Hiya - yep it's definitely the plugin, I tried without an no open conns. The conns are all to the defined listener ports on the app servers.
The one ESTABLISHED connection seems to survive for around 10 seconds before going into TIME_WAIT and being replaced by another ESTABLISHED connection. For a single request it gets to a point of a constant number of conns in ESTABLISHED or TIME_WAIT as the older waiting conns drop off, to be replaced each time a new established connection is made. For a single request with apache configured with startservers=1 & maxclients=1, this seems to be 13 conns in TIME_WAIT and 1 ESTABLISHED at any one time.
Could this be due to the app server terminating the connection after 10 secs, and the load balancer reinitialising after it's seeing a connection dropped (unexpectedly?).
I ran truss which didn't tell me too much without seeing the source but there were a number of errors reported - EAGAIN & EINPROGRESS roughly in equal measure.
I noticed this post but it's impossible to determine if it's related -
http://forums.java.net/jive/thread.jspa?messageID=155501𥽭
[Message sent by forum member 'ocoro02' (ocoro02)]
http://forums.java.net/jive/thread.jspa?messageID=239182