title: What resources leak when Kafka producer is not closed?
body: <p>Reading kafka documentation i got to know we have to close kafka producer after the use else resources will leak.
  In multi threaded programs lets assume if it has been used by various threads and only one kafka producer instance was opened and not closed. Will not JVM mark it for GC if all threads have stopped/crashed? 
  there should be some timespan for producer if its not being used then close the connection and re create the instance.</p>
  
  <p>what kind of resources will leak here. Are they the no of producer instance or the threads that handle producers to send requests.</p>