I noticed that in ngx_http_proxy_module

proxy_pass http://localhost:8000/uri/;
"If a domain name resolves to several addresses, all of them will be
used in a round-robin fashion. In addition, an address can be
specified as a server group."

However this can be confusing for end users who innocently put the
domain name "localhost" then find that round-robin across ipv6 and
ipv4 is occurring, ref:
https://stackoverflow.com/a/58924751/32453
https://stackoverflow.com/a/52550758/32453

Suggestion/feature request: If a domain name resolves to several
addresses, log a warning in error.log file somehow, or at least in the
output of -T, to warn somehow. Then there won't be unexpected
round-robins occurring and "supposedly single" servers being
considered unavailable due to timeouts, surprising people like myself.

Thank you for your attention, and for nginx, it's rocking fast! :)

-Roger Pack-
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