Haproxy doesn't retry to another backend on 503 error

[lukastribus]

Also see:

Redispatch ERROR 503

Redispatch is NOT a magic bullet for server problems, and all those 503 are server generated. https://cbonte.github.io/haproxy-dconv/2.2/configuration.html#4.2-retry-on Requests not fitting in a single buffer will never be retried (see the global tune.bufsize setting). Many of those requests are POST requests and probably don’t fit the buffer size.