fix(site-runtime): ConfigureAwait(false) on remaining script helper awaits (review 2026-10-21 01/SR-U2)

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScopeAccessors.cs

@@ -11,8 +11,11 @@ namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
 /// <para>
 /// Thread-model note: the indexer get/set block synchronously
 /// on the Instance Actor Ask (and, for data-connected attributes, the DCL
-/// round-trip). Runtime helper continuations use ConfigureAwait(false), so they
-/// can complete even when every dedicated worker is blocked in an indexer.
+/// round-trip). The runtime helper awaits in <see cref="ScriptRuntimeContext"/> and
+/// <see cref="SharedScriptLibrary"/> use ConfigureAwait(false), so their continuations run on
+/// the shared thread pool and can complete even when every dedicated worker is blocked in an
+/// indexer. A script that itself blocks on a helper task (<c>.Result</c>/<c>.Wait()</c>) still
+/// holds its worker until the callee finishes, but no longer deadlocks the scheduler against it.
 /// Script bodies execute on the dedicated
 /// <see cref="ScriptExecutionScheduler"/> threads, not the
 /// shared <see cref="System.Threading.ThreadPool"/> — so a blocked accessor

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptRuntimeContext.cs

@@ -1150,7 +1150,7 @@ public class ScriptRuntimeContext
             Trace: _isTraced);
 
         // Ask the Instance Actor, which routes to the appropriate Script Actor
-        var result = await _instanceActor.Ask<ScriptCallResult>(request, _askTimeout);
+        var result = await _instanceActor.Ask<ScriptCallResult>(request, _askTimeout).ConfigureAwait(false);
 
         if (!result.Success)
         {
@@ -1285,7 +1285,7 @@ public class ScriptRuntimeContext
             Guid.NewGuid().ToString(), _instanceName, DateTimeOffset.UtcNow);
 
         var response = await _instanceActor.Ask<GetAlarmSnapshotResponse>(
-            request, _askTimeout, cancellationToken);
+            request, _askTimeout, cancellationToken).ConfigureAwait(false);
 
         return response.Alarms.Select(ToScriptAlarm).ToList();
     }
@@ -1294,7 +1294,7 @@ public class ScriptRuntimeContext
     /// <param name="cancellationToken">Cancels the wait for the actor's reply.</param>
     /// <returns>The MES-reportable subset of the instance's current alarm conditions.</returns>
     internal async Task<IReadOnlyList<ScriptAlarm>> GetMesReportableAlarmsAsync(CancellationToken cancellationToken = default)
-        => (await GetAlarmsAsync(cancellationToken)).Where(a => a.IsMesReportable).ToList();
+        => (await GetAlarmsAsync(cancellationToken).ConfigureAwait(false)).Where(a => a.IsMesReportable).ToList();
 
     /// <summary>
     /// Projects a retained <see cref="AlarmStateChanged"/> onto the flat, script-facing
@@ -1407,7 +1407,7 @@ public class ScriptRuntimeContext
             var childContext = _context.CreateChildContextForSharedScript(nextDepth);
 
             return await _library.ExecuteAsync(
-                scriptName, childContext, ScriptArgs.Normalize(parameters), cancellationToken);
+                scriptName, childContext, ScriptArgs.Normalize(parameters), cancellationToken).ConfigureAwait(false);
         }
     }
 
@@ -1564,7 +1564,7 @@ public class ScriptRuntimeContext
             Exception? thrown = null;
             try
             {
-                result = await _client.CallAsync(systemName, methodName, parameters, cancellationToken);
+                result = await _client.CallAsync(systemName, methodName, parameters, cancellationToken).ConfigureAwait(false);
                 return result;
             }
             catch (Exception ex)
@@ -2269,7 +2269,7 @@ public class ScriptRuntimeContext
             if (_gateway == null)
                 throw new InvalidOperationException("Database gateway not available");
 
-            var inner = await _gateway.GetConnectionAsync(name, cancellationToken);
+            var inner = await _gateway.GetConnectionAsync(name, cancellationToken).ConfigureAwait(false);
 
             // Wrap in an auditing decorator so
             // every script-initiated Execute* / ExecuteReader on the returned
@@ -2735,7 +2735,7 @@ public class ScriptRuntimeContext
             try
             {
                 response = await _siteCommunicationActor
-                    .Ask<NotificationStatusResponse>(query, _askTimeout);
+                    .Ask<NotificationStatusResponse>(query, _askTimeout).ConfigureAwait(false);
             }
             catch (Exception ex)
             {
@@ -2760,7 +2760,7 @@ public class ScriptRuntimeContext
             // genuinely unknown (never sent, or already forwarded and central lost it).
             if (_storeAndForward != null)
             {
-                var buffered = await _storeAndForward.GetMessageByIdAsync(notificationId);
+                var buffered = await _storeAndForward.GetMessageByIdAsync(notificationId).ConfigureAwait(false);
                 if (buffered != null)
                 {
                     return new NotificationDeliveryStatus(
@@ -2943,7 +2943,7 @@ public class ScriptRuntimeContext
                 // thread: buffer due-immediately and kick the sweep. Send returns
                 // in milliseconds whether central is up or down.
                 deferToSweep: true,
-                messageId: notificationId);
+                messageId: notificationId).ConfigureAwait(false);
 
             _logger.LogDebug(
                 "Notify enqueued notification {NotificationId} to list '{List}' for central delivery",

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/SharedScriptLibrary.cs

@@ -102,7 +102,7 @@ public class SharedScriptLibrary
             CancellationToken = cancellationToken
         };
 
-        var state = await script.RunAsync(globals, cancellationToken);
+        var state = await script.RunAsync(globals, cancellationToken).ConfigureAwait(false);
         return state.ReturnValue;
     }
 

tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Scripts/AlarmsAccessorTests.cs

@@ -254,4 +254,24 @@ public class AlarmsAccessorTests : TestKit, IDisposable
 
         Assert.Single(await pending);
     }
+
+    /// <summary>
+    /// The helper's continuation must not capture the script scheduler: a script that blocks its
+    /// only worker on the task (<c>.Wait()</c>) still completes (review 2026-10-21 01/SR-U2).
+    /// </summary>
+    [Fact]
+    public async Task CurrentAsync_ContinuationDoesNotNeedTheScriptScheduler_BlockingWaitCompletes()
+    {
+        using var scheduler = new ScriptExecutionScheduler(1);
+        var probe = CreateTestProbe();
+        var ctx = MakeContext(probe.Ref);
+
+        var run = Task.Factory.StartNew(
+            () => ctx.Alarms.CurrentAsync().Wait(TimeSpan.FromSeconds(10)),
+            CancellationToken.None, TaskCreationOptions.None, scheduler);
+
+        RespondWith(probe);
+
+        Assert.True(await run.WaitAsync(TimeSpan.FromSeconds(15)), "CurrentAsync continuation was queued back onto the blocked script scheduler");
+    }
 }