How to Set Varnish Cache-Control Headers

Question

I am hoping someone can advise on the proper method for getting Varnish to send cache-control headers. Currently, my configuration is sending "Cache-Control: no-cache" to clients.

Thanks in advance to anyone who might be able to help...

Answer 1

[ivy] has good advice, and/but it gets a little complicated when you try to obey a servers intent for end user (browser) caching. I found this resource to be helpful in understanding a way to configure Varnish to hold onto a cache longer than a browser is instructed to...

https://www.varnish-cache.org/trac/wiki/VCLExampleLongerCaching

Answer 2

Your back-end is sending "Cache-Control: no-cache" to Varnish which implies two things:

• Varnish will not store the response in the cache (so a next lookup will fail)
• Your clients (browsers and intermediate proxies) will not cache responses (and request them over and over).

The solution is simple: remove the cache-control headers after fetching the response from the back-end (and before storing them in the cache).

In your vcl file do:

sub vcl_fetch {
  remove beresp.http.Cache-Control;
  set beresp.http.Cache-Control = "public";
}

You can choose to only do this for certain urls (wrap it in ( if req.url ~ "" ) logic) and do way more advanced stuff.

Answer 3

Varnish ignores Cache-Control: nocache as per the documentation. Here is evidence confirming that:

http://drupal.org/node/1418908

To get that result, you should detect the header Cache-Control .nocache. from your backend, and then invalidate the cache, set the backend response to not cacheable, or issue max-age: 0 in the other header (I forget the name right now).