Re: [squid-users] Squid as Reverse Proxy - Backend Server Issues

From: howard chen <howachen_at_gmail.com>
Date: Fri, 6 Jun 2008 01:14:56 +0800

Hi,

On Fri, Jun 6, 2008 at 12:30 AM, Henrik Nordstrom
<henrik_at_henriknordstrom.net> wrote:
> On tor, 2008-06-05 at 23:53 +0800, howard chen wrote:
>
>> 1. I found that if a file only has LM being sent out, the browser
>> seems to cache the file forever and won't request the server until you
>> press F5, is it true?
>
> Browser caches is quite often very agressive and only checks for
> modification once per browsing session.
>

E.g.
http://www.uwants.com/images/home/title_forum.jpg

Which only contains LM, ETAG but not Expire (I think it is Apache default setup)

I use FF 2.0 and LiveHTTP header to view the req/response, and after I
got the file for the first time, my FF will not issue the second time,
even if I close my browser.

If I press F5, then 200 is received.

>> 2. Squid will not cache for a file if expire has not been set, is it true?
>
> False. If there is no freshness assigned to the object Squid uses
> refresh_pattern to calculate one basedon Last-Modified.
>

Since the default Squid conf do not have refresh_pattern being set, so
squid will NOT
cache file if only contains LM but missing Expire or Max-Age?

>> 3. The prioiry of client sending cache-control, max-age=0 is higher
>> than IMS and must force contacting the backend to refresh (i.e. not
>> 304 but 200).
>
> max-age=0 instructs caches to query the next hop to verify freshness
> using a conditional query (i.e. If-Modified-Since). Which means thata
> GET with max-age=0 will be transformed into an If-Modified-Since query
> by Squid if the object is cached.
>

So far, my main problem, my squid never use IMS to call my apache, if
I request a file with max-age=0, the squid will always get from my
apache, which in turn my apache return 200 to squid [not 304], and
squid also return 200 to my client.

I am not sure if squid provided IMS, but my client do send IMS to squid.

(I don't have settings such as refresh_all_ims or reload_into_ims or
refresh_platten )

Thank very much for your help.

Howard
Received on Thu Jun 05 2008 - 17:14:59 MDT

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