FA-30771 / HTTP retries / Open access
Stable client operation identity over retries: Admission consumption violates retry transition semantics · case 01
Admission consumption violates retry transition semantics
ROOT CAUSE
Admission consumption violates retry transition semantics
VERIFIED REPAIR
Restore the specified transition state='sent' elif.
Unsuccessful approach: The attempted repair changes the faulty site to state='uncertain' elif but still violates a regression oracle.
Case contract
begin(provided key or None,body) starts a logical operation and advances a local operation serial. Generated key is operation serial; explicit keys including zero remain exact. send(body) first sends only matching snapshotted body. uncertain authorizes a resend; reject is terminal; success is terminal. Retried sends reuse the initial key. Return sent key/body pairs or refusal reason.
Why this case matters
Offline deterministic model of HTTP request retries.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(events):
serial=0; key=None; original=None; state='idle'; out=[]
for e in events:
if e[0]=='begin':
serial+=1
key=serial if e[1] is None else e[1]
original=e[2]
state='ready'
elif e[0]=='send':
if state not in ('ready','uncertain'): out.append('blocked'); continue
if e[1]!=original: out.append('body-conflict'); continue
out.append([key,original])
state='ready'
elif e[0]=='uncertain':
if state=='sent': state='uncertain'
elif e[0]=='reject': state='rejected'
elif e[0]=='success':
if state=='sent': state='done'
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('begin',None,N),('send',N),('uncertain',),('send',N),('send',N),('success',),('uncertain',),('send',N)]), [[1,N],[1,N],'blocked','blocked'])
check('2', solve([('begin',0,N),('send',N)]), [[0,N]])
check('3', solve([('begin','customer-key',N),('send',N),('uncertain',),('send',N+1),('send',N)]), [['customer-key',N],'body-conflict',['customer-key',N]])
check('4', solve([('begin',None,N),('send',N),('reject',),('uncertain',),('send',N),('begin',None,N+1),('send',N+1)]), [[1,N],'blocked',[2,N+1]])
check('5', solve([('begin',None,N),('send',N+1),('send',N)]), ['body-conflict',[1,N]])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| 0 | [] | [] | Passed |
| 1 | [[1, 1], [1, 1], [1, 1], [1, 1]] | [[1, 1], [1, 1], 'blocked', 'blocked'] | Failed |
| 2 | [[0, 1]] | [[0, 1]] | Passed |
| 3 | [['customer-key', 1], 'body-conflict', ['customer-key', 1]] | [['customer-key', 1], 'body-conflict', ['customer-key', 1]] | Passed |
| 4 | [[1, 1], 'blocked', [2, 2]] | [[1, 1], 'blocked', [2, 2]] | Passed |
| 5 | ['body-conflict', [1, 1]] | ['body-conflict', [1, 1]] | Passed |
SHA-256 / 2930a5b3fd0e73559ce97c969b906f37ce07e1a5f74989ab683d74ebc22cee59
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(events):
serial=0; key=None; original=None; state='idle'; out=[]
for e in events:
if e[0]=='begin':
serial+=1
key=serial if e[1] is None else e[1]
original=e[2]
state='ready'
elif e[0]=='send':
if state not in ('ready','uncertain'): out.append('blocked'); continue
if e[1]!=original: out.append('body-conflict'); continue
out.append([key,original])
state='uncertain'
elif e[0]=='uncertain':
if state=='sent': state='uncertain'
elif e[0]=='reject': state='rejected'
elif e[0]=='success':
if state=='sent': state='done'
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('begin',None,N),('send',N),('uncertain',),('send',N),('send',N),('success',),('uncertain',),('send',N)]), [[1,N],[1,N],'blocked','blocked'])
check('2', solve([('begin',0,N),('send',N)]), [[0,N]])
check('3', solve([('begin','customer-key',N),('send',N),('uncertain',),('send',N+1),('send',N)]), [['customer-key',N],'body-conflict',['customer-key',N]])
check('4', solve([('begin',None,N),('send',N),('reject',),('uncertain',),('send',N),('begin',None,N+1),('send',N+1)]), [[1,N],'blocked',[2,N+1]])
check('5', solve([('begin',None,N),('send',N+1),('send',N)]), ['body-conflict',[1,N]])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| 0 | [] | [] | Passed |
| 1 | [[1, 1], [1, 1], [1, 1], [1, 1]] | [[1, 1], [1, 1], 'blocked', 'blocked'] | Failed |
| 2 | [[0, 1]] | [[0, 1]] | Passed |
| 3 | [['customer-key', 1], 'body-conflict', ['customer-key', 1]] | [['customer-key', 1], 'body-conflict', ['customer-key', 1]] | Passed |
| 4 | [[1, 1], 'blocked', [2, 2]] | [[1, 1], 'blocked', [2, 2]] | Passed |
| 5 | ['body-conflict', [1, 1]] | ['body-conflict', [1, 1]] | Passed |
SHA-256 / e8a7918ab939355ecb9c41fd58795eb884bc4346181145fc26686ea152941abd
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(events):
serial=0; key=None; original=None; state='idle'; out=[]
for e in events:
if e[0]=='begin':
serial+=1
key=serial if e[1] is None else e[1]
original=e[2]
state='ready'
elif e[0]=='send':
if state not in ('ready','uncertain'): out.append('blocked'); continue
if e[1]!=original: out.append('body-conflict'); continue
out.append([key,original])
state='sent'
elif e[0]=='uncertain':
if state=='sent': state='uncertain'
elif e[0]=='reject': state='rejected'
elif e[0]=='success':
if state=='sent': state='done'
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('begin',None,N),('send',N),('uncertain',),('send',N),('send',N),('success',),('uncertain',),('send',N)]), [[1,N],[1,N],'blocked','blocked'])
check('2', solve([('begin',0,N),('send',N)]), [[0,N]])
check('3', solve([('begin','customer-key',N),('send',N),('uncertain',),('send',N+1),('send',N)]), [['customer-key',N],'body-conflict',['customer-key',N]])
check('4', solve([('begin',None,N),('send',N),('reject',),('uncertain',),('send',N),('begin',None,N+1),('send',N+1)]), [[1,N],'blocked',[2,N+1]])
check('5', solve([('begin',None,N),('send',N+1),('send',N)]), ['body-conflict',[1,N]])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| 0 | [] | [] | Passed |
| 1 | [[1, 1], [1, 1], 'blocked', 'blocked'] | [[1, 1], [1, 1], 'blocked', 'blocked'] | Passed |
| 2 | [[0, 1]] | [[0, 1]] | Passed |
| 3 | [['customer-key', 1], 'body-conflict', ['customer-key', 1]] | [['customer-key', 1], 'body-conflict', ['customer-key', 1]] | Passed |
| 4 | [[1, 1], 'blocked', [2, 2]] | [[1, 1], 'blocked', [2, 2]] | Passed |
| 5 | ['body-conflict', [1, 1]] | ['body-conflict', [1, 1]] | Passed |
SHA-256 / ec41f3138206461d49f6277fef0175725ab149b3c379cbf40b672ebdbc1314c2
Verification & scope
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.
Observations recorded using Python 3.12.14 at 2026-09-29T14:41:55.901103+00:00.
Case digest / d05c1c18a824545d4699a60968d208d3efb1f0640be5a46022eb205c8a709f00