One out of three Nginx routes ignores upstream server - nginx

Question

I have configured three locations for a nginx reverse proxy:
location / {
root /var/www/html;
index index.html;
}
location /login {
proxy_pass http://127.0.0.1:9080;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
}
location /app {
rewrite ^/app/(.*)$ /$1 last;
proxy_pass https://10.11.12.13/1020/;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
}
The server listening on port 9080 redirects to the route /app/{generated subpath}. The server on IP 10.11.12.13 processes the request on {generated subpath}. Therefore I remove the prefix path /app with a corresponding rewrite rule, then proxying the request to that server's /1020 endpoint.
For some reason, the nginx reverse proxy doesn't take the 10.11.12.13 upstream server but tries to find the path locally:
8888#8888: *470 open() "/var/www/html/html/createCustomer" failed (2: No such file or directory), client: x.x.x.x, server: 10.10.10.10, request: "GET /app/html/createCustomer?tokenId=0xC00FF3 HTTP/1.1", host: "10.10.10.10"

Answer 1

Instead of last I believe you are looking for break. From the rewrite documentation
last
stops processing the current set of ngx_http_rewrite_module directives and starts a search for a new location matching the changed URI;
The starts a search for a new location matching the changed URi is what is happening as you are removing the /app/ part which then matches the / location.
break
stops processing the current set