/*
* Cloud9: A Hadoop toolkit for working with big data
*
* 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 edu.umd.cloud9.example.pagerank;
import java.io.IOException;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Arrays;
import java.util.Map;
import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.GnuParser;
import org.apache.commons.cli.HelpFormatter;
import org.apache.commons.cli.Option;
import org.apache.commons.cli.OptionBuilder;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.SequenceFileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.mapreduce.lib.partition.HashPartitioner;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.log4j.Logger;
import com.google.common.base.Preconditions;
import com.google.common.collect.Maps;
import edu.umd.cloud9.io.array.ArrayListOfIntsWritable;
import edu.umd.cloud9.mapreduce.lib.input.NonSplitableSequenceFileInputFormat;
import edu.umd.cloud9.util.map.HMapIF;
import edu.umd.cloud9.util.map.MapIF;
/**
* <p>
* Main driver program for running the Schimmy implementation of PageRank.
* </p>
*
* <p>
* The starting and ending iterations will correspond to paths
* <code>/base/path/iterXXXX</code> and <code>/base/path/iterYYYY</code>. As a
* example, if you specify 0 and 10 as the starting and ending iterations, the
* driver program will start with the graph structure stored at
* <code>/base/path/iter0000</code>; final results will be stored at
* <code>/base/path/iter0010</code>.
* </p>
*
* @see RunPageRankBasic
* @author Jimmy Lin
* @author Michael Schatz
*/
public class RunPageRankSchimmy extends Configured implements Tool {
private static final Logger LOG = Logger.getLogger(RunPageRankSchimmy.class);
private static enum PageRank {
nodes, edges, massMessages, massMessagesSaved, massMessagesReceived, missingStructure
};
// Mapper, no in-mapper combining.
private static class MapClass extends
Mapper<IntWritable, PageRankNode, IntWritable, FloatWritable> {
// The neighbor to which we're sending messages.
private static final IntWritable neighbor = new IntWritable();
// Contents of the messages: partial PageRank mass.
private static final FloatWritable intermediateMass = new FloatWritable();
@Override
public void map(IntWritable nid, PageRankNode node, Context context)
throws IOException, InterruptedException {
int massMessages = 0;
// Distribute PageRank mass to neighbors (along outgoing edges).
if (node.getAdjacenyList().size() > 0) {
// Each neighbor gets an equal share of PageRank mass.
ArrayListOfIntsWritable list = node.getAdjacenyList();
float mass = node.getPageRank() - (float) StrictMath.log(list.size());
// Iterate over neighbors.
for (int i = 0; i < list.size(); i++) {
neighbor.set(list.get(i));
intermediateMass.set(mass);
// Emit messages with PageRank mass to neighbors.
context.write(neighbor, intermediateMass);
massMessages++;
}
}
// Bookkeeping.
context.getCounter(PageRank.nodes).increment(1);
context.getCounter(PageRank.massMessages).increment(massMessages);
}
}
// Mapper with in-mapper combiner optimization.
private static class MapWithInMapperCombiningClass extends
Mapper<IntWritable, PageRankNode, IntWritable, FloatWritable> {
// For buffering PageRank mass contributes keyed by destination node.
private static HMapIF map = new HMapIF();
public void map(IntWritable nid, PageRankNode node, Context context)
throws IOException, InterruptedException {
int massMessages = 0;
int massMessagesSaved = 0;
// Distribute PageRank mass to neighbors (along outgoing edges).
if (node.getAdjacenyList().size() > 0) {
// Each neighbor gets an equal share of PageRank mass.
ArrayListOfIntsWritable list = node.getAdjacenyList();
float mass = node.getPageRank() - (float) StrictMath.log(list.size());
// Iterate over neighbors.
for (int i = 0; i < list.size(); i++) {
int neighbor = list.get(i);
if (map.containsKey(neighbor)) {
// Already message destined for that node; add PageRank mass contribution.
massMessagesSaved++;
map.put(neighbor, sumLogProbs(map.get(neighbor), mass));
} else {
// New destination node; add new entry in map.
massMessages++;
map.put(neighbor, mass);
}
}
}
// Bookkeeping.
context.getCounter(PageRank.nodes).increment(1);
context.getCounter(PageRank.massMessages).increment(massMessages);
context.getCounter(PageRank.massMessagesSaved).increment(massMessagesSaved);
}
@Override
public void cleanup(
Mapper<IntWritable, PageRankNode, IntWritable, FloatWritable>.Context context)
throws IOException, InterruptedException {
// Now emit the messages all at once.
IntWritable k = new IntWritable();
FloatWritable v = new FloatWritable();
for (MapIF.Entry e : map.entrySet()) {
k.set(e.getKey());
v.set(e.getValue());
context.write(k, v);
}
}
}
// Combiner: sums partial PageRank contributions.
private static class CombineClass extends
Reducer<IntWritable, FloatWritable, IntWritable, FloatWritable> {
private static final FloatWritable intermediateMass = new FloatWritable();
@Override
public void reduce(IntWritable nid, Iterable<FloatWritable> values, Context context)
throws IOException, InterruptedException {
int massMessages = 0;
// Remember, PageRank mass is stored as a log prob.
float mass = Float.NEGATIVE_INFINITY;
for (FloatWritable n : values) {
// Accumulate PageRank mass contributions
mass = sumLogProbs(mass, n.get());
massMessages++;
}
// emit aggregated results
if (massMessages > 0) {
intermediateMass.set(mass);
context.write(nid, intermediateMass);
}
}
}
// Reduce: sums incoming PageRank contributions, rewrite graph structure.
private static class ReduceClass extends
Reducer<IntWritable, FloatWritable, IntWritable, PageRankNode> {
private float totalMass = Float.NEGATIVE_INFINITY;
private SequenceFile.Reader reader;
private IntWritable hdfsNid = new IntWritable();
private PageRankNode hdfsNode = new PageRankNode();
private boolean hdfsAhead = false;
@Override
public void setup(Context context) throws IOException {
// We're going to open up the file on HDFS that has corresponding node structures. To do this,
// we get the task id and map it to the corresponding part.
Configuration conf = context.getConfiguration();
String taskId = conf.get("mapred.task.id");
Preconditions.checkNotNull(taskId);
// The partition mapping is passed in from the driver.
String mapping = conf.get("PartitionMapping");
Preconditions.checkNotNull(mapping);
Map<Integer, String> map = Maps.newHashMap();
for (String s : mapping.split(";")) {
String[] arr = s.split("=");
LOG.info(arr[0] + "\t" + arr[1]);
map.put(Integer.parseInt(arr[0]), arr[1]);
}
// Get the part number.
int partno = Integer.parseInt(taskId.substring(taskId.length() - 7, taskId.length() - 2));
String f = map.get(partno);
LOG.info("task id: " + taskId);
LOG.info("partno: " + partno);
LOG.info("file: " + f);
// Try and open the node structures...
try {
reader = new SequenceFile.Reader(conf, SequenceFile.Reader.file(new Path(f)));
} catch (IOException e) {
throw new RuntimeException("Couldn't open " + f + " for partno: " + partno + " within: "
+ taskId);
}
}
@Override
public void reduce(IntWritable nid, Iterable<FloatWritable> values, Context context)
throws IOException, InterruptedException {
// The basic algorithm is a merge sort between node structures on HDFS and intermediate
// key-value pairs coming into this reducer (where the keys are the node ids). Both are
// sorted, and the reducer is "pushed" intermediate key-value pairs, so the algorithm boils
// down to properly advancing the node structures file on HDFS.
// The HDFS node structure file is ahead. This means the incoming node ids don't have
// corresponding node structure (i.e., messages addressed to non-existent nodes). This may
// happen if the adjacency lists point to nodes that don't exist. Do nothing.
if (hdfsNid.get() > nid.get()) {
return;
}
// We need to advance the HDFS node structure file.
if (hdfsNid.get() < nid.get()) {
if (hdfsAhead) {
// If we get here, it means that no messages were sent to a particular node in the HDFS
// node structure file. So we want to emit this node structure.
hdfsNode.setPageRank(Float.NEGATIVE_INFINITY);
context.write(hdfsNid, hdfsNode);
hdfsAhead = false;
}
// We're now going to advance the HDFS node structure until we get to the node id of the
// current message we're processing...
while (reader.next(hdfsNid, hdfsNode)) {
if (hdfsNid.get() == nid.get()) {
// Found it!
break;
}
// If we go past the incoming node id in the HDFS node structure file, then it means that
// no corresponding no structure exist. That is, a message was sent to a non-existent
// node: this may happen if adjacency lists point to nodes that don't exist.
if (hdfsNid.get() > nid.get()) {
// We want to note that we've gotten ahead in the HDFS node structure file, and need to
// wait for the incoming key-value pairs to "catch up".
hdfsAhead = true;
return;
}
// This is a node that has not messages sent to it... we don't want to node the node
// structure, so just emit.
hdfsNode.setPageRank(Float.NEGATIVE_INFINITY);
context.write(hdfsNid, hdfsNode);
}
// If we get here, it means that the reader ran out of nodes, i.e., next method returned
// false. This means that the messages were addressed to non-existent nodes.
if (hdfsNid.get() != nid.get()) {
return;
}
}
int massMessagesReceived = 0;
float mass = Float.NEGATIVE_INFINITY;
// Now we process the messages: sum up PageRank mass contributions.
for (FloatWritable f : values) {
float n = f.get();
massMessagesReceived++;
mass = sumLogProbs(mass, n);
}
totalMass = sumLogProbs(totalMass, mass);
// Populate the node structure with the updated PageRank value.
hdfsNode.setPageRank(mass);
// Emit!
context.write(nid, hdfsNode);
context.getCounter(PageRank.massMessagesReceived).increment(massMessagesReceived);
hdfsAhead = false;
}
@Override
public void cleanup(Context context)
throws IOException, InterruptedException {
Configuration conf = context.getConfiguration();
String taskId = conf.get("mapred.task.id");
String path = conf.get("PageRankMassPath");
Preconditions.checkNotNull(taskId);
Preconditions.checkNotNull(path);
FileSystem fs = FileSystem.get(conf);
FSDataOutputStream out = fs.create(new Path(path + "/" + taskId), false);
out.writeFloat(totalMass);
out.close();
// If the HDFS node structure file is ahead, we want to emit the current node structure.
if (hdfsAhead) {
hdfsNode.setPageRank(Float.NEGATIVE_INFINITY);
context.write(hdfsNid, hdfsNode);
hdfsAhead = false;
}
// We have to write out the rest of the nodes we haven't finished reading yet (i.e., these are
// the ones who don't have any messages sent to them)
while (reader.next(hdfsNid, hdfsNode)) {
hdfsNode.setPageRank(Float.NEGATIVE_INFINITY);
context.write(hdfsNid, hdfsNode);
}
reader.close();
}
}
// Mapper that distributes the missing PageRank mass (lost at the dangling nodes) and takes care
// of the random jump factor.
private static class MapPageRankMassDistributionClass extends
Mapper<IntWritable, PageRankNode, IntWritable, PageRankNode> {
private float missingMass = 0.0f;
private int nodeCnt = 0;
@Override
public void setup(Mapper<IntWritable, PageRankNode, IntWritable, PageRankNode>.Context context)
throws IOException {
Configuration conf = context.getConfiguration();
missingMass = conf.getFloat("MissingMass", 0.0f);
nodeCnt = conf.getInt("NodeCount", 0);
}
@Override
public void map(IntWritable nid, PageRankNode node, Context context)
throws IOException, InterruptedException {
float p = node.getPageRank();
float jump = (float) (Math.log(ALPHA) - Math.log(nodeCnt));
float link = (float) Math.log(1.0f - ALPHA)
+ sumLogProbs(p, (float) (Math.log(missingMass) - Math.log(nodeCnt)));
p = sumLogProbs(jump, link);
node.setPageRank(p);
context.write(nid, node);
}
}
private static float ALPHA = 0.15f; // Random jump factor.
private static final NumberFormat FORMAT = new DecimalFormat("0000");
/**
* Dispatches command-line arguments to the tool via the {@code ToolRunner}.
*/
public static void main(String[] args) throws Exception {
ToolRunner.run(new RunPageRankSchimmy(), args);
}
public RunPageRankSchimmy() {}
private static final String BASE = "base";
private static final String NUM_NODES = "numNodes";
private static final String START = "start";
private static final String END = "end";
private static final String COMBINER = "useCombiner";
private static final String INMAPPER_COMBINER = "useInMapperCombiner";
private static final String RANGE = "range";
/**
* Runs this tool.
*/
@SuppressWarnings({ "static-access" })
public int run(String[] args) throws Exception {
Options options = new Options();
options.addOption(new Option(COMBINER, "use combiner"));
options.addOption(new Option(INMAPPER_COMBINER, "user in-mapper combiner"));
options.addOption(new Option(RANGE, "use range partitioner"));
options.addOption(OptionBuilder.withArgName("path").hasArg()
.withDescription("base path").create(BASE));
options.addOption(OptionBuilder.withArgName("num").hasArg()
.withDescription("start iteration").create(START));
options.addOption(OptionBuilder.withArgName("num").hasArg()
.withDescription("end iteration").create(END));
options.addOption(OptionBuilder.withArgName("num").hasArg()
.withDescription("number of nodes").create(NUM_NODES));
CommandLine cmdline;
CommandLineParser parser = new GnuParser();
try {
cmdline = parser.parse(options, args);
} catch (ParseException exp) {
System.err.println("Error parsing command line: " + exp.getMessage());
return -1;
}
if (!cmdline.hasOption(BASE) || !cmdline.hasOption(START) ||
!cmdline.hasOption(END) || !cmdline.hasOption(NUM_NODES)) {
System.out.println("args: " + Arrays.toString(args));
HelpFormatter formatter = new HelpFormatter();
formatter.setWidth(120);
formatter.printHelp(this.getClass().getName(), options);
ToolRunner.printGenericCommandUsage(System.out);
return -1;
}
String basePath = cmdline.getOptionValue(BASE);
int n = Integer.parseInt(cmdline.getOptionValue(NUM_NODES));
int s = Integer.parseInt(cmdline.getOptionValue(START));
int e = Integer.parseInt(cmdline.getOptionValue(END));
boolean useCombiner = cmdline.hasOption(COMBINER);
boolean useInmapCombiner = cmdline.hasOption(INMAPPER_COMBINER);
boolean useRange = cmdline.hasOption(RANGE);
LOG.info("Tool name: RunPageRank");
LOG.info(" - base path: " + basePath);
LOG.info(" - num nodes: " + n);
LOG.info(" - start iteration: " + s);
LOG.info(" - end iteration: " + e);
LOG.info(" - use combiner: " + useCombiner);
LOG.info(" - use in-mapper combiner: " + useInmapCombiner);
LOG.info(" - user range partitioner: " + useRange);
// iterate PageRank
for (int i = s; i < e; i++) {
iteratePageRank(basePath, i, i + 1, n, useCombiner, useInmapCombiner, useRange);
}
return 0;
}
// Run each iteration.
private void iteratePageRank(String path, int i, int j, int n, boolean useCombiner,
boolean useInmapCombiner, boolean useRange) throws Exception {
// Each iteration consists of two phases (two MapReduce jobs).
// Job1: distribute PageRank mass along outgoing edges.
float mass = phase1(path, i, j, n, useCombiner, useInmapCombiner, useRange);
// Find out how much PageRank mass got lost at the dangling nodes.
float missing = 1.0f - (float) StrictMath.exp(mass);
if ( missing < 0.0f ) {
missing = 0.0f;
}
// Job2: distribute missing mass, take care of random jump factor.
phase2(path, i, j, n, missing);
}
private float phase1(String path, int i, int j, int n, boolean useCombiner,
boolean useInmapCombiner, boolean useRange) throws Exception {
Configuration conf = getConf();
String in = path + "/iter" + FORMAT.format(i);
String out = path + "/iter" + FORMAT.format(j) + "t";
String outm = out + "-mass";
FileSystem fs = FileSystem.get(conf);
// We need to actually count the number of part files to get the number
// of partitions (because the directory might contain _log).
int numPartitions = 0;
for (FileStatus s : FileSystem.get(conf).listStatus(new Path(in))) {
if (s.getPath().getName().contains("part-")) {
numPartitions++;
}
}
conf.setInt("NodeCount", n);
Partitioner<IntWritable, Writable> p = null;
if (useRange) {
p = new RangePartitioner();
((Configurable) p).setConf(conf);
} else {
p = new HashPartitioner<IntWritable, Writable>();
}
// This is really annoying: the mapping between the partition numbers on
// disk (i.e., part-XXXX) and what partition the file contains (i.e.,
// key.hash % #reducer) is arbitrary... so this means that we need to
// open up each partition, peek inside to find out.
IntWritable key = new IntWritable();
PageRankNode value = new PageRankNode();
FileStatus[] status = fs.listStatus(new Path(in));
StringBuilder sb = new StringBuilder();
for (FileStatus f : status) {
if (!f.getPath().getName().contains("part-")) {
continue;
}
SequenceFile.Reader reader =
new SequenceFile.Reader(conf, SequenceFile.Reader.file(f.getPath()));
reader.next(key, value);
int np = p.getPartition(key, value, numPartitions);
reader.close();
LOG.info(f.getPath() + "\t" + np);
sb.append(np + "=" + f.getPath() + ";");
}
LOG.info(sb.toString().trim());
LOG.info("PageRankSchimmy: iteration " + j + ": Phase1");
LOG.info(" - input: " + in);
LOG.info(" - output: " + out);
LOG.info(" - nodeCnt: " + n);
LOG.info(" - useCombiner: " + useCombiner);
LOG.info(" - useInmapCombiner: " + useInmapCombiner);
LOG.info(" - numPartitions: " + numPartitions);
LOG.info(" - useRange: " + useRange);
LOG.info("computed number of partitions: " + numPartitions);
int numReduceTasks = numPartitions;
conf.setInt("mapred.min.split.size", 1024 * 1024 * 1024);
//conf.set("mapred.child.java.opts", "-Xmx2048m");
conf.set("PageRankMassPath", outm);
conf.set("BasePath", in);
conf.set("PartitionMapping", sb.toString().trim());
conf.setBoolean("mapred.map.tasks.speculative.execution", false);
conf.setBoolean("mapred.reduce.tasks.speculative.execution", false);
Job job = Job.getInstance(conf);
job.setJobName("PageRankSchimmy:iteration" + j + ":Phase1");
job.setJarByClass(RunPageRankSchimmy.class);
job.setNumReduceTasks(numReduceTasks);
FileInputFormat.setInputPaths(job, new Path(in));
FileOutputFormat.setOutputPath(job, new Path(out));
job.setInputFormatClass(SequenceFileInputFormat.class);
job.setOutputFormatClass(SequenceFileOutputFormat.class);
job.setMapOutputKeyClass(IntWritable.class);
job.setMapOutputValueClass(FloatWritable.class);
job.setOutputKeyClass(IntWritable.class);
job.setOutputValueClass(PageRankNode.class);
if (useInmapCombiner) {
job.setMapperClass(MapWithInMapperCombiningClass.class);
} else {
job.setMapperClass(MapClass.class);
}
if (useCombiner) {
job.setCombinerClass(CombineClass.class);
}
if (useRange) {
job.setPartitionerClass(RangePartitioner.class);
}
job.setReducerClass(ReduceClass.class);
FileSystem.get(conf).delete(new Path(out), true);
FileSystem.get(conf).delete(new Path(outm), true);
long startTime = System.currentTimeMillis();
job.waitForCompletion(true);
System.out.println("Job Finished in " + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
float mass = Float.NEGATIVE_INFINITY;
for (FileStatus f : fs.listStatus(new Path(outm))) {
FSDataInputStream fin = fs.open(f.getPath());
mass = sumLogProbs(mass, fin.readFloat());
fin.close();
}
return mass;
}
private void phase2(String path, int i, int j, int n, float missing) throws Exception {
Configuration conf = getConf();
LOG.info("missing PageRank mass: " + missing);
LOG.info("number of nodes: " + n);
String in = path + "/iter" + FORMAT.format(j) + "t";
String out = path + "/iter" + FORMAT.format(j);
LOG.info("PageRankSchimmy: iteration " + j + ": Phase2");
LOG.info(" - input: " + in);
LOG.info(" - output: " + out);
Job job = Job.getInstance(conf);
job.setJobName("PageRankSchimmy:iteration" + j + ":Phase2");
job.setJarByClass(RunPageRankSchimmy.class);
job.setNumReduceTasks(0);
FileInputFormat.setInputPaths(job, new Path(in));
FileOutputFormat.setOutputPath(job, new Path(out));
job.setInputFormatClass(NonSplitableSequenceFileInputFormat.class);
job.setOutputFormatClass(SequenceFileOutputFormat.class);
job.setMapOutputKeyClass(IntWritable.class);
job.setMapOutputValueClass(PageRankNode.class);
job.setOutputKeyClass(IntWritable.class);
job.setOutputValueClass(PageRankNode.class);
job.setMapperClass(MapPageRankMassDistributionClass.class);
conf.setFloat("MissingMass", (float) missing);
conf.setInt("NodeCount", n);
FileSystem.get(conf).delete(new Path(out), true);
long startTime = System.currentTimeMillis();
job.waitForCompletion(true);
System.out.println("Job Finished in " + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
}
// Adds two log probs.
private static float sumLogProbs(float a, float b) {
if (a == Float.NEGATIVE_INFINITY)
return b;
if (b == Float.NEGATIVE_INFINITY)
return a;
if (a < b) {
return (float) (b + StrictMath.log1p(StrictMath.exp(a - b)));
}
return (float) (a + StrictMath.log1p(StrictMath.exp(b - a)));
}
}