HDFS-13702. Remove HTrace hooks from DFSClient to reduce CPU usage. Contributed by Todd Lipcon.

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

@@ -3070,25 +3070,6 @@ TraceScope newSrcDstTraceScope(String description, String src, String dst) {
     return scope;
   }
 
-  /**
-   * Full detailed tracing for read requests: path, position in the file,
-   * and length.
-   *
-   * @param reqLen requested length
-   */
-  TraceScope newReaderTraceScope(String description, String path, long pos,
-      int reqLen) {
-    TraceScope scope = newPathTraceScope(description, path);
-    scope.addKVAnnotation("pos", Long.toString(pos));
-    scope.addKVAnnotation("reqLen", Integer.toString(reqLen));
-    return scope;
-  }
-
-  /** Add the returned length info to the scope. */
-  void addRetLenToReaderScope(TraceScope scope, int retLen) {
-    scope.addKVAnnotation("retLen", Integer.toString(retLen));
-  }
-
   /**
    * Get the erasure coding policy information for the specified path
    *

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

@@ -85,8 +85,6 @@
 import org.apache.hadoop.util.StopWatch;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.htrace.core.SpanId;
-import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.core.Tracer;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -641,7 +639,6 @@ protected BlockReader getBlockReader(LocatedBlock targetBlock,
         setClientCacheContext(dfsClient.getClientContext()).
         setUserGroupInformation(dfsClient.ugi).
         setConfiguration(dfsClient.getConfiguration()).
-        setTracer(dfsClient.getTracer()).
         build();
   }
 
@@ -821,31 +818,14 @@ public synchronized int read(@Nonnull final byte buf[], int off, int len)
     }
     ReaderStrategy byteArrayReader =
         new ByteArrayStrategy(buf, off, len, readStatistics, dfsClient);
-    try (TraceScope scope =
+    return readWithStrategy(byteArrayReader);
-             dfsClient.newReaderTraceScope("DFSInputStream#byteArrayRead",
-                 src, getPos(), len)) {
-      int retLen = readWithStrategy(byteArrayReader);
-      if (retLen < len) {
-        dfsClient.addRetLenToReaderScope(scope, retLen);
-      }
-      return retLen;
-    }
   }
 
   @Override
   public synchronized int read(final ByteBuffer buf) throws IOException {
     ReaderStrategy byteBufferReader =
         new ByteBufferStrategy(buf, readStatistics, dfsClient);
-    int reqLen = buf.remaining();
+    return readWithStrategy(byteBufferReader);
-    try (TraceScope scope =
-             dfsClient.newReaderTraceScope("DFSInputStream#byteBufferRead",
-                 src, getPos(), reqLen)){
-      int retLen = readWithStrategy(byteBufferReader);
-      if (retLen < reqLen) {
-        dfsClient.addRetLenToReaderScope(scope, retLen);
-      }
-      return retLen;
-    }
   }
 
   private DNAddrPair chooseDataNode(LocatedBlock block,
@@ -1026,16 +1006,12 @@ private Callable<ByteBuffer> getFromOneDataNode(final DNAddrPair datanode,
       final ByteBuffer bb,
       final CorruptedBlocks corruptedBlocks,
       final int hedgedReadId) {
-    final SpanId parentSpanId = Tracer.getCurrentSpanId();
     return new Callable<ByteBuffer>() {
       @Override
       public ByteBuffer call() throws Exception {
         DFSClientFaultInjector.get().sleepBeforeHedgedGet();
-        try (TraceScope ignored = dfsClient.getTracer().
+        actualGetFromOneDataNode(datanode, start, end, bb, corruptedBlocks);
-            newScope("hedgedRead" + hedgedReadId, parentSpanId)) {
+        return bb;
-          actualGetFromOneDataNode(datanode, start, end, bb, corruptedBlocks);
-          return bb;
-        }
       }
     };
   }
@@ -1336,16 +1312,8 @@ public int read(long position, byte[] buffer, int offset, int length)
     if (length == 0) {
       return 0;
     }
-    try (TraceScope scope = dfsClient.
+    ByteBuffer bb = ByteBuffer.wrap(buffer, offset, length);
-        newReaderTraceScope("DFSInputStream#byteArrayPread",
+    return pread(position, bb);
-            src, position, length)) {
-      ByteBuffer bb = ByteBuffer.wrap(buffer, offset, length);
-      int retLen = pread(position, bb);
-      if (retLen < length) {
-        dfsClient.addRetLenToReaderScope(scope, retLen);
-      }
-      return retLen;
-    }
   }
 
   private int pread(long position, ByteBuffer buffer)

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

@@ -75,7 +75,6 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
-import org.apache.htrace.core.Tracer;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -189,11 +188,6 @@ public boolean getSupportsReceiptVerification() {
    */
   private Configuration configuration;
 
-  /**
-   * The HTrace tracer to use.
-   */
-  private Tracer tracer;
-
   /**
    * Information about the domain socket path we should use to connect to the
    * local peer-- or null if we haven't examined the local domain socket.
@@ -298,11 +292,6 @@ public BlockReaderFactory setConfiguration(
     return this;
   }
 
-  public BlockReaderFactory setTracer(Tracer tracer) {
-    this.tracer = tracer;
-    return this;
-  }
-
   @VisibleForTesting
   public static void setFailureInjectorForTesting(FailureInjector injector) {
     failureInjector = injector;
@@ -451,7 +440,7 @@ private BlockReader getLegacyBlockReaderLocal() throws IOException {
     try {
       return BlockReaderLocalLegacy.newBlockReader(conf,
           userGroupInformation, configuration, fileName, block, token,
-          datanode, startOffset, length, storageType, tracer);
+          datanode, startOffset, length, storageType);
     } catch (RemoteException remoteException) {
       ioe = remoteException.unwrapRemoteException(
                 InvalidToken.class, AccessControlException.class);
@@ -509,7 +498,6 @@ private BlockReader getBlockReaderLocal() throws IOException {
         setVerifyChecksum(verifyChecksum).
         setCachingStrategy(cachingStrategy).
         setStorageType(storageType).
-        setTracer(tracer).
         build();
   }
 
@@ -860,7 +848,7 @@ private BlockReader getRemoteBlockReader(Peer peer) throws IOException {
     return BlockReaderRemote.newBlockReader(
         fileName, block, token, startOffset, length,
         verifyChecksum, clientName, peer, datanode,
-        clientContext.getPeerCache(), cachingStrategy, tracer,
+        clientContext.getPeerCache(), cachingStrategy,
         networkDistance);
   }
 

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

@@ -35,8 +35,6 @@
 import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.DirectBufferPool;
 import org.apache.hadoop.util.Timer;
-import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.core.Tracer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -83,7 +81,6 @@ public static class Builder {
     private long dataPos;
     private ExtendedBlock block;
     private StorageType storageType;
-    private Tracer tracer;
     private ShortCircuitConf shortCircuitConf;
 
     public Builder(ShortCircuitConf conf) {
@@ -131,11 +128,6 @@ public Builder setStorageType(StorageType storageType) {
       return this;
     }
 
-    public Builder setTracer(Tracer tracer) {
-      this.tracer = tracer;
-      return this;
-    }
-
     public BlockReaderLocal build() {
       Preconditions.checkNotNull(replica);
       return new BlockReaderLocal(this);
@@ -244,11 +236,6 @@ public BlockReaderLocal build() {
    */
   private StorageType storageType;
 
-  /**
-   * The Tracer to use.
-   */
-  private final Tracer tracer;
-
   private BlockReaderLocal(Builder builder) {
     this.replica = builder.replica;
     this.dataIn = replica.getDataStream().getChannel();
@@ -278,7 +265,6 @@ private BlockReaderLocal(Builder builder) {
     }
     this.maxReadaheadLength = maxReadaheadChunks * bytesPerChecksum;
     this.storageType = builder.storageType;
-    this.tracer = builder.tracer;
 
     if (builder.shortCircuitConf.isScrMetricsEnabled()) {
       metricsInitializationLock.lock();
@@ -360,52 +346,49 @@ private synchronized int drainDataBuf(ByteBuffer buf) {
    */
   private synchronized int fillBuffer(ByteBuffer buf, boolean canSkipChecksum)
       throws IOException {
-    try (TraceScope ignored = tracer.newScope(
+    int total = 0;
-        "BlockReaderLocal#fillBuffer(" + block.getBlockId() + ")")) {
+    long startDataPos = dataPos;
-      int total = 0;
+    int startBufPos = buf.position();
-      long startDataPos = dataPos;
+    while (buf.hasRemaining()) {
-      int startBufPos = buf.position();
+      int nRead = blockReaderIoProvider.read(dataIn, buf, dataPos);
-      while (buf.hasRemaining()) {
+      if (nRead < 0) {
-        int nRead = blockReaderIoProvider.read(dataIn, buf, dataPos);
+        break;
-        if (nRead < 0) {
-          break;
-        }
-        dataPos += nRead;
-        total += nRead;
-      }
-      if (canSkipChecksum) {
-        freeChecksumBufIfExists();
-        return total;
-      }
-      if (total > 0) {
-        try {
-          buf.limit(buf.position());
-          buf.position(startBufPos);
-          createChecksumBufIfNeeded();
-          int checksumsNeeded = (total + bytesPerChecksum - 1) /
-              bytesPerChecksum;
-          checksumBuf.clear();
-          checksumBuf.limit(checksumsNeeded * checksumSize);
-          long checksumPos = BlockMetadataHeader.getHeaderSize()
-              + ((startDataPos / bytesPerChecksum) * checksumSize);
-          while (checksumBuf.hasRemaining()) {
-            int nRead = checksumIn.read(checksumBuf, checksumPos);
-            if (nRead < 0) {
-              throw new IOException("Got unexpected checksum file EOF at " +
-                  checksumPos + ", block file position " + startDataPos +
-                  " for block " + block + " of file " + filename);
-            }
-            checksumPos += nRead;
-          }
-          checksumBuf.flip();
-
-          checksum.verifyChunkedSums(buf, checksumBuf, filename, startDataPos);
-        } finally {
-          buf.position(buf.limit());
-        }
       }
+      dataPos += nRead;
+      total += nRead;
+    }
+    if (canSkipChecksum) {
+      freeChecksumBufIfExists();
       return total;
     }
+    if (total > 0) {
+      try {
+        buf.limit(buf.position());
+        buf.position(startBufPos);
+        createChecksumBufIfNeeded();
+        int checksumsNeeded = (total + bytesPerChecksum - 1) /
+            bytesPerChecksum;
+        checksumBuf.clear();
+        checksumBuf.limit(checksumsNeeded * checksumSize);
+        long checksumPos = BlockMetadataHeader.getHeaderSize()
+            + ((startDataPos / bytesPerChecksum) * checksumSize);
+        while (checksumBuf.hasRemaining()) {
+          int nRead = checksumIn.read(checksumBuf, checksumPos);
+          if (nRead < 0) {
+            throw new IOException("Got unexpected checksum file EOF at " +
+                checksumPos + ", block file position " + startDataPos +
+                " for block " + block + " of file " + filename);
+          }
+          checksumPos += nRead;
+        }
+        checksumBuf.flip();
+
+        checksum.verifyChunkedSums(buf, checksumBuf, filename, startDataPos);
+      } finally {
+        buf.position(buf.limit());
+      }
+    }
+    return total;
   }
 
   private boolean createNoChecksumContext() {

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

@@ -51,8 +51,6 @@
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.DirectBufferPool;
-import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.core.Tracer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -184,7 +182,6 @@ private void removeBlockLocalPathInfo(ExtendedBlock b) {
   private long startOffset;
   private final String filename;
   private long blockId;
-  private final Tracer tracer;
 
   /**
    * The only way this object can be instantiated.
@@ -193,8 +190,8 @@ static BlockReaderLocalLegacy newBlockReader(DfsClientConf conf,
       UserGroupInformation userGroupInformation,
       Configuration configuration, String file, ExtendedBlock blk,
       Token<BlockTokenIdentifier> token, DatanodeInfo node,
-      long startOffset, long length, StorageType storageType,
+      long startOffset, long length, StorageType storageType)
-      Tracer tracer) throws IOException {
+      throws IOException {
     final ShortCircuitConf scConf = conf.getShortCircuitConf();
     LocalDatanodeInfo localDatanodeInfo = getLocalDatanodeInfo(node
         .getIpcPort());
@@ -239,11 +236,10 @@ static BlockReaderLocalLegacy newBlockReader(DfsClientConf conf,
         long firstChunkOffset = startOffset
             - (startOffset % checksum.getBytesPerChecksum());
         localBlockReader = new BlockReaderLocalLegacy(scConf, file, blk,
-            startOffset, checksum, true, dataIn, firstChunkOffset, checksumIn,
+            startOffset, checksum, true, dataIn, firstChunkOffset, checksumIn);
-            tracer);
       } else {
         localBlockReader = new BlockReaderLocalLegacy(scConf, file, blk,
-            startOffset, dataIn, tracer);
+            startOffset, dataIn);
       }
     } catch (IOException e) {
       // remove from cache
@@ -320,17 +316,17 @@ private static int getSlowReadBufferNumChunks(int bufferSizeBytes,
   }
 
   private BlockReaderLocalLegacy(ShortCircuitConf conf, String hdfsfile,
-      ExtendedBlock block, long startOffset, FileInputStream dataIn,
+      ExtendedBlock block, long startOffset, FileInputStream dataIn)
-      Tracer tracer) throws IOException {
+      throws IOException {
     this(conf, hdfsfile, block, startOffset,
         DataChecksum.newDataChecksum(DataChecksum.Type.NULL, 4), false,
-        dataIn, startOffset, null, tracer);
+        dataIn, startOffset, null);
   }
 
   private BlockReaderLocalLegacy(ShortCircuitConf conf, String hdfsfile,
       ExtendedBlock block, long startOffset, DataChecksum checksum,
       boolean verifyChecksum, FileInputStream dataIn, long firstChunkOffset,
-      FileInputStream checksumIn, Tracer tracer) throws IOException {
+      FileInputStream checksumIn) throws IOException {
     this.filename = hdfsfile;
     this.checksum = checksum;
     this.verifyChecksum = verifyChecksum;
@@ -369,7 +365,6 @@ private BlockReaderLocalLegacy(ShortCircuitConf conf, String hdfsfile,
         bufferPool.returnBuffer(checksumBuff);
       }
     }
-    this.tracer = tracer;
   }
 
   /**
@@ -377,23 +372,20 @@ private BlockReaderLocalLegacy(ShortCircuitConf conf, String hdfsfile,
    */
   private int fillBuffer(FileInputStream stream, ByteBuffer buf)
       throws IOException {
-    try (TraceScope ignored = tracer.
+    int bytesRead = stream.getChannel().read(buf);
-        newScope("BlockReaderLocalLegacy#fillBuffer(" + blockId + ")")) {
+    if (bytesRead < 0) {
-      int bytesRead = stream.getChannel().read(buf);
+      //EOF
-      if (bytesRead < 0) {
+      return bytesRead;
+    }
+    while (buf.remaining() > 0) {
+      int n = stream.getChannel().read(buf);
+      if (n < 0) {
         //EOF
         return bytesRead;
       }
-      while (buf.remaining() > 0) {
+      bytesRead += n;
-        int n = stream.getChannel().read(buf);
-        if (n < 0) {
-          //EOF
-          return bytesRead;
-        }
-        bytesRead += n;
-      }
-      return bytesRead;
     }
+    return bytesRead;
   }
 
   /**

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

@@ -49,11 +49,9 @@
 import org.apache.hadoop.hdfs.shortcircuit.ClientMmap;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
-import org.apache.htrace.core.TraceScope;
 
 import com.google.common.annotations.VisibleForTesting;
 
-import org.apache.htrace.core.Tracer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -121,8 +119,6 @@ public class BlockReaderRemote implements BlockReader {
 
   private boolean sentStatusCode = false;
 
-  private final Tracer tracer;
-
   private final int networkDistance;
 
   @VisibleForTesting
@@ -139,10 +135,7 @@ public synchronized int read(byte[] buf, int off, int len)
 
     if (curDataSlice == null ||
         curDataSlice.remaining() == 0 && bytesNeededToFinish > 0) {
-      try (TraceScope ignored = tracer.newScope(
+      readNextPacket();
-          "BlockReaderRemote2#readNextPacket(" + blockId + ")")) {
-        readNextPacket();
-      }
     }
 
     LOG.trace("Finishing read #{}", randomId);
@@ -163,10 +156,7 @@ public synchronized int read(byte[] buf, int off, int len)
   public synchronized int read(ByteBuffer buf) throws IOException {
     if (curDataSlice == null ||
         (curDataSlice.remaining() == 0 && bytesNeededToFinish > 0)) {
-      try (TraceScope ignored = tracer.newScope(
+      readNextPacket();
-          "BlockReaderRemote2#readNextPacket(" + blockId + ")")) {
-        readNextPacket();
-      }
     }
     if (curDataSlice.remaining() == 0) {
       // we're at EOF now
@@ -280,7 +270,6 @@ protected BlockReaderRemote(String file, long blockId,
                               long startOffset, long firstChunkOffset,
                               long bytesToRead, Peer peer,
                               DatanodeID datanodeID, PeerCache peerCache,
-                              Tracer tracer,
                               int networkDistance) {
     // Path is used only for printing block and file information in debug
     this.peer = peer;
@@ -300,7 +289,6 @@ protected BlockReaderRemote(String file, long blockId,
     this.bytesNeededToFinish = bytesToRead + (startOffset - firstChunkOffset);
     bytesPerChecksum = this.checksum.getBytesPerChecksum();
     checksumSize = this.checksum.getChecksumSize();
-    this.tracer = tracer;
     this.networkDistance = networkDistance;
   }
 
@@ -397,7 +385,6 @@ public static BlockReader newBlockReader(String file,
       Peer peer, DatanodeID datanodeID,
       PeerCache peerCache,
       CachingStrategy cachingStrategy,
-      Tracer tracer,
       int networkDistance) throws IOException {
     // in and out will be closed when sock is closed (by the caller)
     final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
@@ -431,7 +418,7 @@ public static BlockReader newBlockReader(String file,
 
     return new BlockReaderRemote(file, block.getBlockId(), checksum,
         verifyChecksum, startOffset, firstChunkOffset, len, peer, datanodeID,
-        peerCache, tracer, networkDistance);
+        peerCache, networkDistance);
   }
 
   static void checkSuccess(

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

@@ -128,7 +128,7 @@ private BlockReader createBlockReader(long offsetInBlock) {
       return BlockReaderRemote.newBlockReader(
           "dummy", block, blockToken, offsetInBlock,
           block.getNumBytes() - offsetInBlock, true, "", peer, source,
-          null, stripedReader.getCachingStrategy(), datanode.getTracer(), -1);
+          null, stripedReader.getCachingStrategy(), -1);
     } catch (IOException e) {
       LOG.info("Exception while creating remote block reader, datanode {}",
           source, e);

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

@@ -1032,7 +1032,6 @@ private void copyBlock(final DFSClient dfs, LocatedBlock lblock,
             setCachingStrategy(CachingStrategy.newDropBehind()).
             setClientCacheContext(dfs.getClientContext()).
             setConfiguration(namenode.getConf()).
-            setTracer(tracer).
             setRemotePeerFactory(new RemotePeerFactory() {
               @Override
               public Peer newConnectedPeer(InetSocketAddress addr,

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/client/impl/BlockReaderTestUtil.java

@@ -30,7 +30,6 @@
 
 import org.apache.commons.io.IOUtils;
 import org.apache.hadoop.fs.FileSystem;
-import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.BlockReader;
 import org.apache.hadoop.hdfs.ClientContext;
@@ -206,7 +205,6 @@ public static BlockReader getBlockReader(final DistributedFileSystem fs,
       setCachingStrategy(CachingStrategy.newDefaultStrategy()).
       setConfiguration(fs.getConf()).
       setAllowShortCircuitLocalReads(true).
-      setTracer(FsTracer.get(fs.getConf())).
       setRemotePeerFactory(new RemotePeerFactory() {
         @Override
         public Peer newConnectedPeer(InetSocketAddress addr,

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/client/impl/TestBlockReaderLocal.java

@@ -52,7 +52,6 @@
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitReplica;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.ShmId;
-import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.net.unix.DomainSocket;
@@ -208,7 +207,6 @@ public void runBlockReaderLocalTest(BlockReaderLocalTest test,
           setShortCircuitReplica(replica).
           setCachingStrategy(new CachingStrategy(false, readahead)).
           setVerifyChecksum(checksum).
-          setTracer(FsTracer.get(conf)).
           build();
       dataIn = null;
       metaIn = null;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockTokenWithDFS.java

@@ -33,7 +33,6 @@
 import org.apache.hadoop.fs.FSDataInputStream;
 import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.fs.FileSystem;
-import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.BlockReader;
 import org.apache.hadoop.hdfs.client.impl.BlockReaderFactory;
@@ -167,7 +166,6 @@ protected void tryRead(final Configuration conf, LocatedBlock lblock,
           setCachingStrategy(CachingStrategy.newDefaultStrategy()).
           setClientCacheContext(ClientContext.getFromConf(conf)).
           setConfiguration(conf).
-          setTracer(FsTracer.get(conf)).
           setRemotePeerFactory(new RemotePeerFactory() {
             @Override
             public Peer newConnectedPeer(InetSocketAddress addr,

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

@@ -40,7 +40,6 @@
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FileUtil;
-import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.BlockReader;
 import org.apache.hadoop.hdfs.ClientContext;
@@ -655,7 +654,6 @@ private void accessBlock(DatanodeInfo datanode, LocatedBlock lblock)
       setCachingStrategy(CachingStrategy.newDefaultStrategy()).
       setClientCacheContext(ClientContext.getFromConf(conf)).
       setConfiguration(conf).
-      setTracer(FsTracer.get(conf)).
       setRemotePeerFactory(new RemotePeerFactory() {
         @Override
         public Peer newConnectedPeer(InetSocketAddress addr,