Remove timed

[FlorentRevest]

We've been talking for a while about removing timed to simplify our daemons stack significantly. I've given this a stab and have a proof of concept already but it's scattered in various places so I'd like to share the high level plan here so we can more easily track progress on the subtasks.

From a high level perspective, we only use timed to:

• change the system time and timezone. this can be done by systemd timedatectl instead
• schedule wake up events. this can either be done directly with timerfds if the caller process stays alive or with systemd timers if the caller process may die

In practice we would need to:

• modify asteroid-btsyncd to use systemd rather than timed when syncing time
• modify asteroid-launcher to use systemd timers to schedule snoozed notifications
• modify lipstick to use timerfd instead of timed to schedule aod refreshes
• modify mkcal to use systemd timers rather than timed in TIMED_SUPPORT
• modify nemo-qml-plugin-alarms to use systemd timers rather than timed to schedule alarms
• modify nemo-qml-plugin-systemsettings to use systemd to retrieve time, timezone and date
• modify nemo-qml-plugin-time to use systemd to retrieve the time and timezone
• modify meta-asteroid to remove dependencies on timed and to install tzdata instead of timed-tzdata

[beroset]

To clarify this, asteroid-settings uses only the DBus org.freedesktop.timedate1 service which relies on systemd but not timed.

[FlorentRevest]

Indeed - I don't know how I got confused - let me drop this from the list

[beroset]

The mechanism in asteroid-launcher could be considerably simplified if we do not need the ability for notifications to outlast the asteroid-launcher process. That is, if we can simply keep a list of times and notifications and dispatch them when needed. What it would mean would be that notifications which are queued but not yet executed would be forgotten if asteroid-launcher is restarted. Would that be an acceptable change?

[FlorentRevest]

Yeah, absolutely. I think that directly using the timerfd API from asteroid-launcher or lipstick is the way to go for this kind of things.

For longer term events, it makes sense to have a daemon that can hold timerfds and save to and restore from disk in case the process restarts. That's the only feature of timed and "iphb" we really need. This could be replicated with systemd timers but starting those is a little bit awkward and ties us to systemd even more.