Follow-up to the per-session event ACL. Part of that change rode into 693a78d
via a concurrent agent's pathspec-less commit; this commit carries the review
fixes and uses pathspecs on the commit itself so it cannot recur in either
direction.
Gating the page's subscribe seam made AttachEvents asynchronous — it awaits the
authentication state — and that await is a suspension point the synchronous
version did not have. On a rapid A -> B navigation the suspended A continuation
resumes after B's parameter set has run to completion, re-reads the live
SessionId (now B's), and attaches B a SECOND time. The ACL is not bypassed —
the newer attach already cleared that same session — but the fields holding B's
first subscription are overwritten in place, so nothing ever disposes it: its
EventsHubViewerRegistry entry is never released, which keeps the mirror cloning
events for a session the page is no longer watching through that handle, and
its pump is never cancelled. A resource leak the ACL work introduced.
OnParametersSetAsync now claims a monotonic _attachGeneration synchronously,
before its first await, and AttachEventsAsync re-checks it after the await and
before any field write or Subscribe call. A stale attach returns rather than
detaching: it owns nothing, and tearing down there would destroy the newer
attach's subscription. DetachEventsAsync needs no such guard — it captures and
nulls the live fields synchronously before it awaits, so a resumed detach only
unwinds what it already took ownership of. Same dispatcher-owned identity idea
as the existing ReferenceEquals guards in PumpEventsAsync and
MarkDisconnectedAsync, one level up.
The interleaving is not expressible with the static HtmlRenderer idiom the other
page tests use: it renders a root component once and exposes no parameter-update
seam. The new test therefore adds a minimal Renderer subclass whose only job is
to mount a component and drive a second SetParametersAsync into it while the
first is parked on a gated AuthenticationStateProvider. That subclass is the
lone reason for a narrowly scoped BL0006 suppression, justified in place: it is
test-only scaffolding that never ships, and the cost of the warning coming true
is a compile break in one test file on an SDK bump. Confirmed non-vacuous by
mutation — with the generation check disabled the test goes red on the doubled
subscription and the two passing ACL tests stay green.
Two decision-table corners are now pinned rather than implied. Admin x
nonexistent session id resolves to ALLOW, because the admin bypass is evaluated
before the registry lookup; a plausible "look the session up first, it reads
better" refactor would flip it, so a test documents the ordering. EventsHub's
remarks said "an unknown session id is denied" without qualification, which read
as universal; they now state that the bypass is checked first and every rule
below it is a non-Admin rule.
HubTokenServiceTests gains the truly-absent-field case: a hand-built payload
JSON with no Tags key at all, protected through the same purpose, which is the
shape every in-flight token has across the deploy that introduces the field. The
existing test covered present-but-empty, which does not exercise the null
coalesce that stands between a legacy token and a crash on the hub auth path.
ProtectorPurpose became internal so the test cannot drift from the real purpose
string.
Tag-count cardinality cap considered and recorded as a deliberate non-goal.
Build 0 warnings / 0 errors; 48 filtered (ACL/hub/token/page) and 257 dashboard
tests pass.
The truncation-cliff fix made alarm transitions truncation-safe but silent:
when GetXmlCurrentAlarms2 returns exactly maxAlmCnt records the worker
suppresses absence-implies-Clear inference and says so only in a rate-limited
stderr warning. No client and no operator could tell a complete active set
from a capped one.
Two additive proto3 booleans carry the verdict out:
- QueryActiveAlarmsReplyPayload.snapshot_truncated = 2 (worker IPC reply)
- ActiveAlarmSnapshot.from_truncated_snapshot = 16 (per record)
The per-record field is not an aesthetic choice. QueryActiveAlarms returns a
bare `stream ActiveAlarmSnapshot` with no envelope, header, or trailer, so a
per-record boolean is the only carrier that stays wire-compatible; an envelope
message would change every existing client's stream element type. The reply
payload states it too because a prefix filter can leave zero records and a
truncated fetch with nothing to report still has to say so. The flag means
"this set may be incomplete", never "this record is unreliable" — it is
independent of the subtag-fallback `degraded` field.
Detection is deliberately UNCHANGED: IsTruncatedFetch remains
`fetchedRecordCount >= maxAlarmsPerFetch`. The live probe (docs/AlarmProbeFindings.md,
ce5d8ae) could not verify whether ALARM_RECORDS/@COUNT reports the total active
count or only the records in the reply, so @COUNT is not parsed for detection;
switching to it stays blocked on probe evidence. The probe's comment
annotations in WnWrapAlarmConsumer.cs are preserved.
Reset semantics: not latched. WnWrapAlarmConsumer.FoldFetch replaces the
verdict on every poll under the same lock as the snapshot merge, so the first
sub-cap fetch clears it; GatewayAlarmMonitor.ClearCache drops it with the cache
generation it describes. A caveat that never turns off is one operators learn
to ignore.
Flow: WnWrapAlarmConsumer.LastSnapshotTruncated -> AlarmDispatcher (stamps every
record) / IAlarmCommandHandler (payload) -> MxAccessCommandExecutor reply ->
GatewayAlarmMonitor._snapshotTruncated -> IGatewayAlarmService.SnapshotTruncated
-> DashboardAlarmQueryResult -> AlarmsPage warning banner (render-side only; the
poll loop and DisposeAsync drain are untouched). The public QueryActiveAlarms
RPC forwards worker snapshots unmodified, so the per-record flag needed no
mapper change — a test pins that.
Parity: this describes OUR fetch mechanics — additive gateway metadata — not
MXAccess provider behavior. No event is synthesized and no MXAccess-observable
semantics change, so it is not a parity deviation.
Tests: worker LastSnapshotTruncated set/reset/consecutive-burst (windev-run);
gateway end-to-end truncated reply -> monitor -> public stream, with the
complete-reply control as the load-bearing assertion; AlarmsPage banner
present/absent. Docs: gateway.md alarm surface, docs/DesignDecisions.md entry.
Joseph Doherty