Passive healthcheck for UDP

Sékine Coulibaly scoulibaly at
Mon Apr 24 15:58:34 UTC 2017


I'm gathering some information regarding UDP load balancing. I've come
accross this in and I'm quite
puzzled :

"NGINX can mark the server as unavailable and stop sending UDP datagrams to
it for some time if the server replies with an error or times out.
The number of consecutive failed connection attempts within a certain time
period is set with the max_fails parameter for an upstream server (default
value is 1)."

What is unclear to me is the "failed connection attempt" term. UDP being a
connectionless protocol, it's unclear what is the actual method used by
NGINX to decide whether a passive health check is successfull or not. Would
the existence of traffic from server to Nginx be a sign of success or are
other methods involved ?

Thank you

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