title: Drop null Flume events before sending to channel
body: <p>I had read in a Flume book that if in the intercept method of interceptor an event is returned as null, the event will be dropped. Hence i have created a custom interceptor which on basis of a condition returns the event as null like:</p>
  
  <pre><code>public Event intercept(Event event) {
      // TODO Auto-generated method stub
      Event finalEvent = event;
      check = new String(event.getBody(),Charsets.UTF_8);
  
      if(check.matches("([0-9]-.+?-.+?-[0-9][0-9]+)")){
  
          try {
              fileWriter.append(new String(event.getBody(),Charsets.UTF_8)+ "\n");
          } catch (IOException e) {
              // TODO Auto-generated catch block
              e.printStackTrace();
          }
          finalEvent = null;
      }
      System.out.println("Event is : " + finalEvent);
      return finalEvent;
  }
  </code></pre>
  
  <p>The interceptor emits null event but the file channel still passes it to the HDFS sink as empty. Why doesn't the event get dropped?? I am using Spooling directory as source.</p>