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From Graham Leggett <>
Subject Re: mod_proxy Cache-Control: no-cache=<directive> support Apache1.3
Date Thu, 07 Mar 2002 23:05:36 GMT
Bill Stoddard wrote:

> mod_disk_cache does not require knowledge of content length. In principle, do you think
> this is a problem for a proxy cache provided we can gracefully detect and handle cases
> where cache thresholds are being exceeded? What does squid and apache 1.3 do?

I have no idea what squid does. Apache v1.3 only makes a cached object
available after it has been downloaded completely, and I think only
objects with content-lengths. This causes the problem of nasty load
spikes hitting a backend server when cached content expires.

I think the following logic is a compromise:

- In mem_cache, objects need content-lengths. Partially cached objects
are fetchable, solving the load spike problem.

- In disk_cache, objects do not need content-lengths, but attempts to
cache may be abandoned once the magic threshhold is reached.

- As a result of the above possibility that downloads might be
abandoned, partially cached objects should not be fetchable.

Does this make sense?

Is there a way you can see to make disk_cache support partial responses
being fetchable?

-----------------------------------------		"There's a moon
					over Bourbon Street
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