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