Add bucket bound hints to Networking histograms

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

@@ -38,6 +38,7 @@
     <Compile Include="System\Net\Http\DelegatingHandler.cs" />
     <Compile Include="System\Net\Http\DiagnosticsHandler.cs" />
     <Compile Include="System\Net\Http\DiagnosticsHandlerLoggingStrings.cs" />
+    <Compile Include="System\Net\Http\DiagnosticsHelper.cs" />
     <Compile Include="System\Net\Http\EmptyContent.cs" />
     <Compile Include="System\Net\Http\EmptyReadStream.cs" />
     <Compile Include="System\Net\Http\FormUrlEncodedContent.cs" />

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

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.Metrics;
+
+namespace System.Net.Http
+{
+    internal static class DiagnosticsHelper
+    {
+        // OTel bucket boundary recommendation for 'http.request.duration':
+        // https://github.com/open-telemetry/semantic-conventions/blob/release/v1.23.x/docs/http/http-metrics.md#metric-httpclientrequestduration
+        // We are using these boundaries for all network requests that are expected to be short.
+        public static InstrumentAdvice<double> ShortHistogramAdvice { 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]
+        };
+    }
+}

src/libraries/System.Net.Http/src/System/Net/Http/Metrics/MetricsHandler.cs

@@ -29,7 +29,8 @@ public MetricsHandler(HttpMessageHandler innerHandler, IMeterFactory? meterFacto
             _requestsDuration = meter.CreateHistogram<double>(
                 "http.client.request.duration",
                 unit: "s",
-                description: "Duration of HTTP client requests.");
+                description: "Duration of HTTP client requests.",
+                advice: DiagnosticsHelper.ShortHistogramAdvice);
         }
 
         internal override ValueTask<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool async, CancellationToken cancellationToken)

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Metrics/SocketsHttpHandlerMetrics.cs

@@ -16,12 +16,18 @@ internal sealed class SocketsHttpHandlerMetrics(Meter meter)
         public readonly Histogram<double> ConnectionDuration = meter.CreateHistogram<double>(
             name: "http.client.connection.duration",
             unit: "s",
-            description: "The duration of successfully established outbound HTTP connections.");
+            description: "The duration of successfully established outbound HTTP connections.",
+            advice: new InstrumentAdvice<double>()
+            {
+                // These values are not based on a standard and may change in the future.
+                HistogramBucketBoundaries = [0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 30, 60, 120, 300]
+            });
 
         public readonly Histogram<double> RequestsQueueDuration = meter.CreateHistogram<double>(
             name: "http.client.request.time_in_queue",
             unit: "s",
-            description: "The amount of time requests spent on a queue waiting for an available connection.");
+            description: "The amount of time requests spent on a queue waiting for an available connection.",
+            advice: DiagnosticsHelper.ShortHistogramAdvice);
 
         public void RequestLeftQueue(HttpRequestMessage request, HttpConnectionPool pool, TimeSpan duration, int versionMajor)
         {

src/libraries/System.Net.Http/tests/FunctionalTests/MetricsTest.cs

@@ -161,6 +161,8 @@ protected sealed class InstrumentRecorder<T> : IDisposable where T : struct
             private Meter? _meter;
 
             public Action? MeasurementRecorded;
+            public Action<IReadOnlyList<T>> VerifyHistogramBucketBoundaries;
+            public int MeasurementCount => _values.Count;
 
             public InstrumentRecorder(string instrumentName)
             {
@@ -193,6 +195,13 @@ private void OnMeasurementRecorded(Instrument instrument, T measurement, ReadOnl
             {
                 _values.Enqueue(new Measurement<T>(measurement, tags));
                 MeasurementRecorded?.Invoke();
+                if (VerifyHistogramBucketBoundaries is not null)
+                {
+                    Histogram<T> histogram = (Histogram<T>)instrument;
+                    IReadOnlyList<T> boundaries = histogram.Advice.HistogramBucketBoundaries;
+                    Assert.NotNull(boundaries);
+                    VerifyHistogramBucketBoundaries(boundaries);
+                }
             }
 
             public IReadOnlyList<Measurement<T>> GetMeasurements() => _values.ToArray();
@@ -328,6 +337,7 @@ public Task RequestDuration_Success_Recorded(string method, HttpStatusCode statu
             {
                 using HttpMessageInvoker client = CreateHttpMessageInvoker();
                 using InstrumentRecorder<double> recorder = SetupInstrumentRecorder<double>(InstrumentNames.RequestDuration);
+
                 using HttpRequestMessage request = new(HttpMethod.Parse(method), uri) { Version = UseVersion };
 
                 using HttpResponseMessage response = await SendAsync(client, request);
@@ -916,6 +926,40 @@ await IgnoreExceptions(async () =>
                 });
             });
         }
+
+        [Fact]
+        public Task DurationHistograms_HaveBucketSizeHints()
+        {
+            return LoopbackServerFactory.CreateClientAndServerAsync(async uri =>
+            {
+                using HttpMessageInvoker client = CreateHttpMessageInvoker();
+                using InstrumentRecorder<double> requestDurationRecorder = SetupInstrumentRecorder<double>(InstrumentNames.RequestDuration);
+                using InstrumentRecorder<double> timeInQueueRecorder = SetupInstrumentRecorder<double>(InstrumentNames.TimeInQueue);
+                using InstrumentRecorder<double> connectionDurationRecorder = SetupInstrumentRecorder<double>(InstrumentNames.ConnectionDuration);
+
+                requestDurationRecorder.VerifyHistogramBucketBoundaries = b =>
+                {
+                    // Verify first and last value of the boundaries defined in
+                    // https://github.com/open-telemetry/semantic-conventions/blob/release/v1.23.x/docs/http/http-metrics.md#metric-httpserverrequestduration
+                    Assert.Equal(0.005, b.First());
+                    Assert.Equal(10, b.Last());
+                };
+                timeInQueueRecorder.VerifyHistogramBucketBoundaries = requestDurationRecorder.VerifyHistogramBucketBoundaries;
+                connectionDurationRecorder.VerifyHistogramBucketBoundaries =
+                    b => Assert.True(b.Last() > 180); // At least 3 minutes for the highest bucket.
+
+                using HttpRequestMessage request = new(HttpMethod.Get, uri) { Version = UseVersion };
+                using HttpResponseMessage response = await SendAsync(client, request);
+
+                Assert.Equal(1, requestDurationRecorder.MeasurementCount);
+                Assert.Equal(1, timeInQueueRecorder.MeasurementCount);
+                client.Dispose(); // terminate the connection
+                Assert.Equal(1, connectionDurationRecorder.MeasurementCount);
+            }, async server =>
+            {
+                await server.AcceptConnectionSendResponseAndCloseAsync();
+            });
+        }
     }
 
     [ActiveIssue("https://github.com/dotnet/runtime/issues/93754", TestPlatforms.Browser)]

src/libraries/System.Net.NameResolution/src/System/Net/NameResolutionMetrics.cs

@@ -15,7 +15,14 @@ internal static class NameResolutionMetrics
         private static readonly Histogram<double> s_lookupDuration = s_meter.CreateHistogram<double>(
             name: "dns.lookup.duration",
             unit: "s",
-            description: "Measures the time taken to perform a DNS lookup.");
+            description: "Measures the time taken to perform a DNS lookup.",
+            advice: new InstrumentAdvice<double>()
+            {
+                // OTel bucket boundary recommendation for 'http.request.duration':
+                // https://github.com/open-telemetry/semantic-conventions/blob/release/v1.23.x/docs/http/http-metrics.md#metric-httpclientrequestduration
+                // We are using these boundaries for all network requests that are expected to be short.
+                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]
+            });
 
         public static bool IsEnabled() => s_lookupDuration.Enabled;
 

src/libraries/System.Net.NameResolution/tests/FunctionalTests/MetricsTest.cs

@@ -41,6 +41,22 @@ await RemoteExecutor.Invoke(async () =>
             }).DisposeAsync();
         }
 
+        [Fact]
+        public static async Task DurationHistogram_HasBucketSizeHints()
+        {
+            await RemoteExecutor.Invoke(async () =>
+            {
+                const string ValidHostName = "localhost";
+
+                using var recorder = new InstrumentRecorder<double>(DnsLookupDuration);
+                recorder.VerifyHistogramBucketBoundaries = b => Assert.True(b.Count > 2);
+
+                await Dns.GetHostEntryAsync(ValidHostName);
+
+                Assert.Equal(1, recorder.MeasurementCount);
+            }).DisposeAsync();
+        }
+
         [Fact]
         public static async Task ResolveInvalidHostName_MetricsRecorded()
         {
@@ -86,6 +102,9 @@ private sealed class InstrumentRecorder<T> : IDisposable where T : struct
             private readonly MeterListener _meterListener = new();
             private readonly ConcurrentQueue<Measurement<T>> _values = new();
 
+            public Action<IReadOnlyList<T>> VerifyHistogramBucketBoundaries;
+            public int MeasurementCount => _values.Count;
+
             public InstrumentRecorder(string instrumentName)
             {
                 _meterListener.InstrumentPublished = (instrument, listener) =>
@@ -99,7 +118,17 @@ public InstrumentRecorder(string instrumentName)
                 _meterListener.Start();
             }
 
-            private void OnMeasurementRecorded(Instrument instrument, T measurement, ReadOnlySpan<KeyValuePair<string, object?>> tags, object? state) => _values.Enqueue(new Measurement<T>(measurement, tags));
+            private void OnMeasurementRecorded(Instrument instrument, T measurement, ReadOnlySpan<KeyValuePair<string, object?>> tags, object? state)
+            {
+                _values.Enqueue(new Measurement<T>(measurement, tags));
+                if (VerifyHistogramBucketBoundaries is not null)
+                {
+                    Histogram<T> histogram = (Histogram<T>)instrument;
+                    IReadOnlyList<T> boundaries = histogram.Advice.HistogramBucketBoundaries;
+                    Assert.NotNull(boundaries);
+                    VerifyHistogramBucketBoundaries(boundaries);
+                }
+            }
             public IReadOnlyList<Measurement<T>> GetMeasurements() => _values.ToArray();
             public void Dispose() => _meterListener.Dispose();
         }