Recover a course-download rename interrupted by process death
A crash between verification and final rename leaves duplicate shelf entries. Introduce a recoverable promotion record.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Crash consistency · Transactions
Estimated field mix
- Storage systems50%
- Mobile30%
- Database engineering20%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
Fictional learning app Birch offers synthetic text and small local media fixtures through a loopback adapter. No copyrighted course assets or network accounts are needed.
Setup prerequisites
- Create small local byte fixtures and a range-response stub.
- Simulate low storage, interruptions and stale manifests.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- CDOWN-102 · Keep mobile download buttons consistent with durable state
- CDOWN-101 · Distinguish unknown course-download sizes from zero bytes
- CDOWN-103 · Validate course manifest paths before creating files
- CDOWN-104 · Resume a mobile course transfer only with matching content identity
- CDOWN-105 · Verify downloaded course bytes before exposing Open
- CDOWN-106 · Pause mobile transfers when storage reservation fails
Acceptance criteria
- Recovery identifies one installed version
- Unverified partials stay hidden
- Repeated recovery is idempotent
Implementation constraints
- Keep metadata and file promotion reconciliation explicit.
Verification to include
- Kill at each promotion boundary
- Repeat recovery after missing temp file
Deliverables
- Promotion journal and crash cases
Rollout and recovery
Disable promotion and retain recoverable temporary files.
Value of the work
For the engineer: Practice mobile file lifecycles and background state recovery.
For the team: Inspect predictable resource usage and truthful download status.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.