fix(dcl): forget an OPC UA condition's last state once it returns to normal (review 2026-10-21 02/L3)

docs/requirements/Component-DataConnectionLayer.md

@@ -468,4 +468,4 @@ The DCL reports the following metrics to the Health Monitoring component via the
 
 OPC UA connection and endpoint verification select exactly the configured security mode. If a protected mode is unavailable, or discovery fails while protection was requested, the operation fails with the requested mode in its diagnostic; it never falls back to an unsecured session.
 
-DCL retains each subscribed alarm source's current standing state and its in-progress snapshot. A new subscriber sharing a feed receives a scoped replay, or the already-received prefix of an in-progress frame followed by the remaining frame. Cache state is discarded on reconnect and last-owner unsubscribe. A new Mx source reopens the shared stream even when the existing prefix covers it, obtaining a fresh standing-state snapshot; callbacks from the canceled stream are ignored. Mx refresh boundaries remain connection-wide but share a distinct per-stream epoch. Both replay cache and runtime mirror ignore stale-epoch rows and apply newer live raises/clears over a concurrent refresh before committing it.
+DCL retains each subscribed alarm source's current standing state and its in-progress snapshot. A new subscriber sharing a feed receives a scoped replay, or the already-received prefix of an in-progress frame followed by the remaining frame. Cache state is discarded on reconnect and last-owner unsubscribe. A new Mx source reopens the shared stream even when the existing prefix covers it, obtaining a fresh standing-state snapshot; callbacks from the canceled stream are ignored. Mx refresh boundaries remain connection-wide but share a distinct per-stream epoch. Both replay cache and runtime mirror ignore stale-epoch rows and apply newer live raises/clears over a concurrent refresh before committing it. The OPC UA client's per-condition `(active, acked)` memory used to derive transition kinds follows the same removal rule as the replay cache — a condition that returns to inactive + acknowledged (the default prior state) is forgotten — so it stays bounded on servers whose condition names carry a per-occurrence component (review 2026-10-21).

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs

@@ -1236,8 +1236,18 @@ public class RealOpcUaClient : IOpcUaClient
         var kind = inRefresh
             ? AlarmTransitionKind.Snapshot
             : OpcUaAlarmMapper.DeriveKind(prevAcked, acked, prevActive, active);
-        lastState?.TryAdd(sourceRef, (active, acked));
+        if (lastState != null)
-        if (lastState != null) lastState[sourceRef] = (active, acked);
+        {
+            // Inactive + acknowledged IS the default prior state above, so forgetting it changes
+            // no derived kind — and keeps the map bounded on servers whose condition names carry
+            // a per-occurrence component (batch, lot, counter), where every occurrence is a new
+            // key for the life of the session (review 2026-10-21 02/L3; mirrors the actor's
+            // CacheAlarmTransition removal rule).
+            if (!active && acked)
+                lastState.Remove(sourceRef);
+            else
+                lastState[sourceRef] = (active, acked);
+        }
 
         onTransition(new NativeAlarmTransition(
             SourceReference: sourceRef,

tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/Adapters/RealOpcUaAlarmLastStateTests.cs

@@ -0,0 +1,89 @@
+using System.Collections.Concurrent;
+using System.Reflection;
+using Opc.Ua;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms;
+using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;
+
+namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests.Adapters;
+
+/// <summary>
+/// Review 2026-10-21 02/L3: the per-condition (active, acked) memory behind
+/// <c>DeriveKind</c> must not grow for the life of a session. A condition that returns to
+/// inactive + acknowledged is indistinguishable from one never seen (the default prior state), so
+/// its key is dropped — otherwise a server whose condition names carry a per-occurrence component
+/// (batch, lot, counter) adds a key per occurrence until the next reconnect.
+/// </summary>
+public class RealOpcUaAlarmLastStateTests
+{
+    private const string Handle = "h1";
+
+    private static readonly MethodInfo Handler =
+        typeof(RealOpcUaClient).GetMethod("HandleAlarmEvent", BindingFlags.Instance | BindingFlags.NonPublic)!;
+
+    private static Dictionary<string, (bool Active, bool Acked)> SeedLastState(RealOpcUaClient client)
+    {
+        var field = typeof(RealOpcUaClient).GetField("_alarmLastState", BindingFlags.Instance | BindingFlags.NonPublic)!;
+        var map = (ConcurrentDictionary<string, Dictionary<string, (bool Active, bool Acked)>>)field.GetValue(client)!;
+        var perHandle = new Dictionary<string, (bool Active, bool Acked)>(StringComparer.Ordinal);
+        map[Handle] = perHandle;
+        return perHandle;
+    }
+
+    private static void Emit(RealOpcUaClient client, string condition, bool active, bool acked, List<NativeAlarmTransition> sink)
+    {
+        var fields = new VariantCollection
+        {
+            new(ObjectTypeIds.AlarmConditionType), // 0 EventType
+            new(new NodeId("Tank01", 2)),          // 1 SourceNode
+            new("Tank01"),                         // 2 SourceName
+            new(DateTime.UtcNow),                  // 3 Time
+            new(new LocalizedText("msg")),         // 4 Message
+            new((ushort)500),                      // 5 Severity
+            new(active),                           // 6 ActiveState/Id
+            new(acked),                            // 7 AckedState/Id
+            Variant.Null,                          // 8 ConfirmedState/Id
+            new(false),                            // 9 SuppressedOrShelved
+            Variant.Null,                          // 10 ShelvingState
+            new(condition),                        // 11 ConditionName
+        };
+        Handler.Invoke(client, [Handle, "ns=2;s=Tank01", new EventFieldList { EventFields = fields },
+            (Action<NativeAlarmTransition>)sink.Add]);
+    }
+
+    /// <summary>A per-occurrence condition that clears and is acknowledged leaves no key behind.</summary>
+    [Fact]
+    public void ReturnToNormal_DropsTheConditionKey()
+    {
+        var client = new RealOpcUaClient();
+        var lastState = SeedLastState(client);
+        var sink = new List<NativeAlarmTransition>();
+
+        for (var lot = 1; lot <= 50; lot++)
+        {
+            Emit(client, $"Hi.Lot{lot}", active: true, acked: false, sink);
+            Emit(client, $"Hi.Lot{lot}", active: false, acked: true, sink);
+        }
+
+        Assert.Empty(lastState);
+        Assert.Equal(100, sink.Count);
+    }
+
+    /// <summary>
+    /// Dropping the key does not change the transition kinds derived for a condition that comes
+    /// back — the dropped state equals the default prior state.
+    /// </summary>
+    [Fact]
+    public void ReRaiseAfterReturnToNormal_StillDerivesARaise()
+    {
+        var client = new RealOpcUaClient();
+        var lastState = SeedLastState(client);
+        var sink = new List<NativeAlarmTransition>();
+
+        Emit(client, "Hi", active: true, acked: false, sink);
+        Emit(client, "Hi", active: false, acked: true, sink);
+        Emit(client, "Hi", active: true, acked: false, sink);
+
+        Assert.Equal(sink[0].Kind, sink[2].Kind);
+        Assert.Single(lastState); // the re-raised condition is tracked again
+    }
+}