title: elasticsearch out of memory error
body: <p>We are using elasticsearch 0.90.0 and java version "1.7.0_25".
  We migrate data from oracle DB to Hadoop through a executable jar kept at DB server.after 15-20 mins of successful running, we get following exception</p>
  
  <pre><code>Caused by: java.lang.OutOfMemoryError: unable to create new native thread
      at java.lang.Thread.start0(Native Method)
      at java.lang.Thread.start(Thread.java:597)
      at java.util.concurrent.ThreadPoolExecutor.addIfUnderMaximumPoolSize(ThreadPoolExecutor.java:727)
      at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:657)
      at org.elasticsearch.common.netty.util.internal.DeadLockProofWorker.start(DeadLockProofWorker.java:38)
      at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioSelector.openSelector(AbstractNioSelector.java:343)
      at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioSelector.&lt;init&gt;(AbstractNioSelector.java:95)
      at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioWorker.&lt;init&gt;(AbstractNioWorker.java:51)
      at org.elasticsearch.common.netty.channel.socket.nio.NioWorker.&lt;init&gt;(NioWorker.java:45)
      at org.elasticsearch.common.netty.channel.socket.nio.NioWorkerPool.createWorker(NioWorkerPool.java:45)
      at org.elasticsearch.common.netty.channel.socket.nio.NioWorkerPool.createWorker(NioWorkerPool.java:28)
      at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioWorkerPool.newWorker(AbstractNioWorkerPool.java:99)
      at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioWorkerPool.init(AbstractNioWorkerPool.java:69)
      at org.elasticsearch.common.netty.channel.socket.nio.NioWorkerPool.&lt;init&gt;(NioWorkerPool.java:39)
      at org.elasticsearch.common.netty.channel.socket.nio.NioWorkerPool.&lt;init&gt;(NioWorkerPool.java:33)
      at org.elasticsearch.transport.netty.NettyTransport.doStart(NettyTransport.java:240)
      at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:85)
      at org.elasticsearch.transport.TransportService.doStart(TransportService.java:90)
      at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:85)
      at org.elasticsearch.client.transport.TransportClient.&lt;init&gt;(TransportClient.java:179)
      at org.elasticsearch.client.transport.TransportClient.&lt;init&gt;(TransportClient.java:119)
  </code></pre>
  
  <p>No exception is caught either in namenode/datanode or elasticsearch logs. This error is caught at DB Server but I think it is related to elastic search.</p>