FA-30186 / HTTP retries / Open access

In-flight retry policy capture: Zero usage violates retry transition semantics · case 01

Zero usage violates retry transition semantics

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Zero usage violates retry transition semantics

THE FAILURE

Zero usage violates retry transition semantics

Unsuccessful approach: The attempted repair changes the faulty site to requests[e[1]]=[current,current[1]] but still violates a regression oracle.

Case contract

configure(version,cap,statuses) sets current policy. begin(request) snapshots it with zero retries used; failure(request,status) uses that request snapshot and admits retry only for configured statuses below cap. update configuration affects later requests only. finish removes request; unknown failures report unknown. Return retry decisions with pinned policy version.

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):
    current=(0,0,()); requests={}; out=[]
    for e in events:
        if e[0]=='configure':
            current=(e[1],e[2],tuple(e[3]))
        elif e[0]=='begin':
            if e[1] in requests: out.append('duplicate'); continue
            requests[e[1]]=[current,1]
        elif e[0]=='finish': requests.pop(e[1],None)
        elif e[0]=='failure':
            if e[1] not in requests: out.append('unknown'); continue
            policy,used=requests[e[1]]
            version,cap,statuses=policy
            if e[2] not in statuses: out.append(['stop',version]); continue
            if used>=cap: out.append(['exhausted',version]); continue
            requests[e[1]][1]+=1
            out.append(['retry',version])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('failure','x',503)]), ['unknown'])
check('2', solve([('configure',N,2,[503,429]),('begin','a'),('failure','a',503),('failure','a',429),('failure','a',503)]), [['retry',N],['retry',N],['exhausted',N]])
check('3', solve([('configure',N,1,[503]),('begin','a'),('configure',N+1,0,[429]),('failure','a',429),('failure','a',503),('failure','a',503),('begin','b'),('failure','b',429)]), [['stop',N],['retry',N],['exhausted',N],['exhausted',N+1]])
check('4', solve([('configure',N,1,[503]),('begin','a'),('failure','a',503),('begin','a'),('failure','a',503)]), [['retry',N],'duplicate',['exhausted',N]])
check('5', solve([('configure',N,1,[503]),('begin','a'),('begin','b'),('finish','a'),('failure','a',503),('failure','b',503)]), ['unknown',['retry',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	`['unknown']`	`['unknown']`	Passed
2	`[['retry', 1], ['exhausted', 1], ['exhausted', 1]]`	`[['retry', 1], ['retry', 1], ['exhausted', 1]]`	Failed
3	`[['stop', 1], ['exhausted', 1], ['exhausted', 1], ['exhausted', 2]]`	`[['stop', 1], ['retry', 1], ['exhausted', 1], ['exhausted', 2]]`	Failed
4	`[['exhausted', 1], 'duplicate', ['exhausted', 1]]`	`[['retry', 1], 'duplicate', ['exhausted', 1]]`	Failed
5	`['unknown', ['exhausted', 1]]`	`['unknown', ['retry', 1]]`	Failed

SHA-256 / 8cbf2244a1839264f5feaff7dab4cdf990de3c87fbd75cf904a3d4f60d3b40ba

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(events):
    current=(0,0,()); requests={}; out=[]
    for e in events:
        if e[0]=='configure':
            current=(e[1],e[2],tuple(e[3]))
        elif e[0]=='begin':
            if e[1] in requests: out.append('duplicate'); continue
            requests[e[1]]=[current,current[1]]
        elif e[0]=='finish': requests.pop(e[1],None)
        elif e[0]=='failure':
            if e[1] not in requests: out.append('unknown'); continue
            policy,used=requests[e[1]]
            version,cap,statuses=policy
            if e[2] not in statuses: out.append(['stop',version]); continue
            if used>=cap: out.append(['exhausted',version]); continue
            requests[e[1]][1]+=1
            out.append(['retry',version])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('failure','x',503)]), ['unknown'])
check('2', solve([('configure',N,2,[503,429]),('begin','a'),('failure','a',503),('failure','a',429),('failure','a',503)]), [['retry',N],['retry',N],['exhausted',N]])
check('3', solve([('configure',N,1,[503]),('begin','a'),('configure',N+1,0,[429]),('failure','a',429),('failure','a',503),('failure','a',503),('begin','b'),('failure','b',429)]), [['stop',N],['retry',N],['exhausted',N],['exhausted',N+1]])
check('4', solve([('configure',N,1,[503]),('begin','a'),('failure','a',503),('begin','a'),('failure','a',503)]), [['retry',N],'duplicate',['exhausted',N]])
check('5', solve([('configure',N,1,[503]),('begin','a'),('begin','b'),('finish','a'),('failure','a',503),('failure','b',503)]), ['unknown',['retry',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	`['unknown']`	`['unknown']`	Passed
2	`[['exhausted', 1], ['exhausted', 1], ['exhausted', 1]]`	`[['retry', 1], ['retry', 1], ['exhausted', 1]]`	Failed
3	`[['stop', 1], ['exhausted', 1], ['exhausted', 1], ['exhausted', 2]]`	`[['stop', 1], ['retry', 1], ['exhausted', 1], ['exhausted', 2]]`	Failed
4	`[['exhausted', 1], 'duplicate', ['exhausted', 1]]`	`[['retry', 1], 'duplicate', ['exhausted', 1]]`	Failed
5	`['unknown', ['exhausted', 1]]`	`['unknown', ['retry', 1]]`	Failed

SHA-256 / d5e698dd17e1d9df36d22b885b7dcb2f29a2afa52f3319814f6b49e49c4dea05

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 6 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.

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 2026-09-29T14:41:50.831104+00:00.

Case digest / 68492805cf4ae3cb93dfef82cdb28c063955083add8055c3272c8f42e55ccd89