Add metric exporter for System.Diagnostics.Metrics

Lidgren.Network/NetPeer.Internal.cs

@@ -23,7 +23,7 @@ public partial class NetPeer
 		internal readonly byte[] m_receiveBuffer;
 		internal readonly NetIncomingMessage m_readHelperMessage;
 		private EndPoint m_senderRemote;
-		private readonly object m_initializeLock = new object();
+		internal readonly object m_initializeLock = new object();
 		private uint m_frameCounter;
 		private double m_lastHeartbeat;
 		private double m_lastSocketBind = float.MinValue;
@@ -43,6 +43,8 @@ public partial class NetPeer
 		private AutoResetEvent? m_messageReceivedEvent;
 		private List<NetTuple<SynchronizationContext, SendOrPostCallback>>? m_receiveCallbacks;
 
+		internal Action? m_onShutdown;
+
 		/// <summary>
 		/// Gets the socket, if Start() has been called
 		/// </summary>
@@ -303,6 +305,8 @@ private void ExecutePeerShutdown()
 				m_connections.Clear();
 				m_connectionLookup.Clear();
 				m_handshakes.Clear();
+
+				m_onShutdown?.Invoke();
 			}
 
 			return;

Lidgren.Network/NetPeerMetrics.cs

@@ -0,0 +1,157 @@
+#if NET8_0_OR_GREATER
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.Metrics;
+
+namespace Lidgren.Network;
+
+/// <summary>
+/// Implements an exporter for exporting statistics about the <see cref="NetPeer"/> into
+/// <c>System.Diagnostics.Metrics</c>.
+/// </summary>
+public static class NetPeerMetrics
+{
+	// I originally had this in NetPeerConfiguration,
+	// but moved it here to a standalone class so that trimming solutions avoid pulling in the
+	// metrics stack if you don't use it.
+
+	private const string MeterName = "Lidgren.Network.NetPeer";
+
+	/// <summary>
+	/// Start exporting metrics for a <see cref="NetPeer"/> to <c>System.Diagnostics.Metrics</c>.
+	/// </summary>
+	/// <remarks>
+	/// <para>
+	/// This function must be called after the <see cref="NetPeer"/> has been started.
+	/// </para>
+	/// <para>
+	/// Exported metrics can be viewed via tools such as <see cref="MeterListener"/> or <c>dotnet-counters</c>.
+	/// </para>
+	/// <para>
+	/// If exporting metrics from multiple peers,
+	/// you should use <paramref name="tags"/> to allow them to be distinguished.
+	/// </para>
+	/// </remarks>
+	/// <param name="netPeer">The <see cref="NetPeer"/> to start exporting metrics for.</param>
+	/// <param name="flags">Flags describing what metric features to enable.</param>
+	/// <param name="tags">Optional tags to add to the created <see cref="Meter"/>.</param>
+	/// <param name="factory">
+	/// An optional <see cref="IMeterFactory"/> to be used to create the <see cref="Meter"/>.
+	/// </param>
+	/// <exception cref="InvalidOperationException">Thrown if the <see cref="NetPeer"/> is not running.</exception>
+	public static void AddMetrics(
+		this NetPeer netPeer,
+		Flags flags = Flags.Statistics,
+		IEnumerable<KeyValuePair<string, object?>>? tags = null,
+		IMeterFactory? factory = null)
+	{
+		lock (netPeer.m_initializeLock)
+		{
+			if (netPeer.Status != NetPeerStatus.Running)
+				throw new InvalidOperationException("Peer must be running.");
+
+			Meter meter;
+			if (factory != null)
+			{
+				meter = factory.Create(MeterName, tags: tags);
+			}
+			else
+			{
+				meter = new Meter(MeterName, null, tags: tags);
+			}
+
+			if ((flags & Flags.Statistics) != 0)
+			{
+				var statistics = netPeer.Statistics;
+
+				meter.CreateObservableCounter(
+					"packets_sent",
+					() => statistics.SentPackets,
+					null,
+					"Number of packets sent by this NetPeer.");
+
+				meter.CreateObservableCounter(
+					"packets_received",
+					() => statistics.ReceivedPackets,
+					null,
+					"Number of packets received by this NetPeer.");
+
+				meter.CreateObservableCounter(
+					"messages_sent",
+					() => statistics.SentMessages,
+					null,
+					"Number of messages sent by this NetPeer.");
+
+				meter.CreateObservableCounter(
+					"messages_received",
+					() => statistics.ReceivedMessages,
+					null,
+					"Number of messages received by this NetPeer.");
+
+				meter.CreateObservableCounter(
+					"sent_bytes",
+					() => statistics.SentBytes,
+					"bytes",
+					"Number of bytes sent by this NetPeer.");
+
+				meter.CreateObservableCounter(
+					"sent_bytes",
+					() => statistics.ReceivedBytes,
+					"bytes",
+					"Number of bytes received by this NetPeer.");
+
+				meter.CreateObservableCounter(
+					"storage_allocated_bytes",
+					() => statistics.StorageBytesAllocated,
+					"bytes",
+					"Number of bytes allocated (and possibly garbage collected) for message storage.");
+
+				meter.CreateObservableUpDownCounter(
+					"recycle_pool_bytes",
+					() => statistics.BytesInRecyclePool,
+					"bytes",
+					"Number of bytes in the recycled pool.");
+
+				meter.CreateObservableCounter(
+					"messages_resent",
+					() => new List<Measurement<long>>
+					{
+						new(statistics.ResentMessagesDueToHole,
+							tags: [new KeyValuePair<string, object?>("drop_reason", "hole")]),
+						new(statistics.ResentMessagesDueToDelay,
+							tags: [new KeyValuePair<string, object?>("drop_reason", "delay")]),
+					},
+					null,
+					"Number of messages that had to be resent.");
+
+				meter.CreateObservableCounter(
+					"messages_dropped",
+					() => statistics.DroppedMessages,
+					null,
+					"Number of messages that were dropped");
+			}
+
+            netPeer.m_onShutdown += () => meter.Dispose();
+		}
+	}
+
+	/// <summary>
+	/// Flag enum describing what metric features to enable.
+	/// </summary>
+	[Flags]
+	public enum Flags
+	{
+		/// <summary>
+		/// No metrics are enabled.
+		/// </summary>
+		None = 0,
+
+		/// <summary>
+		/// Basic statistics from <see cref="NetPeerStatistics"/> are reported.
+		/// </summary>
+		Statistics = 1 << 0,
+	}
+}
+
+#endif

RELEASE-NOTES.md

@@ -11,6 +11,7 @@
 - A separate MTU value is now used for IPv6, as it permits a higher default. You can set it with `NetPeerConfiguration.MaximumTransmissionUnitV6`
 - Fixed MTU expansion not setting internal state correctly and spamming network packets.
 - Fixed `NetPeerConfiguration.ExpandMTUFailAttempts` not being respected completely.
+- The new `NetPeerMetrics` allows exporting metrics about the library to `System.Diagnostics.Metrics`.
 
 ## 0.2.7