feat(api): trim the library feed, so its expiry answer is finally exercised

[InstaZDLL]

RFC-007 decision 7, built.

Until now nothing purged. library.events_purged_through sat at 0 by construction, which meant the feed's whole expiry path — the watermark read, the Conflict, the comment explaining why a floor derived from surviving rows would be wrong — was correct code that had never once run.

The rules

Two bounds, and the floor wins. Thirty days by default, never fewer than ten thousand events per library. Both are refused at startup if zero or negative rather than quietly defaulted, which is what parse_positive_env already does for every other bound here.

The age bound is exclusive: an event exactly thirty days old lives.

The delete and the watermark are one transaction. That is the whole of what makes the expiry answer honest — written separately there is a window where the watermark claims less than has gone, and a client reading into it is handed a catch-up that looks complete while silently skipping the gap. MAX on the update, so a pass cutting an older tail cannot lower a watermark an earlier one raised.

One transaction per library rather than one for all: the writer gate is process-wide, and holding it across every feed on a server with fifty libraries would stall every other mutation for the length of the pass.

Three rules removed to watch the test fall

Removed	What happens
the exclusive bound	the event sitting exactly on it is cut — 3 removed where the test wants 2
the floor	three rows go where one should
the watermark advance	the feed hands back a tail it should have refused

The test was flaky, and it said so on the second run

It read the clock, then let the purge read it again — and with an exclusive bound, "exactly thirty days old" is a single instant. The milliseconds between the two reads put the boundary event on the wrong side, so it passed once and failed the next time for nothing that had changed.

purge_library_events takes now_ms now, the way sweep_expired_sessions already did. A caller that cannot name the instant cannot place an event on it — it can only aim near it and hope, which is not a test of a boundary. Five consecutive runs green.

It was caught because the suite was run again rather than once.

Still decided and not built

Decision 8, the acknowledgement table. RFC-007's section says so, and the Implémentée par line names only what runs.

Gates

cargo fmt --all --check, cargo clippy --all-targets --all-features -- -D warnings, cargo test --all-features — 155 tests across fourteen targets, all green.

Summary by CodeRabbit

• Nouvelles fonctionnalités

  • Ajout d’une purge automatique et quotidienne des événements de bibliothèque.
  • La rétention peut être configurée selon un âge maximal et un nombre minimal d’événements conservés.
  • Les suppressions sont effectuées de manière fiable, avec suivi de leur progression et gestion des erreurs.

• Documentation

  • Mise à jour du RFC concernant l’état d’implémentation des décisions de rétention.

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📒 Files selected for processing (6)

• docs/rfcs/RFC-007-library-event-stream.md
• src/config.rs
• src/main.rs
• src/services/library_events.rs
• src/services/mod.rs
• tests/catalog.rs

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📝 Walkthrough

Walkthrough

La configuration définit les seuils de rétention. Le serveur démarre une purge immédiate puis quotidienne. Chaque bibliothèque est purgée dans une transaction, avec conservation d’un nombre minimal d’événements et mise à jour du watermark.

Changes

Rétention des événements de bibliothèque

Layer / File(s)	Summary
Configuration et transmission des seuils src/config.rs, src/services/mod.rs	LibraryEventRetention définit la durée et le nombre minimal d’événements. Config charge ces valeurs depuis l’environnement et DomainServices les conserve.
Purge périodique et transactionnelle src/services/library_events.rs, src/main.rs	Le serveur démarre le purgeur. Le service exécute une purge immédiate puis quotidienne, supprime les événements éligibles par bibliothèque, respecte min_events et avance events_purged_through atomiquement.
Tests et documentation RFC tests/catalog.rs, docs/rfcs/RFC-007-library-event-stream.md	Le test couvre les bornes d’âge, le plancher, le watermark, les curseurs périmés et l’idempotence. La RFC indique la décision 7 comme construite et la décision 8 comme non construite.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to a61aa

The change adds transactional library-event retention with bounded configuration and exercises the expiry path; no actionable merge-blocking risk remains after normal checks and review.

Sequence Diagram(s)

sequenceDiagram
  participant Serveur
  participant DomainServices
  participant BaseDeDonnees
  Serveur->>DomainServices: Démarrer spawn_library_event_purge()
  DomainServices->>DomainServices: Exécuter purge_library_events(now_ms)
  DomainServices->>BaseDeDonnees: Purger les événements anciens par bibliothèque
  BaseDeDonnees-->>DomainServices: Retourner les suppressions et le watermark
  DomainServices-->>Serveur: Journaliser le résultat ou l’erreur

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 45.45% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 5 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	Le titre décrit clairement l’implémentation de la purge et de l’expiration du flux d’événements de bibliothèque, qui constitue le changement principal.
Description check	✅ Passed	La description est détaillée et couvre l’objectif, les règles de rétention, les garanties transactionnelles, les tests et l’état de la RFC. Elle ne reprend pas exactement les sections du modèle et ne …
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

La description est détaillée et couvre l’objectif, les règles de rétention, les garanties transactionnelles, les tests et l’état de la RFC. Elle ne reprend pas exactement les sections du modèle et ne contient pas la confirmation DCO, mais elle reste globalement complète et pertinente.

Full details: Docstring Coverage

Explanation

Docstring coverage is 45.45% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 5 files. (1 skipped: 1 unsupported.)

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