Apache Reverse Proxy Java Application Server CLOSE_WAIT Connections
This is a known issue with mod_proxy, since 2011.
The ttl needs to be shorter than the application's keepalive, so that apache is always first to send a FIN.
Another difficulty is it's not defined at what point the connection will actually be closed.
ttl - Time to live for inactive connections and associated connection pool entries, in seconds. Once reaching this limit, a connection will not be used again; it will be closed at some later time.