Chapter 31 - Worked Answers

1. Attempt arithmetic

Attempts begins at one. With limit zero, first failure satisfies Attempts greater than limit and ends failed. With limit one, first failure creates attempt two, and its failure ends failed. Thus maximum total attempts are one and two. The helper immediately creates a new pending task and has no timer/backoff delay. Different task IDs preserve attempt history; this does not make repeated external effects idempotent.

2. Missing exit-code defaults

updateJobForTaskLocked defaults stopped to zero and failed to one when the pointer is absent. The former can produce succeeded; the latter enters retry/failure. These defaults interpret accepted reports, not physical proof that a process exited cleanly. A live lab must retain actual Engine exit evidence. The focused fixture injects explicit codes and establishes the selected state transitions only.

3. Backlog and Forbid

Between returns earliest due occurrences: minute one and minute two for a three-minute delay with limit two. If Forbid sees an active referenced pending/running Job at the start, it suppresses creation without advancing LastScheduleAt there. If none is active, the due loop can create several backlog Jobs in that same pass; it does not recalculate overlap after each. This is narrower than a universal no-overlap guarantee.

4. Checkpoint and DST evidence

Inject failure after CreateJob succeeds but before UpdateCronJob saves LastScheduleAt, then inspect next-pass behavior with active and completed same-name Jobs. Stronger scheduling needs atomic/deduplicated occurrence acceptance and external-effect identity, plus durable restart state. For DST, specify an IANA zone and exact spring/fall transition, compute local/UTC occurrences with injected time and retain actual results. Ordinary UTC/Belgrade October13 arithmetic does not establish skipped/repeated-hour policy or exactly-once execution.

These answers use chapter 31 and its scoped claim/execution records. Design changes remain proposals until separately implemented and tested.