Keep incompatible consumers on their last valid configuration
A new configuration schema reaches an older worker that silently ignores a field needed to preserve retry limits.
- Focused work estimate
- 5h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Compatibility · Fail-closed design
Estimated field mix
- Platform engineering80%
- API design20%
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 internal reporting platform changes feature and timeout settings through environment edits. Partial rollouts leave API and worker processes interpreting different values.
Setup prerequisites
- Create local API and worker configuration consumers.
- Use fabricated settings without secrets.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- ACONFIG-101 · Inventory runtime settings with owners and restart requirements
- ACONFIG-102 · Reject invalid timeout combinations as one configuration unit
- ACONFIG-103 · Define an immutable configuration snapshot envelope
- ACONFIG-104 · Atomically adopt a validated configuration snapshot in each process
- ACONFIG-105 · Publish configuration only against the revision reviewed by the operator
Acceptance criteria
- Consumers declare accepted schema versions.
- Incompatible snapshots are rejected with explicit adoption status.
- Critical missing configuration fails closed under the documented startup policy.
Implementation constraints
- Do not coerce unknown versions into the current schema.
Verification to include
- Adopt compatible settings in old and new local consumers.
- Send a new unsupported schema and preserve the old snapshot or fail startup as declared.
Deliverables
- Compatibility handshake and failure matrix
Rollout and recovery
Deploy compatible readers before publishing new schema; repoint to the older supported revision if needed.
Value of the work
For the engineer: Practice configuration contracts, compatibility and failure recovery.
For the team: Review controlled configuration delivery with inspectable blast radius.
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.