src/main/java/org/apache/hadoop/mrunit/mapreduce/ReduceDriver.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.apache.hadoop.mrunit.internal.util.ArgumentChecker.*;

import java.io.IOException;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.mapreduce.Counters;
import org.apache.hadoop.mapreduce.InputFormat;
import org.apache.hadoop.mapreduce.OutputFormat;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mrunit.ReduceDriverBase;
import org.apache.hadoop.mrunit.internal.counters.CounterWrapper;
import org.apache.hadoop.mrunit.internal.mapreduce.ContextDriver;
import org.apache.hadoop.mrunit.internal.mapreduce.MockReduceContextWrapper;
import org.apache.hadoop.mrunit.types.Pair;

/**
 * Harness that allows you to test a Reducer instance. You provide a key and a
 * set of intermediate values for that key that represent inputs that should be
 * sent to the Reducer (as if they came from a Mapper), and outputs you expect
 * to be sent by the Reducer to the collector. By calling runTest(), the harness
 * will deliver the input to the Reducer and will check its outputs against the
 * expected results.
 */
public class ReduceDriver<K1, V1, K2, V2> extends
    ReduceDriverBase<K1, V1, K2, V2, ReduceDriver<K1, V1, K2, V2>> implements
    ContextDriver {

  public static final Log LOG = LogFactory.getLog(ReduceDriver.class);

  private Reducer<K1, V1, K2, V2> myReducer;
  private Counters counters;

  private final MockReduceContextWrapper<K1, V1, K2, V2> wrapper = new MockReduceContextWrapper<K1, V1, K2, V2>(
      inputs, mockOutputCreator, this);


  public ReduceDriver(final Reducer<K1, V1, K2, V2> r) {
    this();
    setReducer(r);
  }

  public ReduceDriver() {
    setCounters(new Counters());
  }

  /**
   * Sets the reducer object to use for this test
   * 
   * @param r
   *          The reducer object to use
   */
  public void setReducer(final Reducer<K1, V1, K2, V2> r) {
    myReducer = returnNonNull(r);
  }

  /**
   * Identical to setReducer(), but with fluent programming style
   * 
   * @param r
   *          The Reducer to use
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withReducer(
      final Reducer<K1, V1, K2, V2> r) {
    setReducer(r);
    return this;
  }

  public Reducer<K1, V1, K2, V2> getReducer() {
    return myReducer;
  }

  /** @return the counters used in this test */
  @Override
  public Counters getCounters() {
    return counters;
  }

  /**
   * Sets the counters object to use for this test.
   * 
   * @param ctrs
   *          The counters object to use.
   */
  public void setCounters(final Counters ctrs) {
    this.counters = ctrs;
    counterWrapper = new CounterWrapper(ctrs);
  }

  /** Sets the counters to use and returns self for fluent style */
  public ReduceDriver<K1, V1, K2, V2> withCounters(final Counters ctrs) {
    setCounters(ctrs);
    return this;
  }

  @SuppressWarnings("rawtypes")
  public ReduceDriver<K1, V1, K2, V2> withOutputFormat(
      final Class<? extends OutputFormat> outputFormatClass,
      final Class<? extends InputFormat> inputFormatClass) {
    mockOutputCreator.setMapreduceFormats(outputFormatClass, inputFormatClass);
    return this;
  }

  @Override
  public List<Pair<K2, V2>> run() throws IOException {
    try {
      preRunChecks(myReducer);
      initDistributedCache();
      myReducer.run(wrapper.getMockContext());
      return wrapper.getOutputs();
    } catch (final InterruptedException ie) {
      throw new IOException(ie);
    } finally {
      cleanupDistributedCache();
    }
  }

  @Override
  public String toString() {
    return "ReduceDriver (0.20+) (" + myReducer + ")";
  }

  /**
   * <p>Obtain Context object for furthering mocking with Mockito.
   * For example, causing write() to throw an exception:</p>
   * 
   * <pre>
   * import static org.mockito.Matchers.*;
   * import static org.mockito.Mockito.*;
   * doThrow(new IOException()).when(context).write(any(), any());
   * </pre>
   * 
   * <p>Or implement other logic:</p>
   * 
   * <pre>
   * import static org.mockito.Matchers.*;
   * import static org.mockito.Mockito.*;
   * doAnswer(new Answer<Object>() {
   *    public Object answer(final InvocationOnMock invocation) {
   *    ...
   *     return null;
   *   }
   * }).when(context).write(any(), any());
   * </pre>
   * @return the mocked context
   */
  public Reducer<K1, V1, K2, V2>.Context getContext() {
    return wrapper.getMockContext();
  }

  /**
   * Returns a new ReduceDriver without having to specify the generic types on
   * the right hand side of the object create statement.
   * 
   * @return new ReduceDriver
   */
  public static <K1, V1, K2, V2> ReduceDriver<K1, V1, K2, V2> newReduceDriver() {
    return new ReduceDriver<K1, V1, K2, V2>();
  }

  /**
   * Returns a new ReduceDriver without having to specify the generic types on
   * the right hand side of the object create statement.
   * 
   * 
   * @param reducer
   *          passed to ReduceDriver constructor
   * @return new ReduceDriver
   */
  public static <K1, V1, K2, V2> ReduceDriver<K1, V1, K2, V2> newReduceDriver(
      final Reducer<K1, V1, K2, V2> reducer) {
    return new ReduceDriver<K1, V1, K2, V2>(reducer);
  }
}