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ngit-grasp/tests/common
DanConwayDev e942199a55 fix(sync): bound concurrent transient REQ subscriptions per relay connection
Historic REQ+EOSE sync subscribed every byte-budgeted filter group of a
batch in one loop and left them all awaiting EOSE concurrently, as did
the REQ+EOSE fallback, negentropy ID fetches and missing-event retries.
On strfry-family relays these REQs share maxSubsPerConnection with
negentropy views and live subscriptions; nos.lol (budget 20) answered
each gitnostr.com startup with a burst of 'ERROR: too many concurrent
REQs' NOTICEs (6 in one second at the 2026-08-05 06:41 startup; 7,739
over the prior three days).

A per-connection semaphore (5 permits, shared across clones) now gates
every auto-close subscription inside subscribe_filters: the permit is
registered against the subscription id on success and released when the
connection's own event loop sees that subscription's EOSE or CLOSED
frame - before forwarding the notification, so release never depends on
downstream channel consumers. This keeps a plain blocking acquire
deadlock-free even though the SyncManager actor both creates
subscriptions and processes EOSE: bursts pipeline at five in flight,
matching the precedent of the actor already stalling inline for
negentropy batches. Permits are additionally freed on unsubscribe,
disconnect, event-loop termination, and by a 30-second watchdog so a
relay that never answers cannot starve later subscriptions. The
negentropy semaphore stays separate (different lifetimes); live
subscriptions are not gated. Budget: 4 NEG + 5 REQ + 2 margin leaves at
least nine slots of the tightest observed budget (20) for live
subscriptions.

Scheduling is deliberately per-REQ rather than per-core-filter: a
paginating filter chain holds no slot between pages, so queued groups
interleave breadth-first. Relay-visible concurrency is identical either
way and pagination chains have no durable identity across disconnects.

Reproduction: a new proxy fixture mimics the strfry limit (rejecting
REQs beyond 5 with the production NOTICE, exempting limit:0 live
subscriptions, delaying EOSE so REQs provably overlap), and a scenario
test syncs 2500 root events into persistent storage, restarts the relay
- startup recomputes filters from the full index, the shape that bursts
in production - and asserts zero rejections with overlap retained.
Unfixed: 3 REQs rejected (opened 91, peak pinned at the limit). Fixed:
zero rejections, peak <= 5, sync completes. The TestRelay fixture gains
same-port restart support with persistent LMDB storage for this.

Deliberately excluded: the unified budget ledger (NIP-11-aware B/M,
per-query result caps), raising the 300-ID exact-ID chunks, and any
configuration surface for the bound.

Validated with the full test suite (nix develop -c cargo test).
2026-08-05 07:50:45 +00:00
..