How to cache websites using Varnish, PHP and Cookies

Question

I consider starting using Varnish on my websites. I just tried out Varnish and I am wondering how to cache pages even if I my websites uses cookies, for Google Analytics. I am trying to remove them but it seems like Varnish isn't caching. This is how my config looks like; http://pastie.org/1254664. If it matters I have one Debian server, and one server using Ubuntu Server. So, how do I cache the website even if I am using cookies?

Thank you in advance!

Addition: I don't get any X-Cache: HIT/MISS neither. What am I doing wrong?

Answer 1

I am fairly new to caching with Varnish, but here is what I've learned so far: There are several factors to consider when using Varnish for caching against an application.

In your case, know what cookies are being set and for what purpose. If varnish sees a cookie with your request, you will be passed to the backend, resulting in a cache miss.

Google Analytics Cookies

If you are using Google Analytics cookies, you can safely unset them in Varnish; don't worry, you will still the data in your GA reports. Use something like this in your vcl_recv

set req.http.Cookie = regsuball(req.http.Cookie, "(^|;\s*)(__[a-z]+|__utma_a2a)=[^;]*", "");

You can try a couple more cleanup lines, also in the vcl_recv

Remove ";" prefixes from Cookies

set req.http.Cookie = regsub(req.http.Cookie, "^;\s*", "");

Unset empty cookies

if (req.http.Cookie ~ "^\s*$") {
  unset req.http.Cookie;
}

Application Specific Cookies

If your application sets a cookie when a user logs in to perform a function, those requests should not be cached and sent to the backend directly. Otherwise, you could cached pages viewed by logged in users (bad).

Use something like this:

if (req.http.Authorization || req.http.Cookie) {
  return (pass);
}

HTH & good luck.

Edit

Use this to see what cookies varnish is seeing come through:

varnishtop -i RxHeader -I Cookie

If you're regex misses any, catch 'em here!

Answer 2

I don't know about Varnish. But according to my experience in server administration, try those stuffs in your LAN first, than move on to the Internet.

Answer 3

That's what the Vary-header in http is for: variations that should return the same resource. Varnish understands a Vary: cookies.

If you are not getting X-Cache headers you meight not be connecting to the cache at all; are you sure it's running on the right ip/port?

Answer 4

You may pass some parts of you site to backend without caching.

Simplest example for vcl_recv and vcl_fetch blocks:

sub vcl_recv {
if (req.url ~ "^/somescript.php") {                       
return (pass);                                                          
}                                                                       
else {                                                                  
unset req.http.Cookie;                                                  
}
return(lookup);
}

sub vcl_fetch {
if (req.url ~ "^/somescript.php") {                       
return (pass);                                                          
}                                                                       
else {                                                                  
unset req.http.Cookie;                                                  
}
return(deliver);
}

Read - read this to understand why Varnish misses

Answer 5

run varnishlog and see if you are actually going through varnish

Answer 6

My recommendation is to check for which URLs you really need cookies (e.g. administration panel) and to remove cookies for all other URLs. See below an example:

sub vcl_recv {
  if (req.url ~ "^/admin/") {
    # administration panel
    set req.http.admin = 1;
  } else {
    # public web site, ignore client request for fresh content, remove cookies
    unset req.http.Cache-Control;
    unset req.http.Max-Age;
    unset req.http.Pragma;
    unset req.http.Cookie;
  }
  ...
}

sub vcl_fetch {
  if (req.http.admin == 1) {
    # administration panel
    return (hit_for_pass);
  } else {
    # public web site, not allowed to set cookies
    unset beresp.http.Set-Cookie;
    ...
  }
  ...
}