If you have a situation where there is only one upstream that you need to proxy_pass, use a variable in the proxy_pass directive, e.g.
server { listen 80; resolver 127.0.0.11 valid=30s; # docker's resolver set $target "http://target-host:3005"; # variable definition location / { proxy_pass $target; } }
This will not error out if the target-host is not available (for example in some Docker setup).
resolver is probably needed even when the target host is not a docker container
The following example however will give you an error if the target-host can not be resolved:
upstream target { server target-host:3005; } server { listen 80; location / { proxy_pass $target; } }