HADOOP-2533 Scanning, just creating MapWritable in next consumes >20% CPU

git-svn-id: https://svn.apache.org/repos/asf/lucene/hadoop/trunk@611629 13f79535-47bb-0310-9956-ffa450edef68

src/contrib/hbase/CHANGES.txt

@@ -33,6 +33,11 @@ Trunk (unreleased changes)
    HADOOP-2479 Save on number of Text object creations
    HADOOP-2485 Make mapfile index interval configurable (Set default to 32
                instead of 128)
+   HADOOP-2553 Don't make Long objects calculating hbase type hash codes
+   HADOOP-2377 Holding open MapFile.Readers is expensive, so use less of them
+   HADOOP-2407 Keeping MapFile.Reader open is expensive: Part 2
+   HADOOP-2533 Performance: Scanning, just creating MapWritable in next
+               consumes >20% CPU
 
   BUG FIXES
    HADOOP-2059 In tests, exceptions in min dfs shutdown should not fail test
@@ -104,8 +109,7 @@ Trunk (unreleased changes)
                deleted
    HADOOP-2468 TestRegionServerExit failed in Hadoop-Nightly #338
    HADOOP-2467 scanner truncates resultset when > 1 column families
-   HADOOP-2503 REST Insert / Select encoding issue
-               (Bryan Duxbury via Stack)
+   HADOOP-2503 REST Insert / Select encoding issue (Bryan Duxbury via Stack)
    HADOOP-2505 formatter classes missing apache license
    HADOOP-2504 REST servlet method for deleting a scanner was not properly
                mapped (Bryan Duxbury via Stack)
@@ -148,11 +152,9 @@ Trunk (unreleased changes)
    HADOOP-2299 Support inclusive scans (Bryan Duxbury via Stack)
    HADOOP-2333 Client side retries happen at the wrong level
    HADOOP-2357 Compaction cleanup; less deleting + prevent possible file leaks
-   HADOOP-2377 Holding open MapFile.Readers is expensive, so use less of them
    HADOOP-2392 TestRegionServerExit has new failure mode since HADOOP-2338
    HADOOP-2370 Allow column families with an unlimited number of versions
                (Edward Yoon via Stack)
-   HADOOP-2407 Keeping MapFile.Reader open is expensive: Part 2
    HADOOP-2047 Add an '--master=X' and '--html' command-line parameters to shell
                (Edward Yoon via Stack)
    HADOOP-2351 If select command returns no result, it doesn't need to show the
@@ -167,7 +169,6 @@ Trunk (unreleased changes)
                (Edward Yoon via Stack)
    HADOOP-2450 Show version (and svn revision) in hbase web ui
    HADOOP-2472 Range selection using filter (Edward Yoon via Stack)
-   HADOOP-2553 Don't make Long objects calculating hbase type hash codes
    HADOOP-2548 Make TableMap and TableReduce generic
                (Frederik Hedberg via Stack)
    HADOOP-2557 Shell count function (Edward Yoon via Stack)

src/contrib/hbase/src/java/org/apache/hadoop/hbase/HBaseAdmin.java

@@ -28,7 +28,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
 import org.apache.hadoop.hbase.util.Writables;
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.ipc.RemoteException;
@@ -190,7 +190,7 @@ public class HBaseAdmin implements HConstants {
         scannerId =
           server.openScanner(firstMetaServer.getRegionInfo().getRegionName(),
             COL_REGIONINFO_ARRAY, tableName, System.currentTimeMillis(), null);
-        MapWritable values = server.next(scannerId);
+        HbaseMapWritable values = server.next(scannerId);
         if (values == null || values.size() == 0) {
           break;
         }
@@ -274,7 +274,7 @@ public class HBaseAdmin implements HConstants {
         boolean isenabled = false;
         
         while (true) {
-          MapWritable values = server.next(scannerId);
+          HbaseMapWritable values = server.next(scannerId);
           if (values == null || values.size() == 0) {
             if (valuesfound == 0) {
               throw new NoSuchElementException(
@@ -375,7 +375,7 @@ public class HBaseAdmin implements HConstants {
         
         boolean disabled = false;
         while (true) {
-          MapWritable values = server.next(scannerId);
+          HbaseMapWritable values = server.next(scannerId);
           if (values == null || values.size() == 0) {
             if (valuesfound == 0) {
               throw new NoSuchElementException("table " + tableName + " not found");

src/contrib/hbase/src/java/org/apache/hadoop/hbase/HConnectionManager.java

@@ -36,7 +36,7 @@ import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
 import org.apache.hadoop.hbase.ipc.HbaseRPC;
 import org.apache.hadoop.hbase.util.Writables;
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.ipc.RemoteException;
@@ -259,7 +259,7 @@ public class HConnectionManager implements HConstants {
               null);
 
           while (true) {
-            MapWritable values = server.next(scannerId);
+            HbaseMapWritable values = server.next(scannerId);
             if (values == null || values.size() == 0) {
               break;
             }
@@ -715,7 +715,7 @@ public class HConnectionManager implements HConstants {
             COLUMN_FAMILY_ARRAY, tableName, System.currentTimeMillis(), null);
 
         while (true) {
-          MapWritable values = server.next(scannerId);
+          HbaseMapWritable values = server.next(scannerId);
           if (values == null || values.size() == 0) {
             if (servers.size() == 0) {
               // If we didn't find any servers then the table does not exist

src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMaster.java

@@ -57,7 +57,7 @@ import org.apache.hadoop.hbase.util.InfoServer;
 import org.apache.hadoop.hbase.util.Sleeper;
 import org.apache.hadoop.hbase.util.Threads;
 import org.apache.hadoop.hbase.util.Writables;
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.ipc.RemoteException;
@@ -224,7 +224,7 @@ public class HMaster extends Thread implements HConstants, HMasterInterface,
         int numberOfRegionsFound = 0;
         while (true) {
           SortedMap<Text, byte[]> results = new TreeMap<Text, byte[]>();
-          MapWritable values = regionServer.next(scannerId);
+          HbaseMapWritable values = regionServer.next(scannerId);
           if (values == null || values.size() == 0) {
             break;
           }
@@ -1185,6 +1185,9 @@ public class HMaster extends Thread implements HConstants, HMasterInterface,
     if (LOG.isDebugEnabled()) {
       LOG.debug("Started service threads");
     }
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("Started service threads");
+    }
   }
 
   /*
@@ -1262,7 +1265,7 @@ public class HMaster extends Thread implements HConstants, HMasterInterface,
 
   /** {@inheritDoc} */
   @SuppressWarnings("unused")
-  public MapWritable regionServerStartup(HServerInfo serverInfo)
+  public HbaseMapWritable regionServerStartup(HServerInfo serverInfo)
     throws IOException {
 
     String s = serverInfo.getServerAddress().toString().trim();
@@ -1315,12 +1318,12 @@ public class HMaster extends Thread implements HConstants, HMasterInterface,
    * @return Subset of configuration to pass initializing regionservers: e.g.
    * the filesystem to use and root directory to use.
    */
-  protected MapWritable createConfigurationSubset() {
-    MapWritable mw = addConfig(new MapWritable(), HConstants.HBASE_DIR);
+  protected HbaseMapWritable createConfigurationSubset() {
+    HbaseMapWritable mw = addConfig(new HbaseMapWritable(), HConstants.HBASE_DIR);
     return addConfig(mw, "fs.default.name");
   }
 
-  private MapWritable addConfig(final MapWritable mw, final String key) {
+  private HbaseMapWritable addConfig(final HbaseMapWritable mw, final String key) {
     mw.put(new Text(key), new Text(this.conf.get(key)));
     return mw;
   }
@@ -1992,7 +1995,7 @@ public class HMaster extends Thread implements HConstants, HMasterInterface,
 
       try {
         while (true) {
-          MapWritable values = null;
+          HbaseMapWritable values = null;
           try {
             values = server.next(scannerId);
           } catch (IOException e) {
@@ -2588,7 +2591,7 @@ public class HMaster extends Thread implements HConstants, HMasterInterface,
       long scannerid = server.openScanner(metaRegionName, COL_REGIONINFO_ARRAY,
           tableName, System.currentTimeMillis(), null);
       try {
-        MapWritable data = server.next(scannerid);
+        HbaseMapWritable data = server.next(scannerid);
             
         // Test data and that the row for the data is for our table. If table
         // does not exist, scanner will return row after where our table would
@@ -2743,7 +2746,7 @@ public class HMaster extends Thread implements HConstants, HMasterInterface,
                   String serverName = null;
                   long startCode = -1L;
 
-                  MapWritable values = server.next(scannerId);
+                  HbaseMapWritable values = server.next(scannerId);
                   if(values == null || values.size() == 0) {
                     break;
                   }

src/contrib/hbase/src/java/org/apache/hadoop/hbase/HMasterRegionInterface.java

@@ -21,7 +21,7 @@ package org.apache.hadoop.hbase;
 
 import java.io.IOException;
 
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.ipc.VersionedProtocol;
 
 /**
@@ -39,7 +39,7 @@ public interface HMasterRegionInterface extends VersionedProtocol {
    * @return Configuration for the regionserver to use: e.g. filesystem,
    * hbase rootdir, etc.
    */
-  public MapWritable regionServerStartup(HServerInfo info) throws IOException;
+  public HbaseMapWritable regionServerStartup(HServerInfo info) throws IOException;
   
   /**
    * Called to renew lease, tell master what the region server is doing and to

src/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionInterface.java

@@ -24,7 +24,7 @@ import java.io.IOException;
 import org.apache.hadoop.hbase.filter.RowFilterInterface;
 import org.apache.hadoop.hbase.io.BatchUpdate;
 
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.ipc.VersionedProtocol;
 
@@ -96,7 +96,7 @@ public interface HRegionInterface extends VersionedProtocol {
    * @return map of values
    * @throws IOException
    */
-  public MapWritable getRow(final Text regionName, final Text row)
+  public HbaseMapWritable getRow(final Text regionName, final Text row)
   throws IOException;
 
   /**
@@ -107,7 +107,7 @@ public interface HRegionInterface extends VersionedProtocol {
    * @return map of values
    * @throws IOException
    */
-  public MapWritable getRow(final Text regionName, final Text row, final long ts)
+  public HbaseMapWritable getRow(final Text regionName, final Text row, final long ts)
   throws IOException;
 
 
@@ -192,7 +192,7 @@ public interface HRegionInterface extends VersionedProtocol {
    * @return map of values
    * @throws IOException
    */
-  public MapWritable next(long scannerId) throws IOException;
+  public HbaseMapWritable next(long scannerId) throws IOException;
   
   /**
    * Close a scanner

src/contrib/hbase/src/java/org/apache/hadoop/hbase/HRegionServer.java

@@ -60,7 +60,7 @@ import org.apache.hadoop.hbase.util.InfoServer;
 import org.apache.hadoop.hbase.util.Sleeper;
 import org.apache.hadoop.hbase.util.Threads;
 import org.apache.hadoop.hbase.util.Writables;
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.ipc.Server;
@@ -909,7 +909,7 @@ public class HRegionServer implements HConstants, HRegionInterface, Runnable {
    * Run init. Sets up hlog and starts up all server threads.
    * @param c Extra configuration.
    */
-  private void init(final MapWritable c) throws IOException {
+  private void init(final HbaseMapWritable c) throws IOException {
     try {
       for (Map.Entry<Writable, Writable> e: c.entrySet()) {
         String key = e.getKey().toString();
@@ -1059,7 +1059,7 @@ public class HRegionServer implements HConstants, HRegionInterface, Runnable {
    * Let the master know we're here
    * Run initialization using parameters passed us by the master.
    */
-  private MapWritable reportForDuty() throws IOException {
+  private HbaseMapWritable reportForDuty() throws IOException {
     if (LOG.isDebugEnabled()) {
       LOG.debug("Telling master at " +
         conf.get(MASTER_ADDRESS) + " that we are up");
@@ -1069,7 +1069,7 @@ public class HRegionServer implements HConstants, HRegionInterface, Runnable {
       HMasterRegionInterface.class, HMasterRegionInterface.versionID,
       new HServerAddress(conf.get(MASTER_ADDRESS)).getInetSocketAddress(),
       this.conf);
-    MapWritable result = null;
+    HbaseMapWritable result = null;
     long lastMsg = 0;
     while(!stopRequested.get()) {
       try {
@@ -1375,20 +1375,20 @@ public class HRegionServer implements HConstants, HRegionInterface, Runnable {
   }
 
   /** {@inheritDoc} */
-  public MapWritable getRow(final Text regionName, final Text row)
+  public HbaseMapWritable getRow(final Text regionName, final Text row)
     throws IOException {
     return getRow(regionName, row, HConstants.LATEST_TIMESTAMP);
   }
 
   /** {@inheritDoc} */
-  public MapWritable getRow(final Text regionName, final Text row, final long ts)
+  public HbaseMapWritable getRow(final Text regionName, final Text row, final long ts)
     throws IOException {
 
     checkOpen();
     requestCount.incrementAndGet();
     try {
       HRegion region = getRegion(regionName);
-      MapWritable result = new MapWritable();
+      HbaseMapWritable result = new HbaseMapWritable();
       Map<Text, byte[]> map = region.getFull(row, ts);
       for (Map.Entry<Text, byte []> es: map.entrySet()) {
         result.put(new HStoreKey(row, es.getKey()),
@@ -1404,7 +1404,7 @@ public class HRegionServer implements HConstants, HRegionInterface, Runnable {
 
 
   /** {@inheritDoc} */
-  public MapWritable next(final long scannerId) throws IOException {
+  public HbaseMapWritable next(final long scannerId) throws IOException {
 
     checkOpen();
     requestCount.incrementAndGet();
@@ -1417,7 +1417,7 @@ public class HRegionServer implements HConstants, HRegionInterface, Runnable {
       this.leases.renewLease(scannerId, scannerId);
 
       // Collect values to be returned here
-      MapWritable values = new MapWritable();
+      HbaseMapWritable values = new HbaseMapWritable();
       HStoreKey key = new HStoreKey();
       TreeMap<Text, byte []> results = new TreeMap<Text, byte []>();
       while (s.next(key, results)) {
@@ -1445,7 +1445,6 @@ public class HRegionServer implements HConstants, HRegionInterface, Runnable {
   /** {@inheritDoc} */
   public void batchUpdate(Text regionName, long timestamp, BatchUpdate b)
     throws IOException {
-    
     checkOpen();
     this.requestCount.incrementAndGet();
     HRegion region = getRegion(regionName);

src/contrib/hbase/src/java/org/apache/hadoop/hbase/HTable.java

@@ -39,7 +39,7 @@ import org.apache.hadoop.hbase.filter.WhileMatchRowFilter;
 import org.apache.hadoop.hbase.io.BatchUpdate;
 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
 import org.apache.hadoop.hbase.util.Writables;
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.ipc.RemoteException;
@@ -366,7 +366,7 @@ public class HTable implements HConstants {
    */
   public SortedMap<Text, byte[]> getRow(Text row, long ts) throws IOException {
     checkClosed();
-    MapWritable value = null;
+    HbaseMapWritable value = null;
     for (int tries = 0; tries < numRetries; tries++) {
       HRegionLocation r = getRegionLocation(row);
       HRegionInterface server =
@@ -1063,7 +1063,7 @@ public class HTable implements HConstants {
       if (this.closed) {
         return false;
       }
-      MapWritable values = null;
+      HbaseMapWritable values = null;
       // Clear the results so we don't inherit any values from any previous
       // calls to next.
       results.clear();

src/contrib/hbase/src/java/org/apache/hadoop/hbase/io/HbaseMapWritable.java

@@ -0,0 +1,204 @@
+/**
+ * Copyright 2008 The Apache Software Foundation
+ *
+ * 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.hbase.io;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.apache.hadoop.conf.Configurable;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.HStoreKey;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.io.Writable;
+import org.apache.hadoop.util.ReflectionUtils;
+
+/**
+ * A Writable Map.
+ * Like {@link org.apache.hadoop.io.MapWritable} but dumb. It will fail
+ * if passed a Writable it has not already been told about. Its also been
+ * primed with hbase Writables.
+ */
+public class HbaseMapWritable implements Map<Writable, Writable>, Writable,
+    Configurable {
+  private AtomicReference<Configuration> conf =
+    new AtomicReference<Configuration>();
+  
+  // Static maps of code to class and vice versa.  Includes types used in hbase
+  // only.
+  static final Map<Byte, Class<? extends Writable>> CODE_TO_CLASS =
+    new HashMap<Byte, Class<? extends Writable>>();
+  static final Map<Class<? extends Writable>, Byte> CLASS_TO_CODE =
+    new HashMap<Class<? extends Writable>, Byte>();
+
+  static {
+    byte code = 0;
+    addToMap(HStoreKey.class, code++);
+    addToMap(ImmutableBytesWritable.class, code++);
+    addToMap(Text.class, code++);
+  }
+
+  @SuppressWarnings("boxing")
+  private static void addToMap(final Class<? extends Writable> clazz,
+      final byte code) {
+    CLASS_TO_CODE.put(clazz, code);
+    CODE_TO_CLASS.put(code, clazz);
+  }
+  
+  private Map<Writable, Writable> instance;
+  
+  /** Default constructor. */
+  public HbaseMapWritable() {
+    super();
+    this.instance = new HashMap<Writable, Writable>();
+  }
+
+  /** @return the conf */
+  public Configuration getConf() {
+    return conf.get();
+  }
+
+  /** @param conf the conf to set */
+  public void setConf(Configuration conf) {
+    this.conf.set(conf);
+  }
+
+  /** {@inheritDoc} */
+  public void clear() {
+    instance.clear();
+  }
+
+  /** {@inheritDoc} */
+  public boolean containsKey(Object key) {
+    return instance.containsKey(key);
+  }
+
+  /** {@inheritDoc} */
+  public boolean containsValue(Object value) {
+    return instance.containsValue(value);
+  }
+
+  /** {@inheritDoc} */
+  public Set<Map.Entry<Writable, Writable>> entrySet() {
+    return instance.entrySet();
+  }
+
+  /** {@inheritDoc} */
+  public Writable get(Object key) {
+    return instance.get(key);
+  }
+  
+  /** {@inheritDoc} */
+  public boolean isEmpty() {
+    return instance.isEmpty();
+  }
+
+  /** {@inheritDoc} */
+  public Set<Writable> keySet() {
+    return instance.keySet();
+  }
+
+  /** {@inheritDoc} */
+  @SuppressWarnings("unchecked")
+  public Writable put(Writable key, Writable value) {
+    return instance.put(key, value);
+  }
+
+  /** {@inheritDoc} */
+  public void putAll(Map<? extends Writable, ? extends Writable> t) {
+    for (Map.Entry<? extends Writable, ? extends Writable> e: t.entrySet()) {
+      instance.put(e.getKey(), e.getValue());
+    }
+  }
+
+  /** {@inheritDoc} */
+  public Writable remove(Object key) {
+    return instance.remove(key);
+  }
+
+  /** {@inheritDoc} */
+  public int size() {
+    return instance.size();
+  }
+
+  /** {@inheritDoc} */
+  public Collection<Writable> values() {
+    return instance.values();
+  }
+  
+  // Writable
+
+  /** @return the Class class for the specified id */
+  @SuppressWarnings({ "unchecked", "boxing" })
+  protected Class<?> getClass(byte id) {
+    return CODE_TO_CLASS.get(id);
+  }
+
+  /** @return the id for the specified Class */
+  @SuppressWarnings({ "unchecked", "boxing" })
+  protected byte getId(Class<?> clazz) {
+    Byte b = CLASS_TO_CODE.get(clazz);
+    if (b == null) {
+      throw new NullPointerException("Nothing for : " + clazz);
+    }
+    return b;
+  }
+
+  public void write(DataOutput out) throws IOException {
+    // Write out the number of entries in the map
+    out.writeInt(instance.size());
+
+    // Then write out each key/value pair
+    for (Map.Entry<Writable, Writable> e: instance.entrySet()) {
+      out.writeByte(getId(e.getKey().getClass()));
+      e.getKey().write(out);
+      out.writeByte(getId(e.getValue().getClass()));
+      e.getValue().write(out);
+    }
+  }
+
+  public void readFields(DataInput in) throws IOException {
+    // First clear the map.  Otherwise we will just accumulate
+    // entries every time this method is called.
+    this.instance.clear();
+    
+    // Read the number of entries in the map
+    int entries = in.readInt();
+    
+    // Then read each key/value pair
+    for (int i = 0; i < entries; i++) {
+      Writable key = (Writable) ReflectionUtils.newInstance(getClass(
+          in.readByte()), getConf());
+      
+      key.readFields(in);
+      
+      Writable value = (Writable) ReflectionUtils.newInstance(getClass(
+          in.readByte()), getConf());
+      
+      value.readFields(in);
+      instance.put(key, value);
+    }
+  }
+}

src/contrib/hbase/src/java/org/apache/hadoop/hbase/io/HbaseObjectWritable.java

@@ -38,7 +38,7 @@ import org.apache.hadoop.hbase.HServerInfo;
 import org.apache.hadoop.hbase.HTableDescriptor;
 import org.apache.hadoop.hbase.filter.RowFilterInterface;
 import org.apache.hadoop.hbase.filter.RowFilterSet;
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.io.ObjectWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
@@ -91,7 +91,7 @@ public class HbaseObjectWritable implements Writable, Configurable {
     // Hadoop types
     addToMap(Text.class, code++);
     addToMap(Writable.class, code++);
-    addToMap(MapWritable.class, code++);
+    addToMap(HbaseMapWritable.class, code++);
     addToMap(NullInstance.class, code++);
     try {
       addToMap(Class.forName("[Lorg.apache.hadoop.io.Text;"), code++);

src/contrib/hbase/src/test/org/apache/hadoop/hbase/DisabledTestScanner2.java

@@ -38,10 +38,9 @@ import org.apache.hadoop.hbase.filter.RowFilterInterface;
 import org.apache.hadoop.hbase.filter.RowFilterSet;
 import org.apache.hadoop.hbase.filter.StopRowFilter;
 import org.apache.hadoop.hbase.filter.WhileMatchRowFilter;
-import org.apache.hadoop.io.MapWritable;
+import org.apache.hadoop.hbase.io.HbaseMapWritable;
 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
 import org.apache.hadoop.hbase.util.Writables;
-import org.apache.hadoop.io.MapWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.io.Writable;
 
@@ -391,7 +390,7 @@ public class DisabledTestScanner2 extends HBaseClusterTestCase {
           System.currentTimeMillis(), null);
       while (true) {
         TreeMap<Text, byte[]> results = new TreeMap<Text, byte[]>();
-        MapWritable values = regionServer.next(scannerId);
+        HbaseMapWritable values = regionServer.next(scannerId);
         if (values == null || values.size() == 0) {
           break;
         }