src/test/java/org/apache/hadoop/mrunit/mapreduce/TestCounters.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.mrunit.mapreduce;

import static org.junit.Assert.assertEquals;

import java.io.IOException;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.junit.Test;

/**
 * Test counters usage in various drivers.
 */
public class TestCounters {

  private static final String GROUP = "GROUP";
  private static final String ELEM = "ELEM";

  private class CounterMapper extends Mapper<Text, Text, Text, Text> {
    @Override
    public void map(final Text k, final Text v, final Context context)
        throws IOException, InterruptedException {

      context.getCounter(GROUP, ELEM).increment(1);

      // Emit the same (k, v) pair twice.
      context.write(k, v);
      context.write(k, v);
    }
  }

  private class CounterReducer extends Reducer<Text, Text, Text, Text> {
    @Override
    public void reduce(final Text k, final Iterable<Text> vals,
        final Context context) throws IOException, InterruptedException {

      for (final Text val : vals) {
        context.getCounter(GROUP, ELEM).increment(1);
        context.write(k, val);
      }
    }
  }

  @Test
  public void testMapper() throws IOException {
    final Mapper<Text, Text, Text, Text> mapper = new CounterMapper();
    final MapDriver<Text, Text, Text, Text> driver = MapDriver
        .newMapDriver(mapper);
    driver.withInput(new Text("foo"), new Text("bar")).run();
    assertEquals("Expected 1 counter increment", 1, driver.getCounters()
        .findCounter(GROUP, ELEM).getValue());
  }

  @Test
  public void testReducer() throws IOException {
    final Reducer<Text, Text, Text, Text> reducer = new CounterReducer();
    final ReduceDriver<Text, Text, Text, Text> driver = ReduceDriver
        .newReduceDriver(reducer);
    driver.withInputKey(new Text("foo")).withInputValue(new Text("bar")).run();
    assertEquals("Expected 1 counter increment", 1, driver.getCounters()
        .findCounter(GROUP, ELEM).getValue());
  }

  @Test
  public void testMapReduce() throws IOException {
    final Mapper<Text, Text, Text, Text> mapper = new CounterMapper();
    final Reducer<Text, Text, Text, Text> reducer = new CounterReducer();
    final MapReduceDriver<Text, Text, Text, Text, Text, Text> driver = MapReduceDriver
        .newMapReduceDriver(mapper, reducer);

    driver.withInput(new Text("foo"), new Text("bar")).run();

    assertEquals("Expected counter=3", 3,
        driver.getCounters().findCounter(GROUP, ELEM).getValue());
  }
}