/**
* 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.IOException;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.client.HTable;
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.Bytes;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.hadoop.hbase.util.RegionSizeCalculator;
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;
/**
* A base for {@link MultiTableInputFormat}s. Receives a list of
* {@link Scan} instances that define the input tables and
* filters etc. Subclasses may use other TableRecordReader implementations.
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public abstract class MultiTableInputFormatBase extends
InputFormat<ImmutableBytesWritable, Result> {
final Log LOG = LogFactory.getLog(MultiTableInputFormatBase.class);
/** Holds the set of scans used to define the input. */
private List<Scan> scans;
/** The reader scanning the table, can be a custom one. */
private TableRecordReader tableRecordReader = null;
/**
* Builds a TableRecordReader. If no 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.
* @throws InterruptedException when record reader initialization 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, InterruptedException {
TableSplit tSplit = (TableSplit) split;
LOG.info(MessageFormat.format("Input split length: {0} bytes.", tSplit.getLength()));
if (tSplit.getTableName() == 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.");
}
Table table =
new HTable(context.getConfiguration(), tSplit.getTableName());
TableRecordReader trr = this.tableRecordReader;
try {
// if no table record reader was provided use default
if (trr == null) {
trr = new TableRecordReader();
}
Scan sc = tSplit.getScan();
sc.setStartRow(tSplit.getStartRow());
sc.setStopRow(tSplit.getEndRow());
trr.setScan(sc);
trr.setHTable(table);
} catch (IOException ioe) {
// If there is an exception make sure that all
// resources are closed and released.
table.close();
trr.close();
throw ioe;
}
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 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 {
if (scans.isEmpty()) {
throw new IOException("No scans were provided.");
}
List<InputSplit> splits = new ArrayList<InputSplit>();
for (Scan scan : scans) {
byte[] tableName = scan.getAttribute(Scan.SCAN_ATTRIBUTES_TABLE_NAME);
if (tableName == null)
throw new IOException("A scan object did not have a table name");
HTable table = null;
try {
table = new HTable(context.getConfiguration(), tableName);
Pair<byte[][], byte[][]> keys = table.getStartEndKeys();
if (keys == null || keys.getFirst() == null ||
keys.getFirst().length == 0) {
throw new IOException("Expecting at least one region for table : "
+ Bytes.toString(tableName));
}
int count = 0;
byte[] startRow = scan.getStartRow();
byte[] stopRow = scan.getStopRow();
RegionSizeCalculator sizeCalculator = new RegionSizeCalculator(table);
for (int i = 0; i < keys.getFirst().length; i++) {
if (!includeRegionInSplit(keys.getFirst()[i], keys.getSecond()[i])) {
continue;
}
HRegionLocation hregionLocation = table.getRegionLocation(keys.getFirst()[i], false);
String regionHostname = hregionLocation.getHostname();
HRegionInfo regionInfo = hregionLocation.getRegionInfo();
// determine if the given start and stop keys fall into the range
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;
long regionSize = sizeCalculator.getRegionSize(regionInfo.getRegionName());
TableSplit split =
new TableSplit(table.getName(),
scan, splitStart, splitStop, regionHostname, regionSize);
splits.add(split);
if (LOG.isDebugEnabled())
LOG.debug("getSplits: split -> " + (count++) + " -> " + split);
}
}
} finally {
if (null != table) table.close();
}
}
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 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 list of {@link Scan} objects.
*/
protected List<Scan> getScans() {
return this.scans;
}
/**
* Allows subclasses to set the list of {@link Scan} objects.
*
* @param scans The list of {@link Scan} used to define the input
*/
protected void setScans(List<Scan> scans) {
this.scans = scans;
}
/**
* Allows subclasses to set the {@link TableRecordReader}.
*
* @param tableRecordReader A different {@link TableRecordReader}
* implementation.
*/
protected void setTableRecordReader(TableRecordReader tableRecordReader) {
this.tableRecordReader = tableRecordReader;
}
}