FA-74847 / CRDT convergence / Member archive

G-Counter gossip: all replicas increment one shared slot · case 02

Concurrent increments from different replicas disappear after gossip.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

Each replica keeps a grow-only map replica->count. ["inc", r, k] adds positive integer k to r's own slot; a non-positive k is rejected and counted. ["sync", src, dst] merges src into dst by pointwise maximum. Return per-replica values (sum of slots), the rejection count, and the first replica's sorted slots.

Why this case matters

State-based counters must converge under repeated, reordered and transitive gossip.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
repeated sync is idempotent	`{"rejected": 0, "state": [["n", 5]], "values": [5, 5, 0, 0]}`	`{"rejected": 0, "state": [["a", 3], ["b", 2]], "values": [5, 5, 0, 0]}`	Failed

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