I am using haproxy 1.5-dev21, and it seems like health check only
happens immediately on startup / after reload for the first backend
defined.
Let's say we have the following haproxy.cfg:
defaults
log global
timeout connect 5s
timeout client 30s
frontend portal :8080
mode http
option httplog
option forwardfor
option http-server-close
default_backend rails
backend rails
mode http
balance roundrobin
timeout server 300s
option redispatch
option httpchk GET /health_check
server xxx x.x.x.x:80 check # nginx with bad upstream, returns 502
server yyy y.y.y.y:80 check backup # nginx with good upstream
With `siege http://localhost:8080/` running on a separate console, we
can keep restarting / reloading haproxy without getting any 502
response. The backup server will always take over.
Next, we add the following dummy config to haproxy.cfg, below the
defaults section:
frontend dummy_frontend :1234
mode tcp
option tcplog
default_backend dummy_backend
backend dummy_backend
mode tcp
balance roundrobin
timeout server 30s
server dummy localhost:5678 check
With `siege http://localhost:8080/` running on a separate console, we
now get a bunch of 502 responses with each restart / reload of
haproxy. It seems like health check for the rails backend doesn't
happen immediately after startup / reload anymore. The gap is much
smaller than the default health check interval of 2 seconds, but there
is still a gap.
