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From Jason Giedymin <jason.giedy...@gmail.com>
Subject Re: Traffic Server: Cache Behavior and Configuration
Date Fri, 26 Mar 2010 20:32:29 GMT
Try to set the cache-control header param in the request so that it  
will fetch and only fetch from cache.

My curl syntax is rusty but I think you can specify:

-h "Cache-Control: only-if-cached"

Prefered testing should be done with a cleared cache so no 304s occur.

Hope that helps?

-Jason

On Mar 26, 2010, at 4:12 PM, Zachary Miller <zacharymmiller@gmail.com>  
wrote:

> Yeah, I just see cache writes on the initial run only, which leads  
> me to believe that the content is being cached, and later runs don't  
> produce hits (based on the hit rate from the traffic_line).
>
> On Fri, Mar 26, 2010 at 12:09 PM, Bryan Call <bcall@yahoo-inc.com>  
> wrote:
> On 03/26/2010 11:33 AM, Zachary Miller wrote:
> Hello,
>
> I am currently conducting a proof-of-concept to explore the value of  
> content caching for a system that automatically fetches a large  
> number of external web pages.  I am mainly interested in using TS as  
> a forward proxy and then serving content locally for subsequent  
> duplicate queries to the sites.  Currently I have the forward proxy  
> enabled, as well as the reverse proxy setting.  Is it necessary or  
> advisable to have both of these enabled if my interest is mainly  
> external content?
>
> I run traffic server as both a reverse and forward proxy without a  
> problem.
>
>
>
> Also, I have been getting metrics using traffic_line and running  
> tests using the web UI and see some odd behavior.  For instance,  
> whenever I run tests against BestBuy.com, on the initial run  
> (through about 3k pages) there are nearly the same number of writes  
> to the cache.  On following runs (using the same pages) no new  
> writes are made to the cache, leading me to believe that the pages  
> already exist, but according to traffic_line, there are no cache  
> hits during the execution period.  Other sites appear to perform as  
> expected, so I expected that this was due to dynamic content.
>
> However, when I access pages through a browser with a clear cache, I  
> see certain pages failing to be added to the cache, while what I  
> would consider collateral content is added.  For instance, if I  
> access http://www.msn.com and inspect the cache through the web UI,  
> I find many cached items from the MSN domain, but nothing containing  
> the actual page content.  Is this expected behavior and something  
> configurable, or am I missing some fundamental aspect of the cache?
>
> If the page has dynamic content and the origin server (best buy /  
> msn) has the headers not to cache the content then it won't be  
> cached by default.  You can override this and cache the content, we  
> do this for some of our crawling.
>
> I am not very familiar with the Web UI and I use the command line  
> tools.  Are you seeing cache writes  on Best Buy on the following  
> runs or just the first crawl?
>
>
>
> Thanks a lot,
>
> Zachary Miller
>
>
>

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