yum-presto occasionally goes into "eternal" loop looking for deltas

[James Antill]

On Thu, 2010-01-07 at 21:19 +0200, Jonathan Dieter wrote:
> On Thu, 2010-01-07 at 20:44 +0200, Pekka Pietikainen wrote:
> > Presto is one of the best things ever, but occasionally it ends up not
> > finding the delta files from any of the mirrors in the mirror list and just
> > loops through them without making any progress. --disablepresto works 
> > a-ok, I think yum clean all; yum update also did the trick once.
> > 
> > Still, this can probably be made a lot better. It shouldn't do that even if the mirrors
> > are out-of-sync. Maybe add some logic that just disables
> > presto if the deltas are nowhere to be found after a few attempts? Anyone
> > else even see this happen?
> 
> Yeah, see https://bugzilla.redhat.com/show_bug.cgi?id=540140.  To
> summarize, the problem is that new updates have been pushed to the
> server between the time you loaded primary.sqlite and prestodelta.xml.
> 
> When you run 'yum clean metadata' or 'yum clean all' it removes the
> outdated cached primary.sqlite and downloads the newer version.
> 
> The bug has been closed as WONTFIX because there have only been a few
> reports; I wouldn't mind revisiting that decision if someone has a
> clever way of fixing it. (And I'm not convinced that checking n mirrors
> and then giving up is the solution.)

 The plugin could require yum >= 3.2.25, and then do something like (in
config or prereposetup):

for repo in repos:
    repo.mdpolicy.append('prestodelta')

...which would auto download presto MD when yum gets new repomd/primary.
People might complain though :) ... another kind of fix would be for the
plugin to call ".cleanExpireCache()" if the MD fails to download.

 The nice server side fix is to keep around more than one complete set
of MD (possible now we have unique MD filenames), so there would have to
be two updates within the client side cache timeout. But I'm not sure
how easy that is.

-- 
James Antill - james at fedoraproject.org
http://yum.baseurl.org/wiki/releases
http://yum.baseurl.org/wiki/whatsnew/3.2.26
http://yum.baseurl.org/wiki/YumMultipleMachineCaching