FA-75022 / CRDT convergence / Member archive

Causal delivery buffer: a delivery does not retry the rest of the buffer · case 02

Buffered messages that became deliverable stay pending until another message arrives.

Member previewVariant 2 · 3 implementations · 10 checks per implementation

Case contract

A receiver starts with an empty delivered vector. An arrival [sender, vector, payload] is a duplicate when its sender entry is at or below the delivered entry or the same (sender, entry) is already buffered. Otherwise it is buffered; then, repeatedly, the oldest buffered message whose sender entry is exactly delivered+1 and whose other entries are all <= delivered is delivered, setting only the sender entry. Return delivered payloads, sorted pending payloads, duplicate count and the delivered vector.

Why this case matters

Operation-based CRDTs converge only if operations are delivered exactly once and in causal order.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
dependency on another sender waits	`{"clock": [["a", 1]], "delivered": ["a1"], "duplicates": 0, "pending": ["b1"]}`	`{"clock": [["a", 1], ["b", 1]], "delivered": ["a1", "b1"], "duplicates": 0, "pending": []}`	Failed

MEMBER ARCHIVE

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