[nginx] uninitialized "proxy_upstream_name" variable while logging request

[cheungpat]

It appears that when there is a 301 Redirect, nginx prints this log:

2017/05/14 00:03:53 [warn] 8590#8590: *560 using uninitialized "proxy_upstream_name" variable while logging request, client: 1.2.3.4, server: www.example.com, request: "GET / HTTP/1.1", host: "www.example.com"

Tested it with curl:

$ curl -v http://www.example.com
...
< HTTP/1.1 301 Moved Permanently
< Server: nginx/1.11.12
< Date: Sun, 14 May 2017 00:10:59 GMT
< Content-Type: text/html
< Content-Length: 186
< Connection: keep-alive
< Location: https://www.example.com/

I suspect that when nginx got a http request, it tries to redirect before the $proxy_upstream_name variable is set. The generated nginx config seems to confirm so:

        # enforce ssl on server side
        if ($pass_access_scheme = http) {
            return 301 https://$best_http_host$request_uri;
        }
        location / {
            set $proxy_upstream_name "www-www-5000";