HDFS-3429. DataNode reads checksums even if client does not need them. Contributed by Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1433117 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -482,6 +482,8 @@ Release 2.0.3-alpha - Unreleased
 
   OPTIMIZATIONS
 
+    HDFS-3429. DataNode reads checksums even if client does not need them (todd)
+
   BUG FIXES
 
     HDFS-3919. MiniDFSCluster:waitClusterUp can hang forever.

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

@@ -380,7 +380,8 @@ public static RemoteBlockReader newBlockReader( Socket sock, String file,
     // in and out will be closed when sock is closed (by the caller)
     final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
           NetUtils.getOutputStream(sock, HdfsServerConstants.WRITE_TIMEOUT)));
-    new Sender(out).readBlock(block, blockToken, clientName, startOffset, len);
+    new Sender(out).readBlock(block, blockToken, clientName, startOffset, len,
+        verifyChecksum);
     
     //
     // Get bytes in block, set streams

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/RemoteBlockReader2.java

@@ -392,7 +392,8 @@ public static BlockReader newBlockReader(Socket sock, String file,
     // in and out will be closed when sock is closed (by the caller)
     final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
           ioStreams.out));
-    new Sender(out).readBlock(block, blockToken, clientName, startOffset, len);
+    new Sender(out).readBlock(block, blockToken, clientName, startOffset, len,
+        verifyChecksum);
 
     //
     // Get bytes in block

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/DataTransferProtocol.java

@@ -55,12 +55,15 @@ public interface DataTransferProtocol {
    * @param clientName client's name.
    * @param blockOffset offset of the block.
    * @param length maximum number of bytes for this read.
+   * @param sendChecksum if false, the DN should skip reading and sending
+   *        checksums
    */
   public void readBlock(final ExtendedBlock blk,
       final Token<BlockTokenIdentifier> blockToken,
       final String clientName,
       final long blockOffset,
-      final long length) throws IOException;
+      final long length,
+      final boolean sendChecksum) throws IOException;
 
   /**
    * Write a block to a datanode pipeline.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/Receiver.java

@@ -88,7 +88,8 @@ private void opReadBlock() throws IOException {
         PBHelper.convert(proto.getHeader().getBaseHeader().getToken()),
         proto.getHeader().getClientName(),
         proto.getOffset(),
-        proto.getLen());
+        proto.getLen(),
+        proto.getSendChecksums());
   }
   
   /** Receive OP_WRITE_BLOCK */

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/Sender.java

@@ -62,6 +62,10 @@ private static void op(final DataOutput out, final Op op
 
   private static void send(final DataOutputStream out, final Op opcode,
       final Message proto) throws IOException {
+    if (LOG.isTraceEnabled()) {
+      LOG.trace("Sending DataTransferOp " + proto.getClass().getSimpleName()
+          + ": " + proto);
+    }
     op(out, opcode);
     proto.writeDelimitedTo(out);
     out.flush();
@@ -72,12 +76,14 @@ public void readBlock(final ExtendedBlock blk,
       final Token<BlockTokenIdentifier> blockToken,
       final String clientName,
       final long blockOffset,
-      final long length) throws IOException {
+      final long length,
+      final boolean sendChecksum) throws IOException {
 
     OpReadBlockProto proto = OpReadBlockProto.newBuilder()
       .setHeader(DataTransferProtoUtil.buildClientHeader(blk, clientName, blockToken))
       .setOffset(blockOffset)
       .setLen(length)
+      .setSendChecksums(sendChecksum)
       .build();
 
     send(out, Op.READ_BLOCK, proto);

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

@@ -388,8 +388,8 @@ void verifyBlock(ExtendedBlock block) {
       try {
         adjustThrottler();
         
-        blockSender = new BlockSender(block, 0, -1, false, true, datanode,
-            null);
+        blockSender = new BlockSender(block, 0, -1, false, true, true, 
+            datanode, null);
 
         DataOutputStream out = 
                 new DataOutputStream(new IOUtils.NullOutputStream());

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

@@ -45,6 +45,8 @@
 import org.apache.hadoop.net.SocketOutputStream;
 import org.apache.hadoop.util.DataChecksum;
 
+import com.google.common.base.Preconditions;
+
 /**
  * Reads a block from the disk and sends it to a recipient.
  * 
@@ -158,12 +160,14 @@ class BlockSender implements java.io.Closeable {
    * @param length length of data to read
    * @param corruptChecksumOk
    * @param verifyChecksum verify checksum while reading the data
+   * @param sendChecksum send checksum to client.
    * @param datanode datanode from which the block is being read
    * @param clientTraceFmt format string used to print client trace logs
    * @throws IOException
    */
   BlockSender(ExtendedBlock block, long startOffset, long length,
               boolean corruptChecksumOk, boolean verifyChecksum,
+              boolean sendChecksum,
               DataNode datanode, String clientTraceFmt)
       throws IOException {
     try {
@@ -175,6 +179,13 @@ class BlockSender implements java.io.Closeable {
       this.shouldDropCacheBehindRead = datanode.getDnConf().dropCacheBehindReads;
       this.datanode = datanode;
       
+      if (verifyChecksum) {
+        // To simplify implementation, callers may not specify verification
+        // without sending.
+        Preconditions.checkArgument(sendChecksum,
+            "If verifying checksum, currently must also send it.");
+      }
+      
       final Replica replica;
       final long replicaVisibleLength;
       synchronized(datanode.data) { 
@@ -213,7 +224,8 @@ class BlockSender implements java.io.Closeable {
        * False,  True: will verify checksum
        * False, False: throws IOException file not found
        */
-      DataChecksum csum;
+      DataChecksum csum = null;
+      if (verifyChecksum || sendChecksum) {
         final InputStream metaIn = datanode.data.getMetaDataInputStream(block);
         if (!corruptChecksumOk || metaIn != null) {
           if (metaIn == null) {
@@ -234,8 +246,15 @@ class BlockSender implements java.io.Closeable {
           csum = header.getChecksum();
         } else {
           LOG.warn("Could not find metadata file for " + block);
-        // This only decides the buffer size. Use BUFFER_SIZE?
-        csum = DataChecksum.newDataChecksum(DataChecksum.Type.NULL, 16 * 1024);
+        }
+      }
+      if (csum == null) {
+        // The number of bytes per checksum here determines the alignment
+        // of reads: we always start reading at a checksum chunk boundary,
+        // even if the checksum type is NULL. So, choosing too big of a value
+        // would risk sending too much unnecessary data. 512 (1 disk sector)
+        // is likely to result in minimal extra IO.
+        csum = DataChecksum.newDataChecksum(DataChecksum.Type.NULL, 512);
       }
 
       /*

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

@@ -1441,7 +1441,7 @@ public void run() {
             HdfsConstants.SMALL_BUFFER_SIZE));
         in = new DataInputStream(unbufIn);
         blockSender = new BlockSender(b, 0, b.getNumBytes(), 
-            false, false, DataNode.this, null);
+            false, false, true, DataNode.this, null);
         DatanodeInfo srcNode = new DatanodeInfo(bpReg);
 
         //

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

@@ -241,7 +241,8 @@ public void readBlock(final ExtendedBlock block,
       final Token<BlockTokenIdentifier> blockToken,
       final String clientName,
       final long blockOffset,
-      final long length) throws IOException {
+      final long length,
+      final boolean sendChecksum) throws IOException {
     previousOpClientName = clientName;
 
     OutputStream baseStream = getOutputStream();
@@ -266,7 +267,7 @@ public void readBlock(final ExtendedBlock block,
     try {
       try {
         blockSender = new BlockSender(block, blockOffset, length,
-            true, false, datanode, clientTraceFmt);
+            true, false, sendChecksum, datanode, clientTraceFmt);
       } catch(IOException e) {
         String msg = "opReadBlock " + block + " received exception " + e; 
         LOG.info(msg);
@@ -654,7 +655,7 @@ public void copyBlock(final ExtendedBlock block,
 
     try {
       // check if the block exists or not
-      blockSender = new BlockSender(block, 0, -1, false, false, datanode, 
+      blockSender = new BlockSender(block, 0, -1, false, false, true, datanode, 
           null);
 
       // set up response stream

hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto

@@ -52,6 +52,7 @@ message OpReadBlockProto {
   required ClientOperationHeaderProto header = 1;
   required uint64 offset = 2;
   required uint64 len = 3;
+  optional bool sendChecksums = 4 [default = true];
 }
 
 

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

@@ -444,21 +444,21 @@ public void testDataTransferProtocol() throws IOException {
     recvBuf.reset();
     blk.setBlockId(blkid-1);
     sender.readBlock(blk, BlockTokenSecretManager.DUMMY_TOKEN, "cl",
-        0L, fileLen);
+        0L, fileLen, true);
     sendRecvData("Wrong block ID " + newBlockId + " for read", false); 
 
     // negative block start offset -1L
     sendBuf.reset();
     blk.setBlockId(blkid);
     sender.readBlock(blk, BlockTokenSecretManager.DUMMY_TOKEN, "cl",
-        -1L, fileLen);
+        -1L, fileLen, true);
     sendRecvData("Negative start-offset for read for block " + 
                  firstBlock.getBlockId(), false);
 
     // bad block start offset
     sendBuf.reset();
     sender.readBlock(blk, BlockTokenSecretManager.DUMMY_TOKEN, "cl",
-        fileLen, fileLen);
+        fileLen, fileLen, true);
     sendRecvData("Wrong start-offset for reading block " +
                  firstBlock.getBlockId(), false);
     
@@ -475,7 +475,7 @@ public void testDataTransferProtocol() throws IOException {
     
     sendBuf.reset();
     sender.readBlock(blk, BlockTokenSecretManager.DUMMY_TOKEN, "cl",
-        0L, -1L-random.nextInt(oneMil));
+        0L, -1L-random.nextInt(oneMil), true);
     sendRecvData("Negative length for reading block " +
                  firstBlock.getBlockId(), false);
     
@@ -488,14 +488,14 @@ public void testDataTransferProtocol() throws IOException {
         recvOut);
     sendBuf.reset();
     sender.readBlock(blk, BlockTokenSecretManager.DUMMY_TOKEN, "cl",
-        0L, fileLen+1);
+        0L, fileLen+1, true);
     sendRecvData("Wrong length for reading block " +
                  firstBlock.getBlockId(), false);
     
     //At the end of all this, read the file to make sure that succeeds finally.
     sendBuf.reset();
     sender.readBlock(blk, BlockTokenSecretManager.DUMMY_TOKEN, "cl",
-        0L, fileLen);
+        0L, fileLen, true);
     readFile(fileSys, file, fileLen);
     } finally {
       cluster.shutdown();

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

@@ -19,6 +19,9 @@
 
 import java.io.IOException;
 
+import org.apache.commons.logging.impl.Log4JLogger;
+import org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtocol;
+import org.apache.log4j.Level;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -56,4 +59,11 @@ public void testParallelReadByteBuffer() throws IOException {
   public void testParallelReadMixed() throws IOException {
     runTestWorkload(new MixedWorkloadHelper());
   }
+  
+  @Test
+  public void testParallelNoChecksums() throws IOException {
+    verifyChecksums = false;
+    runTestWorkload(new MixedWorkloadHelper());
+  }
+
 }

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

@@ -46,6 +46,7 @@ public class TestParallelReadUtil {
   static final int FILE_SIZE_K = 256;
   static Random rand = null;
   static final int DEFAULT_REPLICATION_FACTOR = 2;
+  protected boolean verifyChecksums = true;
 
   static {
     // The client-trace log ends up causing a lot of blocking threads
@@ -317,7 +318,8 @@ boolean runParallelRead(int nFiles, int nWorkerEach, ReadWorkerHelper helper) th
 
       testInfo.filepath = new Path("/TestParallelRead.dat." + i);
       testInfo.authenticData = util.writeFile(testInfo.filepath, FILE_SIZE_K);
-      testInfo.dis = dfsClient.open(testInfo.filepath.toString());
+      testInfo.dis = dfsClient.open(testInfo.filepath.toString(),
+          dfsClient.dfsClientConf.ioBufferSize, verifyChecksums);
 
       for (int j = 0; j < nWorkerEach; ++j) {
         workers[nWorkers++] = new ReadWorker(testInfo, nWorkers, helper);

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

@@ -24,11 +24,14 @@
 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.fs.FSDataInputStream;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtocol;
 import org.apache.hadoop.hdfs.server.datanode.SimulatedFSDataset;
+import org.apache.log4j.Level;
 import org.junit.Test;
 
 /**
@@ -194,11 +197,19 @@ private void cleanupFile(FileSystem fileSys, Path name) throws IOException {
    */
   @Test
   public void testPreadDFS() throws IOException {
-    dfsPreadTest(false); //normal pread
-    dfsPreadTest(true); //trigger read code path without transferTo.
+    dfsPreadTest(false, true); //normal pread
+    dfsPreadTest(true, true); //trigger read code path without transferTo.
   }
   
-  private void dfsPreadTest(boolean disableTransferTo) throws IOException {
+  @Test
+  public void testPreadDFSNoChecksum() throws IOException {
+    ((Log4JLogger)DataTransferProtocol.LOG).getLogger().setLevel(Level.ALL);
+    dfsPreadTest(false, false);
+    dfsPreadTest(true, false);
+  }
+  
+  private void dfsPreadTest(boolean disableTransferTo, boolean verifyChecksum)
+      throws IOException {
     Configuration conf = new HdfsConfiguration();
     conf.setLong(DFSConfigKeys.DFS_BLOCK_SIZE_KEY, 4096);
     conf.setLong(DFSConfigKeys.DFS_CLIENT_READ_PREFETCH_SIZE_KEY, 4096);
@@ -210,6 +221,7 @@ private void dfsPreadTest(boolean disableTransferTo) throws IOException {
     }
     MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).numDataNodes(3).build();
     FileSystem fileSys = cluster.getFileSystem();
+    fileSys.setVerifyChecksum(verifyChecksum);
     try {
       Path file1 = new Path("preadtest.dat");
       writeFile(fileSys, file1);