title: MapOutputTrackerMasterEndpoint output in Spark is slowing my jobs. What does it mean?
body: <p>I am getting this output in my spark jobs, and it is adding a lot of latency to my jobs. Just yesterday, I left the job running at this message overnight, and came home to see that nothing more has processed.</p>
  
  <pre><code>16/01/08 18:51:36 INFO spark.MapOutputTrackerMaster: Size of output statuses for shuffle 0 is 930564 bytes
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.47:37232
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.44:55904
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.38:35491
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.43:60071
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.48:39267
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.39:44310
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.42:51390
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.32:36981
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.30:39261
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.34:58811
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.31:39829
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.40:45521
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.46:35892
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.33:35119
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.36:44486
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.37:35971
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.35:59625
  16/01/08 18:51:36 INFO spark.MapOutputTrackerMasterEndpoint: Asked to send map output locations for shuffle 0 to 172.31.1.45:40861
  </code></pre>
  
  <p>I tried googling it, but documentation was sparse and I could not really understand. Does any one know?</p>