FA-7146 / Network routing / Open access

Failover stays within request replay budget · case 01

Failover stays within request replay budget.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The faulty implementation uses `attempts <= cap and replayable` for the failover-stays-within-request-replay-budget decision.

VERIFIED REPAIR

Apply the explicit failover-stays-within-request-replay-budget contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `attempts < cap` and still violates a separate fixture.

Case contract

Bounded offline decision model: failover stays within request replay budget. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.

Why this case matters

This deterministic network routing model isolates the failover-stays-within-request-replay-budget policy at a network component boundary.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(attempts, cap, replayable):
    return attempts <= cap and replayable
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, 2, True), False)", "check('fixture 2', solve(1, 2, False), False)", "check('fixture 3', solve(1, 2, True), True)", "check('fixture 4', solve(0, 0, True), False)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
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
fixture 2	`False`	`False`	Passed
fixture 3	`True`	`True`	Passed
fixture 4	`True`	`False`	Failed
fixture 1	`True`	`False`	Failed

SHA-256 / 9edf5564a4d78efcca95b860ed6535309ec9777b748f550514f086a320262229

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(attempts, cap, replayable):
    return attempts < cap
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, 2, True), False)", "check('fixture 2', solve(1, 2, False), False)", "check('fixture 3', solve(1, 2, True), True)", "check('fixture 4', solve(0, 0, True), False)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
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
fixture 2	`True`	`False`	Failed
fixture 3	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / 94d9bf9e0d966e2f0a58c42312244c144580ca02daa0aa21c9487aad7db9a377

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(attempts, cap, replayable):
    return attempts < cap and replayable
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, 2, True), False)", "check('fixture 2', solve(1, 2, False), False)", "check('fixture 3', solve(1, 2, True), True)", "check('fixture 4', solve(0, 0, True), False)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
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
fixture 2	`False`	`False`	Passed
fixture 3	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / 19816d2b65662ca5321d8e1ac483aad2b2557f7eef4baaaf0903cca3e256f6b1

Verification & scope

Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. 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 2026-09-29T14:38:08.760342+00:00.

Case digest / ed73e05f18d8a1c8a007e05745c3f8391c545c8fa6ef58374df882f4f79b174a