FA-1038 / Reliability / Member archive

Evict an unhealthy backend: Old failure samples evict a recovered backend · case 03

The health eviction operation is admitted even though old failure samples evict a recovered backend.

Member previewVariant 3 · 3 implementations · 9 checks per implementation

Case contract

Return a Boolean admission decision for evict an unhealthy backend. The record r must satisfy all of: r['consecutive_failures'][0] >= r['consecutive_failures'][1]; r['minimum_survivors'][0]-1 >= r['minimum_survivors'][1]; r['sample_freshness'][0]-r['sample_freshness'][1] <= r['sample_freshness'][2]; (r['ejection_limit'][0]+1)*100 <= r['ejection_limit'][1]*r['ejection_limit'][2]; r['backend_incarnation'][0] == r['backend_incarnation'][1]. Extra tracing fields are ignored; validation does not mutate the record.

Why this case matters

A deterministic local contract for reliability. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
Old failure samples evict a recovered backend	`true`	`false`	Failed

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