Findings: unified surface holds on tokio-postgres with the transactional
property intact (in-tx NOTIFY is commit-atomic; rollback drops all);
LISTEN wake beats poll 5-16x at p50 with 300/300 isolated delivery;
pooled-LISTEN discard (deadpool#360) verified and pinned as our own test;
postgres-notify 0.3.8 evaluated and passed over (lazy reconnect, no
initial-connect script, unquoted identifier LISTENs) in favor of the
~90-line hand-rolled forwarder with test-pinned pitfalls. sqlx PgListener
fallback retired unfired.
Two claims verified independently before folding: (1) deadpool-postgres
discards async notifications — upstream deadpool-rs/deadpool#360 (open,
Oct 2024) confirms the pool's connect task awaits the connection to
completion, dropping what only poll_message exposes; pooled LISTEN is
lost at recycle. The dedicated non-pooled LISTEN connection is now
upstream-verified required, not spec-preferred. (2) postgres-notify
0.3.8 exists as described (MIT, tokio-postgres, auto-reconnect with
backoff+jitter, multi-channel subscribe_notify, connect_script hook)
— admitted as sub-module L's second arm (hand-rolled forwarder vs
turnkey listener substrate), with in-probe verification required:
docs don't explicitly promise subscription restoration across
reconnect; connect_script is the mechanism; single-maintainer posture
recorded. New property test pinned: pooled-LISTEN-discard assertion
(our own evidence for the #360 behavior, flips if upstream fixes).
Probe 5 updated to budget accounting (listener conn outside the pool).
Completes OQ-ST-03: one driver posture (tokio-postgres + deadpool, the
POC #5/#7-validated stack) with three sub-modules — L (LISTEN plumbing:
dedicated connection, multi-channel, payload boundary), T (tx-seam over
the pool: caller-owned tx handle vs closure-scoped, both implemented
and compared — direct OQ-ST-04 input), W (wake-vs-poll parity, LISTEN
reconnect + the replay hole honesty). Property tests are the POC #1
suite's pg twin; seam probe mirrors the POC #1 workload for the
cross-engine relative claim. Gate: commit-atomicity via in-tx NOTIFY
(load-bearing), exactly-once claim, seam costs, LISTEN robustness -
failure names the sqlx PgListener fallback posture. Out of scope:
queue semantics depth (OQ-ST-05), pgboss-rs code adoption, multi-host
stress (OQ-ST-08). Register row added, plan updated (POC #2 running
closes OQ-ST-03).
glm-5.3-flash