The default StatifierOban.Timer.Delivery: feeds a fired event back
into a live Statifier.Session, behind the two-step liveness check
statifier-ex's docs/durable-timers.md spells out.
The two steps run in order because Statifier.Session.status/1 is a
GenServer.call that exits the caller against a dead process - it
cannot itself answer "terminated?":
- Terminated?
Registry.lookup/2againstStatifier.Registryunder the scope (st-ADR-0027 decision 2: sessions register under their session id). Empty means discard: the session no longer exists, or never registered, andstatus/1is not safe to call. - Halted? With a live process confirmed,
status/1. Anything but:runningdiscards too - "live" is stricter than "not terminated": a:donesession keeps its process but declines to drain, so an event fed to it would sit queued forever, not be processed and not be discarded. The process exiting between the two steps is caught and reported as the same:terminatedfact step 1 answers.
Delivery is Statifier.Session.send_event/2 - the same door a fired
in-process timer rejoins through - with the event built from the stored
effect exactly as the session's own delivery path builds it:
origin/origintype stamped as the scxml processor at the sending
session's location, sendid only when the author wrote the id (C.1),
data and caller_context carried through untouched. send_event/2
is a cast, so :delivered means enqueued onto the session's inbox, not
processed.
This module requires Statifier.Supervisor (which owns
Statifier.Registry) to be running: Registry.lookup/2 raises when it
is not, and the job retries rather than discards - a missing registry
is an environment fact about the host, not a liveness fact about the
run. The scope must therefore be the session id the session registered
under (ctx.session_id); a host using any other scope owes its own
StatifierOban.Timer.Delivery implementation.