Re: [squid-users] Update Accelerator, Squid and Windows Update Caching

On Fri, Oct 10, 2008 at 12:30 PM, Amos Jeffries <squid3_at_treenet.co.nz> wrote:
> Richard Wall wrote:
>>
>> Hi,
>>
>> I've been reading through the archive looking for information about
>> squid 2.6 and windows update caching. The FAQ mentions problems with
>> range offsets but it's not really clear which versions of Squid this
>> applies to.
>
> All versions. The FAQ was the result of my experiments mid last year. With
> some tweaks made early his year since Vista came out.
> We haven't done a intensive experiments with Vista yet.

Hi Amos,

I'm still investigating Windows Update caching (with 2.6.STABLE17/18)

First of all, I have been doing some tests to try and find out the
problem with Squid and Content-Range requests.
 * I watch the squid logs as a vista box does its automatic updates
and I can see that *some* of its requests use ranges. (so far I have
only seen these when it requests .psf files...some of which seem to be
very large files...so the range request makes sense) See:
http://groups.google.hr/group/microsoft.public.windowsupdate/browse_thread/thread/af5db07dc2db9713

# zcat squid.log.192.168.1.119.2008-10-16.gz | grep
"multipart/byteranges" | awk '{print $7}' | uniq | while read URL; do
echo $URL; wget --spider $URL 2>&1 | grep Length; done
http://www.download.windowsupdate.com/msdownload/update/software/secu/2008/10/windows6.0-kb956390-x86_2d03c4b14b5bad88510380c14acd2bffc26436a7.psf
Length: 91,225,471 (87M) [application/octet-stream]
http://www.download.windowsupdate.com/msdownload/update/software/secu/2008/05/windows6.0-kb950762-x86_0cc2989b92bc968e143e1eeae8817f08907fd715.psf
Length: 834,868 (815K) [application/octet-stream]
http://www.download.windowsupdate.com/msdownload/update/software/secu/2008/03/windows6.0-kb948590-x86_ed27763e42ee2e20e676d9f6aa13f18b84d7bc96.psf
Length: 755,232 (738K) [application/octet-stream]
http://www.download.windowsupdate.com/msdownload/update/software/crup/2008/09/windows6.0-kb955302-x86_1e40fd3ae8f95723dbd76f837ba096adb25f3829.psf
Length: 7,003,447 (6.7M) [application/octet-stream]
...

 * I have found that curl can make range requests so I've been using
it to test how Squid behaves....and it seems to do the right thing. eg
 - First ask for a range : The correct range is returned X-Cache: MISS
 - Repeat the range request : The correct range is returned X-Cache: MISS
 - Request the entire file: The entire file is correctly returned X-Cache: MISS
 - Repeat the request: X-Cache: HIT
 - Repeat the previous range request: X-Cache: HIT
 - Request a different range: X-Cache: HIT

curl --range 1000-1002 --header Pragma: -v -x http://127.0.0.1:3128
http://www.download.windowsupdate.com/msdownload/update/software/secu/2008/05/windows6.0-kb950762-x86_0cc2989b92bc968e143e1eeae8817f08907fd715.psf
> /dev/null

Looking back through the archive I find this conversation from 2005:
http://www.squid-cache.org/mail-archive/squid-users/200504/0669.html

...but the behaviour there sounds like a result of setting:
range_offset_limit -1

Seems to me that Squid should do a good job of Windows Update caching.
There is another thread discussing how to override MS update cache
control headers:
http://www.squid-cache.org/mail-archive/squid-users/200508/0596.html

....but I don't see anything evil in the server response headers
today. I guess the client may be sending no-cache headers...I'll
double check that later.

Is there some other case that I'm missing?

>> I'm going to experiment, but if anyone has any positive or
>> negative experience of Squid and windows update caching, I'd be really
>> interested to hear from you.
>>
>> In case Squid cannot do windows update caching by its self, I'm also
>> looking at integrating Update Accelerator
>> (http://update-accelerator.advproxy.net/) script with standard squid
>> 2.6 and wondered if anyone else had any experience of this.
>> The update accelerator script is just a perl wrapper around wget which
>> is configured as a Squid url_rewrite_program. It's not clear to me
>> what this script is doing that Squid wouldn't do by its self.
>
> Strange indeed.

I got update accelerator working with Squid but I'm still not
convinced that it's necessary (see above).

-RichardW.
Received on Fri Oct 17 2008 - 05:06:27 MDT