Re: [squid-users] caching dynamic image content

Terry wrote:
> Hello,
>
> I don't have squid implemented yet.
>
> I am researching a web architecture issue I am seeing with a site.
> Squid may be a bandaid for what I think may be some poor development
> architecture decisions. There are concerns that the site is written
> in a way that browsers and reverse proxies cannot cache it
> appropriately. And these aren't my concerns by the way. We also have
> A10 load balancers in house that do some caching. They said they
> can't cache this content. I don't want to go into their reasoning
> because I don't believe it.
>
> Here's an example of an image as seen from the client. I pulled this
> right out of my firefox memory cache:
> http://foo.domain.com/Image.aspx?i=db1edbcd-2375-4bae-b33f-a53ced60deed
>
> 1. If it's in the memory cache, can I assume that browsers and proxies
> can cache it? Also, I never saw these objects in my disk cache. Not
> sure if that's significant or not.

No. The browser has additional information such as who is logged in and
whether your session with the website is the same. They are also allowed
to cache objects personal to you.

Proxies and caches only have the URL and some other limited data to base
the checking on. If there is any chance it was a private object it will
not be cached naturally.

>
> 2. Does firefox still interpret this as an image and cache it as one
> or is this considered dynamic content that may be problematic?

Not enough information to even guess. What headers are present? Does the
website require login? does the same image ever change URL (including
the query string) and why/when/how often? are alternative image formats
available at the exact same URL?

Any one of those answers may make the object non-cacheable by shared
proxies.

>
> I think that's enough information to start a conversation. Thanks for
> any insight!

  foo.domain.com does not resolve here so I can't verify the object.
Please pick some of the URLs and enter them into http://www.redbot.org
for review of cacheability.

Amos

-- 
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