[Fedora-livecd-list] [PATCH 3/6] Setting the yumcache

[Jeremy Katz]

On Wed, 2007-08-08 at 13:31 -0400, Colin Walters wrote:
> On Wed, 2007-08-08 at 12:37 -0400, Jeremy Katz wrote:
> > On Tue, 2007-08-07 at 17:49 -0400, Colin Walters wrote:
> > > On Tue, 2007-08-07 at 17:26 -0400, Jeremy Katz wrote:
> > > > So, I commented a little on Colin's related patch... I'm leaning towards
> > > > this approach, though.
> > > 
> > > If using the system yum cache works, that makes a lot of sense to me.
> > 
> > The nice thing with allowing it to be specified is that you can either
> > end up with
> > a) unspecified does a private cache, just like now (this is an important
> > case to keep working, especially when doing multiple builds at a time
> > from a fast local source)
> 
> I don't quite understand this one - the cache is in the tempdir as far
> as I can see; therefore it's not shared between builds?

Right -- because if I'm creating multiple images at a time, you
otherwise run some risk (at least for now) of stomping over things.  So
having the default be the safe, though slower, route isn't a bad thing.

> > b) you can specify the system cache if you're pointing at the same repos
> > as your system.  that can save you download time, etc if you do
> > keepcache=0 in your system yum.conf or do your system update after
> > creating a live image
> 
> (keepcache=1 I assume you mean)  But is there the potential for things
> to break if multiple yum processes write to it?

Yeah -- right now, the locking is at the "one yum process at a time"
level.  livecd-creator isn't taking that lock as, by default, we're not
using those caches.  It's probably worth looking at per-repo locks in
yum for the future to avoid this sort of thing.  But that starts to get
a little bit more painful.

> > c) you can specify something like /var/tmp/livecd-cache if you want to
> > have a livecd-specific cache.
> 
> I don't really want it to be livecd-specific.  The goal is just to have
> tools that by default do not repeatedly download huge files over the
> internet.  I have plenty of gigs of hard drive space.  Mock drove me
> absolutely nuts for this reason (yes, it has some magic --cache option
> that's not the default, requires manual intervention to update, and was
> broken anyways last I tried).
> 
> Hmm.  Would anything break if we just pointed all the tools
> at /var/cache/yum?  Does yum delete all files it sees there if it has
> keepcache=0?  And what about the concurrency issue?

As of right now, pointing everything at the same place is likely a
recipe for disaster.  Making it _possible_ for things to share when the
user is aware and wants to isn't unreasonable.  And then, when we
eventually get finer grained locking in place, we can look at moving the
default to be shared between everything

Jeremy