title: AWS Glue not using all executors
body: <p>I am using some AWS glue to perform some ETL operations. My program writes a computed dataframe to S3. When I look at the metrics, i find that not all my executors are being used, infact just one is being used.
  How do I make sure all my allocated executors are being busy ?
  Thanks.
  I do not use gluecontext in my program just native sparkcontext</p>