You can try to use this module to resolve the DNS ;)
https://github.com/GUI/nginx-upstream-dynamic-servers

On Wed, Mar 16, 2016 at 1:34 PM, Valentin V. Bartenev <vbart@nginx.com>
wrote:

> On Friday 11 March 2016 07:01:49 Frank Liu wrote:
> > Hi Valentin,
> > Thanks for clearing up . I was looking at the wrong module.
> > Do you have any comments to the other two questions?
>
> 1. That will result in "502 Bad Gateway" response, and corresponding
> message will be written to error_log.
>
> 2. There's the "resolve" parameter of the "server" directive in upstream,
> but it's available in commercial version only.
>
> See the docs:
> http://nginx.org/en/docs/http/ngx_http_upstream_module.html#server
>
> Back to your first question, this parameter has different behavior,
> it will preserve the old IPs in case of resolving error.
>
>
> wbr, Valentin V. Bartenev
>
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