puplet/pup/yum-updatesd... rethinking the mechanism

Jeremy Katz katzj at redhat.com
Fri Jun 16 00:32:22 UTC 2006

On Thu, 2006-06-15 at 18:08 -0400, Bill Nottingham wrote:
> If all of this is on the wiki as future plans, I apologize.

Some of it is in the write-up from Roozbeh, some is scattered across
yum-devel-list and some of it is already done ;-)

> Looking at the update interaction as it currently stands:
> 1) yum-updatesd
> 2) puplet
> 3) user
>   a) clicks 'update'
>   b) enters root password
> 4) pup
>   a) checks repositories
>   b) churns metadata
>   c) builds cache
>   d) generates names of packages to be updated, including dependencies

Note that if you're within the time window of the check (likely), then
the metadata update + check stuff doesn't actually have to happen as
it's already been done.  That's one of the big reasons why yum-updatesd
has to run as root -- this way, it can just update the existing metadata
caches and we can just get the advantages of already having that done.

> 5) user
>   a) reviews and approves package list
> 6) pup
>   e) downloads packages
>   f) checks transaction
>   g) updates
> Note that 4a-4d *completely* duplicates 1a-1d. This seems rather inefficient,
> and leads me to wonder if a different model would be better.

... except that the only thing that's really duplicated is "what are the
updates of this set".

> Consider an implementation where *all* the yum code lies in the updates
> daemon; all puplet does is communicate over d-bus with it. The daemon
> sends the list of packages, and then pup calls:
>    setPackagesToUpdate(kernel, yum, glibc)
>    updatePackages()

I don't want to have to do this securely.  Also, if you're interactively
saying that you want an update to occur, you want to give progress.
Which is no fun either.

> The daemon can return a dependenciesNotSatisfied() error, or similar.
> This leads to a faster experience for the user, as you're not duplicating
> all the metadata reading & dependency handling steps in pup itself.
> Moreover, you can make it seem even more seamless for the user by
> having the option to opportunitstically cache updates in the background,
> downloading them before the user actually asks to install them.

There's already the option to opportunistically cache updates.  And even
to automatically apply them if that's your cup of tea. 


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