Once upon a time, Patrick W. Gilmore <patrick () ianai net> said:
* How many applications are even aware multiple addresses were returned?
Most anything that supports IPv6 should handle this correctly, since
getaddrinfo() will return a list of addresses to try.
* How do you guarantee sub-second failover when most apps will wait longer
than one second to see if an address responds?
That's a bigger issue. Also, for web services, the application might
wait, but the end-user usually won't (if the site doesn't come up in a
second, they move on to the something else).