/**
* CopyRight by Chinamobile
*
* TableInputFormatBase.java
*/
package com.chinamobile.bcbsp.io.db;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import com.chinamobile.bcbsp.io.InputFormat;
import com.chinamobile.bcbsp.io.RecordReader;
import com.chinamobile.bcbsp.util.BSPJob;
/**
* A base for {@link TableInputFormat}s. Receives a {@link HTable}, an
* {@link Scan} instance that defines the input columns etc. Subclasses may use
* other TableRecordReader implementations. *
*/
public abstract class TableInputFormatBase extends
InputFormat<Text, Text> {
final Log LOG = LogFactory.getLog(TableInputFormatBase.class);
/** Holds the details for the internal scanner. */
private Scan scan = null;
/** The table to scan. */
private HTable table = null;
/** The reader scanning the table, can be a custom one. */
private TableRecordReader tableRecordReader = null;
/** The configuration. */
protected Configuration conf = null;
/**
* Builds a TableRecordReader. If no TableRecordReader was provided, uses
* the default.
*
* @param split
* The split to work with.
* @param job
* The current job BSPJob.
* @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<Text, Text> createRecordReader(
InputSplit split, BSPJob job) throws IOException {
if (table == null) {
throw new IOException(
"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.");
}
TableSplit tSplit = ( TableSplit ) split;
TableRecordReader trr = this.tableRecordReader;
// if no table record reader was provided use default
if (trr == null) {
trr = new TableRecordReader();
}
Scan sc = new Scan(this.scan);
sc.setStartRow(tSplit.getStartRow());
sc.setStopRow(tSplit.getEndRow());
trr.setScan(sc);
trr.setHTable(table);
trr.init();
return trr;
}
/**
* 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 job
* The current job BSPJob.
* @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(BSPJob job) throws IOException {
if (table == null) {
throw new IOException("No table was provided.");
}
Pair<byte[][], byte[][]> keys = table.getStartEndKeys();
if (keys == null || keys.getFirst() == null
|| keys.getFirst().length == 0) {
throw new IOException("Expecting at least one region.");
}
int count = 0;
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;
}
String regionLocation = table.getRegionLocation(keys.getFirst()[i])
.getServerAddress().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;
InputSplit split = new TableSplit(table.getTableName(),
splitStart, splitStop, regionLocation);
splits.add(split);
if (LOG.isDebugEnabled())
LOG.debug("getSplits: split -> " + (count++) + " -> "
+ split);
}
}
return splits;
}
/**
*
*
* 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 BSP 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 iterative 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}.
*/
protected HTable getHTable() {
return this.table;
}
/**
* Allows subclasses to set the {@link HTable}.
*
* @param table
* The table to get the data from.
*/
protected void setHTable(HTable table) {
this.table = table;
}
/**
* 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;
}
}