Add rich HTTP health endpoints for cluster monitoring

Enhance /api/health with component-level health, ServiceLevel, and
redundancy state for load balancer probes. Add /health HTML page for
operators to monitor node health in clustered System Platform deployments.

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

src/ZB.MOM.WW.LmxOpcUa.Host/Status/StatusData.cs

@@ -201,6 +201,73 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
         public List<string> ServerUris { get; set; } = new();
     }
 
+    /// <summary>
+    /// DTO for the /api/health endpoint. Includes component-level health, ServiceLevel, and redundancy state.
+    /// </summary>
+    public class HealthEndpointData
+    {
+        /// <summary>
+        /// Gets or sets the overall health status: Healthy, Degraded, or Unhealthy.
+        /// </summary>
+        public string Status { get; set; } = "Unknown";
+
+        /// <summary>
+        /// Gets or sets the computed OPC UA ServiceLevel byte (0-255). Only meaningful when redundancy is enabled.
+        /// </summary>
+        public byte ServiceLevel { get; set; }
+
+        /// <summary>
+        /// Gets or sets whether redundancy is enabled.
+        /// </summary>
+        public bool RedundancyEnabled { get; set; }
+
+        /// <summary>
+        /// Gets or sets this instance's redundancy role when enabled (Primary/Secondary), or null when disabled.
+        /// </summary>
+        public string? RedundancyRole { get; set; }
+
+        /// <summary>
+        /// Gets or sets the redundancy mode when enabled (Warm/Hot), or null when disabled.
+        /// </summary>
+        public string? RedundancyMode { get; set; }
+
+        /// <summary>
+        /// Gets or sets the per-component health breakdown.
+        /// </summary>
+        public ComponentHealth Components { get; set; } = new();
+
+        /// <summary>
+        /// Gets or sets the server uptime since the health endpoint was initialized.
+        /// </summary>
+        public string Uptime { get; set; } = "";
+
+        /// <summary>
+        /// Gets or sets the UTC timestamp of this health snapshot.
+        /// </summary>
+        public DateTime Timestamp { get; set; } = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Per-component health breakdown for the health endpoint.
+    /// </summary>
+    public class ComponentHealth
+    {
+        /// <summary>
+        /// Gets or sets MXAccess runtime connectivity status.
+        /// </summary>
+        public string MxAccess { get; set; } = "Disconnected";
+
+        /// <summary>
+        /// Gets or sets Galaxy repository database connectivity status.
+        /// </summary>
+        public string Database { get; set; } = "Disconnected";
+
+        /// <summary>
+        /// Gets or sets OPC UA server status.
+        /// </summary>
+        public string OpcUaServer { get; set; } = "Stopped";
+    }
+
     /// <summary>
     /// Dashboard model for the status page footer.
     /// </summary>

src/ZB.MOM.WW.LmxOpcUa.Host/Status/StatusReportService.cs

@@ -16,6 +16,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
     {
         private readonly HealthCheckService _healthCheck;
         private readonly int _refreshIntervalSeconds;
+        private readonly DateTime _startTime = DateTime.UtcNow;
 
         private IMxAccessClient? _mxAccessClient;
         private PerformanceMetrics? _metrics;
@@ -229,5 +230,132 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
             var state = _mxAccessClient?.State ?? ConnectionState.Disconnected;
             return _healthCheck.IsHealthy(state, _metrics);
         }
+
+        /// <summary>
+        /// Builds the rich health endpoint data including component health, ServiceLevel, and redundancy state.
+        /// </summary>
+        public HealthEndpointData GetHealthData()
+        {
+            var connectionState = _mxAccessClient?.State ?? ConnectionState.Disconnected;
+            var mxConnected = connectionState == ConnectionState.Connected;
+            var dbConnected = _galaxyStats?.DbConnected ?? false;
+            var health = _healthCheck.CheckHealth(connectionState, _metrics);
+            var uptime = DateTime.UtcNow - _startTime;
+
+            var data = new HealthEndpointData
+            {
+                Status = health.Status,
+                RedundancyEnabled = _redundancyConfig?.Enabled ?? false,
+                Components = new ComponentHealth
+                {
+                    MxAccess = connectionState.ToString(),
+                    Database = dbConnected ? "Connected" : "Disconnected",
+                    OpcUaServer = (_serverHost?.IsRunning ?? false) ? "Running" : "Stopped"
+                },
+                Uptime = FormatUptime(uptime),
+                Timestamp = DateTime.UtcNow
+            };
+
+            if (_redundancyConfig != null && _redundancyConfig.Enabled)
+            {
+                var isPrimary = string.Equals(_redundancyConfig.Role, "Primary", StringComparison.OrdinalIgnoreCase);
+                var baseLevel = isPrimary
+                    ? _redundancyConfig.ServiceLevelBase
+                    : Math.Max(0, _redundancyConfig.ServiceLevelBase - 50);
+                var calculator = new ServiceLevelCalculator();
+
+                data.ServiceLevel = calculator.Calculate(baseLevel, mxConnected, dbConnected);
+                data.RedundancyRole = _redundancyConfig.Role;
+                data.RedundancyMode = _redundancyConfig.Mode;
+            }
+            else
+            {
+                // Non-redundant: 255 when healthy, 0 when both down
+                data.ServiceLevel = mxConnected ? (byte)255 : (byte)0;
+            }
+
+            return data;
+        }
+
+        /// <summary>
+        /// Generates the JSON payload for the /api/health endpoint.
+        /// </summary>
+        public string GenerateHealthJson()
+        {
+            var data = GetHealthData();
+            return JsonSerializer.Serialize(data, new JsonSerializerOptions { WriteIndented = true });
+        }
+
+        /// <summary>
+        /// Generates a focused health status HTML page for operators and monitoring dashboards.
+        /// </summary>
+        public string GenerateHealthHtml()
+        {
+            var data = GetHealthData();
+            var sb = new StringBuilder();
+
+            var statusColor = data.Status == "Healthy" ? "#00cc66" : data.Status == "Degraded" ? "#cccc33" : "#cc3333";
+            var mxColor = data.Components.MxAccess == "Connected" ? "#00cc66" : "#cc3333";
+            var dbColor = data.Components.Database == "Connected" ? "#00cc66" : "#cc3333";
+            var uaColor = data.Components.OpcUaServer == "Running" ? "#00cc66" : "#cc3333";
+
+            sb.AppendLine("<!DOCTYPE html><html><head>");
+            sb.AppendLine("<meta charset='utf-8'>");
+            sb.AppendLine($"<meta http-equiv='refresh' content='{_refreshIntervalSeconds}'>");
+            sb.AppendLine("<title>LmxOpcUa Health</title>");
+            sb.AppendLine("<style>");
+            sb.AppendLine("body { font-family: monospace; background: #1a1a2e; color: #eee; padding: 20px; margin: 0; }");
+            sb.AppendLine(".header { text-align: center; padding: 30px 0; }");
+            sb.AppendLine(".status-badge { display: inline-block; font-size: 2em; font-weight: bold; padding: 15px 40px; border-radius: 12px; letter-spacing: 2px; }");
+            sb.AppendLine(".service-level { text-align: center; font-size: 4em; font-weight: bold; margin: 20px 0; }");
+            sb.AppendLine(".service-level .label { font-size: 0.3em; color: #999; display: block; }");
+            sb.AppendLine(".components { display: flex; justify-content: center; gap: 20px; flex-wrap: wrap; margin: 30px auto; max-width: 800px; }");
+            sb.AppendLine(".component { border: 2px solid #444; border-radius: 8px; padding: 20px; min-width: 200px; text-align: center; }");
+            sb.AppendLine(".component .name { font-size: 0.9em; color: #999; margin-bottom: 8px; }");
+            sb.AppendLine(".component .value { font-size: 1.3em; font-weight: bold; }");
+            sb.AppendLine(".meta { text-align: center; margin-top: 30px; color: #666; font-size: 0.85em; }");
+            sb.AppendLine(".redundancy { text-align: center; margin: 10px 0; color: #999; }");
+            sb.AppendLine(".redundancy b { color: #66ccff; }");
+            sb.AppendLine("</style></head><body>");
+
+            // Status badge
+            sb.AppendLine("<div class='header'>");
+            sb.AppendLine($"<div class='status-badge' style='background: {statusColor}; color: #000;'>{data.Status.ToUpperInvariant()}</div>");
+            sb.AppendLine("</div>");
+
+            // Service Level
+            sb.AppendLine($"<div class='service-level' style='color: {statusColor};'>");
+            sb.AppendLine("<span class='label'>SERVICE LEVEL</span>");
+            sb.AppendLine($"{data.ServiceLevel}");
+            sb.AppendLine("</div>");
+
+            // Redundancy info
+            if (data.RedundancyEnabled)
+            {
+                sb.AppendLine($"<div class='redundancy'>Role: <b>{data.RedundancyRole}</b> | Mode: <b>{data.RedundancyMode}</b></div>");
+            }
+
+            // Component health cards
+            sb.AppendLine("<div class='components'>");
+            sb.AppendLine($"<div class='component' style='border-color: {mxColor};'><div class='name'>MXAccess</div><div class='value' style='color: {mxColor};'>{data.Components.MxAccess}</div></div>");
+            sb.AppendLine($"<div class='component' style='border-color: {dbColor};'><div class='name'>Galaxy Database</div><div class='value' style='color: {dbColor};'>{data.Components.Database}</div></div>");
+            sb.AppendLine($"<div class='component' style='border-color: {uaColor};'><div class='name'>OPC UA Server</div><div class='value' style='color: {uaColor};'>{data.Components.OpcUaServer}</div></div>");
+            sb.AppendLine("</div>");
+
+            // Footer
+            sb.AppendLine($"<div class='meta'>Uptime: {data.Uptime} | {data.Timestamp:O}</div>");
+
+            sb.AppendLine("</body></html>");
+            return sb.ToString();
+        }
+
+        private static string FormatUptime(TimeSpan ts)
+        {
+            if (ts.TotalDays >= 1)
+                return $"{(int)ts.TotalDays}d {ts.Hours}h {ts.Minutes}m";
+            if (ts.TotalHours >= 1)
+                return $"{(int)ts.TotalHours}h {ts.Minutes}m";
+            return $"{(int)ts.TotalMinutes}m {ts.Seconds}s";
+        }
     }
 }

src/ZB.MOM.WW.LmxOpcUa.Host/Status/StatusWebServer.cs

@@ -120,14 +120,19 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                         await WriteResponse(response, _reportService.GenerateHtml(), "text/html", 200);
                         break;
 
+                    case "/health":
+                        await WriteResponse(response, _reportService.GenerateHealthHtml(), "text/html", 200);
+                        break;
+
                     case "/api/status":
                         await WriteResponse(response, _reportService.GenerateJson(), "application/json", 200);
                         break;
 
                     case "/api/health":
-                        var isHealthy = _reportService.IsHealthy();
+                        var healthData = _reportService.GetHealthData();
-                        var healthJson = isHealthy ? "{\"status\":\"healthy\"}" : "{\"status\":\"unhealthy\"}";
+                        var healthJson = _reportService.GenerateHealthJson();
-                        await WriteResponse(response, healthJson, "application/json", isHealthy ? 200 : 503);
+                        var healthStatusCode = healthData.Status == "Unhealthy" ? 503 : 200;
+                        await WriteResponse(response, healthJson, "application/json", healthStatusCode);
                         break;
 
                     default:

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

@@ -132,6 +132,139 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             sut.IsHealthy().ShouldBe(false);
         }
 
+        [Fact]
+        public void GetHealthData_WhenConnected_ReturnsHealthyStatus()
+        {
+            var sut = CreateService();
+            var data = sut.GetHealthData();
+
+            data.Status.ShouldBe("Healthy");
+            data.Components.MxAccess.ShouldBe("Connected");
+            data.Components.Database.ShouldBe("Connected");
+        }
+
+        [Fact]
+        public void GetHealthData_WhenDisconnected_ReturnsUnhealthyStatus()
+        {
+            var mxClient = new FakeMxAccessClient { State = ConnectionState.Disconnected };
+            var galaxyStats = new GalaxyRepositoryStats { DbConnected = false };
+            var sut = new StatusReportService(new HealthCheckService(), 10);
+            sut.SetComponents(mxClient, null, galaxyStats, null);
+
+            var data = sut.GetHealthData();
+
+            data.Status.ShouldBe("Unhealthy");
+            data.ServiceLevel.ShouldBe((byte)0);
+            data.Components.MxAccess.ShouldBe("Disconnected");
+            data.Components.Database.ShouldBe("Disconnected");
+        }
+
+        [Fact]
+        public void GetHealthData_NoRedundancy_ServiceLevel255WhenHealthy()
+        {
+            var sut = CreateService();
+            var data = sut.GetHealthData();
+
+            data.RedundancyEnabled.ShouldBe(false);
+            data.ServiceLevel.ShouldBe((byte)255);
+            data.RedundancyRole.ShouldBeNull();
+            data.RedundancyMode.ShouldBeNull();
+        }
+
+        [Fact]
+        public void GetHealthData_WithRedundancy_IncludesRoleAndServiceLevel()
+        {
+            var sut = CreateServiceWithRedundancy("Primary");
+            var data = sut.GetHealthData();
+
+            data.RedundancyEnabled.ShouldBe(true);
+            data.RedundancyRole.ShouldBe("Primary");
+            data.RedundancyMode.ShouldBe("Warm");
+            data.ServiceLevel.ShouldBe((byte)200);
+        }
+
+        [Fact]
+        public void GetHealthData_SecondaryRole_LowerServiceLevel()
+        {
+            var sut = CreateServiceWithRedundancy("Secondary");
+            var data = sut.GetHealthData();
+
+            data.ServiceLevel.ShouldBe((byte)150);
+        }
+
+        [Fact]
+        public void GetHealthData_ContainsUptime()
+        {
+            var sut = CreateService();
+            var data = sut.GetHealthData();
+
+            data.Uptime.ShouldNotBeNullOrWhiteSpace();
+        }
+
+        [Fact]
+        public void GetHealthData_ContainsTimestamp()
+        {
+            var sut = CreateService();
+            var data = sut.GetHealthData();
+
+            data.Timestamp.ShouldBeGreaterThan(DateTime.UtcNow.AddMinutes(-1));
+        }
+
+        [Fact]
+        public void GenerateHealthJson_ContainsExpectedFields()
+        {
+            var sut = CreateService();
+            var json = sut.GenerateHealthJson();
+
+            json.ShouldContain("Status");
+            json.ShouldContain("ServiceLevel");
+            json.ShouldContain("Components");
+            json.ShouldContain("MxAccess");
+            json.ShouldContain("Database");
+            json.ShouldContain("OpcUaServer");
+            json.ShouldContain("Uptime");
+        }
+
+        [Fact]
+        public void GenerateHealthHtml_ContainsStatusBadge()
+        {
+            var sut = CreateService();
+            var html = sut.GenerateHealthHtml();
+
+            html.ShouldContain("HEALTHY");
+            html.ShouldContain("SERVICE LEVEL");
+            html.ShouldContain("255");
+        }
+
+        [Fact]
+        public void GenerateHealthHtml_ContainsComponentCards()
+        {
+            var sut = CreateService();
+            var html = sut.GenerateHealthHtml();
+
+            html.ShouldContain("MXAccess");
+            html.ShouldContain("Galaxy Database");
+            html.ShouldContain("OPC UA Server");
+        }
+
+        [Fact]
+        public void GenerateHealthHtml_WithRedundancy_ShowsRoleAndMode()
+        {
+            var sut = CreateServiceWithRedundancy("Primary");
+            var html = sut.GenerateHealthHtml();
+
+            html.ShouldContain("Primary");
+            html.ShouldContain("Warm");
+        }
+
+        [Fact]
+        public void GenerateHealthHtml_ContainsAutoRefresh()
+        {
+            var sut = CreateService();
+            var html = sut.GenerateHealthHtml();
+            html.ShouldContain("meta http-equiv='refresh' content='10'");
+        }
+
         /// <summary>
         /// Creates a status report service preloaded with representative runtime, Galaxy, and metrics data.
         /// </summary>
@@ -157,5 +290,21 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             sut.SetComponents(mxClient, metrics, galaxyStats, null);
             return sut;
         }
+
+        private static StatusReportService CreateServiceWithRedundancy(string role)
+        {
+            var mxClient = new FakeMxAccessClient();
+            var galaxyStats = new GalaxyRepositoryStats { GalaxyName = "TestGalaxy", DbConnected = true };
+            var redundancyConfig = new Host.Configuration.RedundancyConfiguration
+            {
+                Enabled = true,
+                Mode = "Warm",
+                Role = role,
+                ServiceLevelBase = 200
+            };
+            var sut = new StatusReportService(new HealthCheckService(), 10);
+            sut.SetComponents(mxClient, null, galaxyStats, null, null, redundancyConfig, "urn:test:instance1");
+            return sut;
+        }
     }
 }

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

@@ -107,6 +107,35 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             response.Headers.CacheControl?.NoStore.ShouldBe(true);
         }
 
+        /// <summary>
+        /// Confirms that the /health route returns an HTML health page.
+        /// </summary>
+        [Fact]
+        public async Task HealthPage_ReturnsHtml200()
+        {
+            var response = await _client.GetAsync("/health");
+            response.StatusCode.ShouldBe(HttpStatusCode.OK);
+            response.Content.Headers.ContentType?.MediaType.ShouldBe("text/html");
+            var body = await response.Content.ReadAsStringAsync();
+            body.ShouldContain("SERVICE LEVEL");
+            body.ShouldContain("MXAccess");
+        }
+
+        /// <summary>
+        /// Confirms that /api/health returns rich JSON with component health details.
+        /// </summary>
+        [Fact]
+        public async Task ApiHealth_ReturnsRichJson()
+        {
+            var response = await _client.GetAsync("/api/health");
+            response.StatusCode.ShouldBe(HttpStatusCode.OK);
+            response.Content.Headers.ContentType?.MediaType.ShouldBe("application/json");
+            var body = await response.Content.ReadAsStringAsync();
+            body.ShouldContain("ServiceLevel");
+            body.ShouldContain("Components");
+            body.ShouldContain("Uptime");
+        }
+
         /// <summary>
         /// Confirms that the server can be started and stopped cleanly.
         /// </summary>