PackageKit not automatically refreshing updates

[christiantosta]

I'm running Fedora 37 with KDE Discover, which uses the PackageKit infrastructure to get updates, and I came across the following problem: if I run a "dnf upgrade" the updates are shown normally, however they are not shown in Discover.

A bug was opened with KDE about this and it became evident that the problem is related to PackageKit or some plugin related to the distribution.

https://bugs.kde.org/show_bug.cgi?id=461962

So, as sugested by Nate from KDE, I ran some pkcon commands (see attachments).

As you can see, it looks like PackageKit is not automatically updating the update lists.
pkcon-commands-output.txt

The packagekitd is running normally as root user.

[ximion]

This is working perfectly fine on Debian/Ubuntu, so I wonder whether this is actually an issue with the DNF backend in PK - maybe DNF doesn't notify the daemon that there were changes to the cache?

[christiantosta]

Please see #9 and Fedora bugzilla#1950041. Maybe is this related to that cache-age issues?

https://bugzilla.redhat.com/show_bug.cgi?id=1950041

PS: If I run pkcon with -c option, the cache refreshes and updates turns available to Discover.

[ximion]

PS: If I run pkcon with -c option, the cache refreshes and updates turns available to Discover.

That's quite telling! This needs someone with DNF experience to resolve then...

[aleasto]

The default maximum-cache-age in PackageKit is G_MAXUINT, which the dnf backend correctly interprets as 'always use the cache'.

Gnome-Software seems to be manually setting the cache age for its transactions, so this doesn't interest them.
Plasma-Discover instead uses the default, which if the default is G_MAXUINT should probably be changed to something sane instead.

The question is why does the apt backend act differently? I think the dnf backend is behaving correctly here.

[aleasto]

So the apt backend ignores cache-age completely. Instead, it relies on manual RefreshCache() calls.

The dnf backend instead honours cache-age for all transactions - which is G_MAXUINT by default - including RefreshCache. That means that while for the apt backend it is enough to call RefreshCache(false /*force*/), to achieve the same thing you'd need to call RefreshCache(true /*force*/). The apt backend ignores the force parameter as without a cache-age every refresh is forced.
So fedora downstream "fixed" this issue with this patch, which I'm now considering adopting in upstream KDE

Overall I'm quite unhappy with how differently different backends behave...

[ximion]

So the apt backend ignores cache-age completely. Instead, it relies on manual RefreshCache() calls.

The dnf backend instead honours cache-age for all transactions

Yes, that's just how APT is designed vs how DNF is designed. They just work differently in that regard, and PackageKit doesn't abstract this away.

[aleasto]

I think it is an issue that RefreshCache() - analogously pkcon refresh - by default will never refresh the cache with the dnf backend.
Because the default cache-age is G_MAXUINT and the default force value is false.
It is implemented correctly (aka not a bug), but very unexpected if you just want to use packagekit without knowing the internals of all backends...