{"abstract":"The write concern operation is admitted even though volatile receipt acknowledgements satisfy durable concern.","category":"Replication","checks":9,"contract":"Return a Boolean admission decision for acknowledge a replicated write concern. The record r must satisfy all of: len(set(r['distinct_replicas'][0])) >= r['distinct_replicas'][1]; sum(r['durable_acks'][0]) >= r['durable_acks'][1]; len(set(r['failure_domains'][0])) >= r['failure_domains'][1]; all(x == r['write_binding'][0] for x in r['write_binding'][1]); r['ack_deadline'][0] < r['ack_deadline'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-write-concern","failed_approach":"Adding the durable acks check repairs the reported defect, but replacing the adjacent failure domains check loses that independent invariant.","family":"xd-write-concern-durable_acks","id":"FA-706","implementations":{"attempt":{"sha256":"63a3d8afa6a11aa104820d45f54bf2ec3f361db669ffad658eed41d926ae00cb","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (len(set(r['distinct_replicas'][0])) >= r['distinct_replicas'][1]) and (sum(r['durable_acks'][0]) >= r['durable_acks'][1]) and (all(x == r['write_binding'][0] for x in r['write_binding'][1])) and (r['ack_deadline'][0] < r['ack_deadline'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'distinct_replicas': [['a', 'b'], 2], 'durable_acks': [[True, True, False], 2], 'failure_domains': [['z1', 'z2'], 2], 'write_binding': ['w2', ['w2', 'w2']], 'ack_deadline': [9, 10]}\ncheck('valid operation', solve(r), True)\ncheck('Repeated acknowledgements count as separate replicas', solve(dict(r, **{'distinct_replicas': [['a', 'a'], 2]})), False)\ncheck('Volatile receipt acknowledgements satisfy durable concern', solve(dict(r, **{'durable_acks': [[True, False, False], 2]})), False)\ncheck('Multiple copies in one failure domain satisfy zone concern', solve(dict(r, **{'failure_domains': [['z1', 'z1'], 2]})), False)\ncheck('Replica acknowledgements refer to another write', solve(dict(r, **{'write_binding': ['w2', ['w1', 'w2']]})), False)\ncheck('A write is reported successful after its response deadline', solve(dict(r, **{'ack_deadline': [10, 10]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'distinct_replicas': [['a', 'a'], 2], 'durable_acks': [[True, False, False], 2], 'failure_domains': [['z1', 'z1'], 2], 'write_binding': ['w2', ['w1', 'w2']], 'ack_deadline': [10, 10]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"c556841fdf4ddc6a46dccf159ee33df030f5dc80e1967d27aa86a812a1fa23f3","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (len(set(r['distinct_replicas'][0])) >= r['distinct_replicas'][1]) and (len(set(r['failure_domains'][0])) >= r['failure_domains'][1]) and (all(x == r['write_binding'][0] for x in r['write_binding'][1])) and (r['ack_deadline'][0] < r['ack_deadline'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'distinct_replicas': [['a', 'b'], 2], 'durable_acks': [[True, True, False], 2], 'failure_domains': [['z1', 'z2'], 2], 'write_binding': ['w2', ['w2', 'w2']], 'ack_deadline': [9, 10]}\ncheck('valid operation', solve(r), True)\ncheck('Repeated acknowledgements count as separate replicas', solve(dict(r, **{'distinct_replicas': [['a', 'a'], 2]})), False)\ncheck('Volatile receipt acknowledgements satisfy durable concern', solve(dict(r, **{'durable_acks': [[True, False, False], 2]})), False)\ncheck('Multiple copies in one failure domain satisfy zone concern', solve(dict(r, **{'failure_domains': [['z1', 'z1'], 2]})), False)\ncheck('Replica acknowledgements refer to another write', solve(dict(r, **{'write_binding': ['w2', ['w1', 'w2']]})), False)\ncheck('A write is reported successful after its response deadline', solve(dict(r, **{'ack_deadline': [10, 10]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'distinct_replicas': [['a', 'a'], 2], 'durable_acks': [[True, False, False], 2], 'failure_domains': [['z1', 'z1'], 2], 'write_binding': ['w2', ['w1', 'w2']], 'ack_deadline': [10, 10]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"db9f09117c9c355156490a5d2d48c5add06f61edc801b1cbadee59668a6c1532","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (len(set(r['distinct_replicas'][0])) >= r['distinct_replicas'][1]) and (sum(r['durable_acks'][0]) >= r['durable_acks'][1]) and (len(set(r['failure_domains'][0])) >= r['failure_domains'][1]) and (all(x == r['write_binding'][0] for x in r['write_binding'][1])) and (r['ack_deadline'][0] < r['ack_deadline'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'distinct_replicas': [['a', 'b'], 2], 'durable_acks': [[True, True, False], 2], 'failure_domains': [['z1', 'z2'], 2], 'write_binding': ['w2', ['w2', 'w2']], 'ack_deadline': [9, 10]}\ncheck('valid operation', solve(r), True)\ncheck('Repeated acknowledgements count as separate replicas', solve(dict(r, **{'distinct_replicas': [['a', 'a'], 2]})), False)\ncheck('Volatile receipt acknowledgements satisfy durable concern', solve(dict(r, **{'durable_acks': [[True, False, False], 2]})), False)\ncheck('Multiple copies in one failure domain satisfy zone concern', solve(dict(r, **{'failure_domains': [['z1', 'z1'], 2]})), False)\ncheck('Replica acknowledgements refer to another write', solve(dict(r, **{'write_binding': ['w2', ['w1', 'w2']]})), False)\ncheck('A write is reported successful after its response deadline', solve(dict(r, **{'ack_deadline': [10, 10]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'distinct_replicas': [['a', 'a'], 2], 'durable_acks': [[True, False, False], 2], 'failure_domains': [['z1', 'z1'], 2], 'write_binding': ['w2', ['w1', 'w2']], 'ack_deadline': [10, 10]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xd-write-concern-durable_acks","generated_at":"2026-09-29T14:36:55.528858+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local contract for replication. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.","repair":"Require sum(r['durable_acks'][0]) >= r['durable_acks'][1] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the durable acks invariant while validating the other operation preconditions.","sha256":"3b91ed7e126cab51df094dcc32f6d91fa9992378f5fa2e7ce88484d7ee32cbf7","title":"Acknowledge a replicated write concern: Volatile receipt acknowledgements satisfy durable concern · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":33.664,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Repeated acknowledgements count as separate replicas","expected":false,"passed":true},{"actual":false,"check":"Volatile receipt acknowledgements satisfy durable concern","expected":false,"passed":true},{"actual":true,"check":"Multiple copies in one failure domain satisfy zone concern","expected":false,"passed":false},{"actual":false,"check":"Replica acknowledgements refer to another write","expected":false,"passed":true},{"actual":false,"check":"A write is reported successful after its response deadline","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"Repeated acknowledgements count as separate replicas\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Volatile receipt acknowledgements satisfy durable concern\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Multiple copies in one failure domain satisfy zone concern\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Replica acknowledgements refer to another write\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A write is reported successful after its response deadline\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":31.913,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Repeated acknowledgements count as separate replicas","expected":false,"passed":true},{"actual":true,"check":"Volatile receipt acknowledgements satisfy durable concern","expected":false,"passed":false},{"actual":false,"check":"Multiple copies in one failure domain satisfy zone concern","expected":false,"passed":true},{"actual":false,"check":"Replica acknowledgements refer to another write","expected":false,"passed":true},{"actual":false,"check":"A write is reported successful after its response deadline","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"Repeated acknowledgements count as separate replicas\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Volatile receipt acknowledgements satisfy durable concern\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Multiple copies in one failure domain satisfy zone concern\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Replica acknowledgements refer to another write\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A write is reported successful after its response deadline\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":30.73,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"Repeated acknowledgements count as separate replicas","expected":false,"passed":true},{"actual":false,"check":"Volatile receipt acknowledgements satisfy durable concern","expected":false,"passed":true},{"actual":false,"check":"Multiple copies in one failure domain satisfy zone concern","expected":false,"passed":true},{"actual":false,"check":"Replica acknowledgements refer to another write","expected":false,"passed":true},{"actual":false,"check":"A write is reported successful after its response deadline","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"Repeated acknowledgements count as separate replicas\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Volatile receipt acknowledgements satisfy durable concern\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Multiple copies in one failure domain satisfy zone concern\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Replica acknowledgements refer to another write\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A write is reported successful after its response deadline\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}