nginx proxy is not working using subdomain - nginx

Question

i have two domains
alpha.mydomain.com and api-alpha.mydomain.com
I am trying to use nginx as a proxy
i am getting the error
Access to XMLHttpRequest at 'https://api-alpha.mydomain.com/dup-check'
from origin 'https://alpha.mydomain.com' has been blocked by CORS
policy: Response to preflight request doesn't pass access control
check: No 'Access-Control-Allow-Origin' header is present on the
requested resource.
i would think based on my setup , the request should not be using api-alpha.mydomain.com but 127.0.0.1 (and not getting the CORS error)
NOTE:: i am using cloudflare https so the console errors are https by cloudflare is the SSL and talking to port 80 to my nginx server
this is part of my nginx config
server {
listen 80;
server_name alpha.mydomain.com ;
access_log /var/log/nginx.access_log main;
root /home/mydomain/react-front/dist;
location / {
try_files $uri $uri/ /index.html;
}
}
server {
listen 80;
server_name api-alpha.mydomain.com ;
access_log /var/log/nginx-api-alpha-access.log main;
location /{
proxy_pass http://127.0.0.1:4001/;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-NginX-Proxy true;
proxy_ssl_session_reuse off;
proxy_set_header Host $http_host;
proxy_redirect off;
}
}
This is the entry from the nginx-api-alpha-access.log
"OPTIONS /dup-check HTTP/1.1" 502 750 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.110 Safari/537.36" "-"
This is the entry from /var/log/nginx/error.log
[error] 1280#1280: *12 connect() failed (111: Connection refused) while connecting to upstream, client: 172.xx.xxx.xxx, server: api-mydomain.trigfig.com, request: "OPTIONS /dup-check HTTP/1.1", upstream: "http://127.0.0.1:4001/dup-check", host: "api-alpha.mydomain.com"
Thanks, not sure what i am missing in my config

Answer 1

try change to
server {
listen 80;
server_name alpha.mydomain.com ;
access_log /var/log/nginx.access_log main;
root /home/mydomain/react-front/dist;
location / {
try_files $uri $uri/ /index.html;
}
}
server {
listen 80;
server_name api-alpha.mydomain.com ;
access_log /var/log/nginx-api-alpha-access.log main;
location /{
if ($request_method = 'OPTIONS') {
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS, PUT, DELETE';
add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Authorization';
add_header 'Access-Control-Max-Age' 1728000;
add_header 'Content-Type' 'text/plain; charset=utf-8';
add_header 'Content-Length' 0;
return 204;
}
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS, PUT, DELETE';
add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Authorization';
add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range,Authorization';
proxy_pass http://127.0.0.1:4001/;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-NginX-Proxy true;
proxy_ssl_session_reuse off;
proxy_set_header Host $http_host;
proxy_redirect off;
}
}