[sdk-metrics] Include Meter.Tags in metric identity resolution

src/OpenTelemetry/CHANGELOG.md

@@ -6,6 +6,12 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+* [Meter.Tags](https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.metrics.meter.tags?view=net-9.0)
+  will now be considered when resolving the SDK metric to update when
+  measurements are recorded. Meters with the same name and different tags will
+  now lead to unique metrics.
+  ([#5982](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5982))
+
 ## 1.11.0-rc.1
 
 Released 2024-Dec-11

src/OpenTelemetry/Metrics/Metric.cs

@@ -234,7 +234,7 @@ internal Metric(
     /// <summary>
     /// Gets the attributes (tags) for the metric stream.
     /// </summary>
-    public IEnumerable<KeyValuePair<string, object?>>? MeterTags => this.InstrumentIdentity.MeterTags;
+    public IEnumerable<KeyValuePair<string, object?>>? MeterTags => this.InstrumentIdentity.MeterTags?.KeyValuePairs;
 
     /// <summary>
     /// Gets the <see cref="MetricStreamIdentity"/> for the metric stream.

src/OpenTelemetry/Metrics/MetricStreamIdentity.cs

@@ -14,7 +14,7 @@ public MetricStreamIdentity(Instrument instrument, MetricStreamConfiguration? me
     {
         this.MeterName = instrument.Meter.Name;
         this.MeterVersion = instrument.Meter.Version ?? string.Empty;
-        this.MeterTags = instrument.Meter.Tags;
+        this.MeterTags = instrument.Meter.Tags != null ? new Tags(instrument.Meter.Tags.ToArray()) : null;
         this.InstrumentName = metricStreamConfiguration?.Name ?? instrument.Name;
         this.Unit = instrument.Unit ?? string.Empty;
         this.Description = metricStreamConfiguration?.Description ?? instrument.Description ?? string.Empty;
@@ -32,6 +32,7 @@ public MetricStreamIdentity(Instrument instrument, MetricStreamConfiguration? me
         hashCode.Add(this.InstrumentType);
         hashCode.Add(this.MeterName);
         hashCode.Add(this.MeterVersion);
+        hashCode.Add(this.MeterTags);
         hashCode.Add(this.InstrumentName);
         hashCode.Add(this.HistogramRecordMinMax);
         hashCode.Add(this.Unit);
@@ -63,8 +64,7 @@ public MetricStreamIdentity(Instrument instrument, MetricStreamConfiguration? me
             hash = (hash * 31) + this.InstrumentType.GetHashCode();
             hash = (hash * 31) + this.MeterName.GetHashCode();
             hash = (hash * 31) + this.MeterVersion.GetHashCode();
-
-            // MeterTags is not part of identity, so not included here.
+            hash = (hash * 31) + this.MeterTags?.GetHashCode() ?? 0;
             hash = (hash * 31) + this.InstrumentName.GetHashCode();
             hash = (hash * 31) + this.HistogramRecordMinMax.GetHashCode();
             hash = (hash * 31) + this.ExponentialHistogramMaxSize.GetHashCode();
@@ -91,7 +91,7 @@ public MetricStreamIdentity(Instrument instrument, MetricStreamConfiguration? me
 
     public string MeterVersion { get; }
 
-    public IEnumerable<KeyValuePair<string, object?>>? MeterTags { get; }
+    public Tags? MeterTags { get; }
 
     public string InstrumentName { get; }
 
@@ -141,6 +141,7 @@ public bool Equals(MetricStreamIdentity other)
             && this.Unit == other.Unit
             && this.Description == other.Description
             && this.ViewId == other.ViewId
+            && this.MeterTags == other.MeterTags
             && this.HistogramRecordMinMax == other.HistogramRecordMinMax
             && this.ExponentialHistogramMaxSize == other.ExponentialHistogramMaxSize
             && this.ExponentialHistogramMaxScale == other.ExponentialHistogramMaxScale

test/OpenTelemetry.Tests/Metrics/MetricApiTests.cs

@@ -192,11 +192,10 @@ public void MetricInstrumentationScopeIsExportedCorrectly()
     }
 
     [Fact]
-    public void MetricInstrumentationScopeAttributesAreNotTreatedAsIdentifyingProperty()
+    public void MetricInstrumentationScopeAttributesAreTreatedAsIdentifyingProperty()
     {
         // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#get-a-meter
-        // Meters are identified by name, version, and schema_url fields
-        // and not with tags.
+        // Meters are identified by name, version, meter tags and schema_url fields.
         var exportedItems = new List<Metric>();
         var meterName = "MyMeter";
         var meterVersion = "1.0";
@@ -224,19 +223,16 @@ public void MetricInstrumentationScopeAttributesAreNotTreatedAsIdentifyingProper
         counter2.Add(15);
         meterProvider.ForceFlush(MaxTimeToAllowForFlush);
 
-        // The instruments differ only in the Meter.Tags, which is not an identifying property.
-        // The first instrument's Meter.Tags is exported.
-        // It is considered a user-error to create Meters with same name,version but with
-        // different tags. TODO: See if we can emit an internal log about this.
-        Assert.Single(exportedItems);
-        var metric = exportedItems[0];
-        Assert.Equal(meterName, metric.MeterName);
-        Assert.Equal(meterVersion, metric.MeterVersion);
+        Assert.Equal(2, exportedItems.Count);
 
-        Assert.NotNull(metric.MeterTags);
+        bool TagComparator(KeyValuePair<string, object?> lhs, KeyValuePair<string, object?> rhs)
+        {
+            return lhs.Key.Equals(rhs.Key) && lhs.Value!.GetHashCode().Equals(rhs.Value!.GetHashCode());
+        }
 
-        Assert.Single(metric.MeterTags.Where(kvp => kvp.Key == meterTags1[0].Key && kvp.Value == meterTags1[0].Value));
-        Assert.DoesNotContain(metric.MeterTags, kvp => kvp.Key == meterTags2[0].Key && kvp.Value == meterTags2[0].Value);
+        var metric = exportedItems.First(m => TagComparator(m.MeterTags!.First(), meterTags1!.First()));
+        Assert.Equal(meterName, metric.MeterName);
+        Assert.Equal(meterVersion, metric.MeterVersion);
 
         List<MetricPoint> metricPoints = new List<MetricPoint>();
         foreach (ref readonly var mp in metric.GetMetricPoints())
@@ -246,7 +242,21 @@ public void MetricInstrumentationScopeAttributesAreNotTreatedAsIdentifyingProper
 
         Assert.Single(metricPoints);
         var metricPoint1 = metricPoints[0];
-        Assert.Equal(25, metricPoint1.GetSumLong());
+        Assert.Equal(10, metricPoint1.GetSumLong());
+
+        metric = exportedItems.First(m => TagComparator(m.MeterTags!.First(), meterTags2!.First()));
+        Assert.Equal(meterName, metric.MeterName);
+        Assert.Equal(meterVersion, metric.MeterVersion);
+
+        metricPoints = new List<MetricPoint>();
+        foreach (ref readonly var mp in metric.GetMetricPoints())
+        {
+            metricPoints.Add(mp);
+        }
+
+        Assert.Single(metricPoints);
+        metricPoint1 = metricPoints[0];
+        Assert.Equal(15, metricPoint1.GetSumLong());
     }
 
     [Fact]