title: HDFS file watcher
body: <p>Can I have <strong>file watcher</strong> on <strong>HDFS</strong>?</p>
  
  <p><strong>Scenario:</strong>
  The files are landing on HDFS continuously.I want to start a Spark Job once the number of files reached a threshold(it can be number of files or size of the files).</p>
  
  <p>Is it possible to implement file watcher on HDFS to achieve this . If yes, then can anyone suggest the way to do it?What are the different options available? Can the Zookeeper or the Oozie do it?</p>
  
  <p>Any help will be appreciated.Thanks.</p>