HDFS-8053. Move DFSIn/OutputStream and related classes to hadoop-hdfs-client. Contributed by Mingliang Liu.

hadoop-hdfs-project/hadoop-hdfs-client/dev-support/findbugsExcludeFile.xml

@@ -32,4 +32,28 @@
     <Method name="allocSlot" />
     <Bug pattern="UL_UNRELEASED_LOCK" />
   </Match>
+  <Match>
+    <Class name="org.apache.hadoop.hdfs.DFSInputStream"/>
+    <Field name="tcpReadsDisabledForTesting"/>
+    <Bug pattern="MS_SHOULD_BE_FINAL"/>
+  </Match>
+
+  <!--
+    ResponseProccessor is thread that is designed to catch RuntimeException.
+  -->
+  <Match>
+    <Class name="org.apache.hadoop.hdfs.DataStreamer$ResponseProcessor" />
+    <Method name="run" />
+    <Bug pattern="REC_CATCH_EXCEPTION" />
+  </Match>
+
+  <!--
+    We use a separate lock to guard cachingStrategy in order to separate
+    locks for p-reads from seek + read invocations.
+  -->
+  <Match>
+    <Class name="org.apache.hadoop.hdfs.DFSInputStream" />
+    <Field name="cachingStrategy" />
+    <Bug pattern="IS2_INCONSISTENT_SYNC" />
+  </Match>
 </FindBugsFilter>

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/BlockReaderFactory.java

@@ -31,8 +31,6 @@ import java.util.List;
 import com.google.common.io.ByteArrayDataOutput;
 import com.google.common.io.ByteStreams;
 import org.apache.commons.lang.mutable.MutableBoolean;
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.StorageType;
@@ -56,7 +54,7 @@ import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitReplica;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitReplicaInfo;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.Slot;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.SlotId;
-import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.hdfs.util.IOUtilsClient;
 import org.apache.hadoop.ipc.RemoteException;
 import org.apache.hadoop.net.unix.DomainSocket;
 import org.apache.hadoop.security.AccessControlException;
@@ -69,13 +67,16 @@ import org.apache.hadoop.util.Time;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 
 /** 
  * Utility class to create BlockReader implementations.
  */
 @InterfaceAudience.Private
 public class BlockReaderFactory implements ShortCircuitReplicaCreator {
-  static final Log LOG = LogFactory.getLog(BlockReaderFactory.class);
+  static final Logger LOG = LoggerFactory.getLogger(BlockReaderFactory.class);
 
   public static class FailureInjector {
     public void injectRequestFileDescriptorsFailure() throws IOException {
@@ -551,14 +552,14 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
           if (LOG.isDebugEnabled()) {
             LOG.debug(this + ": closing stale domain peer " + peer, e);
           }
-          IOUtils.cleanup(LOG, peer);
+          IOUtilsClient.cleanup(LOG, peer);
         } else {
           // Handle an I/O error we got when using a newly created socket.
           // We temporarily disable the domain socket path for a few minutes in
           // this case, to prevent wasting more time on it.
           LOG.warn(this + ": I/O error requesting file descriptors.  " + 
               "Disabling domain socket " + peer.getDomainSocket(), e);
-          IOUtils.cleanup(LOG, peer);
+          IOUtilsClient.cleanup(LOG, peer);
           clientContext.getDomainSocketFactory()
               .disableDomainSocketPath(pathInfo.getPath());
           return null;
@@ -617,7 +618,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
         return null;
       } finally {
         if (replica == null) {
-          IOUtils.cleanup(DFSClient.LOG, fis[0], fis[1]);
+          IOUtilsClient.cleanup(DFSClient.LOG, fis[0], fis[1]);
         }
       }
     case ERROR_UNSUPPORTED:
@@ -685,7 +686,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
         blockReader = getRemoteBlockReader(peer);
         return blockReader;
       } catch (IOException ioe) {
-        IOUtils.cleanup(LOG, peer);
+        IOUtilsClient.cleanup(LOG, peer);
         if (isSecurityException(ioe)) {
           if (LOG.isTraceEnabled()) {
             LOG.trace(this + ": got security exception while constructing " +
@@ -712,7 +713,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
         }
       } finally {
         if (blockReader == null) {
-          IOUtils.cleanup(LOG, peer);
+          IOUtilsClient.cleanup(LOG, peer);
         }
       }
     }
@@ -769,7 +770,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
         }
       } finally {
         if (blockReader == null) {
-          IOUtils.cleanup(LOG, peer);
+          IOUtilsClient.cleanup(LOG, peer);
         }
       }
     }

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/BlockStorageLocationUtil.java

@@ -31,8 +31,6 @@ import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
@@ -54,13 +52,15 @@ import org.apache.htrace.TraceScope;
 
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 @InterfaceAudience.Private
 @InterfaceStability.Unstable
 class BlockStorageLocationUtil {
   
-  static final Log LOG = LogFactory
+  static final Logger LOG = LoggerFactory
-      .getLog(BlockStorageLocationUtil.class);
+      .getLogger(BlockStorageLocationUtil.class);
   
   /**
    * Create a list of {@link VolumeBlockLocationCallable} corresponding to a set

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -55,8 +55,6 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 import javax.net.SocketFactory;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
@@ -157,6 +155,7 @@ import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifie
 import org.apache.hadoop.hdfs.server.datanode.CachingStrategy;
 import org.apache.hadoop.hdfs.server.namenode.SafeModeException;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeStorageReport;
+import org.apache.hadoop.hdfs.util.IOUtilsClient;
 import org.apache.hadoop.io.DataOutputBuffer;
 import org.apache.hadoop.io.EnumSetWritable;
 import org.apache.hadoop.io.IOUtils;
@@ -192,6 +191,9 @@ import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
 import com.google.common.net.InetAddresses;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /********************************************************
  * DFSClient can connect to a Hadoop Filesystem and 
  * perform basic file tasks.  It uses the ClientProtocol
@@ -206,7 +208,7 @@ import com.google.common.net.InetAddresses;
 @InterfaceAudience.Private
 public class DFSClient implements java.io.Closeable, RemotePeerFactory,
     DataEncryptionKeyFactory {
-  public static final Log LOG = LogFactory.getLog(DFSClient.class);
+  public static final Logger LOG = LoggerFactory.getLogger(DFSClient.class);
   public static final long SERVER_DEFAULTS_VALIDITY_PERIOD = 60 * 60 * 1000L; // 1 hour
 
   private final Configuration conf;
@@ -310,7 +312,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
     this.stats = stats;
     this.socketFactory = NetUtils.getSocketFactory(conf, ClientProtocol.class);
     this.dtpReplaceDatanodeOnFailure = ReplaceDatanodeOnFailure.get(conf);
-    this.smallBufferSize = DFSUtil.getSmallBufferSize(conf);
+    this.smallBufferSize = DFSUtilClient.getSmallBufferSize(conf);
 
     this.ugi = UserGroupInformation.getCurrentUser();
     
@@ -323,6 +325,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
         HdfsClientConfigKeys.DFS_CLIENT_TEST_DROP_NAMENODE_RESPONSE_NUM_DEFAULT);
     ProxyAndInfo<ClientProtocol> proxyInfo = null;
     AtomicBoolean nnFallbackToSimpleAuth = new AtomicBoolean(false);
+
     if (numResponseToDrop > 0) {
       // This case is used for testing.
       LOG.warn(HdfsClientConfigKeys.DFS_CLIENT_TEST_DROP_NAMENODE_RESPONSE_NUM_KEY
@@ -732,7 +735,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
     static {
       //Ensure that HDFS Configuration files are loaded before trying to use
       // the renewer.
-      HdfsConfiguration.init();
+      HdfsConfigurationLoader.init();
     }
     
     @Override
@@ -2068,7 +2071,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
       return PBHelperClient.convert(reply.getReadOpChecksumInfo().getChecksum().getType());
     } finally {
-      IOUtils.cleanup(null, pair.in, pair.out);
+      IOUtilsClient.cleanup(null, pair.in, pair.out);
     }
   }
 
@@ -3085,7 +3088,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
       return peer;
     } finally {
       if (!success) {
-        IOUtils.cleanup(LOG, peer);
+        IOUtilsClient.cleanup(LOG, peer);
         IOUtils.closeSocket(sock);
       }
     }
@@ -3157,11 +3160,11 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   /**
    * Probe for encryption enabled on this filesystem.
-   * See {@link DFSUtil#isHDFSEncryptionEnabled(Configuration)}
+   * See {@link DFSUtilClient#isHDFSEncryptionEnabled(Configuration)}
    * @return true if encryption is enabled
    */
   public boolean isHDFSEncryptionEnabled() {
-    return DFSUtil.isHDFSEncryptionEnabled(this.conf);
+    return DFSUtilClient.isHDFSEncryptionEnabled(this.conf);
   }
 
   /**

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClientFaultInjector.java

@@ -30,12 +30,15 @@ import org.apache.hadoop.classification.InterfaceAudience;
 @VisibleForTesting
 @InterfaceAudience.Private
 public class DFSClientFaultInjector {
-  public static DFSClientFaultInjector instance = new DFSClientFaultInjector();
+  private static DFSClientFaultInjector instance = new DFSClientFaultInjector();
   public static AtomicLong exceptionNum = new AtomicLong(0);
 
   public static DFSClientFaultInjector get() {
     return instance;
   }
+  public static void set(DFSClientFaultInjector instance) {
+    DFSClientFaultInjector.instance = instance;
+  }
 
   public boolean corruptPacket() {
     return false;

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSInotifyEventInputStream.java

@@ -44,8 +44,8 @@ import java.util.concurrent.TimeUnit;
 @InterfaceAudience.Public
 @InterfaceStability.Unstable
 public class DFSInotifyEventInputStream {
-  public static Logger LOG = LoggerFactory.getLogger(DFSInotifyEventInputStream
+  public static final Logger LOG = LoggerFactory.getLogger(
-      .class);
+      DFSInotifyEventInputStream.class);
 
   /**
    * The trace sampler to use when making RPCs to the NameNode.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSUtilClient.java

@@ -25,6 +25,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.crypto.key.KeyProvider;
 import org.apache.hadoop.crypto.key.KeyProviderFactory;
 import org.apache.hadoop.fs.BlockLocation;
+import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
@@ -590,6 +591,29 @@ public class DFSUtilClient {
     }
   }
 
+  public static int getIoFileBufferSize(Configuration conf) {
+    return conf.getInt(
+        CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_KEY,
+        CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_DEFAULT);
+  }
+
+  public static int getSmallBufferSize(Configuration conf) {
+    return Math.min(getIoFileBufferSize(conf) / 2, 512);
+  }
+
+  /**
+   * Probe for HDFS Encryption being enabled; this uses the value of
+   * the option {@link HdfsClientConfigKeys#DFS_ENCRYPTION_KEY_PROVIDER_URI},
+   * returning true if that property contains a non-empty, non-whitespace
+   * string.
+   * @param conf configuration to probe
+   * @return true if encryption is considered enabled.
+   */
+  public static boolean isHDFSEncryptionEnabled(Configuration conf) {
+    return !conf.getTrimmed(
+        HdfsClientConfigKeys.DFS_ENCRYPTION_KEY_PROVIDER_URI, "").isEmpty();
+  }
+
   public static InetSocketAddress getNNAddress(String address) {
     return NetUtils.createSocketAddr(address,
         HdfsClientConfigKeys.DFS_NAMENODE_RPC_PORT_DEFAULT);

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DataStreamer.java

@@ -40,8 +40,6 @@ import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.BlockWrite;
@@ -94,6 +92,9 @@ import com.google.common.cache.LoadingCache;
 import com.google.common.cache.RemovalListener;
 import com.google.common.cache.RemovalNotification;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /*********************************************************************
  *
  * The DataStreamer class is responsible for sending data packets to the
@@ -117,7 +118,7 @@ import com.google.common.cache.RemovalNotification;
 
 @InterfaceAudience.Private
 class DataStreamer extends Daemon {
-  static final Log LOG = LogFactory.getLog(DataStreamer.class);
+  static final Logger LOG = LoggerFactory.getLogger(DataStreamer.class);
 
   /**
    * Create a socket for a write pipeline
@@ -1229,7 +1230,7 @@ class DataStreamer extends Daemon {
       unbufOut = saslStreams.out;
       unbufIn = saslStreams.in;
       out = new DataOutputStream(new BufferedOutputStream(unbufOut,
-          DFSUtil.getSmallBufferSize(dfsClient.getConfiguration())));
+          DFSUtilClient.getSmallBufferSize(dfsClient.getConfiguration())));
       in = new DataInputStream(unbufIn);
 
       //send the TRANSFER_BLOCK request
@@ -1494,7 +1495,7 @@ class DataStreamer extends Daemon {
         unbufOut = saslStreams.out;
         unbufIn = saslStreams.in;
         out = new DataOutputStream(new BufferedOutputStream(unbufOut,
-            DFSUtil.getSmallBufferSize(dfsClient.getConfiguration())));
+            DFSUtilClient.getSmallBufferSize(dfsClient.getConfiguration())));
         blockReplyStream = new DataInputStream(unbufIn);
 
         //

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/HdfsConfigurationLoader.java

@@ -0,0 +1,44 @@
+/**
+ * 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.hdfs;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.conf.Configuration;
+
+/**
+ * Load default HDFS configuration resources.
+ */
+@InterfaceAudience.Private
+class HdfsConfigurationLoader {
+
+  static {
+    // adds the default resources
+    Configuration.addDefaultResource("hdfs-default.xml");
+    Configuration.addDefaultResource("hdfs-site.xml");
+  }
+
+  /**
+   * This method is here so that when invoked, default resources are added if
+   * they haven't already been previously loaded.  Upon loading this class, the
+   * static initializer block above will be executed to add the default
+   * resources. It is safe for this method to be called multiple times
+   * as the static initializer block will only get invoked once.
+   */
+  public static void init() {
+  }
+}

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/client/impl/LeaseRenewer.java

@@ -27,8 +27,6 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.hdfs.DFSClient;
@@ -39,6 +37,8 @@ import org.apache.hadoop.util.Daemon;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
 import com.google.common.annotations.VisibleForTesting;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * <p>
@@ -73,7 +73,7 @@ import com.google.common.annotations.VisibleForTesting;
  */
 @InterfaceAudience.Private
 public class LeaseRenewer {
-  static final Log LOG = LogFactory.getLog(LeaseRenewer.class);
+  static final Logger LOG = LoggerFactory.getLogger(LeaseRenewer.class);
 
   static final long LEASE_RENEWER_GRACE_DEFAULT = 60*1000L;
   static final long LEASE_RENEWER_SLEEP_DEFAULT = 1000L;

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -629,6 +629,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8873. Allow the directoryScanner to be rate-limited (Daniel Templeton
     via Colin P. McCabe)
 
+    HDFS-8053. Move DFSIn/OutputStream and related classes to
+    hadoop-hdfs-client. (Mingliang Liu via wheat9)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml

@@ -73,15 +73,6 @@
        <Bug pattern="OBL_UNSATISFIED_OBLIGATION" />
      </Match>
 
-     <!--
-      ResponseProccessor is thread that is designed to catch RuntimeException.
-     -->
-     <Match>
-       <Class name="org.apache.hadoop.hdfs.DataStreamer$ResponseProcessor" />
-       <Method name="run" />
-       <Bug pattern="REC_CATCH_EXCEPTION" />
-     </Match>
-
      <!--
       lastAppliedTxid is carefully unsynchronized in the BackupNode in a couple spots.
       See the comments in BackupImage for justification.
@@ -196,14 +187,4 @@
       <Method name="assertAllResultsEqual" />
       <Bug pattern="NP_LOAD_OF_KNOWN_NULL_VALUE" />
     </Match>
-
-    <!--
-     We use a separate lock to guard cachingStrategy in order to separate
-     locks for p-reads from seek + read invocations.
-    -->
-    <Match>
-        <Class name="org.apache.hadoop.hdfs.DFSInputStream" />
-        <Field name="cachingStrategy" />
-        <Bug pattern="IS2_INCONSISTENT_SYNC" />
-    </Match>
  </FindBugsFilter>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -18,8 +18,6 @@
 
 package org.apache.hadoop.hdfs;
 
-import java.util.concurrent.TimeUnit;
-
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java

@@ -1477,27 +1477,4 @@ public class DFSUtil {
     return cryptoProvider;
   }
 
-  public static int getIoFileBufferSize(Configuration conf) {
-    return conf.getInt(
-      CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_KEY,
-      CommonConfigurationKeysPublic.IO_FILE_BUFFER_SIZE_DEFAULT);
-  }
-
-  public static int getSmallBufferSize(Configuration conf) {
-    return Math.min(getIoFileBufferSize(conf) / 2, 512);
-  }
-
-  /**
-   * Probe for HDFS Encryption being enabled; this uses the value of
-   * the option {@link DFSConfigKeys.DFS_ENCRYPTION_KEY_PROVIDER_URI},
-   * returning true if that property contains a non-empty, non-whitespace
-   * string.
-   * @param conf configuration to probe
-   * @return true if encryption is considered enabled.
-   */
-  public static boolean isHDFSEncryptionEnabled(Configuration conf) {
-    return !conf.getTrimmed(
-        DFSConfigKeys.DFS_ENCRYPTION_KEY_PROVIDER_URI, "").isEmpty();
-  }
-
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/HdfsConfiguration.java

@@ -31,9 +31,7 @@ public class HdfsConfiguration extends Configuration {
     addDeprecatedKeys();
 
     // adds the default resources
-    Configuration.addDefaultResource("hdfs-default.xml");
+    HdfsConfigurationLoader.init();
-    Configuration.addDefaultResource("hdfs-site.xml");
-
   }
 
   public HdfsConfiguration() {
@@ -52,8 +50,9 @@ public class HdfsConfiguration extends Configuration {
    * This method is here so that when invoked, HdfsConfiguration is class-loaded if
    * it hasn't already been previously loaded.  Upon loading the class, the static 
    * initializer block above will be executed to add the deprecated keys and to add
-   * the default resources.   It is safe for this method to be called multiple times 
+   * the default resources via {@link HdfsConfigurationLoader#init()}. It is
-   * as the static initializer block will only get invoked once.
+   * safe for this method to be called multiple times as the static initializer
+   * block will only get invoked once.
    *
    * This replaces the previously, dangerous practice of other classes calling
    * Configuration.addDefaultResource("hdfs-default.xml") directly without loading 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/Dispatcher.java

@@ -49,6 +49,7 @@ import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
@@ -879,7 +880,7 @@ public class Dispatcher {
     this.saslClient = new SaslDataTransferClient(conf,
         DataTransferSaslUtil.getSaslPropertiesResolver(conf),
         TrustedChannelResolver.getInstance(conf), nnc.fallbackToSimpleAuth);
-    this.ioFileBufferSize = DFSUtil.getIoFileBufferSize(conf);
+    this.ioFileBufferSize = DFSUtilClient.getIoFileBufferSize(conf);
   }
 
   public DistributedFileSystem getDistributedFileSystem() {

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

@@ -38,7 +38,7 @@ import org.apache.commons.logging.Log;
 import org.apache.hadoop.fs.ChecksumException;
 import org.apache.hadoop.fs.FSOutputSummer;
 import org.apache.hadoop.fs.StorageType;
-import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.datatransfer.BlockConstructionStage;
@@ -248,7 +248,7 @@ class BlockReceiver implements Closeable {
             out.getClass());
       }
       this.checksumOut = new DataOutputStream(new BufferedOutputStream(
-          streams.getChecksumOut(), DFSUtil.getSmallBufferSize(
+          streams.getChecksumOut(), DFSUtilClient.getSmallBufferSize(
           datanode.getConf())));
       // write data chunk header if creating a new replica
       if (isCreate) {

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

@@ -34,7 +34,7 @@ import java.util.Arrays;
 
 import org.apache.commons.logging.Log;
 import org.apache.hadoop.fs.ChecksumException;
-import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.datatransfer.PacketHeader;
@@ -111,7 +111,7 @@ class BlockSender implements java.io.Closeable {
   private static final int IO_FILE_BUFFER_SIZE;
   static {
     HdfsConfiguration conf = new HdfsConfiguration();
-    IO_FILE_BUFFER_SIZE = DFSUtil.getIoFileBufferSize(conf);
+    IO_FILE_BUFFER_SIZE = DFSUtilClient.getIoFileBufferSize(conf);
   }
   private static final int TRANSFERTO_BUFFER_SIZE = Math.max(
       IO_FILE_BUFFER_SIZE, MIN_BUFFER_WITH_TRANSFERTO);

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

@@ -109,6 +109,7 @@ import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.DFSUtil.ConfiguredNNAddress;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.HDFSPolicyProvider;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.client.BlockReportOptions;
@@ -2186,7 +2187,7 @@ public class DataNode extends ReconfigurableBase
         unbufIn = saslStreams.in;
         
         out = new DataOutputStream(new BufferedOutputStream(unbufOut,
-            DFSUtil.getSmallBufferSize(conf)));
+            DFSUtilClient.getSmallBufferSize(conf)));
         in = new DataInputStream(unbufIn);
         blockSender = new BlockSender(b, 0, b.getNumBytes(), 
             false, false, true, DataNode.this, null, cachingStrategy);

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

@@ -49,7 +49,7 @@ import java.util.Arrays;
 import com.google.common.annotations.VisibleForTesting;
 import org.apache.commons.logging.Log;
 import org.apache.hadoop.fs.StorageType;
-import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.ExtendedBlockId;
 import org.apache.hadoop.hdfs.net.Peer;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
@@ -134,8 +134,8 @@ class DataXceiver extends Receiver implements Runnable {
     this.datanode = datanode;
     this.dataXceiverServer = dataXceiverServer;
     this.connectToDnViaHostname = datanode.getDnConf().connectToDnViaHostname;
-    this.ioFileBufferSize = DFSUtil.getIoFileBufferSize(datanode.getConf());
+    this.ioFileBufferSize = DFSUtilClient.getIoFileBufferSize(datanode.getConf());
-    this.smallBufferSize = DFSUtil.getSmallBufferSize(datanode.getConf());
+    this.smallBufferSize = DFSUtilClient.getSmallBufferSize(datanode.getConf());
     remoteAddress = peer.getRemoteAddressString();
     final int colonIdx = remoteAddress.indexOf(':');
     remoteAddressWithoutPort =

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java

@@ -38,7 +38,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.DU;
 import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
 import org.apache.hadoop.hdfs.protocol.BlockListAsLongs.BlockReportReplica;
@@ -111,7 +111,7 @@ class BlockPoolSlice {
       }
     }
 
-    this.ioFileBufferSize = DFSUtil.getIoFileBufferSize(conf);
+    this.ioFileBufferSize = DFSUtilClient.getIoFileBufferSize(conf);
 
     this.deleteDuplicateReplicas = conf.getBoolean(
         DFSConfigKeys.DFS_DATANODE_DUPLICATE_REPLICA_DELETION,

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java

@@ -59,7 +59,7 @@ import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.ExtendedBlockId;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.protocol.Block;
@@ -268,7 +268,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     this.datanode = datanode;
     this.dataStorage = storage;
     this.conf = conf;
-    this.smallBufferSize = DFSUtil.getSmallBufferSize(conf);
+    this.smallBufferSize = DFSUtilClient.getSmallBufferSize(conf);
     // The number of volumes required for operation is the total number
     // of volumes minus the number of failed volumes we can tolerate.
     volFailuresTolerated =
@@ -961,7 +961,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
       File blockFile, int smallBufferSize, final Configuration conf)
       throws IOException {
     final DataChecksum checksum = BlockMetadataHeader.readDataChecksum(srcMeta,
-        DFSUtil.getIoFileBufferSize(conf));
+        DFSUtilClient.getIoFileBufferSize(conf));
     final byte[] data = new byte[1 << 16];
     final byte[] crcs = new byte[checksum.getChecksumSize(data.length)];
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java

@@ -21,7 +21,7 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
@@ -240,7 +240,7 @@ class RamDiskAsyncLazyPersistService {
       boolean succeeded = false;
       final FsDatasetImpl dataset = (FsDatasetImpl)datanode.getFSDataset();
       try (FsVolumeReference ref = this.targetVolume) {
-        int smallBufferSize = DFSUtil.getSmallBufferSize(EMPTY_HDFS_CONF);
+        int smallBufferSize = DFSUtilClient.getSmallBufferSize(EMPTY_HDFS_CONF);
         // No FsDatasetImpl lock for the file copy
         File targetFiles[] = FsDatasetImpl.copyBlockFiles(
             blockId, genStamp, metaFile, blockFile, lazyPersistDir, true,

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/TransferFsImage.java

@@ -43,7 +43,7 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.server.common.Storage;
 import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
@@ -89,7 +89,7 @@ public class TransferFsImage {
     connectionFactory = URLConnectionFactory
         .newDefaultURLConnectionFactory(conf);
     isSpnegoEnabled = UserGroupInformation.isSecurityEnabled();
-    IO_FILE_BUFFER_SIZE = DFSUtil.getIoFileBufferSize(conf);
+    IO_FILE_BUFFER_SIZE = DFSUtilClient.getIoFileBufferSize(conf);
   }
 
   private static final Log LOG = LogFactory.getLog(TransferFsImage.class);

hadoop-hdfs-project/hadoop-hdfs/src/test/aop/org/apache/hadoop/hdfs/server/datanode/TestFiDataTransferProtocol2.java

@@ -20,7 +20,6 @@ package org.apache.hadoop.hdfs.server.datanode;
 import java.io.IOException;
 import java.util.Random;
 
-import org.apache.commons.logging.impl.Log4JLogger;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fi.DataTransferTestUtil;
 import org.apache.hadoop.fi.DataTransferTestUtil.CountdownDoosAction;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/DFSTestUtil.java

@@ -990,7 +990,7 @@ public class DFSTestUtil {
     final long writeTimeout = dfsClient.getDatanodeWriteTimeout(datanodes.length);
     final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
         NetUtils.getOutputStream(s, writeTimeout),
-        DFSUtil.getSmallBufferSize(dfsClient.getConfiguration())));
+        DFSUtilClient.getSmallBufferSize(dfsClient.getConfiguration())));
     final DataInputStream in = new DataInputStream(NetUtils.getInputStream(s));
 
     // send the request

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSClusterWithNodeGroup.java

@@ -28,8 +28,8 @@ import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.StartupOption;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
 import org.apache.hadoop.hdfs.server.datanode.SecureDataNodeStarter;
-import org.apache.hadoop.hdfs.server.datanode.SimulatedFSDataset;
 import org.apache.hadoop.hdfs.server.datanode.SecureDataNodeStarter.SecureResources;
+import org.apache.hadoop.hdfs.server.datanode.SimulatedFSDataset;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsDatasetSpi;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl;
 import org.apache.hadoop.net.NetUtils;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestBlockStoragePolicy.java

@@ -36,7 +36,6 @@ import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.protocol.*;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
 import org.apache.hadoop.hdfs.server.blockmanagement.*;
-import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
 import org.apache.hadoop.hdfs.server.datanode.DataNodeTestUtils;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestClientProtocolForPipelineRecovery.java

@@ -124,8 +124,8 @@ public class TestClientProtocolForPipelineRecovery {
   public void testPipelineRecoveryForLastBlock() throws IOException {
     DFSClientFaultInjector faultInjector
         = Mockito.mock(DFSClientFaultInjector.class);
-    DFSClientFaultInjector oldInjector = DFSClientFaultInjector.instance;
+    DFSClientFaultInjector oldInjector = DFSClientFaultInjector.get();
-    DFSClientFaultInjector.instance = faultInjector;
+    DFSClientFaultInjector.set(faultInjector);
     Configuration conf = new HdfsConfiguration();
 
     conf.setInt(HdfsClientConfigKeys.BlockWrite.LOCATEFOLLOWINGBLOCK_RETRIES_KEY, 3);
@@ -153,7 +153,7 @@ public class TestClientProtocolForPipelineRecovery {
             + " corrupt replicas.");
       }
     } finally {
-      DFSClientFaultInjector.instance = oldInjector;
+      DFSClientFaultInjector.set(oldInjector);
       if (cluster != null) {
         cluster.shutdown();
       }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestCrcCorruption.java

@@ -76,7 +76,7 @@ public class TestCrcCorruption {
   @Before
   public void setUp() throws IOException {
     faultInjector = Mockito.mock(DFSClientFaultInjector.class);
-    DFSClientFaultInjector.instance = faultInjector;
+    DFSClientFaultInjector.set(faultInjector);
   }
 
   /** 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSUtil.java

@@ -903,16 +903,16 @@ public class TestDFSUtil {
     Configuration conf = new Configuration(false);
     conf.unset(DFSConfigKeys.DFS_ENCRYPTION_KEY_PROVIDER_URI);
     assertFalse("encryption enabled on no provider key",
-        DFSUtil.isHDFSEncryptionEnabled(conf));
+        DFSUtilClient.isHDFSEncryptionEnabled(conf));
     conf.set(DFSConfigKeys.DFS_ENCRYPTION_KEY_PROVIDER_URI, "");
     assertFalse("encryption enabled on empty provider key",
-        DFSUtil.isHDFSEncryptionEnabled(conf));
+        DFSUtilClient.isHDFSEncryptionEnabled(conf));
     conf.set(DFSConfigKeys.DFS_ENCRYPTION_KEY_PROVIDER_URI, "\n\t\n");
     assertFalse("encryption enabled on whitespace provider key",
-        DFSUtil.isHDFSEncryptionEnabled(conf));
+        DFSUtilClient.isHDFSEncryptionEnabled(conf));
     conf.set(DFSConfigKeys.DFS_ENCRYPTION_KEY_PROVIDER_URI, "http://hadoop.apache.org");
     assertTrue("encryption disabled on valid provider key",
-        DFSUtil.isHDFSEncryptionEnabled(conf));
+        DFSUtilClient.isHDFSEncryptionEnabled(conf));
 
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestFileStatus.java

@@ -90,7 +90,7 @@ public class TestFileStatus {
       int fileSize, int blockSize) throws IOException {
     // Create and write a file that contains three blocks of data
     FSDataOutputStream stm = fileSys.create(name, true,
-        DFSUtil.getIoFileBufferSize(conf), (short)repl, (long)blockSize);
+        DFSUtilClient.getIoFileBufferSize(conf), (short)repl, (long)blockSize);
     byte[] buffer = new byte[fileSize];
     Random rand = new Random(seed);
     rand.nextBytes(buffer);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestPread.java

@@ -295,9 +295,8 @@ public class TestPread {
         hedgedReadTimeoutMillis);
     conf.setInt(HdfsClientConfigKeys.Retry.WINDOW_BASE_KEY, 0);
     // Set up the InjectionHandler
-    DFSClientFaultInjector.instance = Mockito
+    DFSClientFaultInjector.set(Mockito.mock(DFSClientFaultInjector.class));
-        .mock(DFSClientFaultInjector.class);
+    DFSClientFaultInjector injector = DFSClientFaultInjector.get();
-    DFSClientFaultInjector injector = DFSClientFaultInjector.instance;
     final int sleepMs = 100;
     Mockito.doAnswer(new Answer<Void>() {
       @Override
@@ -371,9 +370,8 @@ public class TestPread {
         initialHedgedReadTimeoutMillis);
 
     // Set up the InjectionHandler
-    DFSClientFaultInjector.instance = Mockito
+    DFSClientFaultInjector.set(Mockito.mock(DFSClientFaultInjector.class));
-        .mock(DFSClientFaultInjector.class);
+    DFSClientFaultInjector injector = DFSClientFaultInjector.get();
-    DFSClientFaultInjector injector = DFSClientFaultInjector.instance;
     // make preads sleep for 50ms
     Mockito.doAnswer(new Answer<Void>() {
       @Override