fix(site-runtime): resolve SiteRuntime-017..019 — isolated attribute snapshot for child actors, corrected dispatcher doc, remove dead lifecycle handlers

src/ScadaLink.SiteRuntime/Actors/AlarmActor.cs

@@ -56,6 +56,14 @@ public class AlarmActor : ReceiveActor
     private readonly Script<object?>? _compiledTriggerExpression;
     private readonly Dictionary<string, object?> _attributeSnapshot = new();
 
+    /// <summary>
+    /// SiteRuntime-017: the exact dictionary instance this actor was seeded from
+    /// at construction. The Instance Actor must pass a private snapshot here, not
+    /// its live <c>_attributes</c> field. Exposed for regression coverage of that
+    /// isolation contract.
+    /// </summary>
+    internal IReadOnlyDictionary<string, object?>? SeedAttributesReference { get; }
+
     // Rate of change tracking
     private readonly Queue<(DateTimeOffset Timestamp, double Value)> _rateOfChangeWindow = new();
     private readonly TimeSpan _rateOfChangeWindowDuration;
@@ -90,6 +98,7 @@ public class AlarmActor : ReceiveActor
         // Seed the trigger-expression attribute snapshot from the instance's
         // initial attribute set so static attributes (which never re-emit an
         // AttributeValueChanged after deploy) evaluate correctly at startup.
+        SeedAttributesReference = initialAttributes;
         if (initialAttributes != null)
         {
             foreach (var kvp in initialAttributes)

src/ScadaLink.SiteRuntime/Actors/InstanceActor.cs

@@ -4,7 +4,6 @@ using Microsoft.Extensions.Logging;
 using ScadaLink.Commons.Messages.DataConnection;
 using ScadaLink.Commons.Messages.DebugView;
 using ScadaLink.Commons.Messages.Instance;
-using ScadaLink.Commons.Messages.Lifecycle;
 using ScadaLink.Commons.Messages.ScriptExecution;
 using ScadaLink.Commons.Messages.Streaming;
 using ScadaLink.Commons.Types.Enums;
@@ -102,20 +101,13 @@ public class InstanceActor : ReceiveActor
         // Handle static attribute writes
         Receive<SetStaticAttributeCommand>(HandleSetStaticAttribute);
 
-        // Handle lifecycle messages
-        Receive<DisableInstanceCommand>(_ =>
-        {
-            _logger.LogInformation("Instance {Instance} received disable command", _instanceUniqueName);
-            Sender.Tell(new InstanceLifecycleResponse(
-                _.CommandId, _instanceUniqueName, true, null, DateTimeOffset.UtcNow));
-        });
-
-        Receive<EnableInstanceCommand>(_ =>
-        {
-            _logger.LogInformation("Instance {Instance} received enable command", _instanceUniqueName);
-            Sender.Tell(new InstanceLifecycleResponse(
-                _.CommandId, _instanceUniqueName, true, null, DateTimeOffset.UtcNow));
-        });
+        // SiteRuntime-019: the disable/enable lifecycle is owned entirely by the
+        // Deployment Manager — DeploymentManagerActor.HandleDisable/HandleEnable
+        // stop or re-create the Instance Actor directly and reply to the caller.
+        // DisableInstanceCommand / EnableInstanceCommand are never routed to the
+        // Instance Actor, so no handlers are registered here. (The previous no-op
+        // handlers were dead code that implied a non-existent instance-side
+        // acknowledgement contract.)
 
         // WP-15: Handle script call requests — route to appropriate Script Actor (Ask pattern)
         Receive<ScriptCallRequest>(HandleScriptCallRequest);
@@ -590,11 +582,25 @@ public class InstanceActor : ReceiveActor
     /// WP-15: Script Actors spawned per script definition.
     /// WP-16: Alarm Actors spawned per alarm definition, as peers to Script Actors.
     /// WP-32: Compilation errors reject entire instance deployment (logged but actor still starts).
+    ///
+    /// SiteRuntime-017: each child is seeded from a private point-in-time snapshot
+    /// of <c>_attributes</c>, NOT the live dictionary. The snapshot is taken here on
+    /// the Instance Actor thread, so it is race-free; handing the live mutable
+    /// <see cref="System.Collections.Generic.Dictionary{TKey,TValue}"/> by reference
+    /// would let a child constructor enumerate it on the child's mailbox thread while
+    /// this actor mutates it in <c>HandleAttributeValueChanged</c>.
     /// </summary>
     private void CreateChildActors()
     {
         if (_configuration == null) return;
 
+        // SiteRuntime-017: snapshot the live attribute dictionary once, on the
+        // Instance Actor thread, before any child is constructed. Each child
+        // Props closure captures this immutable copy instead of the mutable
+        // _attributes field, so no child constructor ever enumerates a
+        // dictionary this actor is concurrently mutating.
+        var attributeSnapshot = new Dictionary<string, object?>(_attributes);
+
         // Create Script Actors
         foreach (var script in _configuration.Scripts)
         {
@@ -622,7 +628,7 @@ public class InstanceActor : ReceiveActor
                 _options,
                 _logger,
                 triggerExpression,
-                _attributes,
+                attributeSnapshot,
                 _healthCollector,
                 _serviceProvider));
 
@@ -672,7 +678,7 @@ public class InstanceActor : ReceiveActor
                 _options,
                 _logger,
                 triggerExpression,
-                _attributes,
+                attributeSnapshot,
                 _healthCollector));
 
             var actorRef = Context.ActorOf(props, $"alarm-{alarm.CanonicalName}");

src/ScadaLink.SiteRuntime/Actors/ScriptActor.cs

@@ -48,6 +48,15 @@ public class ScriptActor : ReceiveActor, IWithTimers
     private bool _lastExpressionResult;
     private readonly Dictionary<string, object?> _attributeSnapshot = new();
 
+    /// <summary>
+    /// SiteRuntime-017: the exact dictionary instance this actor was seeded from
+    /// at construction. The Instance Actor must pass a private snapshot here, not
+    /// its live <c>_attributes</c> field — sharing the live dictionary lets this
+    /// constructor enumerate it while the Instance Actor mutates it on another
+    /// thread. Exposed for regression coverage of that isolation contract.
+    /// </summary>
+    internal IReadOnlyDictionary<string, object?>? SeedAttributesReference { get; }
+
     public ITimerScheduler Timers { get; set; } = null!;
 
     public ScriptActor(
@@ -80,6 +89,7 @@ public class ScriptActor : ReceiveActor, IWithTimers
         // Seed the trigger-expression attribute snapshot from the instance's
         // initial attribute set so static attributes (which never re-emit an
         // AttributeValueChanged after deploy) evaluate correctly at startup.
+        SeedAttributesReference = initialAttributes;
         if (initialAttributes != null)
         {
             foreach (var kvp in initialAttributes)

src/ScadaLink.SiteRuntime/Actors/ScriptExecutionActor.cs

@@ -14,9 +14,14 @@ namespace ScadaLink.SiteRuntime.Actors;
 /// <summary>
 /// WP-15: Script Execution Actor -- short-lived child of Script Actor.
 /// Receives compiled code, params, Instance Actor ref, and call depth.
-/// Runs on a dedicated blocking I/O dispatcher.
 /// Executes the script via Script Runtime API, returns result, then stops.
 ///
+/// The actor itself and its mailbox run on the default Akka dispatcher; only the
+/// script body is dispatched off the actor thread, onto the dedicated
+/// <see cref="ScadaLink.SiteRuntime.Scripts.ScriptExecutionScheduler"/>
+/// (SiteRuntime-009), so blocking script I/O cannot starve the shared thread pool
+/// or stall other Akka dispatchers.
+///
 /// WP-32: Script failures are logged but do not disable the script.
 /// Supervision: Stop on unhandled exception (parent ScriptActor decides).
 /// </summary>

src/ScadaLink.SiteRuntime/ScadaLink.SiteRuntime.csproj

@@ -20,6 +20,10 @@
     <PackageReference Include="Microsoft.Extensions.Options" />
   </ItemGroup>
 
+  <ItemGroup>
+    <InternalsVisibleTo Include="ScadaLink.SiteRuntime.Tests" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="../ScadaLink.Commons/ScadaLink.Commons.csproj" />
     <ProjectReference Include="../ScadaLink.Communication/ScadaLink.Communication.csproj" />