Nginx rewrite and proxy_pass explanation

Question

I can see a following locations in nginx/okd configuration:

    location /STFlow/ {
        rewrite ^/STFlow(.*)$ $1 last;
#   
#          Are four lines below executed if rewrite has last option ???
#          What's the point of them?          
#
        proxy_pass http://zuul-proxy:8080; 
        proxy_set_header Host      $host;
        proxy_set_header X-Real-IP $http_x_forwarded_for;
        proxy_set_header X-Forwarded-For $http_x_forwarded_for;
    }

    location / {
        add_header debug-header dbg5;   
        set $realip $remote_addr;
        if ($http_x_forwarded_for ~ "^(\d+\.\d+\.\d+\.\d+)") {
            set $realip $1;
        }
        proxy_pass http://zuul-proxy:8080; 
        proxy_set_header Host      $host;
        proxy_set_header X-Real-IP $http_x_forwarded_for;
        proxy_set_header X-Forwarded-For $http_x_forwarded_for;
        client_max_body_size 50M;
    }

In location /STFlow/ are four lines below rewrite ^/STFlow(.*)$ $1 last; ever executed?

If so when?

What's the point of them?

Answer 1

If that rewrite rule had a break flag instead of last , it would remove the /STFlow prefix from /STFlow/some/path URI before passing it to the upstream, ie do the same as the second location block except of setting debug-header and $realip variable. But as far as I understand using the last flag makes that four lines never executed, further URI processing would be done inside the second location block.