils.shutdownCache(containerCache);
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/interfaces/ChunkManager.java

@@ -18,11 +18,10 @@
 
 package org.apache.hadoop.ozone.container.common.interfaces;
 
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.ozone.container.common.helpers.ChunkInfo;
 import org.apache.hadoop.scm.container.common.helpers.Pipeline;
 
-import java.io.IOException;
-
 /**
  * Chunk Manager allows read, write, delete and listing of chunks in
  * a container.
@@ -34,10 +33,10 @@ public interface ChunkManager {
    * @param pipeline - Name and the set of machines that make this container.
    * @param keyName - Name of the Key.
    * @param info - ChunkInfo.
-   * @throws IOException
+   * @throws StorageContainerException
    */
   void writeChunk(Pipeline pipeline, String keyName,
-                  ChunkInfo info, byte[] data) throws IOException;
+                  ChunkInfo info, byte[] data) throws StorageContainerException;
 
   /**
    * reads the data defined by a chunk.
@@ -45,23 +44,23 @@ public interface ChunkManager {
    * @param keyName - Name of the Key
    * @param info - ChunkInfo.
    * @return  byte array
-   * @throws IOException
+   * @throws StorageContainerException
    *
    * TODO: Right now we do not support partial reads and writes of chunks.
    * TODO: Explore if we need to do that for ozone.
    */
   byte[] readChunk(Pipeline pipeline, String keyName, ChunkInfo info) throws
-      IOException;
+      StorageContainerException;
 
   /**
    * Deletes a given chunk.
    * @param pipeline  - Pipeline.
    * @param keyName   - Key Name
    * @param info  - Chunk Info
-   * @throws IOException
+   * @throws StorageContainerException
    */
   void deleteChunk(Pipeline pipeline, String keyName, ChunkInfo info) throws
-      IOException;
+      StorageContainerException;
 
   // TODO : Support list operations.
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/interfaces/ContainerDispatcher.java

@@ -21,8 +21,6 @@ package org.apache.hadoop.ozone.container.common.interfaces;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos.ContainerCommandResponseProto;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos.ContainerCommandRequestProto;
 
-import java.io.IOException;
-
 /**
  * Dispatcher acts as the bridge between the transport layer and
  * the actual container layer. This layer is capable of transforming
@@ -36,10 +34,8 @@ public interface ContainerDispatcher {
    * Dispatches commands to container layer.
    * @param msg - Command Request
    * @return Command Response
-   * @throws IOException
    */
-  ContainerCommandResponseProto dispatch(ContainerCommandRequestProto msg)
+  ContainerCommandResponseProto dispatch(ContainerCommandRequestProto msg);
-      throws IOException;
 
   /**
    * Initialize the Dispatcher.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/interfaces/ContainerManager.java

@@ -23,6 +23,7 @@ import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.server.datanode.StorageLocation;
 import org.apache.hadoop.hdfs.util.RwLock;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.ozone.container.common.helpers.ContainerData;
 import org.apache.hadoop.ozone.protocol.proto
     .StorageContainerDatanodeProtocolProtos.SCMNodeReport;
@@ -43,7 +44,7 @@ public interface ContainerManager extends RwLock {
    *
    * @param config        - Configuration.
    * @param containerDirs - List of Metadata Container locations.
-   * @throws IOException
+   * @throws StorageContainerException
    */
   void init(Configuration config, List<StorageLocation> containerDirs)
       throws IOException;
@@ -53,20 +54,20 @@ public interface ContainerManager extends RwLock {
    *
    * @param pipeline      -- Nodes which make up this container.
    * @param containerData - Container Name and metadata.
-   * @throws IOException
+   * @throws StorageContainerException
    */
   void createContainer(Pipeline pipeline, ContainerData containerData)
-      throws IOException;
+      throws StorageContainerException;
 
   /**
    * Deletes an existing container.
    *
    * @param pipeline      - nodes that make this container.
    * @param containerName - name of the container.
-   * @throws IOException
+   * @throws StorageContainerException
    */
   void deleteContainer(Pipeline pipeline, String containerName)
-      throws IOException;
+      throws StorageContainerException;
 
   /**
    * As simple interface for container Iterations.
@@ -75,25 +76,26 @@ public interface ContainerManager extends RwLock {
    * @param count   - how many to return
    * @param prevKey - Previous key - Server returns results from this point.
    * @param data    - Actual containerData
-   * @throws IOException
+   * @throws StorageContainerException
    */
   void listContainer(String prefix, long count, String prevKey,
                      List<ContainerData> data)
-      throws IOException;
+      throws StorageContainerException;
 
   /**
    * Get metadata about a specific container.
    *
    * @param containerName - Name of the container
    * @return ContainerData - Container Data.
-   * @throws IOException
+   * @throws StorageContainerException
    */
-  ContainerData readContainer(String containerName) throws IOException;
+  ContainerData readContainer(String containerName)
+      throws StorageContainerException;
 
   /**
    * Supports clean shutdown of container.
    *
-   * @throws IOException
+   * @throws StorageContainerException
    */
   void shutdown() throws IOException;
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/interfaces/KeyManager.java

@@ -17,10 +17,10 @@
  */
 package org.apache.hadoop.ozone.container.common.interfaces;
 
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.ozone.container.common.helpers.KeyData;
 import org.apache.hadoop.scm.container.common.helpers.Pipeline;
 
-import java.io.IOException;
 import java.util.List;
 
 /**
@@ -32,24 +32,28 @@ public interface KeyManager {
    *
    * @param pipeline - Pipeline.
    * @param data     - Key Data.
+   * @throws StorageContainerException
    */
-  void putKey(Pipeline pipeline, KeyData data) throws IOException;
+  void putKey(Pipeline pipeline, KeyData data) throws StorageContainerException;
 
   /**
    * Gets an existing key.
    *
    * @param data - Key Data.
    * @return Key Data.
+   * @throws StorageContainerException
    */
-  KeyData getKey(KeyData data) throws IOException;
+  KeyData getKey(KeyData data) throws StorageContainerException;
 
   /**
    * Deletes an existing Key.
    *
    * @param pipeline - Pipeline.
    * @param keyName  Key Data.
+   * @throws StorageContainerException
    */
-  void deleteKey(Pipeline pipeline, String keyName) throws IOException;
+  void deleteKey(Pipeline pipeline, String keyName)
+      throws StorageContainerException;
 
   /**
    * List keys in a container.

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/ozone/container/ContainerTestHelper.java

@@ -44,9 +44,15 @@ import java.util.UUID;
 /**
  * Helpers for container tests.
  */
-public class ContainerTestHelper {
+public final class ContainerTestHelper {
   private static Random r = new Random();
 
+  /**
+   * Never constructed.
+   */
+  private ContainerTestHelper() {
+  }
+
   /**
    * Create a pipeline with single node replica.
    *
@@ -291,8 +297,7 @@ public class ContainerTestHelper {
    * @return ContainerCommandRequestProto.
    */
   public static ContainerCommandResponseProto
-  getCreateContainerResponse(ContainerCommandRequestProto request) throws
+      getCreateContainerResponse(ContainerCommandRequestProto request) {
-      IOException {
     ContainerProtos.CreateContainerResponseProto.Builder createResponse =
         ContainerProtos.CreateContainerResponseProto.newBuilder();
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/ozone/container/common/impl/TestContainerPersistence.java

@@ -25,6 +25,7 @@ import org.apache.hadoop.ozone.MiniOzoneCluster;
 import org.apache.hadoop.ozone.OzoneConfigKeys;
 import org.apache.hadoop.ozone.OzoneConfiguration;
 import org.apache.hadoop.ozone.OzoneConsts;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
 import org.apache.hadoop.ozone.container.common.helpers.ChunkInfo;
 import org.apache.hadoop.ozone.container.common.helpers.ContainerData;
 import org.apache.hadoop.ozone.container.common.helpers.ContainerUtils;
@@ -121,8 +122,8 @@ public class TestContainerPersistence {
 
   @Before
   public void setupPaths() throws IOException {
-    if (!new File(path).exists()) {
+    if (!new File(path).exists() && !new File(path).mkdirs()) {
-      new File(path).mkdirs();
+      throw new IOException("Unable to create paths. " + path);
     }
     pathLists.clear();
     containerManager.getContainerMap().clear();
@@ -157,11 +158,8 @@ public class TestContainerPersistence {
     Assert.assertTrue(new File(status.getContainer().getContainerPath())
         .exists());
 
-    String containerPathString = ContainerUtils.getContainerNameFromFile(new
-        File(status.getContainer().getContainerPath()));
-
     Path meta = Paths.get(status.getContainer().getDBPath()).getParent();
-    Assert.assertTrue(Files.exists(meta));
+    Assert.assertTrue(meta != null && Files.exists(meta));
 
 
     String dbPath = status.getContainer().getDBPath();
@@ -363,8 +361,7 @@ public class TestContainerPersistence {
         sha.update(FileUtils.readFileToByteArray(fname.toFile()));
         String val = Hex.encodeHexString(sha.digest());
         Assert.assertEquals(fileHashMap.get(fname.getFileName().toString())
-                .getChecksum(),
+                .getChecksum(), val);
-            val);
         count++;
         sha.reset();
       }
@@ -486,7 +483,7 @@ public class TestContainerPersistence {
     setDataChecksum(info, data);
     chunkManager.writeChunk(pipeline, keyName, info, data);
     chunkManager.deleteChunk(pipeline, keyName, info);
-    exception.expect(IOException.class);
+    exception.expect(StorageContainerException.class);
     exception.expectMessage("Unable to find the chunk file.");
     chunkManager.readChunk(pipeline, keyName, info);
   }
@@ -572,7 +569,7 @@ public class TestContainerPersistence {
     keyData.setChunks(chunkList);
     keyManager.putKey(pipeline, keyData);
     keyManager.deleteKey(pipeline, keyName);
-    exception.expect(IOException.class);
+    exception.expect(StorageContainerException.class);
     exception.expectMessage("Unable to find the key.");
     keyManager.getKey(keyData);
   }
@@ -596,7 +593,7 @@ public class TestContainerPersistence {
     keyData.setChunks(chunkList);
     keyManager.putKey(pipeline, keyData);
     keyManager.deleteKey(pipeline, keyName);
-    exception.expect(IOException.class);
+    exception.expect(StorageContainerException.class);
     exception.expectMessage("Unable to find the key.");
     keyManager.deleteKey(pipeline, keyName);
   }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/ozone/container/transport/server/TestContainerServer.java

@@ -41,6 +41,9 @@ import java.io.IOException;
 
 import static org.mockito.Mockito.mock;
 
+/**
+ * Test Containers.
+ */
 public class TestContainerServer {
 
   @Test
@@ -69,8 +72,8 @@ public class TestContainerServer {
     XceiverClient client = null;
     String containerName = OzoneUtils.getRequestID();
     try {
-      Pipeline pipeline = ContainerTestHelper.createSingleNodePipeline
+      Pipeline pipeline = ContainerTestHelper.createSingleNodePipeline(
-          (containerName);
+          containerName);
       OzoneConfiguration conf = new OzoneConfiguration();
       conf.setInt(OzoneConfigKeys.DFS_CONTAINER_IPC_PORT,
           pipeline.getLeader().getContainerPort());
@@ -102,8 +105,8 @@ public class TestContainerServer {
     String containerName = OzoneUtils.getRequestID();
 
     try {
-      Pipeline pipeline = ContainerTestHelper.createSingleNodePipeline
+      Pipeline pipeline = ContainerTestHelper.createSingleNodePipeline(
-          (containerName);
+          containerName);
       OzoneConfiguration conf = new OzoneConfiguration();
       conf.setInt(OzoneConfigKeys.DFS_CONTAINER_IPC_PORT,
           pipeline.getLeader().getContainerPort());
@@ -136,17 +139,16 @@ public class TestContainerServer {
     }
   }
 
-  private class TestContainerDispatcher implements ContainerDispatcher {
+  private static class TestContainerDispatcher implements ContainerDispatcher {
     /**
      * Dispatches commands to container layer.
      *
      * @param msg - Command Request
      * @return Command Response
-     * @throws IOException
      */
     @Override
     public ContainerCommandResponseProto
-    dispatch(ContainerCommandRequestProto msg) throws IOException {
+        dispatch(ContainerCommandRequestProto msg)  {
       return ContainerTestHelper.getCreateContainerResponse(msg);
     }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/ozone/scm/TestAllocateContainer.java

@@ -49,6 +49,8 @@ public class TestAllocateContainer {
     conf = new OzoneConfiguration();
     cluster = new MiniOzoneCluster.Builder(conf).numDataNodes(1)
         .setHandlerType("distributed").build();
+    storageContainerLocationClient =
+        cluster.createStorageContainerLocationClient();
   }
 
   @AfterClass
@@ -61,8 +63,6 @@ public class TestAllocateContainer {
 
   @Test
   public void testAllocate() throws Exception {
-    storageContainerLocationClient =
-        cluster.createStorageContainerLocationClient();
     Pipeline pipeline = storageContainerLocationClient.allocateContainer(
         "container0");
     Assert.assertNotNull(pipeline);
@@ -72,8 +72,6 @@ public class TestAllocateContainer {
 
   @Test
   public void testAllocateNull() throws Exception {
-    storageContainerLocationClient =
-        cluster.createStorageContainerLocationClient();
     thrown.expect(NullPointerException.class);
     storageContainerLocationClient.allocateContainer(null);
   }
@@ -81,12 +79,9 @@ public class TestAllocateContainer {
   @Test
   public void testAllocateDuplicate() throws Exception {
     String containerName = RandomStringUtils.randomAlphanumeric(10);
-    storageContainerLocationClient =
-        cluster.createStorageContainerLocationClient();
     thrown.expect(IOException.class);
     thrown.expectMessage("Specified container already exists");
     storageContainerLocationClient.allocateContainer(containerName);
     storageContainerLocationClient.allocateContainer(containerName);
-
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/ozone/scm/TestContainerSmallFile.java

@@ -0,0 +1,131 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.ozone.scm;
+
+import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos;
+import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.ozone.MiniOzoneCluster;
+import org.apache.hadoop.ozone.OzoneConfiguration;
+import org.apache.hadoop.scm.protocolPB
+    .StorageContainerLocationProtocolClientSideTranslatorPB;
+import org.apache.hadoop.scm.XceiverClient;
+import org.apache.hadoop.scm.XceiverClientManager;
+import org.apache.hadoop.scm.container.common.helpers.Pipeline;
+import org.apache.hadoop.scm.container.common.helpers.StorageContainerException;
+import org.apache.hadoop.scm.storage.ContainerProtocolCalls;
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import java.io.IOException;
+import java.util.UUID;
+
+/**
+ * Test Container calls.
+ */
+public class TestContainerSmallFile {
+  @Rule
+  public ExpectedException thrown = ExpectedException.none();
+
+  private static MiniOzoneCluster cluster;
+  private static OzoneConfiguration ozoneConfig;
+  private static StorageContainerLocationProtocolClientSideTranslatorPB
+      storageContainerLocationClient;
+  private static XceiverClientManager xceiverClientManager;
+
+  @BeforeClass
+  public static void init() throws IOException {
+    ozoneConfig = new OzoneConfiguration();
+    cluster = new MiniOzoneCluster.Builder(ozoneConfig)
+        .numDataNodes(1).setHandlerType("distributed").build();
+    storageContainerLocationClient = cluster
+        .createStorageContainerLocationClient();
+    xceiverClientManager = new XceiverClientManager(ozoneConfig);
+  }
+
+  @AfterClass
+  public static void shutdown() throws InterruptedException {
+    if (cluster != null) {
+      cluster.shutdown();
+    }
+    IOUtils.cleanup(null, storageContainerLocationClient, cluster);
+  }
+
+  @Test
+  public void testAllocateWrite() throws Exception {
+    String traceID = UUID.randomUUID().toString();
+    String containerName = "container0";
+    Pipeline pipeline =
+        storageContainerLocationClient.allocateContainer(containerName);
+    XceiverClient client = xceiverClientManager.acquireClient(pipeline);
+    ContainerProtocolCalls.createContainer(client, traceID);
+
+    ContainerProtocolCalls.writeSmallFile(client, containerName,
+        "key", "data123".getBytes(), traceID);
+    ContainerProtos.GetSmallFileResponseProto response =
+        ContainerProtocolCalls.readSmallFile(client, containerName, "key",
+            traceID);
+    String readData = response.getData().getData().toStringUtf8();
+    Assert.assertEquals("data123", readData);
+  }
+
+  @Test
+  public void testInvalidKeyRead() throws Exception {
+    String traceID = UUID.randomUUID().toString();
+    String containerName = "container1";
+    Pipeline pipeline =
+        storageContainerLocationClient.allocateContainer(containerName);
+    XceiverClient client = xceiverClientManager.acquireClient(pipeline);
+    ContainerProtocolCalls.createContainer(client, traceID);
+
+    thrown.expect(StorageContainerException.class);
+    thrown.expectMessage("Unable to find the key");
+
+    // Try to read a Key Container Name
+    ContainerProtos.GetSmallFileResponseProto response =
+        ContainerProtocolCalls.readSmallFile(client, containerName, "key",
+            traceID);
+  }
+
+  @Test
+  public void testInvalidContainerRead() throws Exception {
+    String traceID = UUID.randomUUID().toString();
+    String invalidName = "invalidName";
+    String containerName = "container2";
+    Pipeline pipeline =
+        storageContainerLocationClient.allocateContainer(containerName);
+    XceiverClient client = xceiverClientManager.acquireClient(pipeline);
+    ContainerProtocolCalls.createContainer(client, traceID);
+    ContainerProtocolCalls.writeSmallFile(client, containerName,
+        "key", "data123".getBytes(), traceID);
+
+
+    thrown.expect(StorageContainerException.class);
+    thrown.expectMessage("Unable to find the container");
+
+    // Try to read a invalid key
+    ContainerProtos.GetSmallFileResponseProto response =
+        ContainerProtocolCalls.readSmallFile(client, invalidName, "key",
+            traceID);
+  }
+}
+
+