Hello Maxim,

that does not work for me.

root@tower:~# resolvectl query icinga2
icinga2: 192.168.145.217 -- link: ve-icinga2

-- Information acquired via protocol LLMNR/IPv4 in 105.7ms.
-- Data is authenticated: no

root@tower:~# getent hosts icinga2
192.168.145.217 icinga2

root@tower:~# cat /etc/resolv.conf
nameserver 127.0.0.53
options edns0
root@tower:~#

location / {

proxy_redirect off;
proxy_set_header Host $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header X-Forwarded-Host $remote_addr;
proxy_set_header X-Real-IP $remote_addr;
# proxy_pass https://icinga2;
resolver 127.0.0.53 valid=10s;
set $upstream "https://icinga2";
proxy_pass $upstream;

# WebSocket support
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}

2023/04/18 22:16:28 [error] 779163#779163: *26641 icinga2 could not be
resolved (3: Host not found),

503 bad gateway


Am 18.04.23 um 21:29 schrieb Maxim Dounin:
> Hello!
>
> On Tue, Apr 18, 2023 at 02:58:08PM +0200, mailinglist@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.
>
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