code: public synchronized boolean statusUpdate(TaskAttemptID taskid,
                                                TaskStatus taskStatus)
    throws IOException {
      TaskInProgress tip = tasks.get(taskid);
      if (tip != null) {
        tip.reportProgress(taskStatus);
        myInstrumentation.statusUpdate(tip.getTask(), taskStatus);
        return true;
      } else {
        if (LOG.isDebugEnabled()) {
          LOG.debug("Progress from unknown child task: "+taskid);
        }
        return false;
      }
    }
docs: Called periodically to report Task progress, from 0.0 to 1.0.