I am using haproxy version 1.6.3 and my server is defined using dns.
It is an ELB in amazon web services so it changes IP addresses frequently and that functionality seems to work fine. However, if I delete the DNS entry, the server is not marked down. It then has no way to see updates and keeps sending traffic to the IP address that existed before the DNS entry was deleted.
resolvers dns
nameserver AmazonDNS 169.254.169.253:53
hold valid 1s
backend blue
server blue website.localdomain.org:80 resolvers dns check inter 1000