强制Codeigniter使用清漆

Question

I have a codeiginter application that already use codeiginter build-in caching, I applied Varnish as a new caching layer. But as i can see from varnishstat it's not making that difference.

Hitrate ratio:        1        1        1
Hitrate avg:     0.0480   0.0480   0.0480

I think thats because of Codeiginter cookies and HTTP Headers that are being sent back.

This is the http request coming from varnish.

Accept-Ranges:bytes
Age:0
Cache-Control:no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Connection:keep-alive
Content-Encoding:gzip
Content-Length:1755
Content-Type:text/html
Date:Mon, 29 Jul 2013 07:25:59 GMT
Expires:Thu, 19 Nov 1981 08:52:00 GMT
Pragma:no-cache
Server:Apache/2.2.22 (Ubuntu)
Set-Cookie:ci=%2BEZFRauewyNnl3CXHE0cmz6F3G3moadilt5vXu5gghKXkWm4gg0JObnF2Etq6J5rl3XVigbF0je3funibpvEi4X%2BT3rS2VmazGG3T4Vm1%2B8YcbqRgL4xuMcxybndqJy%2BU9mNmsJjOgmYEZ8oPG8BKOtMaxNiMHmgmbBydxt3SzKfFfFUOydFx%2BeeJ7P1WE7V10m6GyfnFO5DrFYNsE%2F37WNAI%2Bpux%2Fwwch5B4DH1%2F6wssPm%2BNwsLQ1%2FBd44hgUXe3mMzzcqvxNjKqs0gjuwzwPT4nibEHirfaJ7TMVGObMjdrbREnoYS2gwoN15cCeKgXmTJQI2vvTuPcdtZVCjcAX6OvTy491HdIvQIdKRhX2BNi8d7ygo%2F7n5T6%2FN%2B0IohNN9iZ%2Fh959W%2Fz4azEJPfTrluucf6cLnlp2T2zb%2Fb3XroWuPqguk4wMpsAstfLsSfA%2F6yEi4Hph%2BPFxX%2BhyBazs11LJ38FA0flWtYY%2Bk%2B6yoF13sTaENN2pWj0bKDTtres9E4y3xMPr%2FZaO78WRA9CccDzcQfbZ3bZUqoXg4HmX%2BHDHiYPLD6uFpnC28LuDrCSbgXFIlhDrC8j65sxNSKhnzlUP7Konr%2FKRfKNzrgtWHBEzuXArW%2BlgIg1MzaW3GIkRy1gr16ZUjIiv7CCx7Y2twAfKOm4t00MvrTcFoxBPN1lzoasNyRLMIvshU8heWZHy17OPEapuO6N%2BuMl9L8LqU0%2FF%2BUeUDyFVwLG39LGkIVuF93VsIYEp6w2UwtccX4OO4P2uwJEoAJMMqUE%2FztELpCv%2BkfRAiub48n%2BRxK%2FhgUHw1LWsWIPv3xngq3MI8ypWCqkWLjPuu5dc%2FdOd3BSW2MYcBwacoB5CEOPBHGq3hw1QSZfY330hkLuyQPHxkh%2FDTija%2FN2Rz6z47JorsCqHGDBK6%2BPswBWvYZeMd0VMD%2F95j%2BFibi6rBqL3hoE%2BDgcfCdly%2FYH9py%2Fe%2Fa0AUiIINTK8EPtpuKdC8dLhKo2jI5J4e1ifZuWjVd3VnL2CvX; path=/
Vary:Accept-Encoding
Via:1.1 varnish
X-Powered-By:PHP/5.3.10-1ubuntu3.5
X-Varnish:1353481467

I noticed difference things:

1. No matter how hard i try codeiginter won't change the Cache-Control , Age , Expires until i set them manually
2. Codeiginiter Sent an old date 1981 I doubled checked the date on my server it's correct
3. Codeiginiter keep changing the cookies almost each request.

In my app i have several pages that require username/password but i'm trying to focus first on getting the public pages to be cached. after that I will check the account related pages.

I'm testing on this code:

//$this->output->set_header("Cache-Control:public, max-age=9000");
//$this->output->set_header("Vary: Accept-Encoding,Cookie,User-Agent");  
$this->output->cache(2400);
$this->load->view("test");

Answer 1

If your backend is sending Cache-control: max-age=XXX you can forget about Expires header, as it will be ignored in HTTP 1.1 compliant clients & proxys [1] (In fact, it's usual to set it on the past in order to avoid old HTTP 1.0 clients caching items).

Be very careful when setting Vary: User-Agent header, as it can harm your caching chances [2]

And finally, Varnish won't cache a request such as that because of the Set-Cookie header. Varnish needs lazy session initializing (see [3]) to cache thing (or a quite complicated VCL)

If you fix the cookie thing and still have problems the VCL file and varnish version will be really apreciated.

[1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html

[2] https://www.varnish-cache.org/docs/3.0/tutorial/vary.html

[3] How should I implement lazy session creation in PHP?

Answer 2

Your cookie problem is one I'm currently wrestling with. I'm guessing from your sample that you have changed the cookie_name variable to be ci rather than ci_session.

The simplest thing for you - for certain values of simple - may be to jettison CI's session handling for an alternative or switch to db-based cookies rather than cookie-based. If there's a set-cookie - and there always is when you have sessions initialized/auto-loaded - it won't get cached. If the data is all stored server-side instead you won't have this issue.

Personally I'm not gung-ho to introduce databases for our use of sessions so I'm going to experiment with setting the cache-control header to ignore cookies and using header_remove() at the top of views I know will never be user-specific (like our RSS feed).