Fence maintenance writes after a paused scheduler resumes
A scheduler pauses past expiry, then resumes a previously prepared plan after another instance has taken over.
- Focused work estimate
- 5h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Fencing · Concurrency
Estimated field mix
- Distributed systems70%
- Database engineering30%
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 document service runs periodic retention planning on multiple application instances. Paused instances resume after lease expiry and can overlap newer schedulers.
Setup prerequisites
- Create a synthetic maintenance queue and two independent scheduler clients.
- Use fake time where possible and no destructive real retention actions.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- ALEASE-101 · Specify scheduler lease state with a separate authority epoch
- ALEASE-102 · Use one authoritative clock boundary for lease decisions
- ALEASE-103 · Classify maintenance actions that require fencing before side effects
- ALEASE-104 · Acquire a scheduler lease atomically under competing instances
- ALEASE-105 · Renew a scheduler lease only for the current holder and epoch
Acceptance criteria
- Every protected write checks current authority epoch.
- A stale owner cannot complete or activate a plan.
- Record rejected stale activity without overwriting current progress.
Implementation constraints
- Carry epoch through the command and recheck at commit.
Verification to include
- Pause owner A, let B acquire, then finish B's plan.
- Resume A and verify its write is rejected even if it began earlier.
Deliverables
- Commit-time fencing and pause reproduction
Rollout and recovery
Canary synthetic plan activation; disable unfenced writes until every path passes the stale-owner probe.
Value of the work
For the engineer: Practice lease assumptions, fencing and stale-owner rejection.
For the team: Review safe coordination that remains explainable under pauses and recovery.
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.