Prototype HistogramAdvice API.

src/libraries/System.Diagnostics.DiagnosticSource/ref/System.Diagnostics.DiagnosticSourceActivity.cs

@@ -356,6 +356,7 @@ internal UpDownCounter(Meter meter, string name, string? unit, string? descripti
     }
     public sealed class Histogram<T> : Instrument<T> where T : struct
     {
+        public HistogramAdvice<T>? Advice { get { throw null; } }
         internal Histogram(Meter meter, string name, string? unit, string? description) : base(meter, name, unit, description) { throw null; }
         public void Record(T value) { throw null; }
         public void Record(T value, System.Collections.Generic.KeyValuePair<string, object?> tag) { throw null; }
@@ -410,7 +411,8 @@ public class Meter : IDisposable
         public UpDownCounter<T> CreateUpDownCounter<T>(string name, string? unit = null, string? description = null) where T : struct  { throw null; }
         public UpDownCounter<T> CreateUpDownCounter<T>(string name, string? unit, string? description, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>> tags) where T : struct  { throw null; }
         public Histogram<T> CreateHistogram<T>(string name, string? unit = null, string? description = null) where T : struct { throw null; }
-        public Histogram<T> CreateHistogram<T>(string name, string? unit, string? description, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>> tags) where T : struct { throw null; }
+        public Histogram<T> CreateHistogram<T>(string name, string? unit, string? description, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>>? tags) where T : struct { throw null; }
+        public Histogram<T> CreateHistogram<T>(string name, string? unit, string? description, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>>? tags, HistogramAdvice<T>? advice) where T : struct { throw null; }
         public ObservableCounter<T> CreateObservableCounter<T>(
                             string name,
                             Func<T> observeValue,
@@ -567,4 +569,8 @@ public abstract class ObservableInstrument<T> : Instrument where T : struct
         protected ObservableInstrument(Meter meter, string name, string? unit, string? description, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>> tags) : base(meter, name, unit, description) { throw null; }
         protected abstract System.Collections.Generic.IEnumerable<Measurement<T>> Observe();
     }
+    public sealed class HistogramAdvice<T> where T : struct
+    {
+        public System.Collections.Generic.IReadOnlyList<T>? ExplicitBucketBoundaries { get { throw null; } init { throw null; } }
+    }
 }

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -54,6 +54,7 @@ System.Diagnostics.DiagnosticSource</PackageDescription>
     <Compile Include="System\Diagnostics\Metrics\Counter.cs" />
     <Compile Include="System\Diagnostics\Metrics\ExponentialHistogramAggregator.cs" />
     <Compile Include="System\Diagnostics\Metrics\Histogram.cs" />
+    <Compile Include="System\Diagnostics\Metrics\HistogramAdvice.cs" />
     <Compile Include="System\Diagnostics\Metrics\IMeterFactory.cs" />
     <Compile Include="System\Diagnostics\Metrics\Instrument.cs" />
     <Compile Include="System\Diagnostics\Metrics\Instrument.common.cs" />

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Metrics/Histogram.cs

@@ -15,12 +15,16 @@ namespace System.Diagnostics.Metrics
     /// </remarks>
     public sealed class Histogram<T> : Instrument<T> where T : struct
     {
-        internal Histogram(Meter meter, string name, string? unit, string? description) : this(meter, name, unit, description, tags: null)
+        public HistogramAdvice<T>? Advice { get; }
+
+        internal Histogram(Meter meter, string name, string? unit, string? description) : this(meter, name, unit, description, tags: null, advice: null)
         {
         }
 
-        internal Histogram(Meter meter, string name, string? unit, string? description, IEnumerable<KeyValuePair<string, object?>>? tags) : base(meter, name, unit, description, tags)
+        internal Histogram(Meter meter, string name, string? unit, string? description, IEnumerable<KeyValuePair<string, object?>>? tags, HistogramAdvice<T>? advice) : base(meter, name, unit, description, tags)
         {
+            Advice = advice;
+
             Publish();
         }
 

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Metrics/HistogramAdvice.cs

@@ -0,0 +1,12 @@
+// 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;
+
+namespace System.Diagnostics.Metrics
+{
+    public sealed class HistogramAdvice<T> where T : struct
+    {
+        public IReadOnlyList<T>? ExplicitBucketBoundaries { get; init; }
+    }
+}

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Metrics/Meter.cs

@@ -152,7 +152,8 @@ public Counter<T> CreateCounter<T>(string name, string? unit, string? descriptio
         /// <remarks>
         /// Example uses for Histogram: the request duration and the size of the response payload.
         /// </remarks>
-        public Histogram<T> CreateHistogram<T>(string name, string? unit = null, string? description = null) where T : struct => CreateHistogram<T>(name, unit, description, tags: null);
+        public Histogram<T> CreateHistogram<T>(string name, string? unit = null, string? description = null) where T : struct
+            => CreateHistogram<T>(name, unit, description, tags: null, advice: null);
 
         /// <summary>
         /// Histogram is an Instrument which can be used to report arbitrary values that are likely to be statistically meaningful. It is intended for statistics such as histograms, summaries, and percentile.
@@ -165,7 +166,21 @@ public Counter<T> CreateCounter<T>(string name, string? unit, string? descriptio
         /// Example uses for Histogram: the request duration and the size of the response payload.
         /// </remarks>
         public Histogram<T> CreateHistogram<T>(string name, string? unit, string? description, IEnumerable<KeyValuePair<string, object?>>? tags) where T : struct
-                => (Histogram<T>)GetOrCreateInstrument<T>(typeof(Histogram<T>), name, unit, description, tags, () => new Histogram<T>(this, name, unit, description, tags));
+                => CreateHistogram<T>(name, unit, description, tags, advice: null);
+
+        /// <summary>
+        /// Histogram is an Instrument which can be used to report arbitrary values that are likely to be statistically meaningful. It is intended for statistics such as histograms, summaries, and percentile.
+        /// </summary>
+        /// <param name="name">The instrument name. cannot be null.</param>
+        /// <param name="unit">Optional instrument unit of measurements.</param>
+        /// <param name="description">Optional instrument description.</param>
+        /// <param name="tags">tags to attach to the counter.</param>
+        /// <param name="advice"><see cref="HistogramAdvice{T}"/> to attach to the counter.</param>
+        /// <remarks>
+        /// Example uses for Histogram: the request duration and the size of the response payload.
+        /// </remarks>
+        public Histogram<T> CreateHistogram<T>(string name, string? unit, string? description, IEnumerable<KeyValuePair<string, object?>>? tags, HistogramAdvice<T>? advice) where T : struct
+                => (Histogram<T>)GetOrCreateInstrument<T>(typeof(Histogram<T>), name, unit, description, tags, () => new Histogram<T>(this, name, unit, description, tags, advice));
 
         /// <summary>
         /// Create a metrics UpDownCounter object.