HttpClientHandler request metrics

src/libraries/System.Net.Http/ref/System.Net.Http.cs

@@ -135,6 +135,8 @@ public HttpClientHandler() { }
         public long MaxRequestContentBufferSize { get { throw null; } set { } }
         [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public int MaxResponseHeadersLength { get { throw null; } set { } }
+        [System.CLSCompliantAttribute(false)]
+        public System.Diagnostics.Metrics.Meter Meter { get { throw null; } set { } }
         [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public bool PreAuthenticate { get { throw null; } set { } }
         public System.Collections.Generic.IDictionary<string, object?> Properties { get { throw null; } }
@@ -299,6 +301,11 @@ public sealed class HttpRequestOptions : System.Collections.Generic.IDictionary<
         public void Set<TValue>(HttpRequestOptionsKey<TValue> key, TValue value) { throw null; }
     }
 
+    public static class HttpRequestOptionsExtensions
+    {
+        public static void SetCustomMetricsTags(this HttpRequestOptions options, IReadOnlyCollection<KeyValuePair<string, object?>> tags) { throw null; }
+    }
+
     public partial class HttpResponseMessage : System.IDisposable
     {
         public HttpResponseMessage() { }
@@ -391,6 +398,8 @@ public SocketsHttpHandler() { }
         public int MaxConnectionsPerServer { get { throw null; } set { } }
         public int MaxResponseDrainSize { get { throw null; } set { } }
         public int MaxResponseHeadersLength { get { throw null; } set { } }
+        [System.CLSCompliantAttribute(false)]
+        public System.Diagnostics.Metrics.Meter Meter { get { throw null; } set { } }
         public System.TimeSpan PooledConnectionIdleTimeout { get { throw null; } set { } }
         public System.TimeSpan PooledConnectionLifetime { get { throw null; } set { } }
         public bool PreAuthenticate { get { throw null; } set { } }

src/libraries/System.Net.Http/src/System.Net.Http.csproj

@@ -58,12 +58,14 @@
     <Compile Include="System\Net\Http\HttpRequestException.cs" />
     <Compile Include="System\Net\Http\HttpRequestMessage.cs" />
     <Compile Include="System\Net\Http\HttpRequestOptions.cs" />
+    <Compile Include="System\Net\Http\HttpRequestOptionsExtensions.cs" />
     <Compile Include="System\Net\Http\HttpRequestOptionsKey.cs" />
     <Compile Include="System\Net\Http\HttpResponseMessage.cs" />
     <Compile Include="System\Net\Http\HttpRuleParser.cs" />
     <Compile Include="System\Net\Http\HttpTelemetry.cs" />
     <Compile Include="System\Net\Http\HttpVersionPolicy.cs" />
     <Compile Include="System\Net\Http\MessageProcessingHandler.cs" />
+    <Compile Include="System\Net\Http\MetricsHandler.cs" />
     <Compile Include="System\Net\Http\MultipartContent.cs" />
     <Compile Include="System\Net\Http\MultipartFormDataContent.cs" />
     <Compile Include="System\Net\Http\NetEventSource.Http.cs" />

src/libraries/System.Net.Http/src/System/Net/Http/BrowserHttpHandler/SocketsHttpHandler.cs

@@ -9,6 +9,7 @@
 using System.Threading.Tasks;
 using System.Diagnostics.CodeAnalysis;
 using System.Diagnostics;
+using System.Diagnostics.Metrics;
 
 namespace System.Net.Http
 {
@@ -91,6 +92,13 @@ public int MaxResponseDrainSize
             set => throw new PlatformNotSupportedException();
         }
 
+        [CLSCompliant(false)]
+        public Meter Meter
+        {
+            get => throw new PlatformNotSupportedException();
+            set => throw new PlatformNotSupportedException();
+        }
+
         public TimeSpan ResponseDrainTimeout
         {
             get => throw new PlatformNotSupportedException();

src/libraries/System.Net.Http/src/System/Net/Http/HttpClient.cs

@@ -622,6 +622,7 @@ private void HandleFailure(Exception e, bool telemetryStarted, HttpResponseMessa
             }
 
             LogRequestFailed(e, telemetryStarted);
+            response?.RequestFailedMetricsLogger?.Invoke(response);
 
             if (NetEventSource.Log.IsEnabled()) NetEventSource.Error(this, e);
 

src/libraries/System.Net.Http/src/System/Net/Http/HttpClientHandler.AnyMobile.cs

@@ -6,6 +6,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Metrics;
 using System.Globalization;
 using System.Net.Security;
 using System.Reflection;
@@ -73,6 +74,13 @@ protected override void Dispose(bool disposing)
             base.Dispose(disposing);
         }
 
+        [CLSCompliant(false)]
+        public Meter Meter
+        {
+            get => throw new NotImplementedException();
+            set => throw new NotImplementedException();
+        }
+
         [UnsupportedOSPlatform("browser")]
         public bool UseCookies
         {

src/libraries/System.Net.Http/src/System/Net/Http/HttpClientHandler.cs

@@ -10,6 +10,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using System.Diagnostics;
+using System.Diagnostics.Metrics;
 #if TARGET_BROWSER
 using HttpHandlerType = System.Net.Http.BrowserHttpHandler;
 #else
@@ -21,11 +22,10 @@ namespace System.Net.Http
     public partial class HttpClientHandler : HttpMessageHandler
     {
         private readonly HttpHandlerType _underlyingHandler;
+        private HttpMessageHandler? _handler;
 
 #if TARGET_BROWSER
-        private HttpMessageHandler Handler { get; }
-#else
-        private HttpHandlerType Handler => _underlyingHandler;
+        private Meter _meter = MetricsHandler.DefaultMeter;
 #endif
 
         private ClientCertificateOption _clientCertificateOptions;
@@ -36,15 +36,25 @@ public HttpClientHandler()
         {
             _underlyingHandler = new HttpHandlerType();
 
+            ClientCertificateOptions = ClientCertificateOption.Manual;
+        }
+
+        private HttpMessageHandler SetupHandlerChain()
+        {
+            HttpMessageHandler handler = _underlyingHandler;
 #if TARGET_BROWSER
-            Handler = _underlyingHandler;
             if (DiagnosticsHandler.IsGloballyEnabled())
             {
-                Handler = new DiagnosticsHandler(Handler, DistributedContextPropagator.Current);
+                handler = new DiagnosticsHandler(handler, DistributedContextPropagator.Current);
             }
+            handler = new MetricsHandler(handler, _meter);
 #endif
-
-            ClientCertificateOptions = ClientCertificateOption.Manual;
+            // Ensure a single handler is used for all requests.
+            if (Interlocked.CompareExchange(ref _handler, handler, null) != null)
+            {
+                handler.Dispose();
+            }
+            return handler;
         }
 
         protected override void Dispose(bool disposing)
@@ -62,6 +72,29 @@ protected override void Dispose(bool disposing)
         public virtual bool SupportsProxy => HttpHandlerType.SupportsProxy;
         public virtual bool SupportsRedirectConfiguration => HttpHandlerType.SupportsRedirectConfiguration;
 
+        [CLSCompliant(false)]
+        public Meter Meter
+        {
+#if TARGET_BROWSER
+            get => _meter;
+            set
+            {
+                ArgumentNullException.ThrowIfNull(value);
+                if (value.Name != "System.Net.Http")
+                {
+                    throw new ArgumentException("Meter name must be 'System.Net.Http'.");
+                }
+
+                CheckDisposedOrStarted();
+                _meter = value;
+            }
+#else
+            get => _underlyingHandler.Meter;
+            set => _underlyingHandler.Meter = value;
+#endif
+        }
+
+
         [UnsupportedOSPlatform("browser")]
         public bool UseCookies
         {
@@ -304,10 +337,10 @@ public SslProtocols SslProtocols
         //[UnsupportedOSPlatform("ios")]
         //[UnsupportedOSPlatform("tvos")]
         protected internal override HttpResponseMessage Send(HttpRequestMessage request, CancellationToken cancellationToken) =>
-            Handler.Send(request, cancellationToken);
+            (_handler ?? SetupHandlerChain()).Send(request, cancellationToken);
 
         protected internal override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) =>
-            Handler.SendAsync(request, cancellationToken);
+            (_handler ?? SetupHandlerChain()).SendAsync(request, cancellationToken);
 
         // lazy-load the validator func so it can be trimmed by the ILLinker if it isn't used.
         private static Func<HttpRequestMessage, X509Certificate2?, X509Chain?, SslPolicyErrors, bool>? s_dangerousAcceptAnyServerCertificateValidator;
@@ -323,5 +356,16 @@ private void ThrowForModifiedManagedSslOptionsIfStarted()
             // SslOptions is changed, since SslOptions itself does not do any such checks.
             _underlyingHandler.SslOptions = _underlyingHandler.SslOptions;
         }
+
+#if TARGET_BROWSER
+        private void CheckDisposedOrStarted()
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+            if (_handler != null)
+            {
+                throw new InvalidOperationException(SR.net_http_operation_started);
+            }
+        }
+#endif
     }
 }

src/libraries/System.Net.Http/src/System/Net/Http/HttpMessageInvoker.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.IO;
-using System.Net.Http.Headers;
 using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
@@ -124,7 +122,6 @@ protected virtual void Dispose(bool disposing)
             if (disposing && !_disposed)
             {
                 _disposed = true;
-
                 if (_disposeHandler)
                 {
                     _handler.Dispose();

src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestMessage.cs

@@ -30,7 +30,7 @@ public class HttpRequestMessage : IDisposable
         private Version _version;
         private HttpVersionPolicy _versionPolicy;
         private HttpContent? _content;
-        private HttpRequestOptions? _options;
+        internal HttpRequestOptions? _options;
 
         public Version Version
         {

src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestOptionsExtensions.cs

@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Net.Http
+{
+    public static class HttpRequestOptionsExtensions
+    {
+        private static readonly HttpRequestOptionsKey<IReadOnlyCollection<KeyValuePair<string, object?>>> s_CustomMetricsTagsKey = new("CustomMetricsTags");
+
+        public static void SetCustomMetricsTags(this HttpRequestOptions options, IReadOnlyCollection<KeyValuePair<string, object?>> tags)
+        {
+            options.Set(s_CustomMetricsTagsKey, tags);
+        }
+
+        internal static bool TryGetCustomMetricsTags(this HttpRequestOptions options, [MaybeNullWhen(false)] out IReadOnlyCollection<KeyValuePair<string, object?>>? tags) =>
+            options.TryGetValue(s_CustomMetricsTagsKey, out tags);
+    }
+}

src/libraries/System.Net.Http/src/System/Net/Http/HttpResponseMessage.cs

@@ -22,6 +22,8 @@ public class HttpResponseMessage : IDisposable
         private HttpContent? _content;
         private bool _disposed;
 
+        internal Action<HttpResponseMessage>? RequestFailedMetricsLogger { get; set; }
+
         public Version Version
         {
             get { return _version; }