Hello!
On Tue, Apr 18, 2023 at 02:58:08PM +0200, mailingl...@unix-solution.de wrote:
> Hello,
> I have a nginx proxy in front of systemd-nspawn containers.
> The IP's of the containers are dynamic.
>
> When I start nginx *after* the containers it works.
> When the IP of the container is changed while nginx is running i get a
> "Bad Gateway" error.
>
> The config looks like:
>
> server {
> server_name foobar.example.com
> ...
> location / {
> resolver 127.0.0.53 valid=10s;
> ...
> proxy_pass http://container;
> }
> }
>
> nginx is 1.1.18 so it should work as documented in
> http://nginx.org/en/docs/http/ngx_http_core_module.html#resolver
> The workaround there
> https://stackoverflow.com/questions/42720618/docker-nginx-stopped-emerg-11-host-not-found-in-upstream/52319161#52319161
>
> doesn't work.
>
> I have also try to config a upstream backend and the resolver in the
> server part or in the http part.
> The errors are: "upstream timed out" or "container could not be resolved
> (3: Host not found)"
>
> Whats wrong there?
The "resolver" directive is only used when the "proxy_pass"
directive contain variables, and therefore nginx isn't able to
determine upstream addresses when parsing configuration. Quoting
http://nginx.org/r/proxy_pass:
: Parameter value can contain variables. In this case, if an
: address is specified as a domain name, the name is searched among
: the described server groups, and, if not found, is determined
: using a resolver.
The "workaround", however, should work fine. Something like this
should be enough:
resolver 127.0.0.53 valid=10s;
set $upstream "http://container";;
proxy_pass $upstream;
Note though that there should be an actual DNS name which can be
resolved with the DNS server configured with the "resolver"
directive. The "container could not be resolved (3: Host not
found)" error suggests that your DNS server does not return
anything for the name - you may want to dig further into systemd
to find out why it doesn't return anything.
--
Maxim Dounin
http://mdounin.ru/
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