An empty replay ring reported oldest_available_sequence = 0 even when gap was
true. Clients follow the documented after_worker_sequence = oldest - 1 formula,
so an unsigned client computed ulong.MaxValue: the follow-up resume replayed
nothing, reported no gap, and the live filter dropped every subsequent event —
a silently dead stream in the headline detach-and-resume scenario, reachable on
default config once ReplayRetentionSeconds (300) age-evicts the ring.
GWC-25: SessionEventDistributor.RegisterWithReplay's empty-ring branch now
reports _highestSequenceSeen + 1 — the next sequence that can possibly be
delivered — when gap is true, so oldest - 1 lands exactly on the highest
observed sequence and the resume delivers everything newer. Still 0 when there
is no gap, where the field is meaningless and never emitted. Nothing is lost:
the evicted interval was unrecoverable either way, and the sentinel's job is to
say "re-snapshot".
CLI-35: the Python CLI fed every stream item into MessageToDict, which raised on
the ReplayGap dataclass and aborted the command after consuming the stream. A
new _event_row helper renders a gap as {"replayGap": {...}} — the same camelCase
shape the Rust CLI emits — and leaves proto events on the existing path.
CLI-36: the Go CLI formatted result.Event on every row, but the library
deliberately clears Event on a gap, so text mode printed
"0 MX_EVENT_FAMILY_UNSPECIFIED" and JSON mode an empty object, discarding the
resume cursors. The loop now branches on result.IsReplayGap() and renders the
typed row in both modes, counting it toward -limit like any other row. The JSON
row's cursors are typed by hand rather than marshalled with protojson: the
proto3 JSON mapping renders 64-bit integers as strings ("7") while the Rust and
Python CLIs emit numbers (7), so going through protojson would have made Go the
only canonical CLI with a different value type.
Docs in the same change: docs/Sessions.md documents the empty-ring sentinel
value and that oldest - 1 is the universal resume formula in both the retained
and fully-evicted cases; docs/CrossLanguageSmokeMatrix.md gains a per-CLI
gap-rendering table covering both client findings, and records exactly what is
and is not comparable across CLIs (same keys and numeric cursors for Rust/Go/
Python; quoted cursors for .NET/Java; differing key order, whitespace, and
container), so a matrix runner compares parsed values rather than raw bytes.
Tests, all written red first and each reproducing its defect verbatim:
- SessionEventDistributorTests: RegisterWithReplayReportsNextDeliverableSequence
WhenRingEmptiedByAge, ...WithRetentionDisabled, and
ResumeUsingSentinelFormulaAfterEmptyRingGapDeliversLiveEvents.
- GatewayEndToEndReconnectReplayTests.ReconnectAfterFullAgeEvictionResumesWith
SentinelFormula — fake-worker e2e resume walk on a fake clock; the fixture now
takes a retention window and a TimeProvider.
- clients/python test_stream_events_renders_replay_gap.
- clients/go TestRunStreamEventsPrintsReplayGap.
GWC-25's ReplayGap.oldest_available_sequence proto-comment amendment is
deliberately deferred to the later codegen wave (see the tracker change log): it
is comment-only but triggers the full five-client regen fan-out.
Replace the replay buffer's LinkedList<ReplayEntry> (a node allocation per
retained event on the fan-out hot path) with a preallocated ReplayEntry[] ring
sized to ReplayBufferCapacity, tracked by _replayHead (oldest) + _replayCount.
Appending a retained event now allocates nothing.
Behavior preserved exactly: ascending-WorkerSequence append order; capacity
eviction (overwrite head + advance when full); time trim via
_timeProvider.GetUtcNow() cutoff at the same three call sites; oldest-read for
ReplayGap math; both replay-from-sequence query paths + highest-seen tracking;
same _replayLock. Capacity-0 stays retain-nothing (guarded early return, no
modulo-by-zero).
Server build clean (0 warnings); Distributor/Replay tests 33/33 incl. two new
cases (multi-wrap ring keeps newest in order; capacity-1 overwrite + gap).
Claude-Session: https://claude.ai/code/session_01DMXXvNuPekkkrTEyPNxEkW
Server-054/055/056, Contracts-020/021/022, Tests-036/038/039,
IntegrationTests-030/031/032 (+033 deferred to live rig),
Client.Dotnet-026/028/029 (+027 won't-fix), Client.Go-030..034,
Client.Python-032..036, Client.Rust-033..038.
Key fix: SessionEventDistributor orphaned a subscriber that registered after
the pump completed but before disposal (Server-056) -> register paths now
complete late registrants under _lifecycleLock; regression test added. The
racy dashboard-mirror gRPC test made deterministic (Tests-039).
Verified green locally: gateway Tests targeted classes (GatewaySession,
SessionEventDistributor, GatewayOptionsValidator, ProtobufContractRoundTrip,
GatewaySessionDashboardMirror) + dotnet/go/python/rust client suites.
- EventStreamService: remove dead per-item sequence guard in the replay
loop (RegisterWithReplay already returns only events > afterSequence)
and correct the comment that falsely claimed a "per-item constraint
filter" is applied; the event stream has no per-event constraint
filtering today.
- SessionEventDistributor.RegisterWithReplay: set oldestAvailableSequence=0
when gap==false so the implementation matches the documented contract
(OldestAvailableSequence is meaningful only when Gap is true).
Update the two RegisterWithReplay tests that asserted the old non-zero
value in the no-gap path.
- RegisterSubscriber: remove stray blank line at method entry.
- SessionEventDistributorTests: add RegisterWithReplay_AfterDispose_
ThrowsObjectDisposedException to pin nested-lock disposal behavior.
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.
- Issue 1: document the isOnlySubscriber snapshot race-safety assumption in
OnSubscriberOverflow; flags the Task 7/8 revisit point explicitly.
- Issue 2: pin StreamDisconnects==1 in the FailFast overflow test so a
regression dropping the StreamDisconnected("Detached") finally call is caught.
- Issue 3: replace plain int/bool? reads in SlowSubscriberOverflow test with
Volatile.Read/Write + Interlocked.Increment stores to close the C# memory
model data race on overflowCalls and observedIsOnlySubscriber.
- Issue 4: add SlowSubscriberOverflow_WithMultipleSubscribers_... distributor
test pinning that isOnlySubscriber==false disables the session-fault path;
includes TODO(Task 8) note for the GatewaySession-level assertion.
- Issue 5: reword SubscriberOverflowHandler XML doc to make explicit that the
handler must NOT complete the subscriber's channel; the distributor owns that.
#2: Replace afterSequence+1<oldestRetained with overflow-safe oldestRetained>0&&afterSequence<oldestRetained-1 to prevent ulong wrap at MaxValue falsely reporting gap=true.
#3: Add ReplayBufferCapacity and ReplayRetentionSeconds to EffectiveEventConfiguration and populate from EventOptions in GatewayConfigurationProvider.
#4: Add four new SessionEventDistributorTests covering capacity=0 gap/no-gap paths and the ulong.MaxValue boundary case.
#5: Update class-level <remarks> to describe the Task 3 replay ring buffer (capacity + age eviction, TryGetReplayFrom) rather than its absence.
#6: Add O(n)-is-acceptable comment at TryGetReplayFrom linear scan.
#8: Narrow no-replay 4-arg ctor to internal; InternalsVisibleTo already covers the test project.
Joseph Doherty