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Date: Tue, 9 May 2006 11:39:19 +0200
Message-ID: <8C29B2F93BAE9047A906EF6D6F9C5D4301E436CC@exchange2k301.gaia.fr>
Thread-Topic: [users@httpd] mod_cache behavior with proxied images - urls not
 cached
Thread-Index: AcZzCQMVplls1szbSpyak6S7tzApbAAQzOKw
From: =?iso-8859-1?Q?Axel-St=E9phane__SMORGRAV?=
 <Axel-Stephane.SMORGRAV@europe.adp.com>
To: <users@httpd.apache.org>
Subject: RE: [users@httpd] mod_cache behavior with proxied images - urls not
 cached

If this is really an issue, you could write a script (using curl) that =
requests all of the images through you caching (reverse?) proxy in order =
to prime the cache...

-ascs


________________________________

From: edward.dunkle@verizon.com [mailto:edward.dunkle@verizon.com]=20
Sent: Tuesday, May 09, 2006 3:36 AM
To: users@httpd.apache.org
Cc: steve.huie@verizon.com; ravi.meduri@verizon.com
Subject: [users@httpd] mod_cache behavior with proxied images - urls not =
cached


We are looking into caching images on Apache that are proxied from a =
backend server.  However, it looks like a lot of traffic will still go =
to the backend.=20

We have Apache configured like this:=20

<IfModule mod_cache.c>=20

    <IfModule mod_mem_cache.c>=20
        CacheIgnoreCacheControl On=20
        CacheIgnoreNoLastMod On=20
        CacheIgnoreHeaders Set-Cookie=20
        CacheDefaultExpire 3600=20
        CacheMaxExpire 86400=20
        CacheEnable mem /backend/images=20
        MCacheRemovalAlgorithm LRU=20
        MCacheSize 32768=20
        MCacheMaxObjectCount 1024=20
        MCacheMinObjectSize 1=20
        MCacheMaxObjectSize 1048576=20
    </IfModule>=20

</IfModule>=20

If I remove all my local temporary files, then this seems to work well.  =
The image is retrieved from the backend and cached on Apache.  Then =
subsequent requests are handled by Apache.=20

But, we have a large base of existing clients who will most likely =
already have local copies of images.  When such a client loads a page, =
the requests are passed through to the backend only to find that they =
have not been modified and a 302 is returned for each image.  This =
causes a lot of unnecessary traffic to the backend.  How can we avoid =
that?=20

When Apache starts up, the cache is empty.  These images are not getting =
cached because the client issues a conditional GET.  The file is not in =
the Apache cache, so the request is passed to the backed.=20
Then the backend responds with a 302 so Apache is not able to retrieve =
the image and put it in the cache.  Do we have to initialize the cache =
somehow?  =20

Thanks,=20
Ed=20


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