Surface historian plugin and alarm-tracking health in the status dashboard so operators can detect misconfiguration and runtime degradation that previously showed as fully healthy

Wraps the 4 HistoryRead overrides and OnAlarmAcknowledge with PerformanceMetrics.BeginOperation, adds alarm counters to LmxNodeManager, publishes a structured HistorianPluginOutcome from HistorianPluginLoader, and extends HealthCheckService with plugin-load, history-read, and alarm-ack-failure degradation rules.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/ZB.MOM.WW.LmxOpcUa.Tests/Historian/HistorianPluginLoaderTests.cs

@@ -0,0 +1,45 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.LmxOpcUa.Host.Configuration;
+using ZB.MOM.WW.LmxOpcUa.Host.Historian;
+
+namespace ZB.MOM.WW.LmxOpcUa.Tests.Historian
+{
+    /// <summary>
+    ///     Verifies the load-outcome state machine of <see cref="HistorianPluginLoader"/>.
+    /// </summary>
+    public class HistorianPluginLoaderTests
+    {
+        /// <summary>
+        ///     MarkDisabled publishes a Disabled outcome so the dashboard can distinguish
+        ///     "feature off" from "load failed."
+        /// </summary>
+        [Fact]
+        public void MarkDisabled_PublishesDisabledOutcome()
+        {
+            HistorianPluginLoader.MarkDisabled();
+
+            HistorianPluginLoader.LastOutcome.Status.ShouldBe(HistorianPluginStatus.Disabled);
+            HistorianPluginLoader.LastOutcome.Error.ShouldBeNull();
+        }
+
+        /// <summary>
+        ///     When the plugin directory is missing, TryLoad reports NotFound — not LoadFailed —
+        ///     and returns null so the server can start with history disabled.
+        /// </summary>
+        [Fact]
+        public void TryLoad_PluginMissing_ReturnsNullWithNotFoundOutcome()
+        {
+            // The test process runs from a bin directory that does not contain a Historian/
+            // subfolder, so TryLoad will take the file-missing branch.
+            var config = new HistorianConfiguration { Enabled = true };
+
+            var result = HistorianPluginLoader.TryLoad(config);
+
+            result.ShouldBeNull();
+            HistorianPluginLoader.LastOutcome.Status.ShouldBe(HistorianPluginStatus.NotFound);
+            HistorianPluginLoader.LastOutcome.PluginPath.ShouldContain("ZB.MOM.WW.LmxOpcUa.Historian.Aveva.dll");
+            HistorianPluginLoader.LastOutcome.Error.ShouldBeNull();
+        }
+    }
+}

tests/ZB.MOM.WW.LmxOpcUa.Tests/Status/HealthCheckServiceTests.cs

@@ -105,5 +105,108 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             var result = _sut.CheckHealth(ConnectionState.Reconnecting, null);
             result.Status.ShouldBe("Unhealthy");
         }
+
+        /// <summary>
+        ///     Historian enabled but plugin failed to load → Degraded with the plugin error in the message.
+        /// </summary>
+        [Fact]
+        public void HistorianEnabled_PluginLoadFailed_ReturnsDegraded()
+        {
+            var historian = new HistorianStatusInfo
+            {
+                Enabled = true,
+                PluginStatus = "LoadFailed",
+                PluginError = "aahClientManaged.dll could not be loaded"
+            };
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, null, historian);
+
+            result.Status.ShouldBe("Degraded");
+            result.Color.ShouldBe("yellow");
+            result.Message.ShouldContain("LoadFailed");
+            result.Message.ShouldContain("aahClientManaged.dll");
+        }
+
+        /// <summary>
+        ///     Historian disabled is healthy regardless of plugin status string.
+        /// </summary>
+        [Fact]
+        public void HistorianDisabled_ReturnsHealthy()
+        {
+            var historian = new HistorianStatusInfo
+            {
+                Enabled = false,
+                PluginStatus = "Disabled"
+            };
+
+            _sut.CheckHealth(ConnectionState.Connected, null, historian).Status.ShouldBe("Healthy");
+        }
+
+        /// <summary>
+        ///     Historian enabled and plugin loaded is healthy.
+        /// </summary>
+        [Fact]
+        public void HistorianEnabled_PluginLoaded_ReturnsHealthy()
+        {
+            var historian = new HistorianStatusInfo { Enabled = true, PluginStatus = "Loaded" };
+            _sut.CheckHealth(ConnectionState.Connected, null, historian).Status.ShouldBe("Healthy");
+        }
+
+        /// <summary>
+        ///     HistoryRead operations degrade after only 11 samples with &lt;50% success rate
+        ///     (lower threshold than the regular 100-sample rule).
+        /// </summary>
+        [Fact]
+        public void HistoryReadLowSuccessRate_WithLowSampleCount_ReturnsDegraded()
+        {
+            using var metrics = new PerformanceMetrics();
+            for (var i = 0; i < 4; i++)
+                metrics.RecordOperation("HistoryReadRaw", TimeSpan.FromMilliseconds(10));
+            for (var i = 0; i < 8; i++)
+                metrics.RecordOperation("HistoryReadRaw", TimeSpan.FromMilliseconds(10), false);
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, metrics);
+
+            result.Status.ShouldBe("Degraded");
+            result.Message.ShouldContain("HistoryReadRaw");
+        }
+
+        /// <summary>
+        ///     A HistoryRead sample under the 10-sample threshold does not degrade the service.
+        /// </summary>
+        [Fact]
+        public void HistoryReadLowSuccessRate_BelowThreshold_ReturnsHealthy()
+        {
+            using var metrics = new PerformanceMetrics();
+            for (var i = 0; i < 5; i++)
+                metrics.RecordOperation("HistoryReadRaw", TimeSpan.FromMilliseconds(10), false);
+
+            _sut.CheckHealth(ConnectionState.Connected, metrics).Status.ShouldBe("Healthy");
+        }
+
+        /// <summary>
+        ///     Alarm acknowledge write failures are latched — any non-zero count degrades the service.
+        /// </summary>
+        [Fact]
+        public void AlarmAckWriteFailures_AnyCount_ReturnsDegraded()
+        {
+            var alarms = new AlarmStatusInfo { TrackingEnabled = true, AckWriteFailures = 1 };
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, null, null, alarms);
+
+            result.Status.ShouldBe("Degraded");
+            result.Message.ShouldContain("Alarm acknowledge");
+        }
+
+        /// <summary>
+        ///     Alarm tracking disabled ignores any failure count.
+        /// </summary>
+        [Fact]
+        public void AlarmAckWriteFailures_TrackingDisabled_ReturnsHealthy()
+        {
+            var alarms = new AlarmStatusInfo { TrackingEnabled = false, AckWriteFailures = 99 };
+
+            _sut.CheckHealth(ConnectionState.Connected, null, null, alarms).Status.ShouldBe("Healthy");
+        }
     }
 }

tests/ZB.MOM.WW.LmxOpcUa.Tests/Status/StatusReportServiceTests.cs

@@ -108,9 +108,65 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             json.ShouldContain("Subscriptions");
             json.ShouldContain("Galaxy");
             json.ShouldContain("Operations");
+            json.ShouldContain("Historian");
+            json.ShouldContain("Alarms");
             json.ShouldContain("Footer");
         }
 
+        /// <summary>
+        ///     The dashboard JSON exposes the historian plugin status so operators can distinguish
+        ///     "disabled by config" from "plugin crashed on load."
+        /// </summary>
+        [Fact]
+        public void GenerateJson_Historian_IncludesPluginStatus()
+        {
+            var sut = CreateService();
+            var json = sut.GenerateJson();
+
+            json.ShouldContain("PluginStatus");
+            json.ShouldContain("PluginPath");
+        }
+
+        /// <summary>
+        ///     The dashboard JSON exposes alarm counters so operators can see transition/ack activity.
+        /// </summary>
+        [Fact]
+        public void GenerateJson_Alarms_IncludesCounters()
+        {
+            var sut = CreateService();
+            var json = sut.GenerateJson();
+
+            json.ShouldContain("TrackingEnabled");
+            json.ShouldContain("TransitionCount");
+            json.ShouldContain("AckWriteFailures");
+        }
+
+        /// <summary>
+        ///     The Historian and Alarms panels render in the HTML dashboard.
+        /// </summary>
+        [Fact]
+        public void GenerateHtml_IncludesHistorianAndAlarmPanels()
+        {
+            var sut = CreateService();
+            var html = sut.GenerateHtml();
+
+            html.ShouldContain("<h2>Historian</h2>");
+            html.ShouldContain("<h2>Alarms</h2>");
+        }
+
+        /// <summary>
+        ///     The /api/health payload exposes Historian and Alarms component status.
+        /// </summary>
+        [Fact]
+        public void GetHealthData_Components_IncludeHistorianAndAlarms()
+        {
+            var sut = CreateService();
+            var data = sut.GetHealthData();
+
+            data.Components.Historian.ShouldNotBeNullOrEmpty();
+            data.Components.Alarms.ShouldNotBeNullOrEmpty();
+        }
+
         /// <summary>
         ///     Confirms that the report service reports healthy when the runtime connection is up.
         /// </summary>