systemd-sysupdate support for slow rollout (aka A/B testing)

[Nils Kattenbeck]

Hello and happy New Year,

I tried to solve this by adding percent-specifiers as query parameters to
the Path= property of the sysupdate definition though to my dismay I had to
find out that they are discarded by the sd-import logic. Removing this
restriction could solve this problem as one could easily send machine id,
os version and similar information to the server.

This would in general enable fine grained control over which updates a
devices sees. Also see
https://lists.freedesktop.org/archives/systemd-devel/2024-January/049889.html
for a case where this is desirable.

Kind regards, Nils

On Wed, Dec 20, 2023, 19:04 Nils Kattenbeck <nilskemail at gmail.com> wrote:

> Hey everyone,
>
> does sysupdate currently support any way to slowly roll out updates
> where the server providing the files can be in control? This would be
> used to slowly make a new version available and have it at e.g. 1%
> adoption for a day to monitor regressions before increasing the
> coverage. I was unable to find any information about it in the
> documentation.
>
> Currently it seems like I would have to implement a different service
> which calls the sysupdate binary (or uses dbus once #28134 has landed)
> and then decides based on some other information.
>
> One idea I had would be that systemd-pull could send the machine-id
> based on which the server could then decide to provide the newer file
> (e.g. last two chars == "00" would roll it out to ~1/255). Though I am
> not sure if sd-pull is supposed to be "anonymous", i.e. do not provide
> this identifying information. Another drawback of this would be that
> stateless systems which reboot often get a new machine-id each boot,
> thus having an increased chance to get the newer version.
>
> Does anything like this already exist or is planned? Or should that be
> done by different applications on the client side?
> I also remember there being a discussion about plugging in different
> sd-pull like implementations/backends[1] to support delta updates,
> other transports, or TLS client authentication. This could at least be
> adapted to support my idea to send the machine-id as an HTTP header
> (e.g. X-MACHINE-ID).
>
> Greetings, Nils
>
> [1]
> https://lists.freedesktop.org/archives/systemd-devel/2023-February/048856.html
>
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