Re: [squid-users] Squid caching SSI pages?

Henrik Nordstrom wrote:
> On Wed, 31 Mar 2004, Greg Swallow wrote:
>
>
>>Assuming documentation at
>>http://www.bowiesnyder.com/writings/caching_shtml.htm is true, my
>>squid-based reverse proxies shouldn't be caching HTML documents that are
>>server parsed. However, it appears that the four reverse proxies I have
>>sitting in front of my webservers are?
>
>
> How the page was generated on the server does not matter that much other
> than that server generated pages usually does not have caching
> information, what matters is the HTTP headers of the response and to some
> extent your refresh_pattern settings in squid.conf.
>
> Some good references to understand these concepts better:
>
> Caching Tutorial for Web Authors and Webmasters
> <url:http://www.mnot.net/cache_docs/>
>
> Cacheability Engine
> <url:http://www.mnot.net/cacheability/>

Wow, those are kick-ass docs. I'll have to bookmark them.

Let me give you a little more background. The closest related
configuration directives I can find are:

cache_peer 157.91.12.68 sibling 80 3130 proxy-only
cache_peer 157.91.12.70 sibling 80 3130 proxy-only
cache_peer 157.91.12.71 sibling 80 3130 proxy-only
refresh_pattern \.cfm$ 0 0% 0
refresh_pattern \.asp$ 0 0% 0
refresh_pattern \.aspx$ 0 0% 0
refresh_pattern . 59 20% 240

These (along with the 59 minutes minimum, above) are new, as of
upgrading to 2.5-stable4:

digest_generation on
digest_rebuild_period 600 seconds
digest_rewrite_period 3600 seconds
refresh_pattern -i \.pdf$ 59 20% 240 reload-into-ims
override-lastmod override-expire

squid.conf is functionally identical on all four systems -- I've checked
them with diff.

The page in question is our main index page: http://www.IN.gov/
According to the cache-docs page I read, this page is not cacheable when:

There are no validators (ETags or Last-Modified headers. Maybe
Cache-control?)

The content in question, in our page, is:

<div id="bannerimage"> <div id="amberalert"><!--#include
virtual="/amber/include.html"--></div>

This include is either a zero-length file or a graphic, depending on
conditions.

So I used the caching engine to test our page, but I'm afraid the
results are skewed, since that's visiting our cache. The caching engine
reports that my page isn't cacheable, but I decided to do some testing
with curl instead.

curling my own site (no SSI):

curl -z 040113342004.00 -D headers http://www.netgawds.com/

HTTP/1.1 200 OK
Date: Thu, 01 Apr 2004 14:53:08 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4 mod_ssl/2.8.16 OpenSSL/0.9.7c
Last-Modified: Wed, 31 Mar 2004 03:58:20 GMT
ETag: "18a480-289e-406a41dc"
Accept-Ranges: bytes
Content-Length: 10398
Connection: close
Content-Type: text/html

curl -z 040113342004.00 -D headers http://www.IN.gov/ (direct to the
origin server -- inside a firewall)

HTTP/1.1 200 OK
Date: Thu, 01 Apr 2004 15:08:51 GMT
Server: Apache
Connection: close
Content-Type: text/html

You're right about the 304's. However, I'm still a bit confused about
why this is happening:

cache1# grep 'GET http:\/\/www.in.gov\/ HTTP' access.log | awk '{print
$NF}' | sort | uniq -c | sort
    1 TCP_HIT:NONE
  153 TCP_IMS_HIT:NONE
  169 TCP_MISS:DIRECT
  480 TCP_MISS:NONE
4456 TCP_MEM_HIT:NONE

cache2# grep 'GET http:\/\/www.in.gov\/ HTTP' access.log | awk '{print
$NF}' | sort | uniq -c | sort
  176 TCP_MISS:DIRECT
1186 TCP_MISS:CD_SIBLING_HIT

cache3# grep 'GET http:\/\/www.in.gov\/ HTTP' access.log | awk '{print
$NF}' | sort | uniq -c | sort
  162 TCP_MISS:DIRECT
1118 TCP_MISS:CD_SIBLING_HIT

cache4# grep 'GET http:\/\/www.in.gov\/ HTTP' access.log | awk '{print
$NF}' | sort | uniq -c | sort
  161 TCP_MISS:DIRECT
1205 TCP_MISS:CD_SIBLING_HIT

On the bright side, my hit ratios are better than they ever have been
before :)

Hey, BTW, how "stable" is Squid 3? I'd like to start using ESI within
the year.

-- 
+--------------+------+----------------------+---------------+
| Greg Swallow | CCNA | System Administrator | accessIndiana |
+--(http://www.IN.gov/)----------------------(888.4IN.EGOV)--+
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