[120] | 1 | /** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 3 | * or more contributor license agreements. See the NOTICE file |
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| 4 | * distributed with this work for additional information |
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| 5 | * regarding copyright ownership. The ASF licenses this file |
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| 6 | * to you under the Apache License, Version 2.0 (the |
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| 7 | * "License"); you may not use this file except in compliance |
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| 8 | * with the License. You may obtain a copy of the License at |
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| 9 | * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 11 | * |
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| 12 | * Unless required by applicable law or agreed to in writing, software |
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| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 15 | * See the License for the specific language governing permissions and |
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| 16 | * limitations under the License. |
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| 17 | */ |
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| 18 | package org.apache.hadoop.fs; |
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| 19 | |
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| 20 | import java.io.IOException; |
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| 21 | import java.util.Iterator; |
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| 22 | |
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| 23 | import org.apache.commons.logging.Log; |
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| 24 | import org.apache.commons.logging.LogFactory; |
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| 25 | import org.apache.hadoop.io.UTF8; |
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| 26 | import org.apache.hadoop.io.WritableComparable; |
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| 27 | import org.apache.hadoop.mapred.MapReduceBase; |
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| 28 | import org.apache.hadoop.mapred.OutputCollector; |
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| 29 | import org.apache.hadoop.mapred.Reducer; |
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| 30 | import org.apache.hadoop.mapred.Reporter; |
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| 31 | |
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| 32 | /** |
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| 33 | * Reducer that accumulates values based on their type. |
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| 34 | * <p> |
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| 35 | * The type is specified in the key part of the key-value pair |
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| 36 | * as a prefix to the key in the following way |
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| 37 | * <p> |
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| 38 | * <tt>type:key</tt> |
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| 39 | * <p> |
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| 40 | * The values are accumulated according to the types: |
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| 41 | * <ul> |
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| 42 | * <li><tt>s:</tt> - string, concatenate</li> |
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| 43 | * <li><tt>f:</tt> - float, summ</li> |
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| 44 | * <li><tt>l:</tt> - long, summ</li> |
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| 45 | * </ul> |
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| 46 | * |
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| 47 | */ |
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| 48 | public class AccumulatingReducer extends MapReduceBase |
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| 49 | implements Reducer<UTF8, UTF8, UTF8, UTF8> { |
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| 50 | private static final Log LOG = LogFactory.getLog(AccumulatingReducer.class); |
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| 51 | |
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| 52 | protected String hostName; |
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| 53 | |
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| 54 | public AccumulatingReducer () { |
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| 55 | LOG.info("Starting AccumulatingReducer !!!"); |
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| 56 | try { |
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| 57 | hostName = java.net.InetAddress.getLocalHost().getHostName(); |
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| 58 | } catch(Exception e) { |
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| 59 | hostName = "localhost"; |
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| 60 | } |
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| 61 | LOG.info("Starting AccumulatingReducer on " + hostName); |
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| 62 | } |
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| 63 | |
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| 64 | public void reduce(UTF8 key, |
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| 65 | Iterator<UTF8> values, |
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| 66 | OutputCollector<UTF8, UTF8> output, |
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| 67 | Reporter reporter |
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| 68 | ) throws IOException { |
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| 69 | String field = key.toString(); |
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| 70 | |
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| 71 | reporter.setStatus("starting " + field + " ::host = " + hostName); |
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| 72 | |
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| 73 | // concatenate strings |
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| 74 | if (field.startsWith("s:")) { |
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| 75 | String sSum = ""; |
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| 76 | while (values.hasNext()) |
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| 77 | sSum += values.next().toString() + ";"; |
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| 78 | output.collect(key, new UTF8(sSum)); |
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| 79 | reporter.setStatus("finished " + field + " ::host = " + hostName); |
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| 80 | return; |
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| 81 | } |
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| 82 | // sum long values |
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| 83 | if (field.startsWith("f:")) { |
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| 84 | float fSum = 0; |
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| 85 | while (values.hasNext()) |
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| 86 | fSum += Float.parseFloat(values.next().toString()); |
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| 87 | output.collect(key, new UTF8(String.valueOf(fSum))); |
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| 88 | reporter.setStatus("finished " + field + " ::host = " + hostName); |
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| 89 | return; |
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| 90 | } |
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| 91 | // sum long values |
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| 92 | if (field.startsWith("l:")) { |
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| 93 | long lSum = 0; |
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| 94 | while (values.hasNext()) { |
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| 95 | lSum += Long.parseLong(values.next().toString()); |
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| 96 | } |
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| 97 | output.collect(key, new UTF8(String.valueOf(lSum))); |
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| 98 | } |
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| 99 | reporter.setStatus("finished " + field + " ::host = " + hostName); |
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| 100 | } |
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| 101 | } |
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