I have a machine running Haproxy. Under heavy load, I can see that all the response codes are 503. The back end server for a lot of the entries in the log file is NOSRV, but not all:
https_proxy https_proxy/NOSRV -1/1/2/-1/1034 503 https_proxy https_proxy/MYSERVER3 -1/1/0/-1/562 503
(removed angle brackets around NOSRV above as wasn't displaying properly with them)
MYSERVER3 has a lot of connections in CLOSE_WAIT. I'm not sure how to approach the problem - perhaps forceclose in Haproxy, increase kernel parameter net.core.somaxconn on the Haproxy box, something else?
Any guidance greatly appreciated.