feat(sessions): replay-on-reconnect with ReplayGap sentinel

2026-06-16 07:22:19 -04:00
parent 042f5e3d82
commit 36ab8d15f1
7 changed files with 736 additions and 29 deletions
@@ -0,0 +1,43 @@
+using ZB.MOM.WW.MxGateway.Contracts.Proto;
+
+namespace ZB.MOM.WW.MxGateway.Server.Sessions;
+
+/// <summary>
+///     The result of a reconnect/resume attach
+///     (<see cref="GatewaySession.AttachEventSubscriberWithReplay"/>, Task 12): the live
+///     subscriber lease plus the replay batch and resume watermarks snapshotted atomically
+///     with the registration, so the replay→live handoff has no gap and no duplicate.
+/// </summary>
+/// <param name="Lease">
+///     The live event subscriber lease. Disposing it unregisters the distributor subscriber
+///     and decrements the session's active-subscriber count, exactly as a fresh attach.
+/// </param>
+/// <param name="ReplayedEvents">
+///     Retained events with worker sequence strictly greater than the requested
+///     <c>afterSequence</c>, in ascending order. These must be yielded (after the optional
+///     gap sentinel) before live events. Never null; empty when nothing newer is retained.
+/// </param>
+/// <param name="Gap">
+///     <see langword="true"/> when events between the requested <c>afterSequence</c> and the
+///     oldest retained event were already evicted, so the client missed unrecoverable events.
+///     When <see langword="true"/> the caller emits a <c>ReplayGap</c> sentinel before the
+///     replay batch.
+/// </param>
+/// <param name="OldestAvailableSequence">
+///     The oldest worker sequence still retained and replayable; <c>0</c> when nothing is
+///     retained. Populates the <c>ReplayGap.oldest_available_sequence</c> field. Meaningful
+///     only when <paramref name="Gap"/> is <see langword="true"/>.
+/// </param>
+/// <param name="LiveResumeSequence">
+///     The worker sequence the live channel must resume strictly after: the highest replayed
+///     sequence, or the requested <c>afterSequence</c> when nothing was replayed. The caller
+///     applies this as the per-subscriber live filter so any event both replayed and fanned
+///     into the live channel is dropped exactly once (no duplicate) while every newer event
+///     is delivered (no gap).
+/// </param>
+public readonly record struct EventSubscriberReplayAttachment(
+    IEventSubscriberLease Lease,
+    IReadOnlyList<MxEvent> ReplayedEvents,
+    bool Gap,
+    ulong OldestAvailableSequence,
+    ulong LiveResumeSequence);