fix(host): rate-limit dead-letter warnings (10/min + suppression summary); metric counting unchanged

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/DeadLetterMonitorTests.cs

@@ -1,8 +1,10 @@
+using System.Linq;
 using Akka.Actor;
 using Akka.Event;
 using Akka.TestKit.Xunit2;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
+using NSubstitute;
 using ZB.MOM.WW.ScadaBridge.Host.Actors;
 
 namespace ZB.MOM.WW.ScadaBridge.Host.Tests;
@@ -48,6 +50,33 @@ public class DeadLetterMonitorTests : TestKit
         });
     }
 
+    [Fact]
+    public async Task DeadLetterStorm_LogsAtMostWindowLimit_ButCountsAll()
+    {
+        // Review 01 [Low]: a failover/undeploy storm produced one Warning per
+        // dead letter — unbounded log flood. Health metric counting is untouched.
+        var logger = Substitute.For<ILogger<DeadLetterMonitorActor>>();
+        var monitor = Sys.ActorOf(Props.Create(() => new DeadLetterMonitorActor(logger, null)));
+
+        // Ensure the actor has started before the storm.
+        monitor.Tell(GetDeadLetterCount.Instance);
+        ExpectMsg<DeadLetterCountResponse>();
+
+        for (var i = 0; i < 50; i++)
+            monitor.Tell(new DeadLetter($"m{i}", TestActor, TestActor));
+
+        var count = await monitor.Ask<DeadLetterCountResponse>(GetDeadLetterCount.Instance);
+        Assert.Equal(50, count.Count); // every dead letter still counted
+
+        var warnings = logger.ReceivedCalls().Count(c =>
+            c.GetMethodInfo().Name == "Log"
+            && (Microsoft.Extensions.Logging.LogLevel)c.GetArguments()[0]!
+                == Microsoft.Extensions.Logging.LogLevel.Warning);
+        // The per-letter cap plus the one "limit reached" notice.
+        Assert.True(warnings <= DeadLetterMonitorActor.MaxWarningsPerWindow + 1,
+            $"expected <= {DeadLetterMonitorActor.MaxWarningsPerWindow + 1} warnings, got {warnings}");
+    }
+
     [Fact]
     public void DeadLetterMonitor_CountAccumulates()
     {

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/ZB.MOM.WW.ScadaBridge.Host.Tests.csproj

@@ -18,6 +18,7 @@
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="NSubstitute" />
     <PackageReference Include="Serilog" />
     <PackageReference Include="xunit" />
     <PackageReference Include="xunit.runner.visualstudio" />