I've been thinking about it recently. But it hasn't come to the top of
my priority queue yet.
Some of the content providers are making the mapping of fixed asset ID
to URL more and more obscure, so ultimately a hash-based solution
becomes necessary. You pay some on startup costs (having to fetch a
fixed portion of the data to compute the hash), but as you point out the
hash-based solution is more resilient in the face of URL changes and/or
content changes.
This paper from Alcatel describes the trade-offs nicely
http://www.nctatechnicalpapers.com/Paper/2014/2014-application-of-policy-based-indexes-and-unified-caching-for-content-delivery/download
From my thinking so far, the hash solution would require partial object
based caching. Unless you are concentrating on very small content, you
don't want to force grabbing the whole asset at once for performance
reasons. Or you want to be fetching at the same rate as the client
requestor. So if the client requests data in 10 second increments,
you'll want to store those increments as they come in rather than
requesting all 30 minutes (or 2 hours or more) up front.
Alan has a plan for adding partial object caching which has been
discussed at one of the summits in the past year.
http://network-geographics.com/ats/docs/partial-object-caching.en.html.
On 8/27/2014 11:17 AM, Rasim Saltuk Alakuş wrote:
Hi All,
ATS uses URL hash for cache storage. And CacheUrl plugin adds some more
flexibility in URL hashing strategy.
We think of creating hash based on packet content and use it as the hash while
storing and retrieving from cache This looks a better solution, so that URI
changes won't hurt caching system. One immediate benefit for example if you
cache YouTube , each request for same video can have different URL and CacheUrl
plugin does not always provide a good solution. Also maintaining site based
hash filters looks not an elegant solution.
Is there any previous or active work for implementing content based hashing?
What kind of problems and constrains you may guess. Is there any volunteer to
implement this feature together with us?
Kind regards
Saltuk Alakuş
Rasim Saltuk Alakuş
Kıdemli Uzman
Senior Specialist
Bilişim Ar-Ge ve Teknoloji Direktörlüğü
IT R & D and Technology
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