hadoop MultiFileSplit 源码
haddop MultiFileSplit 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MultiFileSplit.java
/**
* 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.mapred;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.BlockLocation;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapred.lib.CombineFileSplit;
/**
* A sub-collection of input files. Unlike {@link FileSplit}, MultiFileSplit
* class does not represent a split of a file, but a split of input files
* into smaller sets. The atomic unit of split is a file. <br>
* MultiFileSplit can be used to implement {@link RecordReader}'s, with
* reading one record per file.
* @see FileSplit
* @see MultiFileInputFormat
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class MultiFileSplit extends CombineFileSplit {
MultiFileSplit() {}
public MultiFileSplit(JobConf job, Path[] files, long[] lengths) {
super(job, files, lengths);
}
public String[] getLocations() throws IOException {
HashSet<String> hostSet = new HashSet<String>();
for (Path file : getPaths()) {
FileSystem fs = file.getFileSystem(getJob());
FileStatus status = fs.getFileStatus(file);
BlockLocation[] blkLocations = fs.getFileBlockLocations(status,
0, status.getLen());
if (blkLocations != null && blkLocations.length > 0) {
addToSet(hostSet, blkLocations[0].getHosts());
}
}
return hostSet.toArray(new String[hostSet.size()]);
}
private void addToSet(Set<String> set, String[] array) {
for(String s:array)
set.add(s);
}
@Override
public String toString() {
StringBuffer sb = new StringBuffer();
for(int i=0; i < getPaths().length; i++) {
sb.append(getPath(i).toUri().getPath() + ":0+" + getLength(i));
if (i < getPaths().length -1) {
sb.append("\n");
}
}
return sb.toString();
}
}
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