The Executor represents a thread pool that can be shared 
     between components in Tomcat. Historically there has been a thread pool per
     connector created but this allows you to share a thread pool, between (primarly) connector
     but also other components when those get configured to support executors
  The executor has to implement the org.apache.catalina.Executor interface.
  
  The executor is a nested element to the Service element.
     And in order for it to be picked up by the connectors, the Executor element has to appear
     prior to the Connector element in server.xml