Bug (verified vs SQLAlchemy 2.0.49): on GC-cleanup of an abandoned async connection, _finalize_fairy routes through fairy.detach(), which nulls the record's dbapi_connection so NullPool's close is a no-op (the `close` event never fires) then emits `detach` with the record. Listening only to close/invalidate left the marker unpopped, so db_connections_open leaked upward and never reset until restart. Listen to `detach` too — it carries the ConnectionRecord and the marker dedupes, so exactly one decrement occurs.
Also: strip a bare PR-number provenance tag from the test docstring (plastic-labs comment-reconciliation rule); disambiguate db_connections_open from the existing db_pool_connections; note in initialize_bounded_metrics that DB-instrumentation metrics zero-init in their registrar.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Add db_connections_open (gauge) and db_connections_established (counter), driven by SQLAlchemy connection-lifecycle events so they report real connections under every pool class — including NullPool, where the pool-object collector (db_pool_connections) reads zero. Under NullPool the establishment rate approximates request rate.
DBConnectionTracker mirrors DBQueryInflightTracker: a ConnectionRecord.info marker makes each physical connection increment once and decrement at most once (no leak, no negative). Registered per-process in the API and deriver; zero-init via the pre-resolved labeled children, matching db_queries_in_flight_gauge.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Phil