Deck #67 data-plane slice: tenant Pods record billable operations
(embedding queries, pages/chunks embedded) into an app-DB usage_events
table that the control plane later pulls read-only into the billing
ledger and syncs to Stripe Meter Events.
- migration 007: usage_events table (Postgres TIMESTAMPTZ/JSONB/UUID
with portable SQLite fallbacks), indexed (occurred_at, metric) for the
CP rollup's per-day range scan + GROUP BY metric.
- UsageEventStore: best-effort, flag-gated writer reusing the shared
RefreshTokenStorage engine; ON CONFLICT (event_id) DO NOTHING for
idempotent retries; dialect-branched occurred_at bind. All work
(incl. metadata JSON encode) is swallowed so a metering failure never
surfaces to the user op.
- USAGE_METERING_ENABLED flag (default off) wired through Settings +
env map; off-path touches no storage, so OSS self-hosters get an empty
table and zero write overhead.
- two recording hooks: embeddings_queries (per nc_semantic_search, which
nc_semantic_search_answer reuses) and pages_chunks (after dense
embedding succeeds, covering both in-process and procrastinate paths).
- storage.acquire()/.dialect public seams so the sibling store doesn't
reach into the underscored internal.
- tests parametrized over SQLite + Postgres: flag-off no-op, roundtrip,
ON CONFLICT dedup, JSON/NULL metadata, and the best-effort swallow of
both DB errors and unserializable metadata.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
