Add support for OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE env…

…ironment variable (#4667)
open-telemetry · Jul 19, 2023 · 4edd9b6 · 4edd9b6
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diff --git a/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md b/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 ## Unreleased
 
+* Added support for configuring the metric exporter's temporality using the
+  environment variable `OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE` as
+  defined in the
+  [specification](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.23.0/specification/metrics/sdk_exporters/otlp.md#additional-configuration).
+  ([#4667](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4667))
+
 ## 1.6.0-alpha.1
 
 Released 2023-Jul-12

diff --git a/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpMetricExporterExtensions.cs b/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpMetricExporterExtensions.cs
@@ -14,6 +14,7 @@
 // limitations under the License.
 // </copyright>
 
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 using OpenTelemetry.Exporter;
@@ -26,6 +27,8 @@ namespace OpenTelemetry.Metrics
     /// </summary>
     public static class OtlpMetricExporterExtensions
     {
+        internal const string OtlpMetricExporterTemporalityPreferenceEnvVarKey = "OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE";
+
         /// <summary>
         /// Adds <see cref="OtlpMetricExporter"/> to the <see cref="MeterProviderBuilder"/> using default options.
         /// </summary>
@@ -69,6 +72,17 @@ public static MeterProviderBuilder AddOtlpExporter(this MeterProviderBuilder bui
                 }
 
                 OtlpExporterOptions.RegisterOtlpExporterOptionsFactory(services);
+
+                services.AddOptions<MetricReaderOptions>(finalOptionsName).Configure<IConfiguration>(
+                    (readerOptions, config) =>
+                    {
+                        var otlpTemporalityPreference = config[OtlpMetricExporterTemporalityPreferenceEnvVarKey];
+                        if (!string.IsNullOrWhiteSpace(otlpTemporalityPreference)
+                            && Enum.TryParse<MetricReaderTemporalityPreference>(otlpTemporalityPreference, ignoreCase: true, out var enumValue))
+                        {
+                            readerOptions.TemporalityPreference = enumValue;
+                        }
+                    });
             });
 
             return builder.AddReader(sp =>
@@ -135,6 +149,17 @@ public static MeterProviderBuilder AddOtlpExporter(this MeterProviderBuilder bui
             builder.ConfigureServices(services =>
             {
                 OtlpExporterOptions.RegisterOtlpExporterOptionsFactory(services);
+
+                services.AddOptions<MetricReaderOptions>(name).Configure<IConfiguration>(
+                    (readerOptions, config) =>
+                    {
+                        var otlpTemporalityPreference = config[OtlpMetricExporterTemporalityPreferenceEnvVarKey];
+                        if (!string.IsNullOrWhiteSpace(otlpTemporalityPreference)
+                            && Enum.TryParse<MetricReaderTemporalityPreference>(otlpTemporalityPreference, ignoreCase: true, out var enumValue))
+                        {
+                            readerOptions.TemporalityPreference = enumValue;
+                        }
+                    });
             });
 
             return builder.AddReader(sp =>

diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMetricsExporterTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMetricsExporterTests.cs
@@ -15,6 +15,8 @@
 // </copyright>
 
 using System.Diagnostics.Metrics;
+using System.Reflection;
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation;
 using OpenTelemetry.Metrics;
@@ -704,6 +706,50 @@ public void TestHistogramToOtlpMetric(string name, string description, string un
             Assert.Empty(dataPoint.Exemplars);
         }
 
+        [Theory]
+        [InlineData("cumulative", MetricReaderTemporalityPreference.Cumulative)]
+        [InlineData("Cumulative", MetricReaderTemporalityPreference.Cumulative)]
+        [InlineData("CUMULATIVE", MetricReaderTemporalityPreference.Cumulative)]
+        [InlineData("delta", MetricReaderTemporalityPreference.Delta)]
+        [InlineData("Delta", MetricReaderTemporalityPreference.Delta)]
+        [InlineData("DELTA", MetricReaderTemporalityPreference.Delta)]
+        public void TestTemporalityPreferenceConfiguration(string configValue, MetricReaderTemporalityPreference expectedTemporality)
+        {
+            var configData = new Dictionary<string, string> { ["OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE"] = configValue };
+            var configuration = new ConfigurationBuilder()
+                .AddInMemoryCollection(configData)
+                .Build();
+
+            // Check for both the code paths:
+            // 1. The final extension method which accepts `Action<OtlpExporterOptions>`.
+            // 2. The final extension method which accepts `Action<OtlpExporterOptions, MetricReaderOptions>`.
+
+            // Test 1st code path
+            using var meterProvider1 = Sdk.CreateMeterProviderBuilder()
+                .ConfigureServices(services => services.AddSingleton<IConfiguration>(configuration))
+                .AddOtlpExporter() // This would in turn call the extension method which accepts `Action<OtlpExporterOptions>`
+                .Build();
+
+            var assembly = typeof(Sdk).Assembly;
+            var type = assembly.GetType("OpenTelemetry.Metrics.MeterProviderSdk");
+            var fieldInfo = type.GetField("reader", BindingFlags.Instance | BindingFlags.NonPublic);
+            var reader = fieldInfo.GetValue(meterProvider1) as MetricReader;
+            var temporality = reader.TemporalityPreference;
+
+            Assert.Equal(expectedTemporality, temporality);
+
+            // Test 2nd code path
+            using var meterProvider2 = Sdk.CreateMeterProviderBuilder()
+                .ConfigureServices(services => services.AddSingleton<IConfiguration>(configuration))
+                .AddOtlpExporter((_, _) => { }) // This would in turn call the extension method which accepts `Action<OtlpExporterOptions, MetricReaderOptions>`
+                .Build();
+
+            reader = fieldInfo.GetValue(meterProvider2) as MetricReader;
+            temporality = reader.TemporalityPreference;
+
+            Assert.Equal(expectedTemporality, temporality);
+        }
+
         private static IEnumerable<KeyValuePair<string, object>> ToAttributes(object[] keysValues)
         {
             var keys = keysValues?.Where((_, index) => index % 2 == 0).ToArray();