Retry sooner than every 24h in case of unavailable base schedule

[thbar]

The work done in #107/#109 already improved the boot process by ensuring that a dataset is not "unregistered" (disappears from the routes) completely until next deploy if the static part is not available at boot time.

After #109 is merged, though, in case of unavailability at boot, the dataset download will only be retried 24h later at the moment, via this code:

transpo-rt/src/actors/update_actors.rs

Lines 54 to 64 in ee95aa2

	impl actix::Actor for BaseScheduleReloader {
	type Context = actix::Context<Self>;
	fn started(&mut self, ctx: &mut Self::Context) {
	info!(self.log, "Starting the base schedule updater actor");
	ctx.run_interval(std::time::Duration::from_secs(60 * 60 * 24), |act, ctx| {
	info!(act.log, "reloading baseschedule data");
	act.update_data(ctx);
	});
	}
	}

Detecting the unavailability (at boot and also later) and rescheduling with shorter timeframes (possibly with a form of backoff) would be a real improvement.

Todos

• Figure out how to move forward in time, to implement proper tests on this workflow. It could be done via introspection of scheduled run_interval in Actix, if available, or via another form of tweak.
• Make sure to avoid cascading downloads (e.g. all of a sudden, we end up downloading multiple times) - see cascading failures in distributed systems for the overall idea