Add initial Activity / Metric support (#183)

Author: stephentoub

Directory.Packages.props

@@ -33,6 +33,8 @@
     <PackageVersion Include="Microsoft.Extensions.Logging.Console" Version="$(MicrosoftExtensionsVersion)" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageVersion Include="Moq" Version="4.20.72" />
+    <PackageVersion Include="OpenTelemetry" Version="1.11.2" />
+    <PackageVersion Include="OpenTelemetry.Exporter.InMemory" Version="1.11.2" />
     <PackageVersion Include="Serilog.Extensions.Hosting" Version="9.0.0" />
     <PackageVersion Include="Serilog.Extensions.Logging" Version="9.0.0" />
     <PackageVersion Include="Serilog.Sinks.Console" Version="6.0.0" />

src/ModelContextProtocol/Diagnostics.cs

@@ -0,0 +1,29 @@
+using System.Diagnostics;
+using System.Diagnostics.Metrics;
+
+namespace ModelContextProtocol;
+
+internal static class Diagnostics
+{
+    internal static ActivitySource ActivitySource { get; } = new("ModelContextProtocol");
+
+    /// <summary>
+    /// Follows boundaries from http.server.request.duration/http.client.request.duration
+    /// </summary>
+    internal static InstrumentAdvice<double> ShortSecondsBucketBoundaries { get; } = new()
+    {
+        HistogramBucketBoundaries = [0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10],
+    };
+
+    /// <summary>
+    /// Not based on a standard. Larger bucket sizes for longer lasting operations, e.g. HTTP connection duration.
+    /// See https://github.com/open-telemetry/semantic-conventions/issues/336
+    /// </summary>
+    internal static InstrumentAdvice<double> LongSecondsBucketBoundaries { get; } = new()
+    {
+        HistogramBucketBoundaries = [0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 30, 60, 120, 300],
+    };
+
+    internal static Meter Meter { get; } = new("ModelContextProtocol");
+
+}

src/ModelContextProtocol/Protocol/Messages/ProgressToken.cs

@@ -12,44 +12,45 @@ namespace ModelContextProtocol.Protocol.Messages;
 [JsonConverter(typeof(Converter))]
 public readonly struct ProgressToken : IEquatable<ProgressToken>
 {
-    /// <summary>The id, either a string or a boxed long or null.</summary>
-    private readonly object? _id;
+    /// <summary>The token, either a string or a boxed long or null.</summary>
+    private readonly object? _token;
 
     /// <summary>Initializes a new instance of the <see cref="ProgressToken"/> with a specified value.</summary>
     /// <param name="value">The required ID value.</param>
     public ProgressToken(string value)
     {
         Throw.IfNull(value);
-        _id = value;
+        _token = value;
     }
 
     /// <summary>Initializes a new instance of the <see cref="ProgressToken"/> with a specified value.</summary>
     /// <param name="value">The required ID value.</param>
     public ProgressToken(long value)
     {
         // Box the long. Progress tokens are almost always strings in practice, so this should be rare.
-        _id = value;
+        _token = value;
     }
 
-    /// <summary>Gets whether the identifier is uninitialized.</summary>
-    public bool IsDefault => _id is null;
+    /// <summary>Gets the underlying object for this token.</summary>
+    /// <remarks>This will either be a <see cref="string"/>, a boxed <see cref="long"/>, or <see langword="null"/>.</remarks>
+    public object? Token => _token;
 
     /// <inheritdoc />
     public override string? ToString() =>
-        _id is string stringValue ? $"\"{stringValue}\"" :
-        _id is long longValue ? longValue.ToString(CultureInfo.InvariantCulture) :
+        _token is string stringValue ? $"{stringValue}" :
+        _token is long longValue ? longValue.ToString(CultureInfo.InvariantCulture) :
         null;
 
     /// <summary>
     /// Compares this ProgressToken to another ProgressToken.
     /// </summary>
-    public bool Equals(ProgressToken other) => Equals(_id, other._id);
+    public bool Equals(ProgressToken other) => Equals(_token, other._token);
 
     /// <inheritdoc />
     public override bool Equals(object? obj) => obj is ProgressToken other && Equals(other);
 
     /// <inheritdoc />
-    public override int GetHashCode() => _id?.GetHashCode() ?? 0;
+    public override int GetHashCode() => _token?.GetHashCode() ?? 0;
 
     /// <summary>
     /// Compares two ProgressTokens for equality.
@@ -83,7 +84,7 @@ public override void Write(Utf8JsonWriter writer, ProgressToken value, JsonSeria
         {
             Throw.IfNull(writer);
 
-            switch (value._id)
+            switch (value._token)
             {
                 case string str:
                     writer.WriteStringValue(str);

src/ModelContextProtocol/Protocol/Messages/RequestId.cs

@@ -31,12 +31,13 @@ public RequestId(long value)
         _id = value;
     }
 
-    /// <summary>Gets whether the identifier is uninitialized.</summary>
-    public bool IsDefault => _id is null;
+    /// <summary>Gets the underlying object for this id.</summary>
+    /// <remarks>This will either be a <see cref="string"/>, a boxed <see cref="long"/>, or <see langword="null"/>.</remarks>
+    public object? Id => _id;
 
     /// <inheritdoc />
     public override string ToString() =>
-        _id is string stringValue ? $"\"{stringValue}\"" :
+        _id is string stringValue ? stringValue :
         _id is long longValue ? longValue.ToString(CultureInfo.InvariantCulture) :
         string.Empty;
 

src/ModelContextProtocol/Shared/McpJsonRpcEndpoint.cs

@@ -3,6 +3,7 @@
 using ModelContextProtocol.Logging;
 using ModelContextProtocol.Protocol.Messages;
 using ModelContextProtocol.Protocol.Transport;
+using ModelContextProtocol.Server;
 using ModelContextProtocol.Utils;
 using System.Diagnostics.CodeAnalysis;
 
@@ -63,7 +64,7 @@ public Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancella
     protected void StartSession(ITransport sessionTransport)
     {
         _sessionCts = new CancellationTokenSource();
-        _session = new McpSession(sessionTransport, EndpointName, _requestHandlers, _notificationHandlers, _logger);
+        _session = new McpSession(this is IMcpServer, sessionTransport, EndpointName, _requestHandlers, _notificationHandlers, _logger);
         MessageProcessingTask = _session.ProcessMessagesAsync(_sessionCts.Token);
     }