code: public synchronized void cleanup()
      {
          stateCheck(State.SHUTDOWN);
          io.netty.util.concurrent.FastThreadLocal.removeAll();
          io.netty.util.concurrent.FastThreadLocal.destroy();
      }
docs: Cleans up any Thread-Local variables after shutdown.
  This operation is useful when you are in a container environment, and you
  do not want to leave the thread local variables in the threads you do not manage.
  Call this method when your application is being unloaded from the container, <b>after</b>
  all {@link RiakNode}, {@link RiakCluster}, and {@link com.basho.riak.client.api.RiakClient}
  objects are in the shutdown state.