FA-090 / Distributed coordination / Member archive

Overlapping identical reads start duplicate remote jobs · case 05

Concurrent callers start separate fetches, or a completed fetch incorrectly absorbs a later request.

Member previewVariant 5 · 3 implementations · 6 checks per implementation

Case contract

Events are ['start',key,waiter] or ['complete',key,value]. Distinct waiters share an active job. Completion emits [waiter,value] in registration order and removes that flight. Later starts create new jobs. Return [jobs started,deliveries]; unsolicited completions are ignored.

Why this case matters

Models request coalescing for distributed reads. This is not durable event deduplication: completed requests deliberately do not establish a cache or permanent idempotency record.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
overlapping callers share work	`[6, [["w0", 5], ["w1", 5], ["w2", 5], ["w3", 5], ["w4", 5], ["w5", 5]]]`	`[1, [["w0", 5], ["w1", 5], ["w2", 5], ["w3", 5], ["w4", 5], ["w5", 5]]]`	Failed

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