Nothing counted open import sessions and nothing logged a rejection at
MaxConcurrentImportSessions (default 8), so the register-row-43 session leak
could only be inferred from rotating test failures.
- Gauge scadabridge.central.transport.import_sessions.open on the existing
ZB.MOM.WW.ScadaBridge meter — already in SiteServiceRegistration.ObservedMeters
(the ZbTelemetryOptions.Meters allowlist), so no telemetry config change is
needed and the series is not silently dropped. Provider-backed, mirroring the
StoreAndForward queue-depth gauge: registered by BundleSessionEvictionService
.StartAsync (Transport's only lifecycle seam) and identity-checked-cleared on
StopAsync so a late stop cannot clobber a newer registrant.
- IBundleSessionStore.OpenSessionCount counts only UNEXPIRED sessions. The raw
dictionary count would report the node as pinned at the cap for up to a
one-minute sweep interval after a burst had drained — the exact false positive
the instrument exists to rule out.
- BundleSessionStore.Open logs Warning with open count, cap and TTL when it
rejects. Fires only on a real cap hit: a store full of expired sessions is
reclaimed first and logs nothing.
- Docs: docs/components/Transport.md + docs/requirements/Component-Transport.md.
Tests: Transport 173 passed (+6 new — Warning content, two negative controls,
unexpired-only counting, gauge register/clear, no-clobber-on-late-stop).
Every AttributeValueChanged/AlarmStateChanged rode its own gRPC message on
SiteStreamService; at target scale that is ~37.5k messages/s/site of pure
framing overhead. Coalesce them, additively, with no new RPC.
Wire (sitestream.proto, regenerated via docker/regen-proto.sh sitestream):
InstanceStreamRequest.batching_supported = 3
SiteStreamRequest.batching_supported = 2
SiteStreamEvent.batch = 4 (new oneof case)
SiteStreamEventBatch { repeated SiteStreamEvent events = 1 }
The proto3 default of batching_supported IS the negotiation, and it is
load-bearing: a batch frame reaches a pre-R2 central as EventOneofCase.None,
whose ConvertToDomainEvent returns null — the whole batch would vanish with
no error anywhere. An old central cannot set the flag so it never receives
one; an old site ignores the unknown request field and keeps sending
per-event frames, which the new client's ForEachEvent handles as the
single-event case. Both skew directions are covered by tests that go through
a real proto serialize/parse round-trip.
Server: SiteStreamEventBatcher, a per-subscriber pump replacing the handler's
await-foreach/WriteAsync loop and byte-identical to it at a cap of 1. It
never delays a lone event — it drains the already-queued backlog for free and
lingers only once a backlog is proven — emits a single-event buffer as a
plain frame, preserves order and per-event Timestamps exactly, and flushes
what is buffered when the send channel's writer completes. It sits DOWNSTREAM
of StreamRelayActor's bounded DropOldest channel, so it changes framing only
and does not move the burst ceiling (deferred register row 31, which lives in
the shared publish stage upstream of the BroadcastHub).
Client: sets the flag on both subscriptions and unpacks in order into the
existing per-event pipeline, so SiteAlarmAggregatorActor,
DebugStreamBridgeActor, consumer-keepalive/orphan logic,
reconnect-on-graceful-completion, generation fencing, the (siteId, endpoint)
factory key and IsLive semantics are untouched.
Options (validated): GrpcStreamBatchMaxEvents 100 (1 disables),
GrpcStreamBatchWindow 25 ms — validated strictly under 250 ms, the load
test's end-to-end P99 threshold. Measured worst case (trickle-with-backlog,
window-bound rather than cap-bound): P50 13.8 ms, P99 25.4 ms, max 25.8 ms;
cap-bound case sent 600 queued events in 6 frames.
Telemetry: histogram scadabridge.site.stream.batch_size tagged by stream
kind, recorded only on negotiated streams (per-event otherwise). It rides
ScadaBridgeTelemetry.MeterName, already in the ObservedMeters allowlist.
Docs: Component-Communication.md gains an Event Batching section; CLAUDE.md's
gRPC streaming bullet records the wire shape and the negotiation rationale.
Extend CommunicationOptionsValidator with eager bounds for the four T4
live-alarm-cache options (linger >= 0, reconcile > 0, seed concurrency 1..64,
subscribers-per-site >= 1). Enforce the per-site viewer cap fail-safe in
SiteAlarmLiveCacheService.Subscribe (reject excess viewers with a no-op
disposable rather than growing the list or throwing into the Blazor render
path). Surface two telemetry instruments on the existing ScadaBridgeTelemetry
meter: an active-aggregator observable gauge and a reconnect counter, wired from
the aggregator actor's PreStart/PostStop and its NodeA<->NodeB flip /
reconcile-driven reopen.
Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj
Remediation from the full per-module code review at 4307c381 (findings recorded
separately in code-reviews/).
Highs fixed:
- DeploymentManager-025/SiteRuntime-031: stop broadcasting notification lists + SMTP
configs (incl. credentials) to sites; site purges already-persisted rows on apply
(enforces the central-only delivery design; clears plaintext SMTP creds at rest).
- DataConnectionLayer-023: guard the native-alarm subscribe path against the
mid-flight-unsubscribe adapter-feed leak (mirrors the DCL-021 tag-path fix).
- SiteEventLogging-024: normalize From/To query bounds to UTC (the -016 fix the
audit trail claimed but never committed).
- KpiHistory-001: add an in-flight guard to the recorder sample tick.
- ScriptAnalysis-001: harden the trust analyzer's TPA-absent fallback (resolve
forbidden anchors in the minimal reference set; warn on degraded mode) — anchors
added to validation references only, never the compile gate.
(InboundAPI-026 left to the feat/ipsen-movein effort per owner decision.)
Medium/Low: DM-026 deterministic deploy-status tiebreaker; SR-027/028/029/030
native-alarm leak/phantom-active/delete-during-redeploy fixes; AL-013/014/016;
TE-024 (folder-mutation audit rows now persisted)/025; SF-025 gauge-provider
clear-on-stop; ESG-025/026; SEC-023/024/025; SCA-007/008/009; plus doc/test
accuracy COM-023/024, HOST-025/026, HM-024/025, NS-027/028.
Full-solution build 0 warnings; ~3560 tests across 18 touched suites green.
Joseph Doherty