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MarkLogic Connector for Hadoop MapReduce
/*
* Copyright 2003-2019 MarkLogic Corporation
*
* Licensed 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 com.marklogic.mapreduce.examples;
import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import net.sf.saxon.s9api.Processor;
import net.sf.saxon.s9api.SaxonApiException;
import net.sf.saxon.s9api.XPathCompiler;
import net.sf.saxon.s9api.XPathSelector;
import net.sf.saxon.s9api.XdmNode;
import net.sf.saxon.s9api.XdmItem;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import org.w3c.dom.Document;
import org.xml.sax.SAXException;
public class LinkCountHDFS {
public static class RefMapper
extends Mapper {
private final static IntWritable one = new IntWritable(1);
private Text refURI = new Text();
public void map(IntWritable key, Text value, Context context)
throws IOException, InterruptedException {
refURI.set(value);
context.write(refURI, one);
}
}
public static class IntSumReducer
extends Reducer {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable values,
Context context) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
if (args.length < 2) {
System.err.println("Usage: LinkCountHDFS inputDir outputDir");
System.exit(2);
}
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
Job job = Job.getInstance(conf, "link count hdfs");
job.setJarByClass(LinkCountHDFS.class);
job.setInputFormatClass(HDFSInputFormat.class);
job.setMapperClass(RefMapper.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputFormatClass(TextOutputFormat.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
HDFSInputFormat.setInputPaths(job, new Path(otherArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
class HDFSInputFormat extends FileInputFormat {
protected boolean isSplitable(JobContext context, Path filename) {
return false;
}
@Override
public RecordReader createRecordReader(InputSplit arg0,
TaskAttemptContext arg1) throws IOException, InterruptedException {
return new LinkRecordReader();
}
}
class LinkRecordReader extends RecordReader {
private static final String PATH_EXPRESSION =
"//wp:a[@title and @href and not (starts-with(@href, '#') or " +
"starts-with(@href, 'http://') or starts-with(@href, 'File:') " +
" or starts-with(@href, 'Image:'))]/@title";
private IntWritable key;
private Text value;
private int count = 0;
private List items;
private static final ThreadLocal builderLocal =
new ThreadLocal() {
@Override protected DocumentBuilder initialValue() {
try {
return
DocumentBuilderFactory.newInstance().newDocumentBuilder();
} catch (ParserConfigurationException e) {
e.printStackTrace();
return null;
}
}
};
private static Processor proc = new Processor(false);
private static final ThreadLocal
saxonBuilderLocal =
new ThreadLocal() {
@Override protected net.sf.saxon.s9api.DocumentBuilder initialValue() {
return proc.newDocumentBuilder();
}
};
@Override
public void close() throws IOException {
}
@Override
public IntWritable getCurrentKey() throws IOException, InterruptedException {
return key;
}
@Override
public Text getCurrentValue() throws IOException, InterruptedException {
return value;
}
@Override
public float getProgress() throws IOException, InterruptedException {
if (items != null) {
return (float)count/items.size();
} else {
return 0;
}
}
@Override
public void initialize(InputSplit inSplit, TaskAttemptContext context)
throws IOException, InterruptedException {
Path file = ((FileSplit)inSplit).getPath();
FileSystem fs = file.getFileSystem(context.getConfiguration());
FSDataInputStream fileIn = fs.open(file);
DocumentBuilder docBuilder = builderLocal.get();
try {
Document document = docBuilder.parse(fileIn);
net.sf.saxon.s9api.DocumentBuilder db = saxonBuilderLocal.get();
XdmNode xdmDoc = db.wrap(document);
XPathCompiler xpath = proc.newXPathCompiler();
xpath.declareNamespace("wp",
"http://www.mediawiki.org/xml/export-0.4/");
XPathSelector selector = xpath.compile(PATH_EXPRESSION).load();
selector.setContextItem(xdmDoc);
items = new ArrayList();
for (XdmItem item : selector) {
items.add(item);
}
} catch (SAXException ex) {
ex.printStackTrace();
throw new IOException(ex);
} catch (SaxonApiException e) {
e.printStackTrace();
} finally {
if (fileIn != null) {
fileIn.close();
}
}
}
@Override
public boolean nextKeyValue() throws IOException, InterruptedException {
if (items.size() > count) {
if (key == null) {
key = new IntWritable();
}
key.set(count);
if (value == null) {
value = new Text();
}
value.set(items.get(count++).getStringValue());
return true;
}
return false;
}
}