{"abstract":"An old timeout invalidates a newer retry attempt","category":"HTTP retries","checks":6,"contract":"start allocates a strictly increasing generation. complete(generation,value) publishes only the current active generation and terminates it; duplicate/stale results are rejected. timeout(generation) deactivates only that generation. cancel terminates the logical request permanently. Return accepted/rejected results plus current generation and cancellation flag.","evaluation_group":"s3-http_retries-attempt-fences","failed_approach":"The attempted repair changes the faulty site to if e[1]<=generation: active=False but still violates a regression oracle.","family":"s3-http_retries-attempt-fences-timeout-scope","id":"FA-29541","implementations":{"attempt":{"sha256":"d4cb865f9e59dbfca5cfd76c591a55ba72be9b3ca8ac54a6d8feb711f4dc9056","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(events):\n    generation=0; active=False; cancelled=False; out=[]\n    for e in events:\n        if e[0]=='start':\n            if cancelled: out.append('cancelled'); continue\n            generation+=1\n            active=True\n            out.append(['started',generation])\n        elif e[0]=='timeout':\n            if e[1]<=generation: active=False\n        elif e[0]=='cancel':\n            cancelled=True\n            active=False\n        elif e[0]=='complete':\n            if cancelled: out.append('cancelled'); continue\n            if e[1]!=generation or not active:\n                out.append('stale'); continue\n            out.append(['accepted',e[2]])\n            active=False\n    return [out,generation,cancelled]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('0', solve([]), [[],0,False])\ncheck('1', solve([('start',),('complete',1,N),('complete',1,N+1)]), [[['started',1],['accepted',N],'stale'],1,False])\ncheck('2', solve([('start',),('start',),('timeout',1),('complete',1,0),('complete',2,N+5)]), [[['started',1],['started',2],'stale',['accepted',N+5]],2,False])\ncheck('3', solve([('start',),('timeout',1),('complete',1,N)]), [[['started',1],'stale'],1,False])\ncheck('4', solve([('start',),('cancel',),('complete',1,N),('start',)]), [[['started',1],'cancelled','cancelled'],1,True])\ncheck('5', solve([('start',),('complete',2,N),('complete',1,N+3)]), [[['started',1],'stale',['accepted',N+3]],1,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":"bb4ac95945e684936e3c71b1b1fe76709abc3ef227d93971a1d2aaa1758d1307","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(events):\n    generation=0; active=False; cancelled=False; out=[]\n    for e in events:\n        if e[0]=='start':\n            if cancelled: out.append('cancelled'); continue\n            generation+=1\n            active=True\n            out.append(['started',generation])\n        elif e[0]=='timeout':\n            active=False\n        elif e[0]=='cancel':\n            cancelled=True\n            active=False\n        elif e[0]=='complete':\n            if cancelled: out.append('cancelled'); continue\n            if e[1]!=generation or not active:\n                out.append('stale'); continue\n            out.append(['accepted',e[2]])\n            active=False\n    return [out,generation,cancelled]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('0', solve([]), [[],0,False])\ncheck('1', solve([('start',),('complete',1,N),('complete',1,N+1)]), [[['started',1],['accepted',N],'stale'],1,False])\ncheck('2', solve([('start',),('start',),('timeout',1),('complete',1,0),('complete',2,N+5)]), [[['started',1],['started',2],'stale',['accepted',N+5]],2,False])\ncheck('3', solve([('start',),('timeout',1),('complete',1,N)]), [[['started',1],'stale'],1,False])\ncheck('4', solve([('start',),('cancel',),('complete',1,N),('start',)]), [[['started',1],'cancelled','cancelled'],1,True])\ncheck('5', solve([('start',),('complete',2,N),('complete',1,N+3)]), [[['started',1],'stale',['accepted',N+3]],1,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":"8e8a2bf9e28bc971355127f54fa2c3ceb07446320764b1c5ecca727355503ee9","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(events):\n    generation=0; active=False; cancelled=False; out=[]\n    for e in events:\n        if e[0]=='start':\n            if cancelled: out.append('cancelled'); continue\n            generation+=1\n            active=True\n            out.append(['started',generation])\n        elif e[0]=='timeout':\n            if e[1]==generation: active=False\n        elif e[0]=='cancel':\n            cancelled=True\n            active=False\n        elif e[0]=='complete':\n            if cancelled: out.append('cancelled'); continue\n            if e[1]!=generation or not active:\n                out.append('stale'); continue\n            out.append(['accepted',e[2]])\n            active=False\n    return [out,generation,cancelled]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('0', solve([]), [[],0,False])\ncheck('1', solve([('start',),('complete',1,N),('complete',1,N+1)]), [[['started',1],['accepted',N],'stale'],1,False])\ncheck('2', solve([('start',),('start',),('timeout',1),('complete',1,0),('complete',2,N+5)]), [[['started',1],['started',2],'stale',['accepted',N+5]],2,False])\ncheck('3', solve([('start',),('timeout',1),('complete',1,N)]), [[['started',1],'stale'],1,False])\ncheck('4', solve([('start',),('cancel',),('complete',1,N),('start',)]), [[['started',1],'cancelled','cancelled'],1,True])\ncheck('5', solve([('start',),('complete',2,N),('complete',1,N+3)]), [[['started',1],'stale',['accepted',N+3]],1,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":"Stipulated bounded simulator, not a complete HTTP implementation or a standards conformance claim. 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":"s3-http_retries-attempt-fences-timeout-scope","generated_at":"2026-09-29T14:41:44.205493+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Offline deterministic model of HTTP request retries.","repair":"Restore the specified transition if e[1]==generation: active=False.","root_cause":"An old timeout invalidates a newer retry attempt","sha256":"42181ce953224d2796e7a9e361cc7d6696894433bb7c40c229979a27b7ad1267","title":"Late response fencing between retry attempts: An old timeout invalidates a newer retry attempt · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":47.721,"exit_code":1,"observations":[{"actual":[[],0,false],"check":"0","expected":[[],0,false],"passed":true},{"actual":[[["started",1],["accepted",1],"stale"],1,false],"check":"1","expected":[[["started",1],["accepted",1],"stale"],1,false],"passed":true},{"actual":[[["started",1],["started",2],"stale","stale"],2,false],"check":"2","expected":[[["started",1],["started",2],"stale",["accepted",6]],2,false],"passed":false},{"actual":[[["started",1],"stale"],1,false],"check":"3","expected":[[["started",1],"stale"],1,false],"passed":true},{"actual":[[["started",1],"cancelled","cancelled"],1,true],"check":"4","expected":[[["started",1],"cancelled","cancelled"],1,true],"passed":true},{"actual":[[["started",1],"stale",["accepted",4]],1,false],"check":"5","expected":[[["started",1],"stale",["accepted",4]],1,false],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"0\", \"actual\": [[], 0, false], \"expected\": [[], 0, false], \"passed\": true}, {\"check\": \"1\", \"actual\": [[[\"started\", 1], [\"accepted\", 1], \"stale\"], 1, false], \"expected\": [[[\"started\", 1], [\"accepted\", 1], \"stale\"], 1, false], \"passed\": true}, {\"check\": \"2\", \"actual\": [[[\"started\", 1], [\"started\", 2], \"stale\", \"stale\"], 2, false], \"expected\": [[[\"started\", 1], [\"started\", 2], \"stale\", [\"accepted\", 6]], 2, false], \"passed\": false}, {\"check\": \"3\", \"actual\": [[[\"started\", 1], \"stale\"], 1, false], \"expected\": [[[\"started\", 1], \"stale\"], 1, false], \"passed\": true}, {\"check\": \"4\", \"actual\": [[[\"started\", 1], \"cancelled\", \"cancelled\"], 1, true], \"expected\": [[[\"started\", 1], \"cancelled\", \"cancelled\"], 1, true], \"passed\": true}, {\"check\": \"5\", \"actual\": [[[\"started\", 1], \"stale\", [\"accepted\", 4]], 1, false], \"expected\": [[[\"started\", 1], \"stale\", [\"accepted\", 4]], 1, false], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":46.114,"exit_code":1,"observations":[{"actual":[[],0,false],"check":"0","expected":[[],0,false],"passed":true},{"actual":[[["started",1],["accepted",1],"stale"],1,false],"check":"1","expected":[[["started",1],["accepted",1],"stale"],1,false],"passed":true},{"actual":[[["started",1],["started",2],"stale","stale"],2,false],"check":"2","expected":[[["started",1],["started",2],"stale",["accepted",6]],2,false],"passed":false},{"actual":[[["started",1],"stale"],1,false],"check":"3","expected":[[["started",1],"stale"],1,false],"passed":true},{"actual":[[["started",1],"cancelled","cancelled"],1,true],"check":"4","expected":[[["started",1],"cancelled","cancelled"],1,true],"passed":true},{"actual":[[["started",1],"stale",["accepted",4]],1,false],"check":"5","expected":[[["started",1],"stale",["accepted",4]],1,false],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"0\", \"actual\": [[], 0, false], \"expected\": [[], 0, false], \"passed\": true}, {\"check\": \"1\", \"actual\": [[[\"started\", 1], [\"accepted\", 1], \"stale\"], 1, false], \"expected\": [[[\"started\", 1], [\"accepted\", 1], \"stale\"], 1, false], \"passed\": true}, {\"check\": \"2\", \"actual\": [[[\"started\", 1], [\"started\", 2], \"stale\", \"stale\"], 2, false], \"expected\": [[[\"started\", 1], [\"started\", 2], \"stale\", [\"accepted\", 6]], 2, false], \"passed\": false}, {\"check\": \"3\", \"actual\": [[[\"started\", 1], \"stale\"], 1, false], \"expected\": [[[\"started\", 1], \"stale\"], 1, false], \"passed\": true}, {\"check\": \"4\", \"actual\": [[[\"started\", 1], \"cancelled\", \"cancelled\"], 1, true], \"expected\": [[[\"started\", 1], \"cancelled\", \"cancelled\"], 1, true], \"passed\": true}, {\"check\": \"5\", \"actual\": [[[\"started\", 1], \"stale\", [\"accepted\", 4]], 1, false], \"expected\": [[[\"started\", 1], \"stale\", [\"accepted\", 4]], 1, false], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":45.535,"exit_code":0,"observations":[{"actual":[[],0,false],"check":"0","expected":[[],0,false],"passed":true},{"actual":[[["started",1],["accepted",1],"stale"],1,false],"check":"1","expected":[[["started",1],["accepted",1],"stale"],1,false],"passed":true},{"actual":[[["started",1],["started",2],"stale",["accepted",6]],2,false],"check":"2","expected":[[["started",1],["started",2],"stale",["accepted",6]],2,false],"passed":true},{"actual":[[["started",1],"stale"],1,false],"check":"3","expected":[[["started",1],"stale"],1,false],"passed":true},{"actual":[[["started",1],"cancelled","cancelled"],1,true],"check":"4","expected":[[["started",1],"cancelled","cancelled"],1,true],"passed":true},{"actual":[[["started",1],"stale",["accepted",4]],1,false],"check":"5","expected":[[["started",1],"stale",["accepted",4]],1,false],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"0\", \"actual\": [[], 0, false], \"expected\": [[], 0, false], \"passed\": true}, {\"check\": \"1\", \"actual\": [[[\"started\", 1], [\"accepted\", 1], \"stale\"], 1, false], \"expected\": [[[\"started\", 1], [\"accepted\", 1], \"stale\"], 1, false], \"passed\": true}, {\"check\": \"2\", \"actual\": [[[\"started\", 1], [\"started\", 2], \"stale\", [\"accepted\", 6]], 2, false], \"expected\": [[[\"started\", 1], [\"started\", 2], \"stale\", [\"accepted\", 6]], 2, false], \"passed\": true}, {\"check\": \"3\", \"actual\": [[[\"started\", 1], \"stale\"], 1, false], \"expected\": [[[\"started\", 1], \"stale\"], 1, false], \"passed\": true}, {\"check\": \"4\", \"actual\": [[[\"started\", 1], \"cancelled\", \"cancelled\"], 1, true], \"expected\": [[[\"started\", 1], \"cancelled\", \"cancelled\"], 1, true], \"passed\": true}, {\"check\": \"5\", \"actual\": [[[\"started\", 1], \"stale\", [\"accepted\", 4]], 1, false], \"expected\": [[[\"started\", 1], \"stale\", [\"accepted\", 4]], 1, false], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}