tez-examples/src/main/java/org/apache/tez/examples/OrderedWordCount.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.tez.examples;

import java.io.IOException;

import org.apache.tez.client.CallerContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.ToolRunner;
import org.apache.tez.client.TezClient;
import org.apache.tez.dag.api.DAG;
import org.apache.tez.dag.api.DataSinkDescriptor;
import org.apache.tez.dag.api.DataSourceDescriptor;
import org.apache.tez.dag.api.Edge;
import org.apache.tez.dag.api.ProcessorDescriptor;
import org.apache.tez.dag.api.TezConfiguration;
import org.apache.tez.dag.api.Vertex;
import org.apache.tez.examples.WordCount.TokenProcessor;
import org.apache.tez.mapreduce.input.MRInput;
import org.apache.tez.mapreduce.output.MROutput;
import org.apache.tez.mapreduce.processor.SimpleMRProcessor;
import org.apache.tez.runtime.api.ProcessorContext;
import org.apache.tez.runtime.library.api.KeyValueWriter;
import org.apache.tez.runtime.library.api.KeyValuesReader;
import org.apache.tez.runtime.library.conf.OrderedPartitionedKVEdgeConfig;
import org.apache.tez.runtime.library.partitioner.HashPartitioner;
import org.apache.tez.runtime.library.processor.SimpleProcessor;

import org.apache.tez.common.Preconditions;

/**
 * Simple example that extends the WordCount example to show a chain of processing.
 * The example extends WordCount by sorting the words by their count.
 */
public class OrderedWordCount extends TezExampleBase {
  
  private static String INPUT = WordCount.INPUT;
  private static String OUTPUT = WordCount.OUTPUT;
  private static String TOKENIZER = WordCount.TOKENIZER;
  private static String SUMMATION = WordCount.SUMMATION;
  private static String SORTER = "Sorter";
  private static final Logger LOG = LoggerFactory.getLogger(OrderedWordCount.class);

  /*
   * SumProcessor similar to WordCount except that it writes the count as key and the 
   * word as value. This is because we can and ordered partitioned key value edge to group the 
   * words with the same count (as key) and order the counts.
   */
  public static class SumProcessor extends SimpleProcessor {
    public SumProcessor(ProcessorContext context) {
      super(context);
    }

    @Override
    public void run() throws Exception {
      Preconditions.checkArgument(getInputs().size() == 1);
      Preconditions.checkArgument(getOutputs().size() == 1);
      // the recommended approach is to cast the reader/writer to a specific type instead
      // of casting the input/output. This allows the actual input/output type to be replaced
      // without affecting the semantic guarantees of the data type that are represented by
      // the reader and writer.
      // The inputs/outputs are referenced via the names assigned in the DAG.
      KeyValueWriter kvWriter = (KeyValueWriter) getOutputs().get(SORTER).getWriter();
      KeyValuesReader kvReader = (KeyValuesReader) getInputs().get(TOKENIZER).getReader();
      while (kvReader.next()) {
        Text word = (Text) kvReader.getCurrentKey();
        int sum = 0;
        for (Object value : kvReader.getCurrentValues()) {
          sum += ((IntWritable) value).get();
        }
        // write the sum as the key and the word as the value
        kvWriter.write(new IntWritable(sum), word);
      }
    }
  }
  
  /**
   * No-op sorter processor. It does not need to apply any logic since the ordered partitioned edge 
   * ensures that we get the data sorted and grouped by the the sum key.
   */
  public static class NoOpSorter extends SimpleMRProcessor {

    public NoOpSorter(ProcessorContext context) {
      super(context);
    }

    @Override
    public void run() throws Exception {
      Preconditions.checkArgument(getInputs().size() == 1);
      Preconditions.checkArgument(getOutputs().size() == 1);
      KeyValueWriter kvWriter = (KeyValueWriter) getOutputs().get(OUTPUT).getWriter();
      KeyValuesReader kvReader = (KeyValuesReader) getInputs().get(SUMMATION).getReader();
      while (kvReader.next()) {
        Object sum = kvReader.getCurrentKey();
        for (Object word : kvReader.getCurrentValues()) {
          kvWriter.write(word, sum);
        }
      }
      // deriving from SimpleMRProcessor takes care of committing the output
    }
  }
  
  public static DAG createDAG(TezConfiguration tezConf, String inputPath, String outputPath,
      int numPartitions, boolean disableSplitGrouping, boolean isGenerateSplitInClient, String dagName) throws IOException {

    DataSourceDescriptor dataSource = MRInput.createConfigBuilder(new Configuration(tezConf),
        TextInputFormat.class, inputPath).groupSplits(!disableSplitGrouping)
          .generateSplitsInAM(!isGenerateSplitInClient).build();

    DataSinkDescriptor dataSink = MROutput.createConfigBuilder(new Configuration(tezConf),
        TextOutputFormat.class, outputPath).build();

    Vertex tokenizerVertex = Vertex.create(TOKENIZER, ProcessorDescriptor.create(
        TokenProcessor.class.getName()));
    tokenizerVertex.addDataSource(INPUT, dataSource);

    // Use Text key and IntWritable value to bring counts for each word in the same partition
    // The setFromConfiguration call is optional and allows overriding the config options with
    // command line parameters.
    OrderedPartitionedKVEdgeConfig summationEdgeConf = OrderedPartitionedKVEdgeConfig
        .newBuilder(Text.class.getName(), IntWritable.class.getName(),
            HashPartitioner.class.getName())
        .setFromConfiguration(tezConf)
        .build();

    // This vertex will be reading intermediate data via an input edge and writing intermediate data
    // via an output edge.
    Vertex summationVertex = Vertex.create(SUMMATION, ProcessorDescriptor.create(
        SumProcessor.class.getName()), numPartitions);
    
    // Use IntWritable key and Text value to bring all words with the same count in the same 
    // partition. The data will be ordered by count and words grouped by count. The
    // setFromConfiguration call is optional and allows overriding the config options with
    // command line parameters.
    OrderedPartitionedKVEdgeConfig sorterEdgeConf = OrderedPartitionedKVEdgeConfig
        .newBuilder(IntWritable.class.getName(), Text.class.getName(),
            HashPartitioner.class.getName())
        .setFromConfiguration(tezConf)
        .build();

    // Use 1 task to bring all the data in one place for global sorted order. Essentially the number
    // of partitions is 1. So the NoOpSorter can be used to produce the globally ordered output
    Vertex sorterVertex = Vertex.create(SORTER, ProcessorDescriptor.create(
        NoOpSorter.class.getName()), 1);
    sorterVertex.addDataSink(OUTPUT, dataSink);

    // No need to add jar containing this class as assumed to be part of the tez jars.
    
    DAG dag = DAG.create(dagName);
    dag.addVertex(tokenizerVertex)
        .addVertex(summationVertex)
        .addVertex(sorterVertex)
        .addEdge(
            Edge.create(tokenizerVertex, summationVertex,
                summationEdgeConf.createDefaultEdgeProperty()))
        .addEdge(
            Edge.create(summationVertex, sorterVertex, sorterEdgeConf.createDefaultEdgeProperty()));
    return dag;  
  }

  @Override
  protected void printUsage() {
    System.err.println("Usage: " + " orderedwordcount in out [numPartitions]");
  }


  @Override
  protected int validateArgs(String[] otherArgs) {
    if (otherArgs.length < 2 || otherArgs.length > 3) {
      return 2;
    }
    return 0;
  }

  @Override
  protected int runJob(String[] args, TezConfiguration tezConf,
      TezClient tezClient) throws Exception {
    DAG dag = createDAG(tezConf, args[0], args[1],
        args.length == 3 ? Integer.parseInt(args[2]) : 1, isDisableSplitGrouping(),
        isGenerateSplitInClient(), "OrderedWordCount");
    LOG.info("Running OrderedWordCount");
    return runDag(dag, isCountersLog(), LOG);
  }

  public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(new Configuration(), new OrderedWordCount(), args);
    System.exit(res);
  }
}