Document lease guarantees and the provider conditions they depend on
A release note says exactly one scheduler runs, even though stale processes may execute until downstream fences reject their writes.
- Focused work estimate
- 2h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Distributed reasoning · Technical communication
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.
- 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
- ALEASE-106 · Fence maintenance writes after a paused scheduler resumes
- ALEASE-107 · Make scheduled maintenance occurrences idempotent across leadership changes
- ALEASE-108 · Expose lease health without implying the holder is making progress
- ALEASE-109 · Recover coordination after a database connection partition
Acceptance criteria
- Describe mutual authority separately from process execution.
- List clock, transaction and provider fencing assumptions.
- Link each guarantee to a race or partition probe.
Implementation constraints
- Avoid claiming leases alone guarantee exactly-once effects.
Verification to include
- Trace a protected-write guarantee to its fencing test.
- Identify an unfenced provider and state the unsupported guarantee.
Deliverables
- Coordination operating contract
Rollout and recovery
Review before enabling external actions; revise the contract when provider semantics change.
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.