Remove the per-call allowMultipleSubscribers param from AttachEventSubscriber and
derive the mode internally from _eventStreaming.AllowMultipleEventSubscribers — the
same source SessionEventDistributor uses for singleSubscriberMode — so the two can
never structurally diverge. The maxSubscribers cap param is kept because
MaxEventSubscribersPerSession lives in SessionOptions, which the session does not hold
directly (only EventOptions flows through SessionEventStreaming).
Other nits:
- SubscriberCount XML doc clarifies it includes internal subscribers and differs from
GatewaySession.ActiveEventSubscriberCount (external/gRPC only).
- SingleSubscriberMode_LoneExternalOverflow test: add Assert.Equal(1, observedSet) guard
before the value assertion so the test cannot pass vacuously if the handler never fired.
- GatewayOptionsValidator.ValidateSessions: add explanatory code comment documenting why
!AllowMultipleEventSubscribers && MaxEventSubscribersPerSession > 1 is NOT rejected as
a hard error (the default config ships with this combination; the cap is simply unused
in single-subscriber mode, not a behavior bug).
- GatewaySession.DetachEventSubscriber: add Debug.Assert before the clamp so a genuine
double-decrement surfaces in debug builds.
(1) GatewaySession.StartDashboardMirror: publish _dashboardMirrorLease and _dashboardMirrorTask
atomically under one _syncRoot section; if the session is already Closing/Closed/Faulted,
dispose the just-created lease and return without starting the mirror task so nothing is orphaned.
(2) WaitUntilAsync test helper: catch OperationCanceledException and call Assert.Fail with the
timeout duration and predicate source text instead of letting the exception propagate raw.
(3) New SessionEventDistributorTests.InternalSubscriberOverflow_HandlerSeesIsOnlySubscriberFalse:
verifies CountExternalSubscribers excludes the internal subscriber, so isOnlySubscriber==false
even when the internal subscriber is the only registered subscriber.
(4) SubscriberOverflowHandler delegate gains isInternal parameter; overflow metric label is
"dashboard-mirror" for internal subscribers and "grpc-event-stream" for external ones.
(5) DashboardEventBroadcaster.Publish: wrap SendAsync Task acquisition in try/catch so a
synchronous throw cannot escape the never-throw Publish interface contract.
Joseph Doherty