Subscriber metrics

Source/IMetricsHandler.cs

@@ -20,12 +20,15 @@ public interface IMetricsHandler : IMetricsClient, IWithStateFrom<MetricsHandler
     [Counter(Name = "messages_sent_total", Unit = "count", Description = "The total number of messages sent", Exported = true)]
     public void NumberOfMessagesSent(int value);
 
+    #region DataPointParser.cs
     [Counter(Name = "opcua_bad_statuscode_received", Unit = "count", Description = "The total number of bad status code received from OPCUA server", Exported = true)]
     public void NumberOfBadStatusCodesFor(int value, string nodeId);
 
     [Counter(Name = "opcua_invalid_timestamp_received", Unit = "count", Description = "The total number of invalid timestamps received from OPCUA server or source", Exported = true)]
     public void InvalidTimestampReceived(int value);
+    #endregion
 
+    #region Client.cs
     [Counter(Name = "opcua_session_connection_attempts_total", Unit = "count", Description = "The total number of connection attempts to the OPCUA server", Exported = true)]
     public void NumberOfSessionConnectionAttempts(long value);
 
@@ -34,6 +37,21 @@ public interface IMetricsHandler : IMetricsClient, IWithStateFrom<MetricsHandler
 
     [Counter(Name = "opcua_session_connection_time_seconds_total", Unit = "count", Description = "The total time spent waiting for connections to the OPCUA server to open", Exported = true)]
     public void SessionConnectionTime(double value);
+    #endregion
+
+    #region Subscriber.cs
+    [Counter(Name = "opcua_subscription_attempts_total", Unit = "count", Description = "The total number of subscription attempts to the OPCUA server", Exported = true)]
+    public void NumberOfSubscriptionAttempts(long value);
+
+    [Counter(Name = "opcua_subscriptions_total", Unit = "count", Description = "The total number of successful subscriptions to the OPCUA server", Exported = true)]
+    public void NumberOfSubscriptions(long value);
+
+    [Counter(Name = "opcua_subscription_setup_time_seconds_total", Unit = "count", Description = "The total time spent setting up subscriptions to the OPCUA server", Exported = true)]
+    public void SubscriptionSetupTime(double value);
+
+    [Counter(Name = "opcua_subscription_notifications_received_total", Unit = "count", Description = "The total number of notifications received from the OPCUA server", Exported = true)]
+    public void NumberOfReceivedMonitorNotifications(long value);
+    #endregion
 }
 
 [ExcludeFromCodeCoverage]

Source/Subscriber.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading;
 using System.Threading.Channels;
 using System.Threading.Tasks;
@@ -23,6 +24,8 @@ public Subscriber(IMetricsHandler metrics, ILogger logger)
     public async Task SubscribeToChangesFor(ISession connection, TimeSpan publishInterval, IEnumerable<(NodeId node, TimeSpan samplingInterval)> nodes, Func<NodeValue, Task> handleValue, CancellationToken cancellationToken)
     {
         _logger.Debug("Creating subscription with publish interval {PublishInterval}", publishInterval);
+        _metrics.NumberOfSubscriptionAttempts(1);
+        var timer = Stopwatch.StartNew();
 
         using var subscription = CreateEmptySubscription(publishInterval);
         var channel = Channel.CreateUnbounded<NodeValue>(new(){ SingleReader = true });
@@ -40,10 +43,14 @@ public async Task SubscribeToChangesFor(ISession connection, TimeSpan publishInt
         DeleteSubscriptionWhenCancelled(subscription, cancellationToken);
         CompleteChannelWhenSubscriptionCompletes(subscription, channel);
 
+        _metrics.NumberOfSubscriptions(1);
+        _metrics.SubscriptionSetupTime(timer.Elapsed.TotalSeconds);
+
         _logger.Debug("Starting to read values from subscription");
         await foreach (var value in channel.Reader.ReadAllAsync(CancellationToken.None))
         {
             _logger.Verbose("Received value {Value} from subscription", value);
+            _metrics.NumberOfReceivedMonitorNotifications(1);
             await handleValue(value).ConfigureAwait(false);
         }
     }