Hey @lukastribus! Thanks for your help, we’ve managed to figure out some additional stuff: There’s a client, that does small http POST requests every 60 seconds, and client|server timeouts are also set to 60 sec. So we came up with theory, that frontend/backend connection might be closing at the moment of forwarding client request to backend resulting in the above-described behavior. To test this theory, we simply bumped up client|server timeouts to 70 sec, and errors are gone now (there used to be around 6-10 errors per 24 hours, 0 errors for straight 3 days of testing new config).
I wonder if there’s some kind of race condition in haproxy? In theory, once http request is sent successfully from client, haproxy should be aware of it and not end up closing the connection.