Nginx upstream return name instead of server ip

[Maxim Dounin]

Hello!

On Wed, Sep 29, 2021 at 09:20:20AM -0400, rjvbzeoibvpzie wrote:

> Here is my config:
> 
> -----
> upstream http_backend {
>     server 127.0.0.1:81;
>     server 10.1.1.2 backup;
> }
> 
> server {
>     ...
> 
>     location /http/ {
>         proxy_pass http://http_backend;
>         ...
>     }
> }
> -----
> 
> As long as everything is working, $upstream_addr returns the IP
> (127.0.0.1:81). But when any backend returns HTTP/502, $upstream_addr
> returns the upstream name (http_backend) as the $upstream_addr.
> 
> Shouldn't this return the lastest server IP tried before failure?

The upstream name can be seen in $upstream_addr as long as nginx 
is not able to select an upstream server because all servers are 
not available per max_fails/fail_timeout.  The "no live upstreams" 
error is logged at the same time.

-- 
Maxim Dounin
http://mdounin.ru/