[sdk-metrics] Add support for .NET 9 Advice API (#5854)

Co-authored-by: Mikel Blanchard <mblanchard@macrosssoftware.com>
Co-authored-by: Reiley Yang <reyang@microsoft.com>

src/OpenTelemetry/CHANGELOG.md

@@ -17,6 +17,20 @@ Notes](../../RELEASENOTES.md).
   `9.0.0-rc.1.24431.7`.
   ([#5853](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5853))
 
+* Added support in metrics for histogram bucket boundaries set via the .NET 9
+  [InstrumentAdvice<T>](https://learn.microsoft.com/dotnet/api/system.diagnostics.metrics.instrumentadvice-1)
+  API.
+
+  Note: With this change explicit bucket histogram boundary resolution will
+  apply in the following order:
+
+    1. View API
+    2. Advice API
+    3. SDK defaults
+
+  See [#5854](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5854)
+  for details.
+
 ## 1.9.0
 
 Released 2024-Jun-14

src/OpenTelemetry/Metrics/MetricStreamIdentity.cs

@@ -22,7 +22,7 @@ public MetricStreamIdentity(Instrument instrument, MetricStreamConfiguration? me
         this.ViewId = metricStreamConfiguration?.ViewId;
         this.MetricStreamName = $"{this.MeterName}.{this.MeterVersion}.{this.InstrumentName}";
         this.TagKeys = metricStreamConfiguration?.CopiedTagKeys;
-        this.HistogramBucketBounds = (metricStreamConfiguration as ExplicitBucketHistogramConfiguration)?.CopiedBoundaries;
+        this.HistogramBucketBounds = GetExplicitBucketHistogramBounds(instrument, metricStreamConfiguration);
         this.ExponentialHistogramMaxSize = (metricStreamConfiguration as Base2ExponentialBucketHistogramConfiguration)?.MaxSize ?? 0;
         this.ExponentialHistogramMaxScale = (metricStreamConfiguration as Base2ExponentialBucketHistogramConfiguration)?.MaxScale ?? 0;
         this.HistogramRecordMinMax = (metricStreamConfiguration as HistogramConfiguration)?.RecordMinMax ?? true;
@@ -150,6 +150,52 @@ public bool Equals(MetricStreamIdentity other)
 
     public override readonly int GetHashCode() => this.hashCode;
 
+    private static double[]? GetExplicitBucketHistogramBounds(Instrument instrument, MetricStreamConfiguration? metricStreamConfiguration)
+    {
+        if (metricStreamConfiguration is ExplicitBucketHistogramConfiguration explicitBucketHistogramConfiguration
+            && explicitBucketHistogramConfiguration.CopiedBoundaries != null)
+        {
+            return explicitBucketHistogramConfiguration.CopiedBoundaries;
+        }
+
+        return instrument switch
+        {
+            Histogram<long> longHistogram => GetExplicitBucketHistogramBoundsFromAdvice(longHistogram),
+            Histogram<int> intHistogram => GetExplicitBucketHistogramBoundsFromAdvice(intHistogram),
+            Histogram<short> shortHistogram => GetExplicitBucketHistogramBoundsFromAdvice(shortHistogram),
+            Histogram<byte> byteHistogram => GetExplicitBucketHistogramBoundsFromAdvice(byteHistogram),
+            Histogram<float> floatHistogram => GetExplicitBucketHistogramBoundsFromAdvice(floatHistogram),
+            Histogram<double> doubleHistogram => GetExplicitBucketHistogramBoundsFromAdvice(doubleHistogram),
+            _ => null,
+        };
+    }
+
+    private static double[]? GetExplicitBucketHistogramBoundsFromAdvice<T>(Histogram<T> histogram)
+        where T : struct
+    {
+        var adviceExplicitBucketBoundaries = histogram.Advice?.HistogramBucketBoundaries;
+        if (adviceExplicitBucketBoundaries == null)
+        {
+            return null;
+        }
+
+        if (typeof(T) == typeof(double))
+        {
+            return ((IReadOnlyList<double>)adviceExplicitBucketBoundaries).ToArray();
+        }
+        else
+        {
+            double[] explicitBucketBoundaries = new double[adviceExplicitBucketBoundaries.Count];
+
+            for (int i = 0; i < adviceExplicitBucketBoundaries.Count; i++)
+            {
+                explicitBucketBoundaries[i] = Convert.ToDouble(adviceExplicitBucketBoundaries[i]);
+            }
+
+            return explicitBucketBoundaries;
+        }
+    }
+
     private static bool HistogramBoundsEqual(double[]? bounds1, double[]? bounds2)
     {
         if (ReferenceEquals(bounds1, bounds2))

test/OpenTelemetry.Tests/Metrics/MetricViewTests.cs

@@ -570,6 +570,177 @@ public void ViewToProduceCustomHistogramBound()
         Assert.Equal(boundaries.Length + 1, actualCount);
     }
 
+    [Fact]
+    public void HistogramWithAdviceBoundaries_HandlesAllTypes()
+    {
+        using var meter = new Meter(Utils.GetCurrentMethodName());
+        var exportedItems = new List<Metric>();
+        int counter = 0;
+
+        using var container = this.BuildMeterProvider(out var meterProvider, builder =>
+        {
+            builder.AddMeter(meter.Name);
+            builder.AddInMemoryExporter(exportedItems);
+        });
+
+        // Test cases for different histogram types
+        var histograms = new Instrument[]
+        {
+            meter.CreateHistogram<long>("longHistogram", unit: null, description: null, tags: null, new() { HistogramBucketBoundaries = new List<long>() { 10, 20 } }),
+            meter.CreateHistogram<int>("intHistogram", unit: null, description: null, tags: null, new() { HistogramBucketBoundaries = new List<int>() { 10, 20 } }),
+            meter.CreateHistogram<short>("shortHistogram", unit: null, description: null, tags: null, new() { HistogramBucketBoundaries = new List<short>() { 10, 20 } }),
+            meter.CreateHistogram<float>("floatHistogram", unit: null, description: null, tags: null, new() { HistogramBucketBoundaries = new List<float>() { 10.0F, 20.0F } }),
+            meter.CreateHistogram<double>("doubleHistogram", unit: null, description: null, tags: null, new() { HistogramBucketBoundaries = new List<double>() { 10.0, 20.0 } }),
+        };
+
+        foreach (var histogram in histograms)
+        {
+            exportedItems.Clear();
+
+            if (histogram is Histogram<long> longHistogram)
+            {
+                longHistogram.Record(-10);
+                longHistogram.Record(9);
+                longHistogram.Record(19);
+            }
+            else if (histogram is Histogram<int> intHistogram)
+            {
+                intHistogram.Record(-10);
+                intHistogram.Record(9);
+                intHistogram.Record(19);
+                counter++;
+            }
+            else if (histogram is Histogram<short> shortHistogram)
+            {
+                shortHistogram.Record(-10);
+                shortHistogram.Record(9);
+                shortHistogram.Record(19);
+                counter++;
+            }
+            else if (histogram is Histogram<float> floatHistogram)
+            {
+                floatHistogram.Record(-10.0F);
+                floatHistogram.Record(9.0F);
+                floatHistogram.Record(19.0F);
+                counter++;
+            }
+            else if (histogram is Histogram<double> doubleHistogram)
+            {
+                doubleHistogram.Record(-10.0);
+                doubleHistogram.Record(9.0);
+                doubleHistogram.Record(19.0);
+                counter++;
+            }
+
+            meterProvider.ForceFlush(MaxTimeToAllowForFlush);
+            var metricCustom = exportedItems[counter];
+
+            List<MetricPoint> metricPointsCustom = new List<MetricPoint>();
+            foreach (ref readonly var mp in metricCustom.GetMetricPoints())
+            {
+                metricPointsCustom.Add(mp);
+            }
+
+            Assert.Single(metricPointsCustom);
+            var histogramPoint = metricPointsCustom[0];
+
+            var count = histogramPoint.GetHistogramCount();
+            var sum = histogramPoint.GetHistogramSum();
+
+            Assert.Equal(18, sum);
+            Assert.Equal(3, count);
+
+            var index = 0;
+            var actualCount = 0;
+            long[] expectedBucketCounts = new long[] { 2, 1, 0 };
+
+            foreach (var histogramMeasurement in histogramPoint.GetHistogramBuckets())
+            {
+                Assert.Equal(expectedBucketCounts[index], histogramMeasurement.BucketCount);
+                index++;
+                actualCount++;
+            }
+
+            Assert.Equal(3, actualCount);
+        }
+    }
+
+    [Theory]
+    [InlineData(false)]
+    [InlineData(true)]
+    public void HistogramWithAdviceBoundariesSpecifiedTests(bool useViewToOverride)
+    {
+        using var meter = new Meter(Utils.GetCurrentMethodName());
+        var exportedItems = new List<Metric>();
+        IReadOnlyList<long> adviceBoundaries = new List<long>() { 5, 10, 20 };
+        double[] viewBoundaries = new double[] { 10, 20 };
+
+        using var container = this.BuildMeterProvider(out var meterProvider, builder =>
+        {
+            builder.AddMeter(meter.Name);
+
+            if (useViewToOverride)
+            {
+                builder.AddView("MyHistogram", new ExplicitBucketHistogramConfiguration { Boundaries = viewBoundaries });
+            }
+
+            builder.AddInMemoryExporter(exportedItems);
+        });
+
+        var histogram = meter.CreateHistogram<long>(
+            "MyHistogram",
+            unit: null,
+            description: null,
+            tags: null,
+            new()
+            {
+                HistogramBucketBoundaries = adviceBoundaries,
+            });
+
+        histogram.Record(-10);
+        histogram.Record(0);
+        histogram.Record(1);
+        histogram.Record(9);
+        histogram.Record(10);
+        histogram.Record(11);
+        histogram.Record(19);
+        histogram.Record(22);
+
+        meterProvider.ForceFlush(MaxTimeToAllowForFlush);
+        Assert.Single(exportedItems);
+        var metricCustom = exportedItems[0];
+
+        Assert.Equal("MyHistogram", metricCustom.Name);
+
+        List<MetricPoint> metricPointsCustom = new List<MetricPoint>();
+        foreach (ref readonly var mp in metricCustom.GetMetricPoints())
+        {
+            metricPointsCustom.Add(mp);
+        }
+
+        Assert.Single(metricPointsCustom);
+        var histogramPoint = metricPointsCustom[0];
+
+        var count = histogramPoint.GetHistogramCount();
+        var sum = histogramPoint.GetHistogramSum();
+
+        Assert.Equal(62, sum);
+        Assert.Equal(8, count);
+
+        var index = 0;
+        var actualCount = 0;
+        long[] expectedBucketCounts = useViewToOverride ? new long[] { 5, 2, 1 } : new long[] { 3, 2, 2, 1 };
+
+        foreach (var histogramMeasurement in histogramPoint.GetHistogramBuckets())
+        {
+            Assert.Equal(expectedBucketCounts[index], histogramMeasurement.BucketCount);
+            index++;
+            actualCount++;
+        }
+
+        Assert.Equal(useViewToOverride ? viewBoundaries.Length + 1 : adviceBoundaries.Count + 1, actualCount);
+    }
+
     [Fact]
     public void ViewToProduceExponentialHistogram()
     {