FA-6671 / HTTP retries / Open access

A retry starts only when both backoff and minimum service time fit · case 01

A retry starts only when both backoff and minimum service time fit.

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

ROOT CAUSE

The faulty implementation uses `backoff < remaining` for the retry-deadline decision.

VERIFIED REPAIR

Apply the explicit retry-deadline contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `backoff + service < remaining` and still violates a separate fixture.

Case contract

A retry starts only when both backoff and minimum service time fit: return the result specified by the explicit input/output boundary fixtures.

Why this case matters

This deterministic http retries model isolates the retry-deadline 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(remaining, backoff, service):
    return backoff < remaining
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(10, 8, 3), False)", "check('fixture 2', solve(10, 8, 2), True)", "check('fixture 3', solve(0, 0, 0), True)", "check('fixture 4', solve(2, 3, 0), 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`	`True`	Passed
fixture 3	`False`	`True`	Failed
fixture 4	`False`	`False`	Passed
fixture 1	`True`	`False`	Failed

SHA-256 / 1851a715e9a85824af7d793208f8fc9e7692e4e60df8c6bafa3992910a22f395

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(remaining, backoff, service):
    return backoff + service < remaining
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(10, 8, 3), False)", "check('fixture 2', solve(10, 8, 2), True)", "check('fixture 3', solve(0, 0, 0), True)", "check('fixture 4', solve(2, 3, 0), 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`	`True`	Failed
fixture 3	`False`	`True`	Failed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / 5eba4ac30a1d0a3104ab00a74ef80c1d9cfce9e279b0ae9d8d7f1fd98312195b

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(remaining, backoff, service):
    return backoff + service <= remaining
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(10, 8, 3), False)", "check('fixture 2', solve(10, 8, 2), True)", "check('fixture 3', solve(0, 0, 0), True)", "check('fixture 4', solve(2, 3, 0), 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`	`True`	Passed
fixture 3	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / ba2de0fbec04c4ae3d30b1d3afdedfe27d9d7197741762032a9992aea19af634

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 2026-09-29T14:38:04.249776+00:00.

Case digest / 418add486b7bdb2b4b07a6b644626153bf024bf136661e38fbc2f21bb48a1fcc