Classify maintenance actions that require fencing before side effects
The design adds a lease but assumes every downstream operation automatically knows whether its caller is still leader.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Boundary analysis · Fencing
Estimated field mix
- Distributed systems60%
- System design40%
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.
Acceptance criteria
- List each protected mutation and its fencing check location.
- Separate read-only planning from state-changing execution.
- Mark unfenceable external effects as unresolved.
Implementation constraints
- Use synthetic retention plans; delete no real objects.
Verification to include
- Trace a plan-state update to its epoch guard.
- Identify an external adapter without epoch support and block its destructive action.
Deliverables
- Fencing coverage matrix
Rollout and recovery
Require coverage before enabling actions; keep unresolved provider operations read-only.
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.