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Load-subset replay oracle: failed marker load after marker truncate leaves the live query in a terminal error

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  • Qualcosa non va?
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Valutazione

Difficoltà
4/5
Tempo stimato
1-2 giorni
Idoneità per principianti
45/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
typescript
Ambito
database, testing

Direzione di ricerca

Start with packages/db/tests/query/load-subset-replay-refinement-oracle.test.ts, especially the named random-campaign test and fatalLoadFailed() near line 1875. Reproduce with the supplied seed and inspect how the oracle models a held load that fails after marker truncation; compare that with the recovery behavior described in ARCHITECTURE.md. Done means deciding whether the model or production behavior is wrong and updating the relevant code or oracle so the seeded case and fixed campaign agree.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Summary

The random campaign of the load-subset replay refinement oracle fails on main (427a7c31e). A live query ends in the error status after a failed marker load. The oracle's model says no fatal load failed in this history, so it expects the window to recover.

  • Test: packages/db/tests/query/load-subset-replay-refinement-oracle.test.ts › "Ordered windows across truncate replays › keeps the ordered window under load and release faults (random campaign)"
  • Assertion: convergence: terminal error: expected false to be true (line 1875: expect(fatalLoadFailed(), ...).toBe(true))

Reproduce

cd packages/db
TANSTACK_DB_ORACLE_SEED=1930131799 npx vitest run \
  tests/query/load-subset-replay-refinement-oracle.test.ts \
  -t "load and release faults \(random"

fast-check output:

{ seed: 1930131799, path: "33:3:1:4:0:2:3:2:2", endOnFailure: true }
Counterexample: [[{"type":"hold"},{"type":"truncateMarkers"},{"type":"settle","ok":false}],{"direction":"asc","offset":0,"limit":1,"ties":false,"peer":false,"joined":"none","markerMode":"on-demand","includes":true}]
Shrunk 8 time(s)

The shrunk history:

  1. hold the loads;
  2. truncate the marker source;
  3. settle the held loads with a failure.

The scenario is an ascending window (offset 0, limit 1) with on-demand markers and includes, no ties, no peer and no join.

What the oracle checks

After the faults, the recovery step truncates every source, settles, and moves the window again explicitly. A failed replay keeps the last complete publication until a later authoritative replay, and a failed window operation stays private until a later explicit move revalidates it (see ARCHITECTURE.md). After that, the live query must either show the expected window, or be in error only if fatalLoadFailed() (demandFailed || failedWhileLoading) holds. In this history the query is in error, but fatalLoadFailed() is false.

Undecided

Two explanations fit this result, and I haven't decided between them:

  • Production defect: a marker load that fails while held across a marker truncate becomes a terminal query error, though the documented recovery should clear it.
  • Model gap: this failure really is fatal, and fatalLoadFailed() misses the case where a marker load fails after a marker truncate.

The fixed campaign passes. I found this while working on #2220 (branch issue-2220-sync-metadata-held-reads), but it reproduces on a clean main checkout, and that branch doesn't touch this oracle or its production path.

Lingua principale
TypeScript
Stelle
4k
Fork
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Merge medio
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PR unite (30g)
227

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