Using an Nginx proxy cache to prevent duplicate requests?

Question

I am using an Nginx proxy as a front-end to a web application that tends to get identical duplicate requests milliseconds apart, causing duplicate items in my database.

I thought I might be able to fix this by letting Nginx cache content for 1s, so that duplicate requests would not hit my app at all

I configured it with

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=prevent_duplicates:10m max_size=1g inactive=1s use_temp_path=off;

And then added proxy_cache prevent_duplicates; to my root location section, where I have proxy_pass

But my application gets hit on all requests anyway - is it a timing thing? Multiple threads all starting at once for each request all thinking they are first?

Answer 1

Maybe rate limiting can be the solution?

limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s;
 
server {
    location /login/ {
        limit_req zone=mylimit;
        
        proxy_pass http://my_upstream;
    }
}

Source: https://www.nginx.com/blog/rate-limiting-nginx/

The rate=1r/s can be tweaked, if you put 2r/s NGINX will allow 1 request every 500 milliseconds...