title: How does back pressure property work in Spark Streaming?
body: <p>I have a CustomReceiver which receives a single event(String).The received single event is used during spark application's run time to read data from nosql and to apply transformations.When the processing time for each batch was observed to be greater than batch interval I set this property.</p>
  
  <p><strong>spark.streaming.backpressure.enabled=true</strong></p>
  
  <p>After which I expected the CustomReceiver to not trigger and receive the event when a batch is processing longer than batch window, which didn't happen and still a backlog of batches were being added. Am I missing something here?</p>