WorkerCronTrigger — takoform_worker_cron_trigger

Workload and consumer

A team runs periodic work — cache refresh, cleanup, digests — by having the platform invoke its worker's scheduled handler on a cron schedule.

Role

attachment. The trigger activates the worker from the outside; deleting the trigger never deletes the worker.

Observable semantics

cron is the portable five-field cron subset, interpreted in UTC only. There is no timezone field, so two conforming hosts can never fire the same trigger at different instants. Each match invokes the scheduled handler of the worker's active deployment; a missed window is skipped, not queued.

The grammar is closed and deliberately small: exactly five single-value fields separated by single spaces, where minute is a literal 0-59, hour a literal 0-23, day-of-month * or 1-31, month * or 1-12, and day-of-week * or 0-6. Ranges, lists, steps, and names are rejected, and * is not accepted in the minute or hour field: * * * * *, 0 * * * *, and */5 * * * * are all invalid. The most frequent representable schedule is therefore once per day at one fixed UTC time, and hourly or sub-hourly work cannot be declared with this Form. Widening the grammar changes the observable firing set, so it is a new definition version of this Form rather than a host-side relaxation; every conforming host must reject what this grammar rejects until then.

Why this is one Form

Schedule plus target is one observable fact. The UTC-only rule is the completeness boundary of decision 0008: leaving the zone open would let two hosts fire at observably different times.

What would require a separate Form

Timezone-aware or calendar-aware scheduling (a TimezoneSchedule) carries different firing semantics and is separate family work.

Provided Interfaces

None.

Accepted Bindings

None.

Lifecycle risks

Attaching a trigger to a worker whose versions do not declare the scheduled handler must fail closed. Updating cron is an in-place update; changing worker replaces the attachment.

Prior art

The cron trigger of a proven edge platform, restricted to the interoperable five-field UTC subset already used by the retained catalog.