Re: ICAP vectoring points

On 11/29/2012 02:32 AM, Steve Hill wrote:
> On 29.11.12 04:16, Eliezer Croitoru wrote:
>
>> I was just wondering what exactly you need to do?
>> What is the goal\task of the ICAP server.
>
> The ICAP server does on-the-fly content filtering - it analyses the
> request headers (in reqmod), the response headers and streaming content
> (in respmod) to categorise the page and decide whether to block it. The
> filtering criteria are done on a per-user basis, so filtering it before
> it enters the cache doesn't make sense,

but categorizing a response before it enters the cache does make a lot
of sense in many cases.

> It would be possible to do all the possible analysis that could be
> needed, insert their results as http headers and allow the object to go
> into the cache, then check those headers using ACLs when it is retrieved
> from the cache, but this would result in a large overhead of unnecessary
> analysis since for most users those criteria are not needed.

You asked for a specific example of how post-cache adaptation can be
avoided. The above is such an example :-).

Please note that the amount of overhead may actually _decrease_ with
this solution:

  pre-cache + ACLs: analyze each miss + filter each access.
  post-cache: analyze and filter each access.

Which approach results in less overheads depending on hit/miss ratios
and other factors, so I do not think one can claim that only one of the
two approaches make sense in general.

Cheers,

Alex.
Received on Fri Nov 30 2012 - 17:18:52 MST