[http] Add http.client.request.duration metric and .NET Framework support

src/OpenTelemetry.Instrumentation.Http/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+* Added support for publishing `http.client.duration` metric on .NET Framework
+  ([#4870](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4870))
+
 ## 1.5.1-beta.1
 
 Released 2023-Jul-20

src/OpenTelemetry.Instrumentation.Http/HttpClientMetrics.cs

@@ -14,8 +14,6 @@
 // limitations under the License.
 // </copyright>
 
-using System.Diagnostics.Metrics;
-using System.Reflection;
 using OpenTelemetry.Instrumentation.Http.Implementation;
 
 namespace OpenTelemetry.Instrumentation.Http;
@@ -25,18 +23,13 @@ namespace OpenTelemetry.Instrumentation.Http;
 /// </summary>
 internal sealed class HttpClientMetrics : IDisposable
 {
-    internal static readonly AssemblyName AssemblyName = typeof(HttpClientMetrics).Assembly.GetName();
-    internal static readonly string InstrumentationName = AssemblyName.Name;
-    internal static readonly string InstrumentationVersion = AssemblyName.Version.ToString();
-
     private static readonly HashSet<string> ExcludedDiagnosticSourceEvents = new()
     {
         "System.Net.Http.Request",
         "System.Net.Http.Response",
     };
 
     private readonly DiagnosticSourceSubscriber diagnosticSourceSubscriber;
-    private readonly Meter meter;
 
     private readonly Func<string, object, object, bool> isEnabled = (activityName, obj1, obj2)
         => !ExcludedDiagnosticSourceEvents.Contains(activityName);
@@ -47,15 +40,16 @@ internal sealed class HttpClientMetrics : IDisposable
     /// <param name="options">HttpClient metric instrumentation options.</param>
     public HttpClientMetrics(HttpClientMetricInstrumentationOptions options)
     {
-        this.meter = new Meter(InstrumentationName, InstrumentationVersion);
-        this.diagnosticSourceSubscriber = new DiagnosticSourceSubscriber(new HttpHandlerMetricsDiagnosticListener("HttpHandlerDiagnosticListener", this.meter, options), this.isEnabled, HttpInstrumentationEventSource.Log.UnknownErrorProcessingEvent);
+        this.diagnosticSourceSubscriber = new DiagnosticSourceSubscriber(
+            new HttpHandlerMetricsDiagnosticListener("HttpHandlerDiagnosticListener", options),
+            this.isEnabled,
+            HttpInstrumentationEventSource.Log.UnknownErrorProcessingEvent);
         this.diagnosticSourceSubscriber.Subscribe();
     }
 
     /// <inheritdoc/>
     public void Dispose()
     {
         this.diagnosticSourceSubscriber?.Dispose();
-        this.meter?.Dispose();
     }
 }

src/OpenTelemetry.Instrumentation.Http/Implementation/HttpHandlerMetricsDiagnosticListener.cs

@@ -22,6 +22,7 @@
 #if NETFRAMEWORK
 using System.Net.Http;
 #endif
+using System.Reflection;
 using OpenTelemetry.Trace;
 using static OpenTelemetry.Internal.HttpSemanticConventionHelper;
 
@@ -31,21 +32,24 @@ internal sealed class HttpHandlerMetricsDiagnosticListener : ListenerHandler
 {
     internal const string OnStopEvent = "System.Net.Http.HttpRequestOut.Stop";
 
+    internal static readonly AssemblyName AssemblyName = typeof(HttpClientMetrics).Assembly.GetName();
+    internal static readonly string MeterName = AssemblyName.Name;
+    internal static readonly string MeterVersion = AssemblyName.Version.ToString();
+    internal static readonly Meter Meter = new(MeterName, MeterVersion);
+    private static readonly Histogram<double> HttpClientDuration = Meter.CreateHistogram<double>("http.client.duration", "ms", "Measures the duration of outbound HTTP requests.");
+
     private static readonly PropertyFetcher<HttpRequestMessage> StopRequestFetcher = new("Request");
     private static readonly PropertyFetcher<HttpResponseMessage> StopResponseFetcher = new("Response");
-    private readonly Histogram<double> httpClientDuration;
     private readonly HttpClientMetricInstrumentationOptions options;
     private readonly bool emitOldAttributes;
     private readonly bool emitNewAttributes;
 
-    public HttpHandlerMetricsDiagnosticListener(string name, Meter meter, HttpClientMetricInstrumentationOptions options)
+    public HttpHandlerMetricsDiagnosticListener(string name, HttpClientMetricInstrumentationOptions options)
         : base(name)
     {
-        this.httpClientDuration = meter.CreateHistogram<double>("http.client.duration", "ms", "Measures the duration of outbound HTTP requests.");
         this.options = options;
 
         this.emitOldAttributes = this.options.HttpSemanticConvention.HasFlag(HttpSemanticConvention.Old);
-
         this.emitNewAttributes = this.options.HttpSemanticConvention.HasFlag(HttpSemanticConvention.New);
     }
 
@@ -103,7 +107,7 @@ public override void OnEventWritten(string name, object payload)
                 // We are relying here on HttpClient library to set duration before writing the stop event.
                 // https://github.com/dotnet/runtime/blob/90603686d314147017c8bbe1fa8965776ce607d0/src/libraries/System.Net.Http/src/System/Net/Http/DiagnosticsHandler.cs#L178
                 // TODO: Follow up with .NET team if we can continue to rely on this behavior.
-                this.httpClientDuration.Record(activity.Duration.TotalMilliseconds, tags);
+                HttpClientDuration.Record(activity.Duration.TotalMilliseconds, tags);
             }
         }