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From "Henry C." <he...@cityweb.co.za>
Subject Trying to understand caching inconsistency with dynamic URLs (or cookies)
Date Tue, 18 Oct 2011 11:15:19 GMT
Hi,

Using ATS 3.0.1 on CentOS 5.x.
Setup for reverse proxy (ie, as a web accelerator)

I'm having a bit of difficulty understanding the inconsistency in caching
behaviour in my test setup.

I've simplified things down to a single traffic server, and connecting from
three different IP addresses spread across three different subnets.

Basically, what I expect is that if a page is cached, it *must* be served to
any new/same client irrespective of client no-cache, and irrespective of where
the request is coming from, etc.

What I'm seeing though is the following behaviour (say, for URL "test.com/?a=1"):

>From  Hit/Miss  Expecting
----  --------  ---------
IP1:  Miss      Miss
IP2:  Miss*     Hit
IP3:  Miss*     Hit

*=problem

If I repeat the exercise from all three IPs for the same URL then the
behaviour is as expected:

>From  Hit/Miss  Expecting
----  --------  ---------
IP1:  Hit       Hit
IP2:  Hit       Hit
IP3:  Hit       Hit

This has probably something to do with dynamic URLs since the landing page
(http://test.com/ - ie, without '?a=...') is always served as a HIT from the
cache from any IP.  ... or maybe cookies?

My config (I think these are the ones which are relevant):
CONFIG proxy.config.http.cache.http INT 1
CONFIG proxy.config.http.cache.ignore_client_no_cache INT 1
CONFIG proxy.config.http.cache.ims_on_client_no_cache INT 1
CONFIG proxy.config.http.cache.ignore_server_no_cache INT 1
CONFIG proxy.config.http.cache.ignore_client_cc_max_age INT 1
CONFIG proxy.config.http.cache.cache_responses_to_cookies INT 1
CONFIG proxy.config.http.cache.cache_urls_that_look_dynamic INT 1
CONFIG proxy.config.http.cache.when_to_revalidate INT 3
CONFIG proxy.config.reverse_proxy.enabled INT 1
CONFIG proxy.config.url_remap.remap_required INT 1
CONFIG proxy.config.http.cache.cache_responses_to_cookies INT 1

~# traffic_line -r proxy.process.cluster.nodes
1

I must be missing something obvious and would appreciate any pointers.

-- 
Regards
Henry


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