001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapred.lib.aggregate;
020
021import java.io.IOException;
022import java.util.ArrayList;
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.classification.InterfaceStability;
026import org.apache.hadoop.io.Text;
027import org.apache.hadoop.io.Writable;
028import org.apache.hadoop.io.WritableComparable;
029import org.apache.hadoop.mapred.JobConf;
030import org.apache.hadoop.mapred.Mapper;
031import org.apache.hadoop.mapred.Reducer;
032
033/**
034 * This abstract class implements some common functionalities of the
035 * the generic mapper, reducer and combiner classes of Aggregate.
036 */
037@InterfaceAudience.Public
038@InterfaceStability.Stable
039public abstract class ValueAggregatorJobBase<K1 extends WritableComparable,
040                                             V1 extends Writable>
041  implements Mapper<K1, V1, Text, Text>, Reducer<Text, Text, Text, Text> {
042
043  protected ArrayList<ValueAggregatorDescriptor> aggregatorDescriptorList = null;
044
045  public void configure(JobConf job) {
046    this.initializeMySpec(job);
047    this.logSpec();
048  }
049
050  private static ValueAggregatorDescriptor getValueAggregatorDescriptor(
051      String spec, JobConf job) {
052    if (spec == null)
053      return null;
054    String[] segments = spec.split(",", -1);
055    String type = segments[0];
056    if (type.compareToIgnoreCase("UserDefined") == 0) {
057      String className = segments[1];
058      return new UserDefinedValueAggregatorDescriptor(className, job);
059    }
060    return null;
061  }
062
063  private static ArrayList<ValueAggregatorDescriptor> getAggregatorDescriptors(JobConf job) {
064    String advn = "aggregator.descriptor";
065    int num = job.getInt(advn + ".num", 0);
066    ArrayList<ValueAggregatorDescriptor> retv = new ArrayList<ValueAggregatorDescriptor>(num);
067    for (int i = 0; i < num; i++) {
068      String spec = job.get(advn + "." + i);
069      ValueAggregatorDescriptor ad = getValueAggregatorDescriptor(spec, job);
070      if (ad != null) {
071        retv.add(ad);
072      }
073    }
074    return retv;
075  }
076
077  private void initializeMySpec(JobConf job) {
078    this.aggregatorDescriptorList = getAggregatorDescriptors(job);
079    if (this.aggregatorDescriptorList.size() == 0) {
080      this.aggregatorDescriptorList
081          .add(new UserDefinedValueAggregatorDescriptor(
082              ValueAggregatorBaseDescriptor.class.getCanonicalName(), job));
083    }
084  }
085
086  protected void logSpec() {
087
088  }
089
090  public void close() throws IOException {
091  }
092}