MetricReader TemporalityPreference

examples/Console/TestMetrics.cs

@@ -71,7 +71,7 @@ internal static object Run(MetricsOptions options)
                         exporterOptions.Protocol = options.UseGrpc ? OtlpExportProtocol.Grpc : OtlpExportProtocol.HttpProtobuf;
 
                         metricReaderOptions.PeriodicExportingMetricReaderOptions.ExportIntervalMilliseconds = options.DefaultCollectionPeriodMilliseconds;
-                        metricReaderOptions.Temporality = options.IsDelta ? AggregationTemporality.Delta : AggregationTemporality.Cumulative;
+                        metricReaderOptions.TemporalityPreference = options.IsDelta ? MetricReaderTemporalityPreference.MonotonicDelta : MetricReaderTemporalityPreference.Cumulative;
                     });
             }
             else
@@ -82,7 +82,7 @@ internal static object Run(MetricsOptions options)
                         exporterOptions.Targets = ConsoleExporterOutputTargets.Console;
 
                         metricReaderOptions.PeriodicExportingMetricReaderOptions.ExportIntervalMilliseconds = options.DefaultCollectionPeriodMilliseconds;
-                        metricReaderOptions.Temporality = options.IsDelta ? AggregationTemporality.Delta : AggregationTemporality.Cumulative;
+                        metricReaderOptions.TemporalityPreference = options.IsDelta ? MetricReaderTemporalityPreference.MonotonicDelta : MetricReaderTemporalityPreference.Cumulative;
                     });
             }
 

src/OpenTelemetry.Exporter.Prometheus/PrometheusExporter.cs

@@ -23,7 +23,6 @@ namespace OpenTelemetry.Exporter
     /// <summary>
     /// Exporter of OpenTelemetry metrics to Prometheus.
     /// </summary>
-    [AggregationTemporality(AggregationTemporality.Cumulative)]
     [ExportModes(ExportModes.Pull)]
     public class PrometheusExporter : BaseExporter<Metric>, IPullMetricExporter
     {

src/OpenTelemetry.Exporter.Prometheus/PrometheusExporterMeterProviderBuilderExtensions.cs

@@ -49,6 +49,7 @@ private static MeterProviderBuilder AddPrometheusExporter(MeterProviderBuilder b
 
             var exporter = new PrometheusExporter(options);
             var reader = new BaseExportingMetricReader(exporter);
+            reader.TemporalityPreference = MetricReaderTemporalityPreference.Cumulative;
 
             return builder.AddReader(reader);
         }

src/OpenTelemetry/.publicApi/net461/PublicAPI.Unshipped.txt

@@ -5,17 +5,14 @@ OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration
 OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration.Boundaries.get -> double[]
 OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration.Boundaries.set -> void
 OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration.ExplicitBucketHistogramConfiguration() -> void
+OpenTelemetry.Metrics.MetricReader.TemporalityPreference.get -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReader.TemporalityPreference.set -> void
 OpenTelemetry.Metrics.MetricReaderOptions
 OpenTelemetry.Metrics.MetricReaderOptions.MetricReaderOptions() -> void
 OpenTelemetry.Metrics.MetricReaderOptions.PeriodicExportingMetricReaderOptions.get -> OpenTelemetry.Metrics.PeriodicExportingMetricReaderOptions
-OpenTelemetry.Metrics.MetricReaderOptions.Temporality.get -> OpenTelemetry.Metrics.AggregationTemporality
-OpenTelemetry.Metrics.MetricReaderOptions.Temporality.set -> void
 OpenTelemetry.Metrics.AggregationTemporality
 OpenTelemetry.Metrics.AggregationTemporality.Cumulative = 1 -> OpenTelemetry.Metrics.AggregationTemporality
 OpenTelemetry.Metrics.AggregationTemporality.Delta = 2 -> OpenTelemetry.Metrics.AggregationTemporality
-OpenTelemetry.Metrics.AggregationTemporalityAttribute
-OpenTelemetry.Metrics.AggregationTemporalityAttribute.AggregationTemporalityAttribute(OpenTelemetry.Metrics.AggregationTemporality temporality) -> void
-OpenTelemetry.Metrics.AggregationTemporalityAttribute.Temporality.get -> OpenTelemetry.Metrics.AggregationTemporality
 OpenTelemetry.Metrics.BaseExportingMetricReader
 OpenTelemetry.Metrics.BaseExportingMetricReader.BaseExportingMetricReader(OpenTelemetry.BaseExporter<OpenTelemetry.Metrics.Metric> exporter) -> void
 OpenTelemetry.Metrics.BaseExportingMetricReader.SupportedExportModes.get -> OpenTelemetry.Metrics.ExportModes
@@ -76,8 +73,11 @@ OpenTelemetry.Metrics.MetricReader.Collect(int timeoutMilliseconds = -1) -> bool
 OpenTelemetry.Metrics.MetricReader.Dispose() -> void
 OpenTelemetry.Metrics.MetricReader.MetricReader() -> void
 OpenTelemetry.Metrics.MetricReader.Shutdown(int timeoutMilliseconds = -1) -> bool
-OpenTelemetry.Metrics.MetricReader.Temporality.get -> OpenTelemetry.Metrics.AggregationTemporality
-OpenTelemetry.Metrics.MetricReader.Temporality.set -> void
+OpenTelemetry.Metrics.MetricReaderOptions.TemporalityPreference.get -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReaderOptions.TemporalityPreference.set -> void
+OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReaderTemporalityPreference.Cumulative = 1 -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReaderTemporalityPreference.MonotonicDelta = 2 -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
 OpenTelemetry.Metrics.MetricStreamConfiguration
 OpenTelemetry.Metrics.MetricStreamConfiguration.Description.get -> string
 OpenTelemetry.Metrics.MetricStreamConfiguration.Description.set -> void

src/OpenTelemetry/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt

@@ -5,17 +5,14 @@ OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration
 OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration.Boundaries.get -> double[]
 OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration.Boundaries.set -> void
 OpenTelemetry.Metrics.ExplicitBucketHistogramConfiguration.ExplicitBucketHistogramConfiguration() -> void
+OpenTelemetry.Metrics.MetricReader.TemporalityPreference.get -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReader.TemporalityPreference.set -> void
 OpenTelemetry.Metrics.MetricReaderOptions
 OpenTelemetry.Metrics.MetricReaderOptions.MetricReaderOptions() -> void
 OpenTelemetry.Metrics.MetricReaderOptions.PeriodicExportingMetricReaderOptions.get -> OpenTelemetry.Metrics.PeriodicExportingMetricReaderOptions
-OpenTelemetry.Metrics.MetricReaderOptions.Temporality.get -> OpenTelemetry.Metrics.AggregationTemporality
-OpenTelemetry.Metrics.MetricReaderOptions.Temporality.set -> void
 OpenTelemetry.Metrics.AggregationTemporality
 OpenTelemetry.Metrics.AggregationTemporality.Cumulative = 1 -> OpenTelemetry.Metrics.AggregationTemporality
 OpenTelemetry.Metrics.AggregationTemporality.Delta = 2 -> OpenTelemetry.Metrics.AggregationTemporality
-OpenTelemetry.Metrics.AggregationTemporalityAttribute
-OpenTelemetry.Metrics.AggregationTemporalityAttribute.AggregationTemporalityAttribute(OpenTelemetry.Metrics.AggregationTemporality temporality) -> void
-OpenTelemetry.Metrics.AggregationTemporalityAttribute.Temporality.get -> OpenTelemetry.Metrics.AggregationTemporality
 OpenTelemetry.Metrics.BaseExportingMetricReader
 OpenTelemetry.Metrics.BaseExportingMetricReader.BaseExportingMetricReader(OpenTelemetry.BaseExporter<OpenTelemetry.Metrics.Metric> exporter) -> void
 OpenTelemetry.Metrics.BaseExportingMetricReader.SupportedExportModes.get -> OpenTelemetry.Metrics.ExportModes
@@ -76,8 +73,11 @@ OpenTelemetry.Metrics.MetricReader.Collect(int timeoutMilliseconds = -1) -> bool
 OpenTelemetry.Metrics.MetricReader.Dispose() -> void
 OpenTelemetry.Metrics.MetricReader.MetricReader() -> void
 OpenTelemetry.Metrics.MetricReader.Shutdown(int timeoutMilliseconds = -1) -> bool
-OpenTelemetry.Metrics.MetricReader.Temporality.get -> OpenTelemetry.Metrics.AggregationTemporality
-OpenTelemetry.Metrics.MetricReader.Temporality.set -> void
+OpenTelemetry.Metrics.MetricReaderOptions.TemporalityPreference.get -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReaderOptions.TemporalityPreference.set -> void
+OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReaderTemporalityPreference.Cumulative = 1 -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
+OpenTelemetry.Metrics.MetricReaderTemporalityPreference.MonotonicDelta = 2 -> OpenTelemetry.Metrics.MetricReaderTemporalityPreference
 OpenTelemetry.Metrics.MetricStreamConfiguration
 OpenTelemetry.Metrics.MetricStreamConfiguration.Description.get -> string
 OpenTelemetry.Metrics.MetricStreamConfiguration.Description.set -> void

src/OpenTelemetry/Internal/PeriodicExportingMetricReaderHelper.cs

@@ -34,7 +34,7 @@ internal static PeriodicExportingMetricReader CreatePeriodicExportingMetricReade
 
         var metricReader = new PeriodicExportingMetricReader(exporter, exportInterval, exportTimeout)
         {
-            Temporality = options.Temporality,
+            TemporalityPreference = options.TemporalityPreference,
         };
 
         return metricReader;

src/OpenTelemetry/Metrics/BaseExportingMetricReader.cs

@@ -45,14 +45,7 @@ public BaseExportingMetricReader(BaseExporter<Metric> exporter)
             this.exporter = exporter;
 
             var exportorType = exporter.GetType();
-            var attributes = exportorType.GetCustomAttributes(typeof(AggregationTemporalityAttribute), true);
-            if (attributes.Length > 0)
-            {
-                var attr = (AggregationTemporalityAttribute)attributes[attributes.Length - 1];
-                this.Temporality = attr.Temporality;
-            }
-
-            attributes = exportorType.GetCustomAttributes(typeof(ExportModesAttribute), true);
+            var attributes = exportorType.GetCustomAttributes(typeof(ExportModesAttribute), true);
             if (attributes.Length > 0)
             {
                 var attr = (ExportModesAttribute)attributes[attributes.Length - 1];

src/OpenTelemetry/Metrics/MetricReader.cs

@@ -16,6 +16,7 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.Metrics;
 using System.Threading;
 using System.Threading.Tasks;
 using OpenTelemetry.Internal;
@@ -27,35 +28,74 @@ namespace OpenTelemetry.Metrics
     /// </summary>
     public abstract partial class MetricReader : IDisposable
     {
-        private const AggregationTemporality AggregationTemporalityUnspecified = (AggregationTemporality)0;
+        private const MetricReaderTemporalityPreference MetricReaderTemporalityPreferenceUnspecified = (MetricReaderTemporalityPreference)0;
+
+        private static Func<Type, AggregationTemporality> cumulativeTemporatlityPreferenceFunc =
+            (instrumentType) => AggregationTemporality.Cumulative;
+
+        private static Func<Type, AggregationTemporality> monotonicDeltaTemporatlityPreferenceFunc = (instrumentType) =>
+        {
+            return instrumentType.GetGenericTypeDefinition() switch
+            {
+                var type when type == typeof(Counter<>) => AggregationTemporality.Delta,
+                var type when type == typeof(ObservableCounter<>) => AggregationTemporality.Delta,
+                var type when type == typeof(Histogram<>) => AggregationTemporality.Delta,
+
+                // Temporatlity is not defined for gauges, so this does not really affect anything.
+                var type when type == typeof(ObservableGauge<>) => AggregationTemporality.Delta,
+
+                // With .NET 7 the OpenTelemetry .NET SDK will support UpDownCounters.
+                // These will be aggregated using Cumulative temporatlity.
+                // See:
+                //    https://docs.microsoft.com/dotnet/api/system.diagnostics.metrics.updowncounter-1
+                //    https://docs.microsoft.com/dotnet/api/system.diagnostics.metrics.observableupdowncounter-1
+                // var type when type == typeof(UpDownCounter<>) => AggregationTemporality.Cumulative,
+                // var type when type == typeof(ObservableUpDownCounter<>) => AggregationTemporality.Cumulative,
+
+                // TODO: Consider logging here because we should not fall through to this case.
+                _ => AggregationTemporality.Delta,
+            };
+        };
+
         private readonly object newTaskLock = new();
         private readonly object onCollectLock = new();
         private readonly TaskCompletionSource<bool> shutdownTcs = new();
-        private AggregationTemporality temporality = AggregationTemporalityUnspecified;
+        private MetricReaderTemporalityPreference temporalityPreference = MetricReaderTemporalityPreferenceUnspecified;
+        private Func<Type, AggregationTemporality> temporatlityFunc = cumulativeTemporatlityPreferenceFunc;
         private int shutdownCount;
         private TaskCompletionSource<bool> collectionTcs;
         private BaseProvider parentProvider;
 
-        public AggregationTemporality Temporality
+        public MetricReaderTemporalityPreference TemporalityPreference
         {
             get
             {
-                if (this.temporality == AggregationTemporalityUnspecified)
+                if (this.temporalityPreference == MetricReaderTemporalityPreferenceUnspecified)
                 {
-                    this.temporality = AggregationTemporality.Cumulative;
+                    this.temporalityPreference = MetricReaderTemporalityPreference.Cumulative;
                 }
 
-                return this.temporality;
+                return this.temporalityPreference;
             }
 
             set
             {
-                if (this.temporality != AggregationTemporalityUnspecified)
+                if (this.temporalityPreference != MetricReaderTemporalityPreferenceUnspecified)
                 {
-                    throw new NotSupportedException($"The temporality cannot be modified (the current value is {this.temporality}).");
+                    throw new NotSupportedException($"The temporality preference cannot be modified (the current value is {this.temporalityPreference}).");
                 }
 
-                this.temporality = value;
+                this.temporalityPreference = value;
+                switch (value)
+                {
+                    case MetricReaderTemporalityPreference.MonotonicDelta:
+                        this.temporatlityFunc = monotonicDeltaTemporatlityPreferenceFunc;
+                        break;
+                    case MetricReaderTemporalityPreference.Cumulative:
+                    default:
+                        this.temporatlityFunc = cumulativeTemporatlityPreferenceFunc;
+                        break;
+                }
             }
         }
 

src/OpenTelemetry/Metrics/MetricReaderExt.cs

@@ -36,6 +36,11 @@ public abstract partial class MetricReader
         private Metric[] metricsCurrentBatch;
         private int metricIndex = -1;
 
+        internal AggregationTemporality GetAggregationTemporality(Type instrumentType)
+        {
+            return this.temporatlityFunc(instrumentType);
+        }
+
         internal Metric AddMetricWithNoViews(Instrument instrument)
         {
             var meterName = instrument.Meter.Name;
@@ -70,7 +75,7 @@ internal Metric AddMetricWithNoViews(Instrument instrument)
                     Metric metric = null;
                     try
                     {
-                        metric = new Metric(metricStreamIdentity, this.Temporality, this.maxMetricPointsPerMetricStream);
+                        metric = new Metric(metricStreamIdentity, this.GetAggregationTemporality(metricStreamIdentity.InstrumentType), this.maxMetricPointsPerMetricStream);
                     }
                     catch (NotSupportedException nse)
                     {
@@ -170,7 +175,7 @@ internal List<Metric> AddMetricsListWithViews(Instrument instrument, List<Metric
                     else
                     {
                         Metric metric;
-                        metric = new Metric(metricStreamIdentity, this.Temporality, this.maxMetricPointsPerMetricStream, histogramBucketBounds, tagKeysInteresting);
+                        metric = new Metric(metricStreamIdentity, this.GetAggregationTemporality(metricStreamIdentity.InstrumentType), this.maxMetricPointsPerMetricStream, histogramBucketBounds, tagKeysInteresting);
 
                         this.instrumentIdentityToMetric[metricStreamIdentity] = metric;
                         this.metrics[index] = metric;

src/OpenTelemetry/Metrics/MetricReaderOptions.cs

@@ -22,10 +22,9 @@ namespace OpenTelemetry.Metrics;
 public class MetricReaderOptions
 {
     /// <summary>
-    /// Gets or sets the AggregationTemporality used for Histogram
-    /// and Sum metrics.
+    /// Gets or sets the <see cref="MetricReaderTemporalityPreference" />.
     /// </summary>
-    public AggregationTemporality Temporality { get; set; } = AggregationTemporality.Cumulative;
+    public MetricReaderTemporalityPreference TemporalityPreference { get; set; } = MetricReaderTemporalityPreference.Cumulative;
 
     /// <summary>
     /// Gets the <see cref="PeriodicExportingMetricReaderOptions" /> options.

src/OpenTelemetry/Metrics/MetricReaderTemporalityPreference.cs

@@ -0,0 +1,35 @@
+// <copyright file="MetricReaderTemporalityPreference.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+namespace OpenTelemetry.Metrics;
+
+/// <summary>
+/// Defines the behavior of a <see cref="MetricReader" />
+/// with respect to <see cref="AggregationTemporality" />.
+/// </summary>
+public enum MetricReaderTemporalityPreference
+{
+    /// <summary>
+    /// All aggregations are performed using cumulative temporatlity.
+    /// </summary>
+    Cumulative = 1,
+
+    /// <summary>
+    /// All measurements that are monotnic in nature are aggregated using delta temporality.
+    /// Aggregations of non-monotonic measurements use cumulative temporality.
+    /// </summary>
+    MonotonicDelta = 2,
+}

test/Benchmarks/Metrics/MetricCollectBenchmarks.cs

@@ -88,7 +88,7 @@ void ProcessExport(Batch<Metric> batch)
 
             this.reader = new BaseExportingMetricReader(metricExporter)
             {
-                Temporality = AggregationTemporality.Cumulative,
+                TemporalityPreference = MetricReaderTemporalityPreference.Cumulative,
             };
 
             this.meter = new Meter(Utils.GetCurrentMethodName());