[squid-users] http 302 status and storeid: infinite loop problem

From: Niki Gorchilov <niki_at_gorchilov.com>
Date: Tue, 8 Oct 2013 17:18:48 +0300

Hi there.

Started playing with Squid store_id feature (thanks Eliezer for
the implementation) and discovered an unresolvable issue, due to the
caching of 302 results (I know it's happening when only Expires header
is present, but anyway).

Imagine the following scenario (that happens quite often): an CDN node
currently offline for maintenance, redirecting all the traffic to
another node with 302 Moved Temporary response.

As the first node's url has been normalized by the store_id helper,
the response gets cached under the squid.internal url.

Now, when Squid follows the redirect to the new CDN node, the store_id
helper returns the same normalized url (as intended :-), so the cached
302 result pops up again, forcing squid to reconnect this same node...
Boom! Infinite loop

Any suggestions how to avoid this loop? Tried playing with http_status
acl but discovered it's not applicable in this scenario (as discussed
by Amos and Eliezer more than a year ago).

Without a method to disable caching of 30x results from squid.conf
store_id feature is not usable, IMHO!

Received on Tue Oct 08 2013 - 14:19:40 MDT

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