# `StatifierOban.Timer.Delivery.Session`
[🔗](https://github.com/riddler/statifier_oban/blob/v0.17.3/lib/statifier_oban/timer/delivery/session.ex#L1)

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?":

1. **Terminated?** `Registry.lookup/2` against `Statifier.Registry`
   under the scope (st-ADR-0027 decision 2: sessions register under
   their session id). Empty means discard: the session no longer
   exists, or never registered, and `status/1` is not safe to call.
2. **Halted?** With a live process confirmed, `status/1`. Anything but
   `:running` discards too - "live" is stricter than "not terminated":
   a `:done` session 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 `:terminated` fact step 1 answers.

Delivery is `Statifier.Session.send_event/2` - the same door a fired
in-process timer rejoins through - with the event built by
`StatifierOban.Timer.Delivery.fired_event/2`, 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. The `caller_context` hop is what stitches the firing back to
the trace that armed the timer, hours or a restart later; the behaviour
module's "Restoring the caller's trace context" section spells out why.
`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
execution. 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.

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*Consult [api-reference.md](api-reference.md) for complete listing*