FA-75107 / CRDT convergence / Member archive

Epoch-resettable counter: an older epoch overwrites a newer one · case 02

A replica that has not seen a reset undoes it when it syncs.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Each replica holds an epoch and grow-only slots for that epoch. ["inc", r, k] grows r's slot; ["reset", r] increments r's epoch and clears all its slots. ["sync", s, d]: if s's epoch is higher, d adopts s's epoch and a copy of s's slots; if equal, slots merge by maximum; if lower, nothing changes. Return values (sum of slots) and epochs.

Why this case matters

Reset-wins counters need an epoch so a reset is not undone by increments that were concurrent with it.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
stale epoch is ignored	`{"epochs": [0, 0, 0], "values": [7, 7, 0]}`	`{"epochs": [1, 0, 0], "values": [3, 7, 0]}`	Failed

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