ubuntu-appstore-developers team mailing list archive

[Colin Watson <cjwatson@xxxxxxxxxx>]

On Wed, Jul 31, 2013 at 08:02:35AM +0100, Roberto Alsina wrote:
> At the sprint the whole application upgrade story is being talked about,
> and I have a technical doubt:
> 
> What happens to a running app when you update its click package?
> 
> Obviously since app lifecycle[1] means it could be killed while it's
> upgraded, then maybe it has to reload its state from a archive created by
> the previous version. That's not our problem, it's on the app developer's
> hands.
> 
> OTOH, what happens if it's *not* killed? It may have been stopped and not
> killed because there was no memory pressure.
> 
> 1) Does the click package installer kill it if it were stopped?
> 
> 1a) Would it kill it even if it had focus and was running?

click doesn't do anything with running apps, and I'm inclined to say
that it shouldn't because it shouldn't have to know about this kind of
environment-specific detail; this should be the job of a hook of some
kind if it's needed.

> 2) Does installing a new version deletes the old one?

Not necessarily.  If no users have the old version registered, then the
old version will be garbage-collected (not yet implemented); otherwise
it will be left around.

On a single-user system, I would expect that the old version will be
deleted strictly after the new version has been installed, symlinks
adjusted, and all hooks run (in some order).

> 2a) Doesn't that interfere with the idea of having per-user versions?

Well, indeed; that's why we don't unconditionally delete the old one.
:-)

> 3) Is the old version available to be started while the new one is being
> installed?

Yes; the symlinks aren't re-pointed until the end.

> 4) If the old version is not killed and the new one is started, would we
> end up with two instances of the same app on different versions, which is
> not good?

I expect this should be fixed; it just isn't the job of click itself.
It seems appropriate for a user-level hook to sort this out.

(It is probably not possible to write such a hook quite yet, because you
can't write a hook that runs without specifically being attached to by
an app; however, I already have some comments from Ted in my queue which
should have the effect of addressing this.)

-- 
Colin Watson                                       [cjwatson@xxxxxxxxxx]