Java Reducer類代碼示例

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
/**
 * Creates a simple fail job.
 * 
 * @param conf Configuration object
 * @param outdir Output directory.
 * @param indirs Comma separated input directories.
 * @return Job initialized for a simple fail job.
 * @throws Exception If an error occurs creating job configuration.
 */
public static Job createFailJob(Configuration conf, Path outdir, 
    Path... indirs) throws Exception {
  FileSystem fs = outdir.getFileSystem(conf);
  if (fs.exists(outdir)) {
    fs.delete(outdir, true);
  }
  conf.setInt(MRJobConfig.MAP_MAX_ATTEMPTS, 2);
  Job theJob = Job.getInstance(conf);
  theJob.setJobName("Fail-Job");

  FileInputFormat.setInputPaths(theJob, indirs);
  theJob.setMapperClass(FailMapper.class);
  theJob.setReducerClass(Reducer.class);
  theJob.setNumReduceTasks(0);
  FileOutputFormat.setOutputPath(theJob, outdir);
  theJob.setOutputKeyClass(Text.class);
  theJob.setOutputValueClass(Text.class);
  return theJob;
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
protected void setup(
		Reducer<NullWritable, Text, org.apache.hadoop.io.Text, NullWritable>.Context context)
		throws IOException, InterruptedException {
	Configuration conf = context.getConfiguration();
	this.k = conf.getInt("topk", 1);
	this.type = conf.get("type", "min");
	if("min".equals(this.type)){
		topkSet = new TreeSet<>();
	}else {	
		topkSet = new TreeSet<>(new Comparator<TFIDFWord>() {
			@Override
			public int compare(TFIDFWord o1, TFIDFWord o2) {
				return -o1.compareTo(o2);
			}
		});
	}
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
protected void reduce(NullWritable k2, Iterable<Text> v2s,
		Reducer<NullWritable, Text, Text, NullWritable>.Context context)
		throws IOException, InterruptedException {
	for (Text v2 : v2s) {
		String line = v2.toString();
		topkSet.add(new TFIDFWord(line));
		if(topkSet.size()>k){
			topkSet.pollLast();
		}
	}
	
	for (TFIDFWord v : topkSet) {
		k3.set(v.toString());
		context.write(k3, NullWritable.get());
	}
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
/**
 * Creates a simple fail job.
 * 
 * @param conf Configuration object
 * @param outdir Output directory.
 * @param indirs Comma separated input directories.
 * @return Job initialized for a simple kill job.
 * @throws Exception If an error occurs creating job configuration.
 */
public static Job createKillJob(Configuration conf, Path outdir, 
    Path... indirs) throws Exception {

  Job theJob = Job.getInstance(conf);
  theJob.setJobName("Kill-Job");

  FileInputFormat.setInputPaths(theJob, indirs);
  theJob.setMapperClass(KillMapper.class);
  theJob.setReducerClass(Reducer.class);
  theJob.setNumReduceTasks(0);
  FileOutputFormat.setOutputPath(theJob, outdir);
  theJob.setOutputKeyClass(Text.class);
  theJob.setOutputValueClass(Text.class);
  return theJob;
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
protected void reduce(BytesWritable wordtimeb, Iterable<BooleanWritable> wordBools, Reducer<BytesWritable,BooleanWritable,LongWritable,BytesWritable>.Context context) throws IOException ,InterruptedException {
	ReadWritableStringLong wordtime = IOUtils.deserialize(wordtimeb.getBytes(), ReadWritableStringLong.class);
	long time = wordtime.secondObject();
	boolean seenInPresent = false;
	boolean seenInPast = false;
	for (BooleanWritable isfrompast: wordBools) {
		boolean frompast = isfrompast.get();
		seenInPresent |= !frompast;
		seenInPast |= frompast;
		if(seenInPast && seenInPresent){
			// then we've seen all the ones from this time if we were to see them, so we can break early. MASSIVE SAVINGS HERE
			break;
		}
	}
	ReadWritableBooleanBoolean intersectionUnion = new ReadWritableBooleanBoolean(seenInPast && seenInPresent,seenInPast || seenInPresent);
	context.write(new LongWritable(time), new BytesWritable(IOUtils.serialize(intersectionUnion)));
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
protected static synchronized void loadOptions(Reducer<LongWritable, BytesWritable, NullWritable, Text>.Context context) throws IOException {
	if (options == null) {
		try {
			options = context.getConfiguration().getStrings(Values.ARGS_KEY);
			matlabOut = context.getConfiguration().getBoolean(Values.MATLAB_OUT, false);
			timeIndex = TimeIndex.readTimeCountLines(options[0]);
			if (matlabOut) {
				wordIndex = WordIndex.readWordCountLines(options[0]);
				valuesLocation = options[0] + "/values/values.%d.mat";
			}
			System.out.println("timeindex loaded: " + timeIndex.size());
		} catch (Exception e) {
			throw new IOException(e);
		}
	}
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
public void setup(final Reducer.Context context) throws IOException, InterruptedException {
    faunusConf = ModifiableHadoopConfiguration.of(DEFAULT_COMPAT.getContextConfiguration(context));

    if (!faunusConf.has(LINK_DIRECTION)) {
        Iterator<Entry<String, String>> it = DEFAULT_COMPAT.getContextConfiguration(context).iterator();
        log.error("Broken configuration missing {}", LINK_DIRECTION);
        log.error("---- Start config dump ----");
        while (it.hasNext()) {
            Entry<String,String> ent = it.next();
            log.error("k:{} -> v:{}", ent.getKey(), ent.getValue());
        }
        log.error("---- End config dump   ----");
        throw new NullPointerException();
    }
    direction = faunusConf.get(LINK_DIRECTION).opposite();
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
/**
 * Creates a simple fail job.
 * 
 * @param conf Configuration object
 * @param outdir Output directory.
 * @param indirs Comma separated input directories.
 * @return Job initialized for a simple fail job.
 * @throws Exception If an error occurs creating job configuration.
 */
public static Job createFailJob(Configuration conf, Path outdir, 
    Path... indirs) throws Exception {

  FileSystem fs = outdir.getFileSystem(conf);
  if (fs.exists(outdir)) {
    fs.delete(outdir, true);
  }
  conf.setInt("mapred.map.max.attempts", 2);
  Job theJob = Job.getInstance(conf);
  theJob.setJobName("Fail-Job");

  FileInputFormat.setInputPaths(theJob, indirs);
  theJob.setMapperClass(FailMapper.class);
  theJob.setReducerClass(Reducer.class);
  theJob.setNumReduceTasks(0);
  FileOutputFormat.setOutputPath(theJob, outdir);
  theJob.setOutputKeyClass(Text.class);
  theJob.setOutputValueClass(Text.class);
  return theJob;
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
public SequenceFileTextStage<LongWritable,BytesWritable, LongWritable,LongWritable,NullWritable,Text>stage() {
	return new SequenceFileTextStage<LongWritable,BytesWritable, LongWritable,LongWritable,NullWritable,Text>() {
		
		@Override
		public void setup(Job job) {
			job.setSortComparatorClass(LongWritable.Comparator.class);
			job.setNumReduceTasks(1);
		}
		@Override
		public Class<? extends Mapper<LongWritable, BytesWritable, LongWritable, LongWritable>> mapper() {
			return TimeIndex.Map.class;
		}
		@Override
		public Class<? extends Reducer<LongWritable, LongWritable,NullWritable,Text>> reducer() {
			return TimeIndex.Reduce.class;
		}
		
		@Override
		public String outname() {
			return "times";
		}
	};
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
public void reduce(final IntermediateProspect prospect, final Iterable<LongWritable> counts, final Date timestamp, final Reducer.Context context) throws IOException, InterruptedException {
    long sum = 0;
    for(final LongWritable count : counts) {
        sum += count.get();
    }

    final String indexType = prospect.getTripleValueType().getIndexType();

    // not sure if this is the best idea..
    if ((sum >= 0) || indexType.equals(TripleValueType.PREDICATE.getIndexType())) {
        final Mutation m = new Mutation(indexType + DELIM + prospect.getData() + DELIM + ProspectorUtils.getReverseIndexDateTime(timestamp));

        final String dataType = prospect.getDataType();
        final ColumnVisibility visibility = new ColumnVisibility(prospect.getVisibility());
        final Value sumValue = new Value(("" + sum).getBytes(StandardCharsets.UTF_8));
        m.put(COUNT, prospect.getDataType(), visibility, timestamp.getTime(), sumValue);

        context.write(null, m);
    }
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
protected void reduce(LongWritable time, java.lang.Iterable<Text> words, org.apache.hadoop.mapreduce.Reducer<LongWritable,Text,NullWritable,Text>.Context context) throws java.io.IOException ,InterruptedException {
	HashSet<String> unseenwords = new HashSet<String>();
	StringWriter writer = new StringWriter();
	
	for (Text text : words) {
		unseenwords.add(text.toString());
	}
	long intersection = 0;
	for (String string : unseenwords) {
		if(this.seenwords.contains(string)) intersection += 1;
		this.seenwords.add(string);
	}
	
	JacardIndex index = new JacardIndex(time.get(),intersection,this.seenwords.size());
	IOUtils.writeASCII(writer, index);
	context.write(NullWritable.get(), new Text(writer.toString()));
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
protected void reduce(
			Text key,
			java.lang.Iterable<Vector2SF> value,
			org.apache.hadoop.mapreduce.Reducer<Text, Vector2SF, Text, Vector2SF>.Context context)
			throws java.io.IOException, InterruptedException {
		ArrayList<Vector2SF> vs = new ArrayList<Vector2SF>();
		// sort each vector2SF by similarty
//		System.out.println("combining key: " + key + " value: " );
		for (Vector2SF v : value) {
// 			System.out.println(v.getV1() + ", " + v.getV2());
			vs.add(new Vector2SF(v.getV1(), v.getV2()));
		}
		Collections.sort(vs, new Comparator<Vector2SF>() {
			@Override
			public int compare(Vector2SF o1, Vector2SF o2) {
				return Double.compare(o2.getV2(), o1.getV2());
			}
		});
//		System.out.println("vs after sorting: " + vs);
		int k = context.getConfiguration().getInt("cn.ac.ict.htc.knn.k", 4);

		for (int i = 0; i < k && i < vs.size(); i++) {
 //			System.out.println("key: " + key + " vs[" + i + "]: " + vs.get(i));
			context.write(key, vs.get(i));
		}
	}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
public static int getInmemCubingReduceTaskNum(CubeSegment cubeSeg, CuboidScheduler cuboidScheduler)
        throws IOException {
    KylinConfig kylinConfig = cubeSeg.getConfig();

    Map<Long, Double> cubeSizeMap = new CubeStatsReader(cubeSeg, cuboidScheduler, kylinConfig).getCuboidSizeMap();
    double totalSizeInM = 0;
    for (Double cuboidSize : cubeSizeMap.values()) {
        totalSizeInM += cuboidSize;
    }

    double perReduceInputMB = kylinConfig.getDefaultHadoopJobReducerInputMB();
    double reduceCountRatio = kylinConfig.getDefaultHadoopJobReducerCountRatio();

    // number of reduce tasks
    int numReduceTasks = (int) Math.round(totalSizeInM / perReduceInputMB * reduceCountRatio);

    // at least 1 reducer by default
    numReduceTasks = Math.max(kylinConfig.getHadoopJobMinReducerNumber(), numReduceTasks);
    // no more than 500 reducer by default
    numReduceTasks = Math.min(kylinConfig.getHadoopJobMaxReducerNumber(), numReduceTasks);

    logger.info("Having total map input MB " + Math.round(totalSizeInM));
    logger.info("Having per reduce MB " + perReduceInputMB);
    logger.info("Setting " + Reducer.Context.NUM_REDUCES + "=" + numReduceTasks);
    return numReduceTasks;
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
@Override
public void reduce(LongWritable timeslot, Iterable<LongWritable> counts, Reducer<LongWritable,LongWritable,NullWritable,Text>.Context context){
	try {
		String timeStr = timeslot.toString();
		long total = 0;
		for (LongWritable count : counts) {
			total += count.get();
		}
		StringWriter swriter = new StringWriter();
		CSVPrinter writer = new CSVPrinter(swriter);
		writer.write(new String[]{timeStr,total + ""});
		writer.flush();
		String toWrote = swriter.toString();
		context.write(NullWritable.get(), new Text(toWrote));
		return;
		
	} catch (Exception e) {
		System.err.println("Couldn't reduce to final file");
	}
}
 

import org.apache.hadoop.mapreduce.Reducer; //導入依賴的package包/類
/**
 * Creates and runs an MR job
 *
 * @param conf
 * @throws IOException
 * @throws InterruptedException
 * @throws ClassNotFoundException
 */
public void createAndRunJob(Configuration conf) throws IOException,
    InterruptedException, ClassNotFoundException {
  Job job = Job.getInstance(conf);
  job.setJarByClass(TestLineRecordReaderJobs.class);
  job.setMapperClass(Mapper.class);
  job.setReducerClass(Reducer.class);
  FileInputFormat.addInputPath(job, inputDir);
  FileOutputFormat.setOutputPath(job, outputDir);
  job.waitForCompletion(true);
}