FA-1001 / Reliability / Open access

Enter a dependency bulkhead: Concurrent calls exceed the dependency execution limit · case 01

The bulkhead admission operation is admitted even though concurrent calls exceed the dependency execution limit.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The admission path omits the active capacity invariant while validating the other operation preconditions.

THE FAILURE

The admission path omits the active capacity invariant while validating the other operation preconditions.

Unsuccessful approach: Adding the active capacity check repairs the reported defect, but replacing the adjacent queue capacity check loses that independent invariant.

Case contract

Return a Boolean admission decision for enter a dependency bulkhead. The record r must satisfy all of: r['active_capacity'][0] < r['active_capacity'][1]; r['queue_capacity'][0] < r['queue_capacity'][1]; r['queue_deadline'][0] < r['queue_deadline'][1]; r['priority_reservation'][0] or r['priority_reservation'][1] < r['priority_reservation'][2]-r['priority_reservation'][3]; r['isolation_key'][0] == r['isolation_key'][1]. Extra tracing fields are ignored; validation does not mutate the record.

Why this case matters

A deterministic local contract for reliability. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(r):
    return (r['queue_capacity'][0] < r['queue_capacity'][1]) and (r['queue_deadline'][0] < r['queue_deadline'][1]) and (r['priority_reservation'][0] or r['priority_reservation'][1] < r['priority_reservation'][2]-r['priority_reservation'][3]) and (r['isolation_key'][0] == r['isolation_key'][1])
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
r = {'active_capacity': [2, 3], 'queue_capacity': [4, 5], 'queue_deadline': [8, 9], 'priority_reservation': [False, 2, 5, 2], 'isolation_key': ['db1', 'db1']}
check('valid operation', solve(r), True)
check('Concurrent calls exceed the dependency execution limit', solve(dict(r, **{'active_capacity': [3, 3]})), False)
check('Waiting callers exceed the bounded waiting queue', solve(dict(r, **{'queue_capacity': [5, 5]})), False)
check('A waiting call starts after its queue deadline', solve(dict(r, **{'queue_deadline': [9, 9]})), False)
check('Normal traffic consumes capacity reserved for recovery', solve(dict(r, **{'priority_reservation': [False, 3, 5, 2]})), False)
check('Unrelated dependencies share a bulkhead accounting key', solve(dict(r, **{'isolation_key': ['db2', 'db1']})), False)
check('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)
check('repeat validation is pure', solve(r), True)
invalid = {'active_capacity': [3, 3], 'queue_capacity': [5, 5], 'queue_deadline': [9, 9], 'priority_reservation': [False, 3, 5, 2], 'isolation_key': ['db2', 'db1']}
keys = list(invalid)
pair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}
check('two independent violations in variant', solve(dict(r, **pair)), False)
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
valid operation	`True`	`True`	Passed
Concurrent calls exceed the dependency execution limit	`True`	`False`	Failed
Waiting callers exceed the bounded waiting queue	`False`	`False`	Passed
A waiting call starts after its queue deadline	`False`	`False`	Passed
Normal traffic consumes capacity reserved for recovery	`False`	`False`	Passed
Unrelated dependencies share a bulkhead accounting key	`False`	`False`	Passed
unrelated tracing metadata	`True`	`True`	Passed
repeat validation is pure	`True`	`True`	Passed
two independent violations in variant	`False`	`False`	Passed

SHA-256 / 64e5cb902e049bbcf9f9a9f3be6440aac8a24167cdd921e6759825b4419a2a50

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(r):
    return (r['active_capacity'][0] < r['active_capacity'][1]) and (r['queue_deadline'][0] < r['queue_deadline'][1]) and (r['priority_reservation'][0] or r['priority_reservation'][1] < r['priority_reservation'][2]-r['priority_reservation'][3]) and (r['isolation_key'][0] == r['isolation_key'][1])
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
r = {'active_capacity': [2, 3], 'queue_capacity': [4, 5], 'queue_deadline': [8, 9], 'priority_reservation': [False, 2, 5, 2], 'isolation_key': ['db1', 'db1']}
check('valid operation', solve(r), True)
check('Concurrent calls exceed the dependency execution limit', solve(dict(r, **{'active_capacity': [3, 3]})), False)
check('Waiting callers exceed the bounded waiting queue', solve(dict(r, **{'queue_capacity': [5, 5]})), False)
check('A waiting call starts after its queue deadline', solve(dict(r, **{'queue_deadline': [9, 9]})), False)
check('Normal traffic consumes capacity reserved for recovery', solve(dict(r, **{'priority_reservation': [False, 3, 5, 2]})), False)
check('Unrelated dependencies share a bulkhead accounting key', solve(dict(r, **{'isolation_key': ['db2', 'db1']})), False)
check('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)
check('repeat validation is pure', solve(r), True)
invalid = {'active_capacity': [3, 3], 'queue_capacity': [5, 5], 'queue_deadline': [9, 9], 'priority_reservation': [False, 3, 5, 2], 'isolation_key': ['db2', 'db1']}
keys = list(invalid)
pair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}
check('two independent violations in variant', solve(dict(r, **pair)), False)
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
valid operation	`True`	`True`	Passed
Concurrent calls exceed the dependency execution limit	`False`	`False`	Passed
Waiting callers exceed the bounded waiting queue	`True`	`False`	Failed
A waiting call starts after its queue deadline	`False`	`False`	Passed
Normal traffic consumes capacity reserved for recovery	`False`	`False`	Passed
Unrelated dependencies share a bulkhead accounting key	`False`	`False`	Passed
unrelated tracing metadata	`True`	`True`	Passed
repeat validation is pure	`True`	`True`	Passed
two independent violations in variant	`False`	`False`	Passed

SHA-256 / d1ec0ddab6f2dd40cfd4e12c3601c81990a70eb654b6f80a5617d465450dac85

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 9 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

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 2026-09-29T14:36:57.924012+00:00.

Case digest / 85db2a9c028a47fd55a1078775dd9fea85884c0af4f2befc7be3550300d324a7