While a folder subscriber's SDK channel is full, a condition's later events wait in
its #838 deferral queue and reach i=2253 items only when the drain gets to them, off
Lock. A ConditionRefresh in that window replayed the current state, then the older
deferred events followed RefreshEnd (stale state, or a condition the refresh had just
dropped re-added until the newest drained).
- Condition events are reported as ConditionEventSnapshot (an InstanceStateSnapshot
carrying a report sequence, condition NodeId and Retain); events queued behind a
deferred report are marked Deferred.
- Server-object refresh (ConditionRefresh and ConditionRefresh2, flag on AND off) now
runs in RefreshServerObjectItems: watermark, "anything deferred?", the replay and its
queueing in ONE Lock hold, so the replay is exactly the state at the cut. Per item it
queues the replay and installs a RefreshCut under the item's gate.
- OnConditionReportEvent holds that gate across "superseded? -> QueueEvent" for
deferred events only. Withheld from that item alone: events at/below the cut whose
condition the replay re-sent, or Retain=true events of a condition it omitted; an
older Retain=false event of an omitted condition is still delivered. Queues, other
Server-object items and folder items are untouched; refresh never waits for a drain.
- Lock order Lock -> item gate -> SDK item lock, same as a synchronous report.
- Meter otopcua.opcua.condition_events.superseded.
- Folder items keep a documented residual (SDK channel backlog + memoised per-item
verdict leave no per-event hook).
Tests: ConditionRefreshDeferralWireTests (deterministic overload by holding the folder
item's SDK lock; 6 variants fail before the fix; probe-driven gate test fails with the
gate removed; concurrent reports/refreshes/stall stress test fails before the fix).
Joseph Doherty
1622d07f2e