0470 — The scheduler produces each due job in its own transaction

Context. A scheduler tick may find many due cron_job rows. Producing them all inside one shared tick transaction couples every job’s fate to every other’s and holds locks for the length of the tick.

Decision. The cronscheduler processes one row per transaction: recheck the due predicate, produce the request, and advance next_scheduled_time, then commit before touching the next row. A row whose produce fails is logged at WARN and skipped, and a duplicate produce (idempotency-key hit) is surfaced as a WARN via ProduceResult rather than an error.

Consequences. A poisoned row cannot roll back or stall its siblings’ produces — the failure blast radius is one job. Duplicate detection is observable without failing the tick. Rejected: one shared transaction per tick — a single bad row would abort every job’s produce and back off the whole scheduler.