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FA-29711 / HTTP retries / Open access

Retry after consumer-visible response delivery: Failure leaves the response attempt active for duplicate retry admission · case 01

Failure leaves the response attempt active for duplicate retry admission

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Failure leaves the response attempt active for duplicate retry admission

THE FAILURE

Failure leaves the response attempt active for duplicate retry admission

Unsuccessful approach: The attempted repair changes the faulty site to active=delivered==0 if delivered but still violates a regression oracle.

Case contract

begin starts an attempt only while nonterminal, headers records a status, deliver(bytes) records irreversible delivery, fail allows retry only before any delivered bytes. A zero-byte delivery is reversible. finish terminally succeeds. cancel terminally cancels. New attempts reset their local status but never erase already exposed data. Return retry decisions and exposed byte count.

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):
    active=False; delivered=0; status=None; terminal=False; out=[]
    for e in events:
        if e[0]=='begin':
            if terminal: out.append('terminal'); continue
            active=True
            status=None
        elif e[0]=='headers' and active:
            status=e[1]
        elif e[0]=='deliver' and active:
            delivered+=e[1]
        elif e[0]=='fail':
            if terminal: out.append('terminal'); continue
            if not active: out.append('inactive'); continue
            active=True
            if delivered>0:
                terminal=True
                out.append(['partial',status])
            else: out.append(['retry',status])
        elif e[0]=='finish' and active:
            terminal=True; active=False; out.append('success')
        elif e[0]=='cancel':
            terminal=True; active=False; out.append('cancelled')
    return [out,delivered]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [[],0])
check('1', solve([('fail',)]), [['inactive'],0])
check('2', solve([('begin',),('headers',503),('deliver',0),('fail',),('fail',),('begin',),('fail',)]), [[['retry',503],'inactive',['retry',None]],0])
check('3', solve([('begin',),('headers',200),('deliver',1),('deliver',0),('fail',),('begin',)]), [[['partial',200],'terminal'],1])
check('4', solve([('begin',),('headers',502),('deliver',N+2),('deliver',2),('fail',)]), [[['partial',502]],N+4])
check('5', solve([('begin',),('finish',),('begin',),('fail',)]), [['success','terminal','terminal'],0])
check('6', solve([('begin',),('cancel',),('begin',)]), [['cancelled','terminal'],0])
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 fixtureActualExpectedOutcome
0[[], 0][[], 0]Passed
1[['inactive'], 0][['inactive'], 0]Passed
2[[['retry', 503], ['retry', 503], ['retry', None]], 0][[['retry', 503], 'inactive', ['retry', None]], 0]Failed
3[[['partial', 200], 'terminal'], 1][[['partial', 200], 'terminal'], 1]Passed
4[[['partial', 502]], 5][[['partial', 502]], 5]Passed
5[['success', 'terminal', 'terminal'], 0][['success', 'terminal', 'terminal'], 0]Passed
6[['cancelled', 'terminal'], 0][['cancelled', 'terminal'], 0]Passed

SHA-256 / 2e0075cfa9e03332ae81565304c78686584a6b280abfdad1dc959c427a74f2f9

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(events):
    active=False; delivered=0; status=None; terminal=False; out=[]
    for e in events:
        if e[0]=='begin':
            if terminal: out.append('terminal'); continue
            active=True
            status=None
        elif e[0]=='headers' and active:
            status=e[1]
        elif e[0]=='deliver' and active:
            delivered+=e[1]
        elif e[0]=='fail':
            if terminal: out.append('terminal'); continue
            if not active: out.append('inactive'); continue
            active=delivered==0
            if delivered>0:
                terminal=True
                out.append(['partial',status])
            else: out.append(['retry',status])
        elif e[0]=='finish' and active:
            terminal=True; active=False; out.append('success')
        elif e[0]=='cancel':
            terminal=True; active=False; out.append('cancelled')
    return [out,delivered]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [[],0])
check('1', solve([('fail',)]), [['inactive'],0])
check('2', solve([('begin',),('headers',503),('deliver',0),('fail',),('fail',),('begin',),('fail',)]), [[['retry',503],'inactive',['retry',None]],0])
check('3', solve([('begin',),('headers',200),('deliver',1),('deliver',0),('fail',),('begin',)]), [[['partial',200],'terminal'],1])
check('4', solve([('begin',),('headers',502),('deliver',N+2),('deliver',2),('fail',)]), [[['partial',502]],N+4])
check('5', solve([('begin',),('finish',),('begin',),('fail',)]), [['success','terminal','terminal'],0])
check('6', solve([('begin',),('cancel',),('begin',)]), [['cancelled','terminal'],0])
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 fixtureActualExpectedOutcome
0[[], 0][[], 0]Passed
1[['inactive'], 0][['inactive'], 0]Passed
2[[['retry', 503], ['retry', 503], ['retry', None]], 0][[['retry', 503], 'inactive', ['retry', None]], 0]Failed
3[[['partial', 200], 'terminal'], 1][[['partial', 200], 'terminal'], 1]Passed
4[[['partial', 502]], 5][[['partial', 502]], 5]Passed
5[['success', 'terminal', 'terminal'], 0][['success', 'terminal', 'terminal'], 0]Passed
6[['cancelled', 'terminal'], 0][['cancelled', 'terminal'], 0]Passed

SHA-256 / f03a863da7c12f01846592d06128568ccff0eab9ea12e79503d4621a342a798d

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

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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 2026-09-29T14:41:46.006053+00:00.

Case digest / ca1bbb5fac8eb4b20a8fabdf749f761cc63fb480d7962ec1d90e0ca5f3d8562d