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Re: Yum, Proxy Cache Safety, Storage Backend



On Wed, 2008-01-23 at 21:41 -0500, Warren Togami wrote:
> I just had an in-depth discussion with Henrik Nordström of the Squid
> project about how HTTP mirrors and the yum tool itself could be improved
> to safely handle proxy caches.  He gave me lots of good advice about how
> HTTP mirrors can be configured for cache safety, Squid can be configured
> for yum metadata cache safety, and yum itself can be improved to be more
> robust in dealing with proxy caches.

> "Cache-Control: max-age=0"
> ==========================
> This HTTP header directive can be either in the request or response.

snip

> 3) yum can always include the HTTP directive in its request for
> repodata/* files.  Can we make this the default in future versions of
> yum?  I personally don't see a drawback (unless repodata becomes
> versioned, then we don't want this.)

I recommend this strongly as an option (instead of 'always') but I'd
love to be able to set this network wide (yum.conf over NIS? just
kidding).  

I currently have numerous problems with this because all my systems sit
behind a squid cache used only for caching yum packages, but we have in
internal repo here, and if I push changes to it 'too fast' I get in
trouble.  I've created a shell script which 'invalidates' the squid
cache for repos found in /etc/yum.repos.d using 'wget --no-cache' .
Script attached for instructional purposes.

Another problem not mentioned is the non-stable nature of mirrorlist.
If you use one mirror on one update, and another on the next, the cache
cannot help.

This requires some non-trivial (in terms of setup cost) fiddling with
the yum config on every host to change the way mirror (or baseurl)
selection works, and is brittle w.r.t future change.

David

Attachment: refresh_squid_repo_data.sh
Description: application/shellscript


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