Add instructions for cluster consistency invariants#893
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Signed-off-by: sho-iizuka <sho-iizuka@cybozu.co.jp>
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Pull request overview
Adds a GitHub Copilot instruction set that documents the key safety/consistency invariants for MOCO’s clustering/ logic, intended to help prevent regressions that could lead to data loss or split-brain.
Changes:
- Introduced
.github/instructions/clustering.instructions.mddescribing primary/writability rules, switchover/failover sequencing, errant replica handling, and replica health criteria. - Scoped these invariants to changes under
clustering/*viaapplyTo.
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Signed-off-by: sho-iizuka <sho-iizuka@cybozu.co.jp>
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yamatcha
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Apr 27, 2026
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Summary
This PR adds
clustering.instructions.mdto the instructions directory to formally define the consistency and safety invariants of the MOCO clustering logic.Context
The clustering logic in MOCO is critical for maintaining data consistency across MySQL instances and preventing split-brain scenarios.
By adding these rules as an instruction set, we enable GitHub Copilot code review to automatically verify if new changes in
clustering/*adhere to these invariants. This provides an automated safety net to catch potential violations early in the development cycle.