title: yarn [hadoop 2.2] where is the location mapper or reducer log outputed?
body: <p>I want to check the log mapper or reducer output ？I can not find it in syslog under container foler?So where is the log outputing?</p>
  
  <pre><code>        public class SkipStat {
  private static Log log = LogFactory.getLog(SkipStat.class);
  
  private static BlockWorkerRepository blockWorkerRepository;
  static {
      blockWorkerRepository = new BlockWorkerRepositoryImpl();
  }
  
  private static class SkipInfoMapper extends Mapper&lt;Object, BSONObject, Text, AssignmentWritable&gt; {
  
      private final String invalidResult = "^";
  
      private static final Calendar currentCalendar = Calendar.getInstance();
      static {
          currentCalendar.add(Calendar.HOUR, -24);
      }
  
      protected void map(Object key, BSONObject value, Context context) throws IOException, InterruptedException {
          String result = (String) value.get("result");
          log.info("lol... get one result " + result); // LOG ...
          if (invalidResult.equals(result)) {
  </code></pre>