lua-cache-post-by-body.nginx

http {
    lua_shared_dict cache_key_store 10m;
    
    server {
        location / {
            # Read the request body
            content_by_lua_block {
                ngx.req.read_body()
                local body = ngx.req.get_body_data()

                # If there's a body, hash it to use as part of the cache key
                if body then
                    local resty_md5 = require "resty.md5"
                    local md5 = resty_md5:new()
                    md5:update(body)
                    local digest = md5:final()

                    # Store the hash in a variable
                    ngx.var.cache_key_body_hash = ngx.encode_base64(digest)
                else
                    ngx.var.cache_key_body_hash = "no_body"
                end
            }

            # Use the hashed body as part of the cache key
            set $cache_key "$request_method|$scheme://$host$request_uri|$cache_key_body_hash";

            proxy_cache_key $cache_key;

            # Enable caching for POST requests
            proxy_cache_methods GET POST;

            # Standard proxy cache settings
            proxy_cache my_cache;
            proxy_cache_valid 200 10m;
            proxy_pass http://backend;
        }
    }
}