HDFS-7915. The DataNode can sometimes allocate a ShortCircuitShm slot and fail to tell the DFSClient about it because of a network error (cmccabe)

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

@@ -1177,6 +1177,9 @@ Release 2.7.0 - UNRELEASED
       HDFS-7722. DataNode#checkDiskError should also remove Storage when error
       is found. (Lei Xu via Colin P. McCabe)
 
+      HDFS-7915. The DataNode can sometimes allocate a ShortCircuitShm slot and
+      fail to tell the DFSClient about it because of a network error (cmccabe)
+
 Release 2.6.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -17,6 +17,8 @@
  */
 package org.apache.hadoop.hdfs;
 
+import static org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.ShortCircuitFdResponse.USE_RECEIPT_VERIFICATION;
+
 import java.io.BufferedOutputStream;
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
@@ -69,12 +71,23 @@ import com.google.common.base.Preconditions;
 public class BlockReaderFactory implements ShortCircuitReplicaCreator {
   static final Log LOG = LogFactory.getLog(BlockReaderFactory.class);
 
+  public static class FailureInjector {
+    public void injectRequestFileDescriptorsFailure() throws IOException {
+      // do nothing
+    }
+  }
+
   @VisibleForTesting
   static ShortCircuitReplicaCreator
       createShortCircuitReplicaInfoCallback = null;
 
   private final DFSClient.Conf conf;
 
+  /**
+   * Injects failures into specific operations during unit tests.
+   */
+  private final FailureInjector failureInjector;
+
   /**
    * The file name, for logging and debugging purposes.
    */
@@ -169,6 +182,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
 
   public BlockReaderFactory(DFSClient.Conf conf) {
     this.conf = conf;
+    this.failureInjector = conf.brfFailureInjector;
     this.remainingCacheTries = conf.nCachedConnRetry;
   }
 
@@ -518,11 +532,12 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
     final DataOutputStream out =
         new DataOutputStream(new BufferedOutputStream(peer.getOutputStream()));
     SlotId slotId = slot == null ? null : slot.getSlotId();
-    new Sender(out).requestShortCircuitFds(block, token, slotId, 1);
+    new Sender(out).requestShortCircuitFds(block, token, slotId, 1, true);
     DataInputStream in = new DataInputStream(peer.getInputStream());
     BlockOpResponseProto resp = BlockOpResponseProto.parseFrom(
         PBHelper.vintPrefixed(in));
     DomainSocket sock = peer.getDomainSocket();
+    failureInjector.injectRequestFileDescriptorsFailure();
     switch (resp.getStatus()) {
     case SUCCESS:
       byte buf[] = new byte[1];
@@ -532,8 +547,13 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
       try {
         ExtendedBlockId key =
             new ExtendedBlockId(block.getBlockId(), block.getBlockPoolId());
+        if (buf[0] == USE_RECEIPT_VERIFICATION.getNumber()) {
+          LOG.trace("Sending receipt verification byte for slot " + slot);
+          sock.getOutputStream().write(0);
+        }
         replica = new ShortCircuitReplica(key, fis[0], fis[1], cache,
             Time.monotonicNow(), slot);
+        return new ShortCircuitReplicaInfo(replica);
       } catch (IOException e) {
         // This indicates an error reading from disk, or a format error.  Since
         // it's not a socket communication problem, we return null rather than
@@ -545,7 +565,6 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
           IOUtils.cleanup(DFSClient.LOG, fis[0], fis[1]);
         }
       }
-      return new ShortCircuitReplicaInfo(replica);
     case ERROR_UNSUPPORTED:
       if (!resp.hasShortCircuitAccessVersion()) {
         LOG.warn("short-circuit read access is disabled for " +

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

@@ -337,6 +337,8 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
     final long shortCircuitCacheStaleThresholdMs;
 
     final long keyProviderCacheExpiryMs;
+    public BlockReaderFactory.FailureInjector brfFailureInjector =
+      new BlockReaderFactory.FailureInjector();
 
     public Conf(Configuration conf) {
       // The hdfsTimeout is currently the same as the ipc timeout 

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

@@ -138,10 +138,13 @@ public interface DataTransferProtocol {
    *                          to use no slot id.
    * @param maxVersion      Maximum version of the block data the client 
    *                          can understand.
+   * @param supportsReceiptVerification  True if the client supports
+   *                          receipt verification.
    */
   public void requestShortCircuitFds(final ExtendedBlock blk,
       final Token<BlockTokenIdentifier> blockToken,
-      SlotId slotId, int maxVersion) throws IOException;
+      SlotId slotId, int maxVersion, boolean supportsReceiptVerification)
+        throws IOException;
 
   /**
    * Release a pair of short-circuit FDs requested earlier.

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

@@ -186,7 +186,7 @@ public abstract class Receiver implements DataTransferProtocol {
     try {
       requestShortCircuitFds(PBHelper.convert(proto.getHeader().getBlock()),
           PBHelper.convert(proto.getHeader().getToken()),
-          slotId, proto.getMaxVersion());
+          slotId, proto.getMaxVersion(), true);
     } finally {
       if (traceScope != null) traceScope.close();
     }

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

@@ -181,7 +181,8 @@ public class Sender implements DataTransferProtocol {
   @Override
   public void requestShortCircuitFds(final ExtendedBlock blk,
       final Token<BlockTokenIdentifier> blockToken,
-      SlotId slotId, int maxVersion) throws IOException {
+      SlotId slotId, int maxVersion, boolean supportsReceiptVerification)
+        throws IOException {
     OpRequestShortCircuitAccessProto.Builder builder =
         OpRequestShortCircuitAccessProto.newBuilder()
           .setHeader(DataTransferProtoUtil.buildBaseHeader(
@@ -189,6 +190,7 @@ public class Sender implements DataTransferProtocol {
     if (slotId != null) {
       builder.setSlotId(PBHelper.convert(slotId));
     }
+    builder.setSupportsReceiptVerification(supportsReceiptVerification);
     OpRequestShortCircuitAccessProto proto = builder.build();
     send(out, Op.REQUEST_SHORT_CIRCUIT_FDS, proto);
   }

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

@@ -22,6 +22,8 @@ import static org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status.ER
 import static org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status.ERROR_INVALID;
 import static org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status.ERROR_UNSUPPORTED;
 import static org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status.SUCCESS;
+import static org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.ShortCircuitFdResponse.USE_RECEIPT_VERIFICATION;
+import static org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.ShortCircuitFdResponse.DO_NOT_USE_RECEIPT_VERIFICATION;
 import static org.apache.hadoop.hdfs.server.datanode.DataNode.DN_CLIENTTRACE_FORMAT;
 import static org.apache.hadoop.util.Time.now;
 
@@ -291,10 +293,14 @@ class DataXceiver extends Receiver implements Runnable {
   @Override
   public void requestShortCircuitFds(final ExtendedBlock blk,
       final Token<BlockTokenIdentifier> token,
-      SlotId slotId, int maxVersion) throws IOException {
+      SlotId slotId, int maxVersion, boolean supportsReceiptVerification)
+        throws IOException {
     updateCurrentThreadName("Passing file descriptors for block " + blk);
     BlockOpResponseProto.Builder bld = BlockOpResponseProto.newBuilder();
     FileInputStream fis[] = null;
+    SlotId registeredSlotId = null;
+    boolean success = false;
+    try {
       try {
         if (peer.getDomainSocket() == null) {
           throw new IOException("You cannot pass file descriptors over " +
@@ -305,14 +311,10 @@ class DataXceiver extends Receiver implements Runnable {
               isCached(blk.getBlockPoolId(), blk.getBlockId());
           datanode.shortCircuitRegistry.registerSlot(
               ExtendedBlockId.fromExtendedBlock(blk), slotId, isCached);
+          registeredSlotId = slotId;
         }
-      try {
         fis = datanode.requestShortCircuitFdsForRead(blk, token, maxVersion);
-      } finally {
+        Preconditions.checkState(fis != null);
-        if ((fis == null) && (slotId != null)) {
-          datanode.shortCircuitRegistry.unregisterSlot(slotId);
-        }
-      }
         bld.setStatus(SUCCESS);
         bld.setShortCircuitAccessVersion(DataNode.CURRENT_BLOCK_FORMAT_VERSION);
       } catch (ShortCircuitFdsVersionException e) {
@@ -329,26 +331,45 @@ class DataXceiver extends Receiver implements Runnable {
         bld.setStatus(ERROR);
         bld.setMessage(e.getMessage());
       }
-    try {
       bld.build().writeDelimitedTo(socketOut);
       if (fis != null) {
         FileDescriptor fds[] = new FileDescriptor[fis.length];
         for (int i = 0; i < fds.length; i++) {
           fds[i] = fis[i].getFD();
         }
-        byte buf[] = new byte[] { (byte)0 };
+        byte buf[] = new byte[1];
-        peer.getDomainSocket().
+        if (supportsReceiptVerification) {
-          sendFileDescriptors(fds, buf, 0, buf.length);
+          buf[0] = (byte)USE_RECEIPT_VERIFICATION.getNumber();
+        } else {
+          buf[0] = (byte)DO_NOT_USE_RECEIPT_VERIFICATION.getNumber();
+        }
+        DomainSocket sock = peer.getDomainSocket();
+        sock.sendFileDescriptors(fds, buf, 0, buf.length);
+        if (supportsReceiptVerification) {
+          LOG.trace("Reading receipt verification byte for " + slotId);
+          int val = sock.getInputStream().read();
+          if (val < 0) {
+            throw new EOFException();
+          }
+        } else {
+          LOG.trace("Receipt verification is not enabled on the DataNode.  " +
+                    "Not verifying " + slotId);
+        }
+        success = true;
       }
     } finally {
+      if ((!success) && (registeredSlotId != null)) {
+        LOG.info("Unregistering " + registeredSlotId + " because the " +
+            "requestShortCircuitFdsForRead operation failed.");
+        datanode.shortCircuitRegistry.unregisterSlot(registeredSlotId);
+      }
       if (ClientTraceLog.isInfoEnabled()) {
         DatanodeRegistration dnR = datanode.getDNRegistrationForBP(blk
             .getBlockPoolId());
         BlockSender.ClientTraceLog.info(String.format(
             "src: 127.0.0.1, dest: 127.0.0.1, op: REQUEST_SHORT_CIRCUIT_FDS," +
             " blockid: %s, srvID: %s, success: %b",
-            blk.getBlockId(), dnR.getDatanodeUuid(), (fis != null)
+            blk.getBlockId(), dnR.getDatanodeUuid(), success));
-          ));
       }
       if (fis != null) {
         IOUtils.cleanup(LOG, fis);

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

@@ -30,6 +30,7 @@ import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Set;
 
+import com.google.common.annotations.VisibleForTesting;
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -83,7 +84,7 @@ public class ShortCircuitRegistry {
 
   private static final int SHM_LENGTH = 8192;
 
-  private static class RegisteredShm extends ShortCircuitShm
+  public static class RegisteredShm extends ShortCircuitShm
       implements DomainSocketWatcher.Handler {
     private final String clientName;
     private final ShortCircuitRegistry registry;
@@ -383,4 +384,14 @@ public class ShortCircuitRegistry {
     }
     IOUtils.closeQuietly(watcher);
   }
+
+  public static interface Visitor {
+    void accept(HashMap<ShmId, RegisteredShm> segments,
+                HashMultimap<ExtendedBlockId, Slot> slots);
+  }
+
+  @VisibleForTesting
+  public synchronized void visit(Visitor visitor) {
+    visitor.accept(segments, slots);
+  }
 }

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

@@ -179,6 +179,12 @@ message OpRequestShortCircuitAccessProto {
    * The shared memory slot to use, if we are using one.
    */
   optional ShortCircuitShmSlotProto slotId = 3;
+
+  /**
+   * True if the client supports verifying that the file descriptor has been
+   * sent successfully.
+   */
+  optional bool supportsReceiptVerification = 4 [default = false];
 }
 
 message ReleaseShortCircuitAccessRequestProto {
@@ -230,6 +236,11 @@ enum Status {
   IN_PROGRESS = 12;
 }
 
+enum ShortCircuitFdResponse {
+  DO_NOT_USE_RECEIPT_VERIFICATION = 0;
+  USE_RECEIPT_VERIFICATION = 1;
+}
+
 message PipelineAckProto {
   required sint64 seqno = 1;
   repeated uint32 reply = 2;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/shortcircuit/TestShortCircuitCache.java

@@ -36,13 +36,16 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 
+import com.google.common.collect.HashMultimap;
 import org.apache.commons.lang.mutable.MutableBoolean;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataInputStream;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.BlockReaderFactory;
 import org.apache.hadoop.hdfs.BlockReaderTestUtil;
+import org.apache.hadoop.hdfs.DFSClient;
 import org.apache.hadoop.hdfs.DFSInputStream;
 import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
@@ -52,11 +55,14 @@ import org.apache.hadoop.hdfs.net.DomainPeer;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader;
+import org.apache.hadoop.hdfs.server.datanode.ShortCircuitRegistry;
+import org.apache.hadoop.hdfs.server.datanode.ShortCircuitRegistry.RegisteredShm;
 import org.apache.hadoop.hdfs.shortcircuit.DfsClientShmManager.PerDatanodeVisitorInfo;
 import org.apache.hadoop.hdfs.shortcircuit.DfsClientShmManager.Visitor;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitCache.CacheVisitor;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitCache.ShortCircuitReplicaCreator;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.Slot;
+import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.ShmId;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.net.unix.DomainSocket;
 import org.apache.hadoop.net.unix.TemporarySocketDirectory;
@@ -615,4 +621,61 @@ public class TestShortCircuitCache {
     cluster.shutdown();
     sockDir.close();
   }
+
+  public static class TestCleanupFailureInjector
+        extends BlockReaderFactory.FailureInjector {
+    @Override
+    public void injectRequestFileDescriptorsFailure() throws IOException {
+      throw new IOException("injected I/O error");
+    }
+  }
+
+  // Regression test for HDFS-7915
+  @Test(timeout=60000)
+  public void testDataXceiverCleansUpSlotsOnFailure() throws Exception {
+    BlockReaderTestUtil.enableShortCircuitShmTracing();
+    TemporarySocketDirectory sockDir = new TemporarySocketDirectory();
+    Configuration conf = createShortCircuitConf(
+        "testDataXceiverCleansUpSlotsOnFailure", sockDir);
+    conf.setLong(DFS_CLIENT_READ_SHORTCIRCUIT_STREAMS_CACHE_EXPIRY_MS_KEY,
+        1000000000L);
+    MiniDFSCluster cluster =
+        new MiniDFSCluster.Builder(conf).numDataNodes(1).build();
+    cluster.waitActive();
+    DistributedFileSystem fs = cluster.getFileSystem();
+    final Path TEST_PATH1 = new Path("/test_file1");
+    final Path TEST_PATH2 = new Path("/test_file2");
+    final int TEST_FILE_LEN = 4096;
+    final int SEED = 0xFADE1;
+    DFSTestUtil.createFile(fs, TEST_PATH1, TEST_FILE_LEN,
+        (short)1, SEED);
+    DFSTestUtil.createFile(fs, TEST_PATH2, TEST_FILE_LEN,
+        (short)1, SEED);
+
+    // The first read should allocate one shared memory segment and slot.
+    DFSTestUtil.readFileBuffer(fs, TEST_PATH1);
+
+    // The second read should fail, and we should only have 1 segment and 1 slot
+    // left.
+    fs.getClient().getConf().brfFailureInjector =
+        new TestCleanupFailureInjector();
+    try {
+      DFSTestUtil.readFileBuffer(fs, TEST_PATH2);
+    } catch (Throwable t) {
+      GenericTestUtils.assertExceptionContains("TCP reads were disabled for " +
+          "testing, but we failed to do a non-TCP read.", t);
+    }
+    ShortCircuitRegistry registry =
+      cluster.getDataNodes().get(0).getShortCircuitRegistry();
+    registry.visit(new ShortCircuitRegistry.Visitor() {
+      @Override
+      public void accept(HashMap<ShmId, RegisteredShm> segments,
+                         HashMultimap<ExtendedBlockId, Slot> slots) {
+        Assert.assertEquals(1, segments.size());
+        Assert.assertEquals(1, slots.size());
+      }
+    });
+    cluster.shutdown();
+    sockDir.close();
+  }
 }