title: Spark job is getting stuck with connection manager issue
body: <p>My app gets stuck with this message..</p>
  
  <p><code>
  14/09/10 18:11:45 INFO ConnectionManager: Accepted connection from [ip-xx-xx-xxx-xx.ec2.internal/10.33.139.85]
  14/09/10 18:11:46 INFO SendingConnection: Initiating connection to [ip-1xx-xx-xxx-xx.ec2.internal/10.33.139.85:44309]
  14/09/10 18:11:46 INFO SendingConnection: Connected to [ip-xx-xx-xxx-xx.ec2.internal/10.33.139.85:44309], 1 messages pending
  </code></p>
  
  <p>I'm executing this on EMR cluster as a step.</p>
  
  <p>Spark version : 1.0.1 [Hadoop 2.2]</p>
  
  <p>Kindly request some suggestions ....</p>