nginx反向代理配置

location / {
            #root   html;
            #index  index.html index.htm;
			
			proxy_cache rankCache; 
			proxy_cache_valid  200 301 302 304 1d; 
			proxy_cache_valid any 7d;
			
			proxy_pass              http://127.0.0.1:3000;
			proxy_redirect          off;
			proxy_set_header        X-Real-IP       $remote_addr;
			proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
			proxy_set_header Host $host;
			proxy_pass_header User-Agent;
			

			expires 1d;
}


location ~* .*\.(html|js|css|png|ico|gif|jpg|jpeg)$ {
			proxy_cache rankCache; 
			proxy_cache_valid  200 301 302 304 1d; 
			proxy_cache_valid any 7d;
			
			proxy_pass              http://127.0.0.1:3000;
			proxy_redirect          off;
			proxy_set_header        X-Real-IP       $remote_addr;
			proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
			proxy_set_header Host $host;
			proxy_pass_header User-Agent;
			

			expires 1d;
}

 

worker_processes  1;

events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    #缓存配置
    proxy_cache_path D:/Users/LIWEI564/nginx_rank_cache levels=1:2 keys_zone=rankCache:10m inactive=1d max_size=30m;

    sendfile        on;

    keepalive_timeout  65;

    gzip  on;
	
	
    server {
        listen       80;
        server_name  localhost;

        #导入express-seed.conf中的配置
	include express-seed.conf;
		
	#location /track/ {
        #    root   html;
        #    index  index.html index.htm;
        #}
		
        #location / {
        #    root   html;
        #    index  index.html index.htm;
        #}

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80
        #
        #location ~ \.php$ {
        #    proxy_pass   http://127.0.0.1;
        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        #location ~ \.php$ {
        #    root           html;
        #    fastcgi_pass   127.0.0.1:9000;
        #    fastcgi_index  index.php;
        #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
        #    include        fastcgi_params;
        #}

        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        #location ~ /\.ht {
        #    deny  all;
        #}
    }

}

 想用nginx反向代理express并启用缓存，但在实际操作过程中，css文件却始终不能缓存。被缓存的文件始终从nginx缓存中取，不再向express发起请求。这让我产生疑虑：如果express的文件发生更新，那么nginx如何能知道，并更新他的缓存？望高手指点一二。