fix(lmxproxy): protect probe subscription from ReadAsync teardown, add instance configs

ReadAsync internally subscribes/unsubscribes the same ScanTime tag used
by the persistent probe, which was tearing down the probe subscription
and triggering false reconnects every ~5s. Guard UnsubscribeInternal and
stored subscription state so the probe tag is never removed by other
callers. Also removes DetailedHealthCheckService (redundant with the
persistent probe), adds per-instance config files (appsettings.v2.json,
appsettings.v2b.json) loaded via LMXPROXY_INSTANCE env var so deploys
no longer overwrite port settings.

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

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Health/DetailedHealthCheckService.cs

@@ -1,90 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Threading;
-using System.Threading.Tasks;
-using Microsoft.Extensions.Diagnostics.HealthChecks;
-using Serilog;
-using ZB.MOM.WW.LmxProxy.Host.Domain;
-
-namespace ZB.MOM.WW.LmxProxy.Host.Health
-{
-    /// <summary>
-    ///     Detailed health check: reads a test tag, checks quality and timestamp staleness.
-    /// </summary>
-    public class DetailedHealthCheckService : IHealthCheck
-    {
-        private static readonly ILogger Logger = Log.ForContext<DetailedHealthCheckService>();
-
-        private readonly IScadaClient _scadaClient;
-        private readonly string _testTagAddress;
-
-        public DetailedHealthCheckService(
-            IScadaClient scadaClient,
-            string testTagAddress = "DevPlatform.Scheduler.ScanTime")
-        {
-            _scadaClient = scadaClient;
-            _testTagAddress = testTagAddress;
-        }
-
-        public async Task<HealthCheckResult> CheckHealthAsync(
-            HealthCheckContext context,
-            CancellationToken cancellationToken = default)
-        {
-            try
-            {
-                if (!_scadaClient.IsConnected)
-                {
-                    return HealthCheckResult.Unhealthy("SCADA client is not connected");
-                }
-
-                Vtq vtq;
-                try
-                {
-                    vtq = await _scadaClient.ReadAsync(_testTagAddress, cancellationToken);
-                }
-                catch (Exception ex)
-                {
-                    Logger.Warning(ex, "Could not read test tag {Tag}", _testTagAddress);
-                    return HealthCheckResult.Degraded(
-                        "Could not read test tag: " + ex.Message,
-                        data: new Dictionary<string, object>
-                        {
-                            { "test_tag", _testTagAddress },
-                            { "error", ex.Message }
-                        });
-                }
-
-                var data = new Dictionary<string, object>
-                {
-                    { "test_tag", _testTagAddress },
-                    { "quality", vtq.Quality.ToString() },
-                    { "timestamp", vtq.Timestamp.ToString("o") }
-                };
-
-                if (!vtq.Quality.IsGood())
-                {
-                    return HealthCheckResult.Degraded(
-                        "Test tag quality is not Good: " + vtq.Quality,
-                        data: data);
-                }
-
-                if (DateTime.UtcNow - vtq.Timestamp > TimeSpan.FromMinutes(5))
-                {
-                    return HealthCheckResult.Degraded(
-                        "Test tag data is stale (older than 5 minutes)",
-                        data: data);
-                }
-
-                return HealthCheckResult.Healthy(
-                    "Test tag read successful with good quality",
-                    data: data);
-            }
-            catch (Exception ex)
-            {
-                Logger.Error(ex, "Detailed health check failed");
-                return HealthCheckResult.Unhealthy(
-                    "Detailed health check failed: " + ex.Message, ex);
-            }
-        }
-    }
-}

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/LmxProxyService.cs

@@ -30,7 +30,6 @@ namespace ZB.MOM.WW.LmxProxy.Host
         private ApiKeyService? _apiKeyService;
         private PerformanceMetrics? _performanceMetrics;
         private HealthCheckService? _healthCheckService;
-        private DetailedHealthCheckService? _detailedHealthCheckService;
         private StatusReportService? _statusReportService;
         private StatusWebServer? _statusWebServer;
         private Server? _grpcServer;
@@ -119,13 +118,11 @@ namespace ZB.MOM.WW.LmxProxy.Host
 
                 // 10. Create health check services
                 _healthCheckService = new HealthCheckService(_mxAccessClient, _subscriptionManager, _performanceMetrics);
-                _detailedHealthCheckService = new DetailedHealthCheckService(
-                    _mxAccessClient, _config.HealthCheck.TestTagAddress);
 
                 // 11. Create status report service
                 _statusReportService = new StatusReportService(
                     _mxAccessClient, _subscriptionManager, _performanceMetrics,
-                    _healthCheckService, _detailedHealthCheckService);
+                    _healthCheckService);
 
                 // 12. Start status web server
                 _statusWebServer = new StatusWebServer(_config.WebServer, _statusReportService);

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/MxAccess/MxAccessClient.EventHandlers.cs

@@ -28,7 +28,6 @@ namespace ZB.MOM.WW.LmxProxy.Host.MxAccess
         {
             try
             {
-                Log.Information("OnDataChange FIRED: handle={Handle}", phItemHandle);
                 var quality = MapQuality(pwItemQuality);
                 var timestamp = ConvertTimestamp(pftItemTimeStamp);
 

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/MxAccess/MxAccessClient.Subscription.cs

@@ -36,8 +36,12 @@ namespace ZB.MOM.WW.LmxProxy.Host.MxAccess
                     {
                         SubscribeInternal(address);
 
-                        // Store for reconnect replay
+                        // Store for reconnect replay (but don't overwrite the probe tag's callback)
-                        _storedSubscriptions[address] = callback;
+                        if (_probeTestTagAddress == null ||
+                            !string.Equals(address, _probeTestTagAddress, StringComparison.OrdinalIgnoreCase))
+                        {
+                            _storedSubscriptions[address] = callback;
+                        }
                     }
                 }
             });
@@ -70,7 +74,13 @@ namespace ZB.MOM.WW.LmxProxy.Host.MxAccess
                     foreach (var address in addressList)
                     {
                         UnsubscribeInternal(address);
-                        _storedSubscriptions.Remove(address);
+
+                        // Don't remove probe tag from stored subscriptions — it's permanent
+                        if (_probeTestTagAddress == null ||
+                            !string.Equals(address, _probeTestTagAddress, StringComparison.OrdinalIgnoreCase))
+                        {
+                            _storedSubscriptions.Remove(address);
+                        }
                     }
                 }
             });
@@ -149,6 +159,14 @@ namespace ZB.MOM.WW.LmxProxy.Host.MxAccess
         /// </summary>
         private void UnsubscribeInternal(string address)
         {
+            // Never unsubscribe the probe tag — it's a permanent connection health monitor
+            if (_probeTestTagAddress != null &&
+                string.Equals(address, _probeTestTagAddress, StringComparison.OrdinalIgnoreCase))
+            {
+                Log.Debug("Skipping unsubscribe for probe tag {Address}", address);
+                return;
+            }
+
             if (!_addressToHandle.TryGetValue(address, out int itemHandle))
             {
                 Log.Debug("No active subscription for {Address}, skipping unsubscribe", address);

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Program.cs

@@ -10,10 +10,12 @@ namespace ZB.MOM.WW.LmxProxy.Host
     {
         static int Main(string[] args)
         {
-            // 1. Build configuration
+            // 1. Build configuration (instance override file loaded from LMXPROXY_INSTANCE env var)
+            var instance = Environment.GetEnvironmentVariable("LMXPROXY_INSTANCE");
             var configuration = new ConfigurationBuilder()
                 .SetBasePath(AppDomain.CurrentDomain.BaseDirectory)
                 .AddJsonFile("appsettings.json", optional: false, reloadOnChange: false)
+                .AddJsonFile($"appsettings.{instance}.json", optional: true, reloadOnChange: false)
                 .AddEnvironmentVariables()
                 .Build();
 

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Status/StatusModels.cs

@@ -12,7 +12,6 @@ namespace ZB.MOM.WW.LmxProxy.Host.Status
         public SubscriptionStatus Subscriptions { get; set; } = new SubscriptionStatus();
         public PerformanceStatus Performance { get; set; } = new PerformanceStatus();
         public HealthInfo Health { get; set; } = new HealthInfo();
-        public HealthInfo? DetailedHealth { get; set; }
     }
 
     public class ConnectionStatus

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Status/StatusReportService.cs

@@ -9,7 +9,6 @@ using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
 using Serilog;
 using ZB.MOM.WW.LmxProxy.Host.Domain;
-using ZB.MOM.WW.LmxProxy.Host.Health;
 using HealthCheckService = ZB.MOM.WW.LmxProxy.Host.Health.HealthCheckService;
 using ZB.MOM.WW.LmxProxy.Host.Metrics;
 using ZB.MOM.WW.LmxProxy.Host.Subscriptions;
@@ -27,20 +26,17 @@ namespace ZB.MOM.WW.LmxProxy.Host.Status
         private readonly SubscriptionManager _subscriptionManager;
         private readonly PerformanceMetrics _performanceMetrics;
         private readonly HealthCheckService _healthCheckService;
-        private readonly DetailedHealthCheckService? _detailedHealthCheckService;
 
         public StatusReportService(
             IScadaClient scadaClient,
             SubscriptionManager subscriptionManager,
             PerformanceMetrics performanceMetrics,
-            HealthCheckService healthCheckService,
+            HealthCheckService healthCheckService)
-            DetailedHealthCheckService? detailedHealthCheckService = null)
         {
             _scadaClient = scadaClient;
             _subscriptionManager = subscriptionManager;
             _performanceMetrics = performanceMetrics;
             _healthCheckService = healthCheckService;
-            _detailedHealthCheckService = detailedHealthCheckService;
         }
 
         public async Task<string> GenerateHtmlReportAsync()
@@ -144,24 +140,6 @@ namespace ZB.MOM.WW.LmxProxy.Host.Status
                 }
             }
 
-            // Detailed health check (optional)
-            if (_detailedHealthCheckService != null)
-            {
-                var detailedResult = await _detailedHealthCheckService.CheckHealthAsync(new HealthCheckContext());
-                statusData.DetailedHealth = new HealthInfo
-                {
-                    Status = detailedResult.Status.ToString(),
-                    Description = detailedResult.Description ?? ""
-                };
-                if (detailedResult.Data != null)
-                {
-                    foreach (var kvp in detailedResult.Data)
-                    {
-                        statusData.DetailedHealth.Data[kvp.Key] = kvp.Value?.ToString() ?? "";
-                    }
-                }
-            }
-
             return statusData;
         }
 
@@ -264,18 +242,6 @@ namespace ZB.MOM.WW.LmxProxy.Host.Status
             sb.AppendLine("    </table>");
             sb.AppendLine("  </div>");
 
-            // Detailed health (if available)
-            if (statusData.DetailedHealth != null)
-            {
-                var detailedClass = GetHealthCardClass(statusData.DetailedHealth.Status);
-                var detailedCss = GetHealthStatusCss(statusData.DetailedHealth.Status);
-                sb.AppendLine($"  <div class=\"card {detailedClass}\">");
-                sb.AppendLine("    <h3>Detailed Health Check</h3>");
-                sb.AppendLine($"    <p class=\"{detailedCss}\">{statusData.DetailedHealth.Status}</p>");
-                sb.AppendLine($"    <p>{statusData.DetailedHealth.Description}</p>");
-                sb.AppendLine("  </div>");
-            }
-
             sb.AppendLine($"  <div class=\"footer\">Last updated: {statusData.Timestamp:yyyy-MM-dd HH:mm:ss} UTC | Service: {statusData.ServiceName} v{statusData.Version}</div>");
             sb.AppendLine("</body>");
             sb.AppendLine("</html>");

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/appsettings.v2.json

@@ -0,0 +1,6 @@
+{
+  "GrpcPort": 50100,
+  "WebServer": {
+    "Port": 8081
+  }
+}

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/appsettings.v2b.json

@@ -0,0 +1,6 @@
+{
+  "GrpcPort": 50101,
+  "WebServer": {
+    "Port": 8082
+  }
+}

lmxproxy/tests/ZB.MOM.WW.LmxProxy.Host.Tests/Health/HealthCheckServiceTests.cs

@@ -132,109 +132,4 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Health
         }
     }
 
-    public class DetailedHealthCheckServiceTests
-    {
-        private class FakeScadaClient : IScadaClient
-        {
-            public bool IsConnected { get; set; } = true;
-            public ConnectionState ConnectionState { get; set; } = ConnectionState.Connected;
-            public Vtq? ReadResult { get; set; }
-            public Exception? ReadException { get; set; }
-            public event EventHandler<ConnectionStateChangedEventArgs>? ConnectionStateChanged;
-            public Task ConnectAsync(CancellationToken ct = default) => Task.CompletedTask;
-            public Task DisconnectAsync(CancellationToken ct = default) => Task.CompletedTask;
-            public Task<Vtq> ReadAsync(string address, CancellationToken ct = default)
-            {
-                if (ReadException != null) throw ReadException;
-                return Task.FromResult(ReadResult ?? Vtq.Good(true));
-            }
-            public Task<IReadOnlyDictionary<string, Vtq>> ReadBatchAsync(IEnumerable<string> addresses, CancellationToken ct = default) =>
-                Task.FromResult<IReadOnlyDictionary<string, Vtq>>(new Dictionary<string, Vtq>());
-            public Task WriteAsync(string address, object value, CancellationToken ct = default) => Task.CompletedTask;
-            public Task WriteBatchAsync(IReadOnlyDictionary<string, object> values, CancellationToken ct = default) => Task.CompletedTask;
-            public Task<(bool flagReached, int elapsedMs)> WriteBatchAndWaitAsync(
-                IReadOnlyDictionary<string, object> values, string flagTag, object flagValue,
-                int timeoutMs, int pollIntervalMs, CancellationToken ct = default) =>
-                Task.FromResult((false, 0));
-            public Task UnsubscribeByAddressAsync(IEnumerable<string> addresses) => Task.CompletedTask;
-            public Task<IAsyncDisposable> SubscribeAsync(IEnumerable<string> addresses, Action<string, Vtq> callback, CancellationToken ct = default) =>
-                Task.FromResult<IAsyncDisposable>(new FakeHandle());
-            public ValueTask DisposeAsync() => default;
-            internal void FireEvent() => ConnectionStateChanged?.Invoke(this, null!);
-            private class FakeHandle : IAsyncDisposable { public ValueTask DisposeAsync() => default; }
-        }
-
-        [Fact]
-        public async Task ReturnsUnhealthy_WhenNotConnected()
-        {
-            var client = new FakeScadaClient { IsConnected = false };
-            var svc = new DetailedHealthCheckService(client);
-
-            var result = await svc.CheckHealthAsync(new HealthCheckContext());
-
-            result.Status.Should().Be(HealthStatus.Unhealthy);
-        }
-
-        [Fact]
-        public async Task ReturnsHealthy_WhenTestTagGoodAndRecent()
-        {
-            var client = new FakeScadaClient
-            {
-                IsConnected = true,
-                ReadResult = Vtq.New(true, DateTime.UtcNow, Quality.Good)
-            };
-            var svc = new DetailedHealthCheckService(client);
-
-            var result = await svc.CheckHealthAsync(new HealthCheckContext());
-
-            result.Status.Should().Be(HealthStatus.Healthy);
-        }
-
-        [Fact]
-        public async Task ReturnsDegraded_WhenTestTagQualityNotGood()
-        {
-            var client = new FakeScadaClient
-            {
-                IsConnected = true,
-                ReadResult = Vtq.New(true, DateTime.UtcNow, Quality.Uncertain)
-            };
-            var svc = new DetailedHealthCheckService(client);
-
-            var result = await svc.CheckHealthAsync(new HealthCheckContext());
-
-            result.Status.Should().Be(HealthStatus.Degraded);
-        }
-
-        [Fact]
-        public async Task ReturnsDegraded_WhenTestTagTimestampStale()
-        {
-            var client = new FakeScadaClient
-            {
-                IsConnected = true,
-                ReadResult = Vtq.New(true, DateTime.UtcNow.AddMinutes(-10), Quality.Good)
-            };
-            var svc = new DetailedHealthCheckService(client);
-
-            var result = await svc.CheckHealthAsync(new HealthCheckContext());
-
-            result.Status.Should().Be(HealthStatus.Degraded);
-            result.Description.Should().Contain("stale");
-        }
-
-        [Fact]
-        public async Task ReturnsDegraded_WhenTestTagReadThrows()
-        {
-            var client = new FakeScadaClient
-            {
-                IsConnected = true,
-                ReadException = new InvalidOperationException("COM error")
-            };
-            var svc = new DetailedHealthCheckService(client);
-
-            var result = await svc.CheckHealthAsync(new HealthCheckContext());
-
-            result.Status.Should().Be(HealthStatus.Degraded);
-            result.Description.Should().Contain("Could not read test tag");
-        }
-    }
 }

lmxproxy/tests/ZB.MOM.WW.LmxProxy.Host.Tests/Status/StatusReportServiceTests.cs

@@ -52,8 +52,7 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Status
             var sm = new SubscriptionManager(client);
             var pm = new PerformanceMetrics();
             var health = new HealthCheckService(client, sm, pm);
-            var detailed = new DetailedHealthCheckService(client);
+            var svc = new StatusReportService(client, sm, pm, health);
-            var svc = new StatusReportService(client, sm, pm, health, detailed);
             return (svc, pm, sm);
         }