FA-45646 / Data systems / Open access
Session grouping consumes source arrival order instead of event-time order · case 01
Session grouping consumes source arrival order instead of event-time order.
ROOT CAUSE
session-bridge-grouping: Session grouping consumes source arrival order instead of event-time order.
THE FAILURE
session-bridge-grouping: Session grouping consumes source arrival order instead of event-time order.
Unsuccessful approach: Sorting by event identity does not order event times.
Case contract
Group [key,time,id] events into sessions independently by key. Sort each key by (time,id); consecutive gaps <=gap belong to one transitive session. Emit [key,first-time,last-time,ordered-ids] ordered by key and session time. An intervening bridge may join otherwise distant endpoints.
Why this case matters
A bounded deterministic data engine model makes representation and changelog faults reproducible.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
try:
events,gap=d
out=[]
for key in sorted(set(k for k,t,i in events)):
rows=[(t,i) for k,t,i in events if k==key]
start=last=None; ids=[]
for time,ident in rows:
if ids and time-last>gap:
out.append([key,start,last,ids]); ids=[]
if not ids: start=time
ids.append(ident); last=time
if ids: out.append([key,start,last,ids])
return out
except (IndexError, KeyError, ValueError, StopIteration) as exc:
return {"representation_error": type(exc).__name__}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
check('bridge chain', solve([[['a', 1, 10], ['a', 3, 11], ['a', 5, 12]], 2]), [['a', 1, 5, [10, 11, 12]]])
check('arrival order', solve([[['a', 3, 10], ['a', 1, 11]], 2]), [['a', 1, 3, [11, 10]]])
check('key separation', solve([[['a', 1, 10], ['b', 1, 11]], 2]), [['a', 1, 1, [10]], ['b', 1, 1, [11]]])
check('separate sessions', solve([[['a', 1, 10], ['a', 6, 11]], 2]), [['a', 1, 1, [10]], ['a', 6, 6, [11]]])
check('equal timestamp', solve([[['a', 1, 11], ['a', 1, 10]], 0]), [['a', 1, 1, [10, 11]]])
check('single event', solve([[['a', 1, 10]], 2]), [['a', 1, 1, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 2:
check('bridge chain', solve([[['a', 2, 10], ['a', 4, 11], ['a', 6, 12]], 2]), [['a', 2, 6, [10, 11, 12]]])
check('arrival order', solve([[['a', 4, 10], ['a', 2, 11]], 2]), [['a', 2, 4, [11, 10]]])
check('key separation', solve([[['a', 2, 10], ['b', 2, 11]], 2]), [['a', 2, 2, [10]], ['b', 2, 2, [11]]])
check('separate sessions', solve([[['a', 2, 10], ['a', 7, 11]], 2]), [['a', 2, 2, [10]], ['a', 7, 7, [11]]])
check('equal timestamp', solve([[['a', 2, 11], ['a', 2, 10]], 0]), [['a', 2, 2, [10, 11]]])
check('single event', solve([[['a', 2, 10]], 2]), [['a', 2, 2, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 3:
check('bridge chain', solve([[['a', 3, 10], ['a', 5, 11], ['a', 7, 12]], 2]), [['a', 3, 7, [10, 11, 12]]])
check('arrival order', solve([[['a', 5, 10], ['a', 3, 11]], 2]), [['a', 3, 5, [11, 10]]])
check('key separation', solve([[['a', 3, 10], ['b', 3, 11]], 2]), [['a', 3, 3, [10]], ['b', 3, 3, [11]]])
check('separate sessions', solve([[['a', 3, 10], ['a', 8, 11]], 2]), [['a', 3, 3, [10]], ['a', 8, 8, [11]]])
check('equal timestamp', solve([[['a', 3, 11], ['a', 3, 10]], 0]), [['a', 3, 3, [10, 11]]])
check('single event', solve([[['a', 3, 10]], 2]), [['a', 3, 3, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 4:
check('bridge chain', solve([[['a', 4, 10], ['a', 6, 11], ['a', 8, 12]], 2]), [['a', 4, 8, [10, 11, 12]]])
check('arrival order', solve([[['a', 6, 10], ['a', 4, 11]], 2]), [['a', 4, 6, [11, 10]]])
check('key separation', solve([[['a', 4, 10], ['b', 4, 11]], 2]), [['a', 4, 4, [10]], ['b', 4, 4, [11]]])
check('separate sessions', solve([[['a', 4, 10], ['a', 9, 11]], 2]), [['a', 4, 4, [10]], ['a', 9, 9, [11]]])
check('equal timestamp', solve([[['a', 4, 11], ['a', 4, 10]], 0]), [['a', 4, 4, [10, 11]]])
check('single event', solve([[['a', 4, 10]], 2]), [['a', 4, 4, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 5:
check('bridge chain', solve([[['a', 5, 10], ['a', 7, 11], ['a', 9, 12]], 2]), [['a', 5, 9, [10, 11, 12]]])
check('arrival order', solve([[['a', 7, 10], ['a', 5, 11]], 2]), [['a', 5, 7, [11, 10]]])
check('key separation', solve([[['a', 5, 10], ['b', 5, 11]], 2]), [['a', 5, 5, [10]], ['b', 5, 5, [11]]])
check('separate sessions', solve([[['a', 5, 10], ['a', 10, 11]], 2]), [['a', 5, 5, [10]], ['a', 10, 10, [11]]])
check('equal timestamp', solve([[['a', 5, 11], ['a', 5, 10]], 0]), [['a', 5, 5, [10, 11]]])
check('single event', solve([[['a', 5, 10]], 2]), [['a', 5, 5, [10]]])
check('empty stream', solve([[], 2]), [])
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 |
|---|---|---|---|
| bridge chain | [['a', 1, 5, [10, 11, 12]]] | [['a', 1, 5, [10, 11, 12]]] | Passed |
| arrival order | [['a', 3, 1, [10, 11]]] | [['a', 1, 3, [11, 10]]] | Failed |
| key separation | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | Passed |
| separate sessions | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | Passed |
| equal timestamp | [['a', 1, 1, [11, 10]]] | [['a', 1, 1, [10, 11]]] | Failed |
| single event | [['a', 1, 1, [10]]] | [['a', 1, 1, [10]]] | Passed |
| empty stream | [] | [] | Passed |
SHA-256 / 8b66dd4e28501c7151682e6750e41fdf39170b69d6d177848e7f3a8840b33244
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
try:
events,gap=d
out=[]
for key in sorted(set(k for k,t,i in events)):
rows=sorted(((t,i) for k,t,i in events if k==key),key=lambda r:r[1])
start=last=None; ids=[]
for time,ident in rows:
if ids and time-last>gap:
out.append([key,start,last,ids]); ids=[]
if not ids: start=time
ids.append(ident); last=time
if ids: out.append([key,start,last,ids])
return out
except (IndexError, KeyError, ValueError, StopIteration) as exc:
return {"representation_error": type(exc).__name__}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
check('bridge chain', solve([[['a', 1, 10], ['a', 3, 11], ['a', 5, 12]], 2]), [['a', 1, 5, [10, 11, 12]]])
check('arrival order', solve([[['a', 3, 10], ['a', 1, 11]], 2]), [['a', 1, 3, [11, 10]]])
check('key separation', solve([[['a', 1, 10], ['b', 1, 11]], 2]), [['a', 1, 1, [10]], ['b', 1, 1, [11]]])
check('separate sessions', solve([[['a', 1, 10], ['a', 6, 11]], 2]), [['a', 1, 1, [10]], ['a', 6, 6, [11]]])
check('equal timestamp', solve([[['a', 1, 11], ['a', 1, 10]], 0]), [['a', 1, 1, [10, 11]]])
check('single event', solve([[['a', 1, 10]], 2]), [['a', 1, 1, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 2:
check('bridge chain', solve([[['a', 2, 10], ['a', 4, 11], ['a', 6, 12]], 2]), [['a', 2, 6, [10, 11, 12]]])
check('arrival order', solve([[['a', 4, 10], ['a', 2, 11]], 2]), [['a', 2, 4, [11, 10]]])
check('key separation', solve([[['a', 2, 10], ['b', 2, 11]], 2]), [['a', 2, 2, [10]], ['b', 2, 2, [11]]])
check('separate sessions', solve([[['a', 2, 10], ['a', 7, 11]], 2]), [['a', 2, 2, [10]], ['a', 7, 7, [11]]])
check('equal timestamp', solve([[['a', 2, 11], ['a', 2, 10]], 0]), [['a', 2, 2, [10, 11]]])
check('single event', solve([[['a', 2, 10]], 2]), [['a', 2, 2, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 3:
check('bridge chain', solve([[['a', 3, 10], ['a', 5, 11], ['a', 7, 12]], 2]), [['a', 3, 7, [10, 11, 12]]])
check('arrival order', solve([[['a', 5, 10], ['a', 3, 11]], 2]), [['a', 3, 5, [11, 10]]])
check('key separation', solve([[['a', 3, 10], ['b', 3, 11]], 2]), [['a', 3, 3, [10]], ['b', 3, 3, [11]]])
check('separate sessions', solve([[['a', 3, 10], ['a', 8, 11]], 2]), [['a', 3, 3, [10]], ['a', 8, 8, [11]]])
check('equal timestamp', solve([[['a', 3, 11], ['a', 3, 10]], 0]), [['a', 3, 3, [10, 11]]])
check('single event', solve([[['a', 3, 10]], 2]), [['a', 3, 3, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 4:
check('bridge chain', solve([[['a', 4, 10], ['a', 6, 11], ['a', 8, 12]], 2]), [['a', 4, 8, [10, 11, 12]]])
check('arrival order', solve([[['a', 6, 10], ['a', 4, 11]], 2]), [['a', 4, 6, [11, 10]]])
check('key separation', solve([[['a', 4, 10], ['b', 4, 11]], 2]), [['a', 4, 4, [10]], ['b', 4, 4, [11]]])
check('separate sessions', solve([[['a', 4, 10], ['a', 9, 11]], 2]), [['a', 4, 4, [10]], ['a', 9, 9, [11]]])
check('equal timestamp', solve([[['a', 4, 11], ['a', 4, 10]], 0]), [['a', 4, 4, [10, 11]]])
check('single event', solve([[['a', 4, 10]], 2]), [['a', 4, 4, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 5:
check('bridge chain', solve([[['a', 5, 10], ['a', 7, 11], ['a', 9, 12]], 2]), [['a', 5, 9, [10, 11, 12]]])
check('arrival order', solve([[['a', 7, 10], ['a', 5, 11]], 2]), [['a', 5, 7, [11, 10]]])
check('key separation', solve([[['a', 5, 10], ['b', 5, 11]], 2]), [['a', 5, 5, [10]], ['b', 5, 5, [11]]])
check('separate sessions', solve([[['a', 5, 10], ['a', 10, 11]], 2]), [['a', 5, 5, [10]], ['a', 10, 10, [11]]])
check('equal timestamp', solve([[['a', 5, 11], ['a', 5, 10]], 0]), [['a', 5, 5, [10, 11]]])
check('single event', solve([[['a', 5, 10]], 2]), [['a', 5, 5, [10]]])
check('empty stream', solve([[], 2]), [])
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 |
|---|---|---|---|
| bridge chain | [['a', 1, 5, [10, 11, 12]]] | [['a', 1, 5, [10, 11, 12]]] | Passed |
| arrival order | [['a', 3, 1, [10, 11]]] | [['a', 1, 3, [11, 10]]] | Failed |
| key separation | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | Passed |
| separate sessions | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | Passed |
| equal timestamp | [['a', 1, 1, [10, 11]]] | [['a', 1, 1, [10, 11]]] | Passed |
| single event | [['a', 1, 1, [10]]] | [['a', 1, 1, [10]]] | Passed |
| empty stream | [] | [] | Passed |
SHA-256 / 108cc17cc80ba414929a612560c41dbbb67e7a6bc9ca31181849a01bdfe33238
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.
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Sign in to the archive ↗Verification & scope
Offline stipulated semantics over valid small inputs; no performance, concurrency, or production-engine 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 2026-09-29T14:44:24.438853+00:00.
Case digest / c4a66f1cff3cf68c5ecd5e3e90860e6402a00136db453f2e6d314f5caacfcdf5