Nginx – Combine Expires and Cache-Control: Immutable Headers

nginx

nginx expires directive sets 2 headers, Expires and Cache-Control:

Config:

expires 1d;

Headers:

Expires: Tue, 24 Nov 2020 12:51:31 GMT
Cache-Control: max-age=86400

I would like to keep Expires header but also set Cache-Control to public, max-age=86400, immutable. But that produces double Cache-Control headers:

Config:

expires 1d;
add_header Cache-Control "public, max-age=86400, immutable"

Headers:

Expires: Tue, 24 Nov 2020 12:57:53 GMT
Cache-Control: max-age=86400
Cache-Control: public, max-age=86400, immutable

I can not just use add_header Expires ..., because it requires exact time in future, not just number of seconds.

I tried using more_set_headers from ngx_headers_more module, but Cache-Control header set by expires directive is still there.

Is there any way to combine correct Expires header with Cache-Control set to immutable?

Best Answer

Duplication of the Cache-Control headers isn't a violation of any W3C standard. According to RFC 2616:

Multiple message-header fields with the same field-name MAY be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e., #(values)]. It MUST be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics of the message, by appending each subsequent field-value to the first, each separated by a comma. The order in which header fields with the same field-name are received is therefore significant to the interpretation of the combined field value, and thus a proxy MUST NOT change the order of these field values when a message is forwarded.

Moreover, nginx is aware about it, trying to set a header which shouldn't contain more than one value with the add_header nginx directive will lead to overwrite that header value rather then adding the second one. So you can safely stay with the

expires 1d;
add_header Cache-Control "public, immutable";

configuration.

Related Solutions

Nginx – Expires directive returned in the ngix server response header

If you are using Apache behind Nginx, then I assume you have a dynamic site. So, I guess http://www.yoursite.com serves dynamic content. By default, Nginx sets expires only for static files. So, please do the same test for a static file such as http://www.yoursite.com/style.css and you might notice the difference now.

Nginx – Cache-control for permanent 301 redirects nginx

Have you tried Cache-Control flags in your nginx configuration ?

Sample configuration:

upstream yourappserver{
  server 0.0.0.0:6677;
}


proxy_cache_path  /tmp/cache levels=1:2 keys_zone=my-test-cache:8m max_size=5000m inactive=300m;

server {
    listen 80;
    server_name your.domain.tld;
    root /path/to/the/document/root/;

    access_log  /var/log/nginx/access.log;

    location / {
      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;
      proxy_cache my-test-cache;
      proxy_cache_valid  200 404  1m;
      proxy_cache_valid 302 20m;

      proxy_cache_use_stale   error timeout invalid_header updating;
      proxy_redirect off;

      if (-f $request_filename/index.html) {
        rewrite (.*) $1/index.html break;
      }
      if (-f $request_filename.html) {
        rewrite (.*) $1.html break;
      }
      if (!-f $request_filename) {
        proxy_pass http://yourappserver;
        break;
      }
    }

    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
      root html;
    }
}

I think you are looking for this particular configuration snippet

proxy_cache_valid 302 20m;

Best Answer

Related Solutions

Nginx – Expires directive returned in the ngix server response header

Nginx – Cache-control for permanent 301 redirects nginx

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