/**
    *
    * 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.mapreduce;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  import java.net.UnknownHostException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.List;
  
  import javax.naming.NamingException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionLocation;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.Admin;
  import org.apache.hadoop.hbase.client.Connection;
  import org.apache.hadoop.hbase.client.ConnectionFactory;
  import org.apache.hadoop.hbase.client.HTable;
  import org.apache.hadoop.hbase.client.NeedUnmanagedConnectionException;
  import org.apache.hadoop.hbase.client.RegionLocator;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.client.Table;
  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
  import org.apache.hadoop.hbase.util.Addressing;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.Pair;
  import org.apache.hadoop.hbase.util.RegionSizeCalculator;
  import org.apache.hadoop.hbase.util.Strings;
  import org.apache.hadoop.mapreduce.InputFormat;
  import org.apache.hadoop.mapreduce.InputSplit;
  import org.apache.hadoop.mapreduce.JobContext;
  import org.apache.hadoop.mapreduce.RecordReader;
  import org.apache.hadoop.mapreduce.TaskAttemptContext;
  import org.apache.hadoop.net.DNS;
  import org.apache.hadoop.util.StringUtils;
  
  /**
   * A base for {@link TableInputFormat}s. Receives a {@link Connection}, a {@link TableName},
   * an {@link Scan} instance that defines the input columns etc. Subclasses may use
   * other TableRecordReader implementations.
   *
   * Subclasses MUST ensure initializeTable(Connection, TableName) is called for an instance to
   * function properly. Each of the entry points to this class used by the MapReduce framework,
   * {@link #createRecordReader(InputSplit, TaskAttemptContext)} and {@link #getSplits(JobContext)},
   * will call {@link #initialize(JobContext)} as a convenient centralized location to handle
   * retrieving the necessary configuration information. If your subclass overrides either of these
   * methods, either call the parent version or call initialize yourself.
   *
   * <p>
   * An example of a subclass:
   * <pre>
   *   class ExampleTIF extends TableInputFormatBase {
   *
   *     {@literal @}Override
   *     protected void initialize(JobContext context) throws IOException {
   *       // We are responsible for the lifecycle of this connection until we hand it over in
   *       // initializeTable.
   *       Connection connection = ConnectionFactory.createConnection(HBaseConfiguration.create(
   *              job.getConfiguration()));
   *       TableName tableName = TableName.valueOf("exampleTable");
   *       // mandatory. once passed here, TableInputFormatBase will handle closing the connection.
   *       initializeTable(connection, tableName);
   *       byte[][] inputColumns = new byte [][] { Bytes.toBytes("columnA"),
   *         Bytes.toBytes("columnB") };
   *       // optional, by default we'll get everything for the table.
   *       Scan scan = new Scan();
   *       for (byte[] family : inputColumns) {
   *         scan.addFamily(family);
   *       }
   *       Filter exampleFilter = new RowFilter(CompareOp.EQUAL, new RegexStringComparator("aa.*"));
   *       scan.setFilter(exampleFilter);
   *       setScan(scan);
  *     }
  *   }
  * </pre>
  */
 @InterfaceAudience.Public
 @InterfaceStability.Stable
 public abstract class TableInputFormatBase
 extends InputFormat<ImmutableBytesWritable, Result> {
 
   /** Specify if we enable auto-balance for input in M/R jobs.*/
   public static final String MAPREDUCE_INPUT_AUTOBALANCE = "hbase.mapreduce.input.autobalance";
   /** Specify if ratio for data skew in M/R jobs, it goes well with the enabling hbase.mapreduce
    * .input.autobalance property.*/
   public static final String INPUT_AUTOBALANCE_MAXSKEWRATIO = "hbase.mapreduce.input.autobalance" +
           ".maxskewratio";
   /** Specify if the row key in table is text (ASCII between 32~126),
    * default is true. False means the table is using binary row key*/
   public static final String TABLE_ROW_TEXTKEY = "hbase.table.row.textkey";
 
   private static final Log LOG = LogFactory.getLog(TableInputFormatBase.class);
 
   private static final String NOT_INITIALIZED = "The input format instance has not been properly " +
       "initialized. Ensure you call initializeTable either in your constructor or initialize " +
       "method";
   private static final String INITIALIZATION_ERROR = "Cannot create a record reader because of a" +
             " previous error. Please look at the previous logs lines from" +
             " the task's full log for more details.";
 
   /** Holds the details for the internal scanner.
    *
    * @see Scan */
   private Scan scan = null;
   /** The {@link Admin}. */
   private Admin admin;
   /** The {@link Table} to scan. */
   private Table table;
   /** The {@link RegionLocator} of the table. */
   private RegionLocator regionLocator;
   /** The reader scanning the table, can be a custom one. */
   private TableRecordReader tableRecordReader = null;
   /** The underlying {@link Connection} of the table. */
   private Connection connection;
 
   
   /** The reverse DNS lookup cache mapping: IPAddress => HostName */
   private HashMap<InetAddress, String> reverseDNSCacheMap =
     new HashMap<InetAddress, String>();
 
   /**
    * Builds a {@link TableRecordReader}. If no {@link TableRecordReader} was provided, uses
    * the default.
    *
    * @param split  The split to work with.
    * @param context  The current context.
    * @return The newly created record reader.
    * @throws IOException When creating the reader fails.
    * @see org.apache.hadoop.mapreduce.InputFormat#createRecordReader(
    *   org.apache.hadoop.mapreduce.InputSplit,
    *   org.apache.hadoop.mapreduce.TaskAttemptContext)
    */
   @Override
   public RecordReader<ImmutableBytesWritable, Result> createRecordReader(
       InputSplit split, TaskAttemptContext context)
   throws IOException {
     // Just in case a subclass is relying on JobConfigurable magic.
     if (table == null) {
       initialize(context);
     }
     // null check in case our child overrides getTable to not throw.
     try {
       if (getTable() == null) {
         // initialize() must not have been implemented in the subclass.
         throw new IOException(INITIALIZATION_ERROR);
       }
     } catch (IllegalStateException exception) {
       throw new IOException(INITIALIZATION_ERROR, exception);
     }
     TableSplit tSplit = (TableSplit) split;
     LOG.info("Input split length: " + StringUtils.humanReadableInt(tSplit.getLength()) + " bytes.");
     final TableRecordReader trr =
         this.tableRecordReader != null ? this.tableRecordReader : new TableRecordReader();
     Scan sc = new Scan(this.scan);
     sc.setStartRow(tSplit.getStartRow());
     sc.setStopRow(tSplit.getEndRow());
     trr.setScan(sc);
     trr.setTable(getTable());
     return new RecordReader<ImmutableBytesWritable, Result>() {
 
       @Override
       public void close() throws IOException {
         trr.close();
         closeTable();
       }
 
       @Override
       public ImmutableBytesWritable getCurrentKey() throws IOException, InterruptedException {
         return trr.getCurrentKey();
       }
 
       @Override
       public Result getCurrentValue() throws IOException, InterruptedException {
         return trr.getCurrentValue();
       }
 
       @Override
       public float getProgress() throws IOException, InterruptedException {
         return trr.getProgress();
       }
 
       @Override
       public void initialize(InputSplit inputsplit, TaskAttemptContext context) throws IOException,
           InterruptedException {
         trr.initialize(inputsplit, context);
       }
 
       @Override
       public boolean nextKeyValue() throws IOException, InterruptedException {
         return trr.nextKeyValue();
       }
     };
   }
 
   protected Pair<byte[][],byte[][]> getStartEndKeys() throws IOException {
     return getRegionLocator().getStartEndKeys();
   }
 
   /**
    * Calculates the splits that will serve as input for the map tasks. The
    * number of splits matches the number of regions in a table.
    *
    * @param context  The current job context.
    * @return The list of input splits.
    * @throws IOException When creating the list of splits fails.
    * @see org.apache.hadoop.mapreduce.InputFormat#getSplits(
    *   org.apache.hadoop.mapreduce.JobContext)
    */
   @Override
   public List<InputSplit> getSplits(JobContext context) throws IOException {
     boolean closeOnFinish = false;
 
     // Just in case a subclass is relying on JobConfigurable magic.
     if (table == null) {
       initialize(context);
       closeOnFinish = true;
     }
 
     // null check in case our child overrides getTable to not throw.
     try {
       if (getTable() == null) {
         // initialize() must not have been implemented in the subclass.
         throw new IOException(INITIALIZATION_ERROR);
       }
     } catch (IllegalStateException exception) {
       throw new IOException(INITIALIZATION_ERROR, exception);
     }
 
     try {
     RegionSizeCalculator sizeCalculator = new RegionSizeCalculator(regionLocator, admin);
 
     Pair<byte[][], byte[][]> keys = getStartEndKeys();
     if (keys == null || keys.getFirst() == null ||
         keys.getFirst().length == 0) {
       HRegionLocation regLoc = regionLocator.getRegionLocation(HConstants.EMPTY_BYTE_ARRAY, false);
       if (null == regLoc) {
         throw new IOException("Expecting at least one region.");
       }
       List<InputSplit> splits = new ArrayList<InputSplit>(1);
       long regionSize = sizeCalculator.getRegionSize(regLoc.getRegionInfo().getRegionName());
       TableSplit split = new TableSplit(table.getName(), scan,
           HConstants.EMPTY_BYTE_ARRAY, HConstants.EMPTY_BYTE_ARRAY, regLoc
               .getHostnamePort().split(Addressing.HOSTNAME_PORT_SEPARATOR)[0], regionSize);
       splits.add(split);
       return splits;
     }
     List<InputSplit> splits = new ArrayList<InputSplit>(keys.getFirst().length);
     for (int i = 0; i < keys.getFirst().length; i++) {
       if ( !includeRegionInSplit(keys.getFirst()[i], keys.getSecond()[i])) {
         continue;
       }
       HRegionLocation location = regionLocator.getRegionLocation(keys.getFirst()[i], false);
       // The below InetSocketAddress creation does a name resolution.
       InetSocketAddress isa = new InetSocketAddress(location.getHostname(), location.getPort());
       if (isa.isUnresolved()) {
         LOG.warn("Failed resolve " + isa);
       }
       InetAddress regionAddress = isa.getAddress();
       String regionLocation;
       try {
         regionLocation = reverseDNS(regionAddress);
       } catch (NamingException e) {
         LOG.warn("Cannot resolve the host name for " + regionAddress + " because of " + e);
         regionLocation = location.getHostname();
       }
 
       byte[] startRow = scan.getStartRow();
       byte[] stopRow = scan.getStopRow();
       // determine if the given start an stop key fall into the region
       if ((startRow.length == 0 || keys.getSecond()[i].length == 0 ||
           Bytes.compareTo(startRow, keys.getSecond()[i]) < 0) &&
           (stopRow.length == 0 ||
            Bytes.compareTo(stopRow, keys.getFirst()[i]) > 0)) {
         byte[] splitStart = startRow.length == 0 ||
           Bytes.compareTo(keys.getFirst()[i], startRow) >= 0 ?
             keys.getFirst()[i] : startRow;
         byte[] splitStop = (stopRow.length == 0 ||
           Bytes.compareTo(keys.getSecond()[i], stopRow) <= 0) &&
           keys.getSecond()[i].length > 0 ?
             keys.getSecond()[i] : stopRow;
 
         byte[] regionName = location.getRegionInfo().getRegionName();
         String encodedRegionName = location.getRegionInfo().getEncodedName();
         long regionSize = sizeCalculator.getRegionSize(regionName);
         TableSplit split = new TableSplit(table.getName(), scan,
           splitStart, splitStop, regionLocation, encodedRegionName, regionSize);
         splits.add(split);
         if (LOG.isDebugEnabled()) {
           LOG.debug("getSplits: split -> " + i + " -> " + split);
         }
       }
     }
     //The default value of "hbase.mapreduce.input.autobalance" is false, which means not enabled.
     boolean enableAutoBalance = context.getConfiguration().getBoolean(
       MAPREDUCE_INPUT_AUTOBALANCE, false);
     if (enableAutoBalance) {
       long totalRegionSize=0;
       for (int i = 0; i < splits.size(); i++){
         TableSplit ts = (TableSplit)splits.get(i);
         totalRegionSize += ts.getLength();
       }
       long averageRegionSize = totalRegionSize / splits.size();
       // the averageRegionSize must be positive.
       if (averageRegionSize <= 0) {
         LOG.warn("The averageRegionSize is not positive: "+ averageRegionSize + ", " +
             "set it to 1.");
         averageRegionSize = 1;
       }
       return calculateRebalancedSplits(splits, context, averageRegionSize);
     } else {
       return splits;
     }
     } finally {
       if (closeOnFinish) {
         closeTable();
       }
     }
   }
 
   /**
    * @deprecated mistakenly made public in 0.98.7. scope will change to package-private
    */
   @Deprecated
   public String reverseDNS(InetAddress ipAddress) throws NamingException, UnknownHostException {
     String hostName = this.reverseDNSCacheMap.get(ipAddress);
     if (hostName == null) {
       String ipAddressString = null;
       try {
         ipAddressString = DNS.reverseDns(ipAddress, null);
       } catch (Exception e) {
         // We can use InetAddress in case the jndi failed to pull up the reverse DNS entry from the
         // name service. Also, in case of ipv6, we need to use the InetAddress since resolving
         // reverse DNS using jndi doesn't work well with ipv6 addresses.
         ipAddressString = InetAddress.getByName(ipAddress.getHostAddress()).getHostName();
       }
       if (ipAddressString == null) throw new UnknownHostException("No host found for " + ipAddress);
       hostName = Strings.domainNamePointerToHostName(ipAddressString);
       this.reverseDNSCacheMap.put(ipAddress, hostName);
     }
     return hostName;
   }
 
   /**
    * Calculates the number of MapReduce input splits for the map tasks. The number of
    * MapReduce input splits depends on the average region size and the "data skew ratio" user set in
    * configuration.
    *
    * @param list  The list of input splits before balance.
    * @param context  The current job context.
    * @param average  The average size of all regions .
    * @return The list of input splits.
    * @throws IOException When creating the list of splits fails.
    * @see org.apache.hadoop.mapreduce.InputFormat#getSplits(
    *   org.apache.hadoop.mapreduce.JobContext)
    */
   public List<InputSplit> calculateRebalancedSplits(List<InputSplit> list, JobContext context,
                                                long average) throws IOException {
     List<InputSplit> resultList = new ArrayList<InputSplit>();
     Configuration conf = context.getConfiguration();
     //The default data skew ratio is 3
     long dataSkewRatio = conf.getLong(INPUT_AUTOBALANCE_MAXSKEWRATIO, 3);
     //It determines which mode to use: text key mode or binary key mode. The default is text mode.
     boolean isTextKey = context.getConfiguration().getBoolean(TABLE_ROW_TEXTKEY, true);
     long dataSkewThreshold = dataSkewRatio * average;
     int count = 0;
     while (count < list.size()) {
       TableSplit ts = (TableSplit)list.get(count);
       TableName tableName = ts.getTable();
       String regionLocation = ts.getRegionLocation();
       String encodedRegionName = ts.getEncodedRegionName();
       long regionSize = ts.getLength();
       if (regionSize >= dataSkewThreshold) {
         // if the current region size is large than the data skew threshold,
         // split the region into two MapReduce input splits.
         byte[] splitKey = getSplitKey(ts.getStartRow(), ts.getEndRow(), isTextKey);
         if (Arrays.equals(ts.getEndRow(), splitKey)) {
           // Not splitting since the end key is the same as the split key
           resultList.add(ts);
         } else {
           //Set the size of child TableSplit as 1/2 of the region size. The exact size of the
           // MapReduce input splits is not far off.
           TableSplit t1 = new TableSplit(tableName, scan, ts.getStartRow(), splitKey,
               regionLocation, regionSize / 2);
           TableSplit t2 = new TableSplit(tableName, scan, splitKey, ts.getEndRow(), regionLocation,
               regionSize - regionSize / 2);
           resultList.add(t1);
           resultList.add(t2);
         }
         count++;
       } else if (regionSize >= average) {
         // if the region size between average size and data skew threshold size,
         // make this region as one MapReduce input split.
         resultList.add(ts);
         count++;
       } else {
         // if the total size of several small continuous regions less than the average region size,
         // combine them into one MapReduce input split.
         long totalSize = regionSize;
         byte[] splitStartKey = ts.getStartRow();
         byte[] splitEndKey = ts.getEndRow();
         count++;
         for (; count < list.size(); count++) {
           TableSplit nextRegion = (TableSplit)list.get(count);
           long nextRegionSize = nextRegion.getLength();
           if (totalSize + nextRegionSize <= dataSkewThreshold) {
             totalSize = totalSize + nextRegionSize;
             splitEndKey = nextRegion.getEndRow();
           } else {
             break;
           }
         }
         TableSplit t = new TableSplit(table.getName(), scan, splitStartKey, splitEndKey,
                 regionLocation, encodedRegionName, totalSize);
         resultList.add(t);
       }
     }
     return resultList;
   }
 
   /**
    * select a split point in the region. The selection of the split point is based on an uniform
    * distribution assumption for the keys in a region.
    * Here are some examples:
    *
    * <table>
    *   <tr>
    *     <th>start key</th>
    *     <th>end key</th>
    *     <th>is text</th>
    *     <th>split point</th>
    *   </tr>
    *   <tr>
    *     <td>'a', 'a', 'a', 'b', 'c', 'd', 'e', 'f', 'g'</td>
    *     <td>'a', 'a', 'a', 'f', 'f', 'f'</td>
    *     <td>true</td>
    *     <td>'a', 'a', 'a', 'd', 'd', -78, 50, -77, 51</td>
    *   </tr>
    *   <tr>
    *     <td>'1', '1', '1', '0', '0', '0'</td>
    *     <td>'1', '1', '2', '5', '7', '9', '0'</td>
    *     <td>true</td>
    *     <td>'1', '1', '1', -78, -77, -76, -104</td>
    *   </tr>
    *   <tr>
    *     <td>'1', '1', '1', '0'</td>
    *     <td>'1', '1', '2', '0'</td>
    *     <td>true</td>
    *     <td>'1', '1', '1', -80</td>
    *   </tr>
    *   <tr>
    *     <td>13, -19, 126, 127</td>
    *     <td>13, -19, 127, 0</td>
    *     <td>false</td>
    *     <td>13, -19, 126, -65</td>
    *   </tr>
    * </table>
    *
    * Set this function as "public static", make it easier for test.
    *
    * @param start Start key of the region
    * @param end End key of the region
    * @param isText It determines to use text key mode or binary key mode
    * @return The split point in the region.
    */
   public static byte[] getSplitKey(byte[] start, byte[] end, boolean isText) {
     byte upperLimitByte;
     byte lowerLimitByte;
     //Use text mode or binary mode.
     if (isText) {
       //The range of text char set in ASCII is [32,126], the lower limit is space and the upper
       // limit is '~'.
       upperLimitByte = '~';
       lowerLimitByte = ' ';
     } else {
       upperLimitByte = -1;
       lowerLimitByte = 0;
     }
     // For special case
     // Example 1 : startkey=null, endkey="hhhqqqwww", splitKey="h"
     // Example 2 (text key mode): startKey="ffffaaa", endKey=null, splitkey="f~~~~~~"
     if (start.length == 0 && end.length == 0){
       return new byte[]{(byte) ((lowerLimitByte + upperLimitByte) / 2)};
     }
     if (start.length == 0 && end.length != 0){
       return new byte[]{ end[0] };
     }
     if (start.length != 0 && end.length == 0){
       byte[] result =new byte[start.length];
       result[0]=start[0];
       for (int k = 1; k < start.length; k++){
           result[k] = upperLimitByte;
       }
       return result;
     }
     return Bytes.split(start, end, false, 1)[1];
   }
 
   /**
    *
    *
    * Test if the given region is to be included in the InputSplit while splitting
    * the regions of a table.
    * <p>
    * This optimization is effective when there is a specific reasoning to exclude an entire region from the M-R job,
    * (and hence, not contributing to the InputSplit), given the start and end keys of the same. <br>
    * Useful when we need to remember the last-processed top record and revisit the [last, current) interval for M-R processing,
    * continuously. In addition to reducing InputSplits, reduces the load on the region server as 
    * well, due to the ordering of the keys.
    * <br>
    * <br>
    * Note: It is possible that <code>endKey.length() == 0 </code> , for the last (recent) region.
    * <br>
    * Override this method, if you want to bulk exclude regions altogether from M-R.
    * By default, no region is excluded( i.e. all regions are included).
    *
    *
    * @param startKey Start key of the region
    * @param endKey End key of the region
    * @return true, if this region needs to be included as part of the input (default).
    *
    */
   protected boolean includeRegionInSplit(final byte[] startKey, final byte [] endKey) {
     return true;
   }
 
   /**
    * Allows subclasses to get the {@link HTable}.
    *
    * @deprecated use {@link #getTable()}
    */
   @Deprecated
   protected HTable getHTable() {
     return (HTable) this.getTable();
   }
 
   /**
    * Allows subclasses to get the {@link RegionLocator}.
    */
   protected RegionLocator getRegionLocator() {
     if (regionLocator == null) {
       throw new IllegalStateException(NOT_INITIALIZED);
     }
     return regionLocator;
   }
   
   /**
    * Allows subclasses to get the {@link Table}.
    */
   protected Table getTable() {
     if (table == null) {
       throw new IllegalStateException(NOT_INITIALIZED);
     }
     return table;
   }
 
   /**
    * Allows subclasses to get the {@link Admin}.
    */
   protected Admin getAdmin() {
     if (admin == null) {
       throw new IllegalStateException(NOT_INITIALIZED);
     }
     return admin;
   }
 
   /**
    * Allows subclasses to set the {@link HTable}.
    *
    * Will attempt to reuse the underlying Connection for our own needs, including
    * retreiving an Admin interface to the HBase cluster.
    *
    * @param table  The table to get the data from.
    * @throws IOException 
    * @deprecated Use {@link #initializeTable(Connection, TableName)} instead.
    */
   @Deprecated
   protected void setHTable(HTable table) throws IOException {
     this.table = table;
     this.connection = table.getConnection();
     try {
       this.regionLocator = table.getRegionLocator();
       this.admin = this.connection.getAdmin();
     } catch (NeedUnmanagedConnectionException exception) {
       LOG.warn("You are using an HTable instance that relies on an HBase-managed Connection. " +
           "This is usually due to directly creating an HTable, which is deprecated. Instead, you " +
           "should create a Connection object and then request a Table instance from it. If you " +
           "don't need the Table instance for your own use, you should instead use the " +
           "TableInputFormatBase.initalizeTable method directly.");
       LOG.info("Creating an additional unmanaged connection because user provided one can't be " +
           "used for administrative actions. We'll close it when we close out the table.");
       LOG.debug("Details about our failure to request an administrative interface.", exception);
       // Do we need a "copy the settings from this Connection" method? are things like the User
       // properly maintained by just looking again at the Configuration?
       this.connection = ConnectionFactory.createConnection(this.connection.getConfiguration());
       this.regionLocator = this.connection.getRegionLocator(table.getName());
       this.admin = this.connection.getAdmin();
     }
   }
 
   /**
    * Allows subclasses to initialize the table information.
    *
    * @param connection  The {@link Connection} to the HBase cluster. MUST be unmanaged. We will close.
    * @param tableName  The {@link TableName} of the table to process. 
    * @throws IOException 
    */
   protected void initializeTable(Connection connection, TableName tableName) throws IOException {
     if (this.table != null || this.connection != null) {
       LOG.warn("initializeTable called multiple times. Overwriting connection and table " +
           "reference; TableInputFormatBase will not close these old references when done.");
     }
     this.table = connection.getTable(tableName);
     this.regionLocator = connection.getRegionLocator(tableName);
     this.admin = connection.getAdmin();
     this.connection = connection;
   }
 
   /**
    * Gets the scan defining the actual details like columns etc.
    *
    * @return The internal scan instance.
    */
   public Scan getScan() {
     if (this.scan == null) this.scan = new Scan();
     return scan;
   }
 
   /**
    * Sets the scan defining the actual details like columns etc.
    *
    * @param scan  The scan to set.
    */
   public void setScan(Scan scan) {
     this.scan = scan;
   }
 
   /**
    * Allows subclasses to set the {@link TableRecordReader}.
    *
    * @param tableRecordReader A different {@link TableRecordReader}
    *   implementation.
    */
   protected void setTableRecordReader(TableRecordReader tableRecordReader) {
     this.tableRecordReader = tableRecordReader;
   }
   
   /**
    * Handle subclass specific set up.
    * Each of the entry points used by the MapReduce framework,
    * {@link #createRecordReader(InputSplit, TaskAttemptContext)} and {@link #getSplits(JobContext)},
    * will call {@link #initialize(JobContext)} as a convenient centralized location to handle
    * retrieving the necessary configuration information and calling
    * {@link #initializeTable(Connection, TableName)}.
    *
    * Subclasses should implement their initialize call such that it is safe to call multiple times.
    * The current TableInputFormatBase implementation relies on a non-null table reference to decide
    * if an initialize call is needed, but this behavior may change in the future. In particular,
    * it is critical that initializeTable not be called multiple times since this will leak
    * Connection instances.
    *
    */
   protected void initialize(JobContext context) throws IOException {
   }
 
   /**
    * Close the Table and related objects that were initialized via
    * {@link #initializeTable(Connection, TableName)}.
    *
    * @throws IOException
    */
   protected void closeTable() throws IOException {
     close(admin, table, regionLocator, connection);
     admin = null;
     table = null;
     regionLocator = null;
     connection = null;
   }
 
   private void close(Closeable... closables) throws IOException {
     for (Closeable c : closables) {
       if(c != null) { c.close(); }
     }
   }
 
 }