ex2/mapreduce/SomeMapReduce_ex2a.java

   1 // Created as a template for  Advanced Database Systems 2019
   2
   3 import java.io.*;
   4 import java.util.*;
   5 import org.apache.hadoop.conf.Configuration;
   6 import org.apache.hadoop.fs.Path;
   7 import org.apache.hadoop.io.*;
   8 import org.apache.hadoop.mapreduce.*;
   9 import org.apache.hadoop.mapreduce.lib.input.*;
  10 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
  11
  12 import org.apache.commons.logging.*;
  13
  14
  15 public class SomeMapReduce_ex2a {
  16     public static class TextArrayWritable extends ArrayWritable {
  17         public TextArrayWritable(){
  18             super(Text.class);
  19         }
  20         public TextArrayWritable(String[] strings) {
  21             super(Text.class);
  22             Text[] texts = new Text[strings.length];
  23             for (int i = 0; i < strings.length; i++) {
  24                 texts[i] = new Text(strings[i]);
  25             }
  26             set(texts);
  27         }
  28     }
  29
  30     public static class MyMapper extends Mapper<Object, Text, Text, TextArrayWritable> {
  31         public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
  32             String[] result = CSVSplitter.split(value.toString());
  33
  34             try{
  35                 // format: key: author. vals: mappertype, title, checkouts
  36                 context.write(new Text(result[7]), new TextArrayWritable(new String[]{"MyMapper", result[6].toString(), Integer.toString(Integer.parseInt(result[5]))}));
  37             }catch(NumberFormatException e){} // not an integer (csv header line) or no value.
  38         }
  39     }
  40     public static class MyOtherMapper extends Mapper<Object, Text, Text, TextArrayWritable> {
  41         public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
  42             String[] result = CSVSplitter.split(value.toString());
  43             // format: key: author. vals: mappertype, title, pubyear, subjects, itemlocation
  44             context.write(new Text(result[2]), new TextArrayWritable(new String[]{"MyOtherMapper", result[1].toString(), result[4].toString(), result[6].toString(), result[10].toString()}));
  45         }
  46     }
  47
  48     public static class MyReducer extends Reducer<Text, TextArrayWritable, Text, Text> {
  49         private static final Log LOG = LogFactory.getLog(MyReducer.class);
  50
  51         public void reduce(Text key, Iterable<TextArrayWritable> values, Context context) throws IOException, InterruptedException {
  52             HashMap<String,String[]> hm = new HashMap<String,String[]>();
  53             String[] max = new String[]{"none", "title", "0"};
  54
  55             for (TextArrayWritable val : values) {
  56                 String[] vals = val.toStrings();
  57                 if ("MyOtherMapper".equals(vals[0])){
  58                     hm.put(key.toString()+"_"+vals[1], vals);
  59                 }else{
  60                     if (max == null){
  61                         max = vals;
  62                         continue;
  63                     }
  64                     if (Integer.parseInt(max[2]) < Integer.parseInt(vals[2])){
  65                         max = vals;
  66                         continue;
  67                     }
  68                 }
  69             }
  70
  71             if(Integer.parseInt(max[2]) > 0 && hm.containsKey(key.toString()+"_"+max[1])) {
  72                 String[] additionalData = hm.get(key.toString()+"_"+max[1]);
  73                 // format: key: author. vals: title, pubyear, subjects, itemlocation
  74                 context.write(key, new Text(max[1]+","+additionalData[1]+","+additionalData[2]+","+additionalData[3]));
  75             }
  76         }
  77     }
  78     public static void main(String[] args) throws Exception {
  79         Configuration conf1 = new Configuration();
  80         conf1.set("mapreduce.output.textoutputformat.separator",",");  // This ensures that output is comma separated
  81         Job job = Job.getInstance(conf1);
  82         job.setJarByClass(SomeMapReduce_ex2a.class);
  83         job.setOutputKeyClass(Text.class);
  84         job.setOutputValueClass(Text.class);
  85         job.setMapOutputKeyClass(Text.class);
  86         job.setMapOutputValueClass(TextArrayWritable.class);
  87         job.setReducerClass(MyReducer.class);
  88 //    job.setNumReduceTasks(8);     // Uncomment this to run the job with more than one Reduce tasks. Depending on the system, this may produce a speedup.
  89         MultipleInputs.addInputPath(job, new Path(args[2]), TextInputFormat.class, MyOtherMapper.class);
  90         MultipleInputs.addInputPath(job, new Path(args[1]), TextInputFormat.class, MyMapper.class);
  91         FileOutputFormat.setOutputPath(job, new Path(args[0]));
  92         boolean status = job.waitForCompletion(true);
  93         if (status) {
  94             System.exit(0);
  95         } else {
  96             System.exit(1);
  97         }
  98     }
  99 }