Add flag on metrics feature to disable metrics per request

Author: JamesNK

src/Hosting/Hosting/src/Internal/HostingApplicationDiagnostics.cs

@@ -154,12 +154,12 @@ public void RequestEnd(HttpContext httpContext, Exception? exception, HostingApp
 
             if (context.MetricsEnabled)
             {
+                Debug.Assert(context.MetricsTagsFeature != null, "MetricsTagsFeature should be set if MetricsEnabled is true.");
+
                 var endpoint = HttpExtensions.GetOriginalEndpoint(httpContext);
-                var disableHttpRequestDurationMetric = endpoint?.Metadata.GetMetadata<IDisableHttpMetricsMetadata>() != null;
+                var disableHttpRequestDurationMetric = endpoint?.Metadata.GetMetadata<IDisableHttpMetricsMetadata>() != null || context.MetricsTagsFeature.MetricsDisabled;
                 var route = endpoint?.Metadata.GetMetadata<IRouteDiagnosticsMetadata>()?.Route;
 
-                Debug.Assert(context.MetricsTagsFeature != null, "MetricsTagsFeature should be set if MetricsEnabled is true.");
-
                 _metrics.RequestEnd(
                     context.MetricsTagsFeature.Protocol!,
                     context.MetricsTagsFeature.Scheme!,

src/Hosting/Hosting/src/Internal/HttpMetricsTagsFeature.cs

@@ -8,6 +8,7 @@ namespace Microsoft.AspNetCore.Hosting;
 internal sealed class HttpMetricsTagsFeature : IHttpMetricsTagsFeature
 {
     ICollection<KeyValuePair<string, object?>> IHttpMetricsTagsFeature.Tags => TagsList;
+    public bool MetricsDisabled { get; set; }
 
     public List<KeyValuePair<string, object?>> TagsList { get; } = new List<KeyValuePair<string, object?>>();
 
@@ -20,6 +21,7 @@ internal sealed class HttpMetricsTagsFeature : IHttpMetricsTagsFeature
     public void Reset()
     {
         TagsList.Clear();
+        MetricsDisabled = false;
 
         Method = null;
         Scheme = null;

src/Hosting/Hosting/test/HostingApplicationDiagnosticsTests.cs

@@ -295,7 +295,7 @@ public void Metrics_Route_RouteTagReported()
     }
 
     [Fact]
-    public void Metrics_DisableHttpMetrics_NoMetrics()
+    public void Metrics_DisableHttpMetricsWithMetadata_NoMetrics()
     {
         // Arrange
         var hostingEventSource = new HostingEventSource(Guid.NewGuid().ToString());
@@ -349,6 +349,62 @@ public void Metrics_DisableHttpMetrics_NoMetrics()
         Assert.Empty(requestDurationCollector.GetMeasurementSnapshot());
     }
 
+    [Fact]
+    public void Metrics_DisableHttpMetricsWithFeature_NoMetrics()
+    {
+        // Arrange
+        var hostingEventSource = new HostingEventSource(Guid.NewGuid().ToString());
+
+        var testMeterFactory = new TestMeterFactory();
+        using var activeRequestsCollector = new MetricCollector<long>(testMeterFactory, HostingMetrics.MeterName, "http.server.active_requests");
+        using var requestDurationCollector = new MetricCollector<double>(testMeterFactory, HostingMetrics.MeterName, "http.server.request.duration");
+
+        // Act
+        var hostingApplication = CreateApplication(out var features, eventSource: hostingEventSource, meterFactory: testMeterFactory, configure: c =>
+        {
+            c.Request.Protocol = "1.1";
+            c.Request.Scheme = "http";
+            c.Request.Method = "POST";
+            c.Request.Host = new HostString("localhost");
+            c.Request.Path = "/hello";
+            c.Request.ContentType = "text/plain";
+            c.Request.ContentLength = 1024;
+        });
+        var context = hostingApplication.CreateContext(features);
+
+        Assert.Collection(activeRequestsCollector.GetMeasurementSnapshot(),
+            m =>
+            {
+                Assert.Equal(1, m.Value);
+                Assert.Equal("http", m.Tags["url.scheme"]);
+                Assert.Equal("POST", m.Tags["http.request.method"]);
+            });
+
+        context.HttpContext.Features.Get<IHttpMetricsTagsFeature>().MetricsDisabled = true;
+
+        // Assert 1
+        Assert.True(context.MetricsTagsFeature.MetricsDisabled);
+
+        hostingApplication.DisposeContext(context, null);
+
+        // Assert 2
+        Assert.Collection(activeRequestsCollector.GetMeasurementSnapshot(),
+            m =>
+            {
+                Assert.Equal(1, m.Value);
+                Assert.Equal("http", m.Tags["url.scheme"]);
+                Assert.Equal("POST", m.Tags["http.request.method"]);
+            },
+            m =>
+            {
+                Assert.Equal(-1, m.Value);
+                Assert.Equal("http", m.Tags["url.scheme"]);
+                Assert.Equal("POST", m.Tags["http.request.method"]);
+            });
+        Assert.Empty(requestDurationCollector.GetMeasurementSnapshot());
+        Assert.False(context.MetricsTagsFeature.MetricsDisabled);
+    }
+
     private sealed class TestRouteDiagnosticsMetadata : IRouteDiagnosticsMetadata
     {
         public string Route { get; } = "hello/{name}";

src/Hosting/Hosting/test/HostingMetricsTests.cs

@@ -180,6 +180,7 @@ public void IHttpMetricsTagsFeatureNotUsedFromFeatureCollection()
     private sealed class TestHttpMetricsTagsFeature : IHttpMetricsTagsFeature
     {
         public ICollection<KeyValuePair<string, object>> Tags { get; } = new Collection<KeyValuePair<string, object>>();
+        public bool MetricsDisabled { get; set; }
     }
 
     private static HostingApplication CreateApplication(IHttpContextFactory httpContextFactory = null, bool useHttpContextAccessor = false,

src/Http/Http.Abstractions/src/Metadata/IDisableHttpMetricsMetadata.cs

@@ -3,6 +3,9 @@
 
 namespace Microsoft.AspNetCore.Http.Metadata;
 
+/// <summary>
+/// A marker interface which can be used to identify metadata that disables HTTP request duration metrics.
+/// </summary>
 public interface IDisableHttpMetricsMetadata
 {
 }

src/Http/Http.Abstractions/src/PublicAPI.Unshipped.txt

@@ -3,3 +3,4 @@
 Microsoft.AspNetCore.Http.HostString.HostString(string? value) -> void
 *REMOVED*Microsoft.AspNetCore.Http.HostString.Value.get -> string!
 Microsoft.AspNetCore.Http.HostString.Value.get -> string?
+Microsoft.AspNetCore.Http.Metadata.IDisableHttpMetricsMetadata

src/Http/Http.Features/src/IHttpMetricsTagsFeature.cs

@@ -4,12 +4,18 @@
 namespace Microsoft.AspNetCore.Http.Features;
 
 /// <summary>
-/// Provides access to tags added to the metrics HTTP request counter. This feature isn't set if the counter isn't enabled.
+/// Provides access to tags added to the metrics HTTP request duration counter. This feature isn't set if the counter isn't enabled.
 /// </summary>
 public interface IHttpMetricsTagsFeature
 {
     /// <summary>
     /// Gets the tag collection.
     /// </summary>
     ICollection<KeyValuePair<string, object?>> Tags { get; }
+
+    // MetricsDisabled was added after the initial release of this interface and is intentionally a DIM property.
+    /// <summary>
+    /// Gets or sets a flag that disables recording HTTP request duration counter for the current HTTP request.
+    /// </summary>
+    public bool MetricsDisabled { get; set; }
 }

src/Http/Http.Features/src/PublicAPI.Unshipped.txt

@@ -1 +1,3 @@
 #nullable enable
+Microsoft.AspNetCore.Http.Features.IHttpMetricsTagsFeature.MetricsDisabled.get -> bool
+Microsoft.AspNetCore.Http.Features.IHttpMetricsTagsFeature.MetricsDisabled.set -> void