feat(historian): drain/capacity/retention config knobs + startup config-warning validation

src/Server/ZB.MOM.WW.OtOpcUa.Host/appsettings.json

@@ -15,6 +15,9 @@
     "Enabled": false,
     "DatabasePath": "alarm-historian.db",
     "PipeName": "OtOpcUaHistorian",
-    "SharedSecret": ""
+    "SharedSecret": "",
+    "DrainIntervalSeconds": 5,
+    "Capacity": 1000000,
+    "DeadLetterRetentionDays": 30
   }
 }

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Historian/AlarmHistorianOptions.cs

@@ -1,3 +1,6 @@
+using System.Collections.Generic;
+using System.IO;
+
 namespace ZB.MOM.WW.OtOpcUa.Runtime.Historian;
 
 /// <summary>
@@ -29,4 +32,28 @@ public sealed class AlarmHistorianOptions
 
     /// <summary>Maximum number of queued rows the drain worker forwards in a single batch.</summary>
     public int BatchSize { get; init; } = 100;
+
+    /// <summary>Seconds between drain-worker ticks. Defaults to 5.</summary>
+    public int DrainIntervalSeconds { get; init; } = 5;
+
+    /// <summary>Maximum queued rows before the sink evicts the oldest. Defaults to 1,000,000
+    /// (matches <c>SqliteStoreAndForwardSink</c>'s <c>DefaultCapacity</c>).</summary>
+    public long Capacity { get; init; } = 1_000_000;
+
+    /// <summary>Days to retain dead-lettered rows before purge. Defaults to 30.</summary>
+    public int DeadLetterRetentionDays { get; init; } = 30;
+
+    /// <summary>Returns operator-facing misconfiguration warnings for an <c>Enabled</c> historian
+    /// (empty when disabled or correctly configured). Pure — the registration logs each entry.</summary>
+    /// <returns>Zero or more human-readable warning messages.</returns>
+    public IReadOnlyList<string> Validate()
+    {
+        var warnings = new List<string>();
+        if (!Enabled) return warnings;
+        if (string.IsNullOrWhiteSpace(SharedSecret))
+            warnings.Add("AlarmHistorian:SharedSecret is empty while the historian is enabled — the Wonderware sidecar Hello frame will carry an empty secret.");
+        if (!Path.IsPathRooted(DatabasePath))
+            warnings.Add($"AlarmHistorian:DatabasePath '{DatabasePath}' is relative — it resolves against the process working directory (e.g. System32 for a Windows service). Set an absolute path.");
+        return warnings;
+    }
 }

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/ServiceCollectionExtensions.cs

@@ -72,6 +72,9 @@ public static class ServiceCollectionExtensions
         var opts = configuration.GetSection(AlarmHistorianOptions.SectionName).Get<AlarmHistorianOptions>();
         if (opts is not { Enabled: true }) return services; // leave the Null default from AddOtOpcUaRuntime
 
+        foreach (var warning in opts.Validate())
+            Serilog.Log.Logger.ForContext<SqliteStoreAndForwardSink>().Warning("{HistorianConfigWarning}", warning);
+
         services.AddSingleton<IAlarmHistorianSink>(sp =>
         {
             // SqliteStoreAndForwardSink takes a Serilog ILogger (not Microsoft.Extensions.Logging).
@@ -81,8 +84,10 @@ public static class ServiceCollectionExtensions
                 opts.DatabasePath,
                 writerFactory(opts, sp),
                 Serilog.Log.Logger.ForContext<SqliteStoreAndForwardSink>(),
-                batchSize: opts.BatchSize);
-            sink.StartDrainLoop(TimeSpan.FromSeconds(5));
+                batchSize: opts.BatchSize,
+                capacity: opts.Capacity,
+                deadLetterRetention: TimeSpan.FromDays(opts.DeadLetterRetentionDays));
+            sink.StartDrainLoop(TimeSpan.FromSeconds(opts.DrainIntervalSeconds));
             return sink;
         });
         return services;