title: AWS EMR Auto Scaling
body: <p>I was looking into Hive on AWS (EMR to be particular). They have provide two options</p>
  
  <ol>
  <li>Spawning an Ad-hoc cluster, wherein the EMR cluster is teared-down after execution of a pre-specified Hive query (in bootstrap) is evaluated.</li>
  <li>Spawning a Hive cluster in interactive mode where one can SSH to the master and provide Hive queries using the <code>hive</code> command line client.</li>
  </ol>
  
  <p>Obviously in 2nd option the cluster will remain alive until explicitly asked to be terminated.</p>
  
  <p>I want to modify number of slave nodes in a keep alive hive cluster. I read in <a href="http://aws.amazon.com/elasticmapreduce/faqs/#cluster-16" rel="nofollow">emr faq</a> that it just supports addition and removal of <code>task-nodes</code> but mere addition (but not removal) of <code>core-nodes</code>. Core-nodes contribute to HDFS storage but task-nodes do not.</p>
  
  <p>I want to add more core nodes to a running cluster and scale them down when number of queries being run is less. Is there a way to achieve this (may be using cloudwatch)?</p>