On 11/12/10 21:37, Rodolfo Alcazar Portillo wrote:
On Sat, 2010-12-11 at 02:59 +1300, Amos Jeffries wrote:
...
Second thing I notice is the absence of ETag features for variant identification. Which Squid could use to identify that Chrome wants the
cached object, or that the 304 response Chrome got is allowed to update the firefox variant's object details.
Chrome is sending an If-Modified-Since header and the 304 applies to that. So if Squid is behaving properly and not sharing the variants with
different possible encodings then it has no stored object to replace the firefox variant with and each IMS request will be a MISS.
To test this out there are some permutations that will show if it's working:
- check two Chrome requests in a row. When the browser cache is erased before testing and between requests. (good behaviour: the second is a HIT).
Cool! Clearing cache between requests makes the second a HIT with
chrome!
First request after clearing browser's cache:
1292054351.774 37 127.0.0.1 TCP_MISS/200 617 GET http://www.elpais.com/css/i_portadillas.css? - DIRECT/80.156.250.8 text/css
...
Second request after clearing browser's cache:
1292054375.498 1 127.0.0.1 TCP_MEM_HIT/200 624 GET http://www.elpais.com/css/i_portadillas.css? - NONE/- text/css
...
For a fix:
Adding ETag support by the web server may fix this or reduce the MISS
a lot.
Grats, you solved the issue! But I dont want to ask hundreds of sites to
apply the etag to their servers. Isn't there a way of using squid and
chrome and cache gifs, jpgs and css as firefox does? Maybe some obscure
squid ~"please-ignore-evil-etag"~ header? Or should we migrate to
firefox to use caching?
So this confirms the underlying problem is Squids lack of support for
caching multiple variants objects simultaneously. Combined with Squid
not converting IMS requests to regular fetches on MISS.
ETag avoids the problem, as will using a uniform set of browsers due to
their uniform feature support (regardless of which particular is
picked). It's just more visible with Chrome vs Firefox due to sdch
encoding support.
Amos
--
Please be using
Current Stable Squid 2.7.STABLE9 or 3.1.9
Beta testers wanted for 3.2.0.3
