Recover an orphaned temporary replacement after restart
A crash leaves temporary files beside the destination; startup cannot tell whether they are incomplete writes or a replacement ready to finish.
- Focused work estimate
- 6h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Crash consistency · Reconciliation · Filesystem safety
Estimated field mix
- Systems programming70%
- Site reliability30%
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
A fictional local agent watches generated inbox files and schedules bounded processing. Direct system calls are scattered across the code, mishandle interrupted operations, and make tests platform-dependent. Build a Rust OS adapter with temporary fixture directories; no kernel module, elevated privilege, or production host modification is required.
Setup prerequisites
- System calls
- File descriptors
- Monotonic clocks
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- SKERNEL-102 · Write a durable replacement without exposing a half file
- SKERNEL-101 · Read a file completely across short system calls
- SKERNEL-104 · Keep wall-clock changes out of elapsed-time deadlines
- SKERNEL-105 · Normalize watcher bursts into a bounded rescan request
- SKERNEL-106 · Bound open descriptors while scanning a deep inbox
- SKERNEL-107 · Prevent path traversal through a watched-root handle
- SKERNEL-108 · Expose platform capability instead of silently changing semantics
Acceptance criteria
- Temporary name binds operation identity and expected content hash
- Recovery verifies destination and temporary content before action
- Ambiguous or foreign files remain untouched and visible
Implementation constraints
- Cleanup is scoped to the opened trusted root and never follows links.
Verification to include
- Recover before-rename and after-rename crash fixtures idempotently.
- Place a foreign matching-looking file and confirm the agent records but does not delete it.
Deliverables
- Replacement journal and startup reconciliation drill
Rollout and recovery
Run recovery in report-only mode before enabling scoped cleanup.
Value of the work
For the engineer: Practice OS error semantics, partial I/O, portability and deterministic abstraction boundaries.
For the team: Review host-facing code whose retries, resource limits, and platform differences are explicit before packaging it as a local agent.
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.