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From "Presto, Patrick" <Patrick.Pre...@qwest.com>
Subject [users@httpd] Caching is serving up the wrong user content to some users who log in.
Date Mon, 21 Jun 2010 14:13:17 GMT
We have just started enabling caching on our Apache 2.2.3 Web Server to take advantage of the
performance increase.  We use Apache as a proxy to our back end Java applications.  One of
our larger portal applications has had reports of users logging in and getting other users
content.  We don't have this problem when we disable the cache so we are somehow caching user
specific content sometimes.  We don't see this with most users in production, and we are unable
to replicate this behavior in test or production at this time.

Does anyone have any ideas what could cause this intermittent caching behavior?


I looked at the Change log and found something that could be a possibility, but I don't fully
understand this bug.
Under 2.2.12 Changes:
 *) mod_disk_cache/mod_mem_cache: Fix handling of CacheIgnoreHeaders
    directive to correctly remove headers before storing them.
    [Lars Eilebrecht]

Could it be possible that CacheIgnoreHeaders is sometimes storing a "Set-Cookie" header for
content when it shouldn't be?  If so, would it be possible that the next request for that
content comes with the original requestors cached "Set-Cookie" header and resets the current
users Cookie or ID. This could then cause the current user to access the original requestors
data since the "Set-Cookie" header might have been accidentally stored in the cache.
If this could be the cause does anyone know how I could prove this in test?

Here is our current caching configuration using mod_expires, mod_cache, and mod_disk_cache.
 We are disabling some areas of the site that use velocity because we don't want to cache
some of the dynamic stuff like sessionVariable property files for example.

Any help is appreciated!  Thank you!

<IfModule mod_cache.c>
    <IfModule mod_disk_cache.c>
        CacheRoot  /opt/apache/cache/
        CacheEnable disk /
        # FORCE caching for all requests (without Cache-Control: no-cache)
        # If Last-Modified header is removed you need to set this to ON to cache
        CacheIgnoreNoLastMod On

        CacheDisable /business/sessionVariableSetup.vm
        CacheDisable /business/education/
        CacheDisable /business/partners/
        CacheDisable /business/consultants/
        CacheDisable /business/home/

        CacheIgnoreHeaders Set-Cookie Set-Cookie2

    </IfModule>

    <IfModule mod_expires.c>
        # Add expires headers for images, css & js files
        ExpiresActive On
        ExpiresByType image/gif A28800
        ExpiresByType image/jpeg A28800
        ExpiresByType image/png A28800
        ExpiresByType text/css A28800
        ExpiresByType text/javascript A28800
        ExpiresByType application/x-javascript A28800
        ExpiresByType application/javascript A28800
        ExpiresByType application/ecmascript A28800
        ExpiresByType image/x-icon A28800
    </IfModule>
</IfModule>
Patrick

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