Deep-review round 1 found the new tests asserted end-state only, so both
safety mechanisms this change adds were untested (a regression would ship
green):
- Per-page cursor durability: add test_a_mid_run_failure_leaves_the_prior_page
_durably_committed, which fails the 2nd page's fetch after page 1 committed
and asserts the cursor + rows are already persisted (re-read via db.expire).
Mutation-verified: reverting to a single end-of-loop commit makes it fail
while the pre-existing paging tests stay green — the property the original
test could not distinguish.
- Reserve guard: add test_backfill_reserve_reached_tracks_the_boundary, driving
real record_usage spend across the 9000/2000 default boundary and asserting
the un-mocked quota.backfill_reserve_reached() flips at exactly remaining<=reserve.
Full backend suite: 244 passed, 2 skipped (network-gated).
Transaction ownership (C-A5):
- quota.record_usage / log_action write in their OWN SessionLocal(), committed
immediately, and no longer take/commit the caller's db. The spend stays DURABLE
regardless of the caller (read-only YouTube paths never commit; a failed job rolls
back) — under-counting the shared daily budget would risk overspending the real
YouTube quota — AND quota stops flushing a job's partial state mid-run behind its
own `except: db.rollback()`. units_used_today switches to a scalar SELECT so
measured()'s before/after diff sees the separate session's commits (READ COMMITTED).
Call sites updated (youtube/client.py ×3, routes/search.py ×1).
- plex sync commits PER SECTION (moved the end-of-loop commit inside), so a PlexError
on a later library keeps the ones already mirrored (idempotent; next run reconciles).
The sync jobs did NOT rely on record_usage's incidental commit for persistence — their
per-item functions (apply_rss_feed, backfill_channel_recent, import_subscriptions,
sync_user_playlists, apply_channel_autotags) all commit internally, so the in-loop
rollback handlers already isolate a failed item. No loop restructuring needed.
DB-lane tests (test_quota_ownership, 4): spend survives a caller rollback while the
caller's uncommitted row does NOT leak; accumulation; measured-style mid-txn read.
Gate: ruff clean; DB lane 180 green.
peter