Confuse with nginx proxy location - nginx

Question

I have two proxy location settings.
server {
listen 80;
server_name domain;
charset utf-8;
return 307 https://$server_name$request_uri;
}
server {
# SSL configuration
listen 443 ssl http2;
listen [::]:443 ssl http2;
charset utf-8;
ssl_certificate /etc/letsencrypt/live/domain/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/domain/privkey.pem;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers HIGH:!aNULL:!MD5;
root /usr/share/nginx/html;
# Add index.php to the list if you are using PHP
index index.html index.htm index.nginx-debian.html;
server_name domain;
location /OPQ/api {
proxy_redirect off;
proxy_pass http://127.0.0.1:6666/v1/api;
proxy_http_version 1.1;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
}
location /OPQ {
proxy_redirect off;
proxy_pass http://127.0.0.1:6666;
proxy_http_version 1.1;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
}
}
Expect the results：
http://domain/OPQ/v1/Login -> http://127.0.0.1:6666/v1/Login
http://domain/OPQ/api?abc=1234 -> http://127.0.0.1:6666/v1/api?abc=1234
Actual results:
http://domain/OPQ/v1/Login -> 404 Error
http://domain/OPQ/api?abc=1234 -> http://127.0.0.1:6666/v1/api?abc=1234
I have tested the http://127.0.0.1:6666/v1/Login, it works fine.
This makes me confused. Why the OPQ/api setting as I expected and the other not so. How can I fix it?

Answer 1

The value of the proxy_pass statement contains two components, (1) the protocol & address of the service, and (2) an optional URI. See this document for details.
In your second case, there is no optional URI, so the requested URI is not changed. The URI /OPQ/foo is sent upstream as /OPQ/foo.
You need to replace /OPQ/ with /, this is achieved by adding a trailing / to both the location and proxy_pass statements.
For example:
location /OPQ/ {
...
proxy_pass http://127.0.0.1:6666/;
...
}