Add option to control publish request metrics

src/Configuration/CliOptions.cs

@@ -77,6 +77,7 @@ public static (PlcSimulation PlcSimulationInstance, List<string> ExtraArgs) Init
             { "otlpee|otlpendpoint=", $"the endpoint URI to which the OTLP exporter is going to send information.\nDefault: '{config.OtlpEndpointUri}'", (s) => config.OtlpEndpointUri = s },
             { "otlpei|otlpexportinterval=", $"the interval for exporting OTLP information in seconds.\nDefault: {config.OtlpExportInterval.TotalSeconds}", (uint i) => config.OtlpExportInterval = TimeSpan.FromSeconds(i) },
             { "otlpep|otlpexportprotocol=", $"the protocol for exporting OTLP information.\n(allowed values: grpc, protobuf).\nDefault: {config.OtlpExportProtocol}", (string s) => config.OtlpExportProtocol = s },
+            { "otlpub|otlpublishmetrics=", $"how to handle metrics for publish requests.\n(allowed values: disable=Always disabled, enable=Always enabled, auto=Auto-disable when sessions > 40 or monitored items > 500).\nDefault: {config.OtlpPublishMetrics}", (string s) => config.OtlpPublishMetrics = s },
 
             { "lr|ldsreginterval=", $"the LDS(-ME) registration interval in ms. If 0, then the registration is disabled.\nDefault: {config.OpcUa.LdsRegistrationInterval}", (int i) => {
                     if (i >= 0)

src/Configuration/Configuration.cs

@@ -51,6 +51,15 @@ public class OpcPlcConfiguration
     /// </summary>
     public string OtlpExportProtocol { get; set; } = "grpc";
 
+    /// <summary>
+    /// Gets or sets how to handle metrics for publish requests.
+    /// Allowed values:
+    /// disable=Always disabled,
+    /// enable=Always enabled,
+    /// auto=Auto-disable when sessions > 40 or monitored items > 500.
+    /// </summary>
+    public string OtlpPublishMetrics { get; set; } = "auto";
+
     /// <summary>
     /// Show OPC Publisher configuration file using IP address as EndpointUrl.
     /// </summary>

src/PlcServer.cs

@@ -42,7 +42,7 @@ public partial class PlcServer : StandardServer
     private readonly ILogger _logger;
     private readonly Timer _periodicLoggingTimer;
 
-    private bool _disablePublishMetrics;
+    private bool _autoDisablePublishMetrics;
     private uint _countCreateSession;
     private uint _countCreateSubscription;
     private uint _countCreateMonitoredItems;
@@ -70,7 +70,7 @@ public PlcServer(OpcPlcConfiguration config, PlcSimulation plcSimulation, TimeSe
                     IList<Subscription> subscriptions = ServerInternal.SubscriptionManager.GetSubscriptions();
                     int monitoredItemsCount = subscriptions.Sum(s => s.MonitoredItemCount);
 
-                    _disablePublishMetrics = sessionCount > 40 || monitoredItemsCount > 500;
+                    _autoDisablePublishMetrics = sessionCount > 40 || monitoredItemsCount > 500;
 
                     LogPeriodicInfo(
                         sessionCount,
@@ -87,7 +87,7 @@ public PlcServer(OpcPlcConfiguration config, PlcSimulation plcSimulation, TimeSe
                         _countPublish,
                         _countRead,
                         _countWrite,
-                        MetricsHelper.IsEnabled && !_disablePublishMetrics);
+                        PublishMetricsEnabled);
 
                     _countCreateSession = 0;
                     _countCreateSubscription = 0;
@@ -106,6 +106,20 @@ public PlcServer(OpcPlcConfiguration config, PlcSimulation plcSimulation, TimeSe
         MetricsHelper.IsEnabled = Config.OtlpEndpointUri is not null;
     }
 
+    /// <summary>
+    /// Enable publish requests metrics only if the following apply:
+    /// 1) Metrics are enabled by specifying OtlpEndpointUri,
+    /// 2) OtlpPublishMetrics is "enable",
+    /// 3) OtlpPublishMetrics is not "disable",
+    /// 4) When OtlpPublishMetrics is "auto": sessions <= 40 and monitored items <= 500.
+    /// </summary>
+    private bool PublishMetricsEnabled =>
+        MetricsHelper.IsEnabled &&
+        (
+         (Config.OtlpPublishMetrics == "enable" && Config.OtlpPublishMetrics != "disable") ||
+         (Config.OtlpPublishMetrics == "auto" && !_autoDisablePublishMetrics)
+        );
+
     public override ResponseHeader CreateSession(
         RequestHeader requestHeader,
         ApplicationDescription clientDescription,
@@ -249,7 +263,7 @@ public override ResponseHeader Publish(
 
             var responseHeader = base.Publish(requestHeader, subscriptionAcknowledgements, out subscriptionId, out availableSequenceNumbers, out moreNotifications, out notificationMessage, out results, out diagnosticInfos);
 
-            if (MetricsHelper.IsEnabled && !_disablePublishMetrics)
+            if (PublishMetricsEnabled)
             {
                 MetricsHelper.AddPublishedCount(context.SessionId.ToString(), subscriptionId.ToString(), notificationMessage, _logger);
             }