[Exporter.Geneva] Skip dispose for ETW singleton of GenevaMetricExporter

src/OpenTelemetry.Exporter.Geneva/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* Fix a bug in `GenevaMetricExporter` where the `MetricEtwDataTransport` singleton
+  is disposed.
+  ([#1537](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/1537))
+
 ## 1.7.0
 
 Released 2023-Dec-11

src/OpenTelemetry.Exporter.Geneva/Metrics/GenevaMetricExporter.cs

@@ -74,7 +74,7 @@ public GenevaMetricExporter(GenevaMetricExporterOptions options)
             case TransportProtocol.Unspecified:
                 if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                 {
-                    this.metricDataTransport = MetricEtwDataTransport.Shared;
+                    this.metricDataTransport = MetricEtwDataTransport.Instance;
                     break;
                 }
                 else
@@ -268,7 +268,12 @@ protected override void Dispose(bool disposing)
         {
             try
             {
-                this.metricDataTransport?.Dispose();
+                // The ETW data transport singleton on Windows should NOT be disposed.
+                // On Linux, Unix Domain Socket is used and should be disposed.
+                if (this.metricDataTransport != MetricEtwDataTransport.Instance)
+                {
+                    this.metricDataTransport.Dispose();
+                }
             }
             catch (Exception ex)
             {

src/OpenTelemetry.Exporter.Geneva/Metrics/Transport/MetricEtwDataTransport.cs

@@ -10,13 +10,9 @@ namespace OpenTelemetry.Exporter.Geneva;
 internal sealed class MetricEtwDataTransport : EventSource, IMetricDataTransport
 {
     private readonly int fixedPayloadEndIndex;
+    private bool isDisposed;
 
-    static MetricEtwDataTransport()
-    {
-        Shared = new();
-    }
-
-    public static readonly MetricEtwDataTransport Shared;
+    public static MetricEtwDataTransport Instance { get; private set; } = new();
 
     private MetricEtwDataTransport()
     {
@@ -57,4 +53,23 @@ private void ExternallyAggregatedDoubleDistributionMetric()
     private void TLVMetricEvent()
     {
     }
+
+    protected override void Dispose(bool disposing)
+    {
+        if (this.isDisposed)
+        {
+            return;
+        }
+
+        if (disposing)
+        {
+            // No managed resources to release.
+            // The singleton instance is kept alive for the lifetime of the application.
+            // Set the instance to null so that future calls to the singleton property can fail explicitly.
+            Instance = null;
+        }
+
+        this.isDisposed = true;
+        base.Dispose(disposing);
+    }
 }

src/OpenTelemetry.Exporter.Geneva/Metrics/Transport/MetricUnixDataTransport.cs

@@ -33,7 +33,7 @@ public void Dispose()
             return;
         }
 
-        this.udsDataTransport?.Dispose();
+        this.udsDataTransport.Dispose();
         this.isDisposed = true;
     }
 }

src/OpenTelemetry.Exporter.Geneva/TLDExporter/TldLogExporter.cs

@@ -160,7 +160,7 @@ public void Dispose()
         try
         {
             // DO NOT Dispose eventBuilder, keyValuePairs, and partCFields as they are static
-            this.eventProvider?.Dispose();
+            this.eventProvider.Dispose();
             this.serializationData?.Dispose();
         }
         catch (Exception ex)

src/OpenTelemetry.Exporter.Geneva/TLDExporter/TldTraceExporter.cs

@@ -153,7 +153,7 @@ public void Dispose()
         try
         {
             // DO NOT Dispose eventBuilder, keyValuePairs, and partCFields as they are static
-            this.eventProvider?.Dispose();
+            this.eventProvider.Dispose();
         }
         catch (Exception ex)
         {

test/OpenTelemetry.Exporter.Geneva.Tests/GenevaMetricExporterTests.cs

@@ -251,6 +251,35 @@ public void SuccessfulExportOnLinux()
         }
     }
 
+    [Fact]
+    public void MultipleCallsOnWindowsReusesSingletonEtwDataTransport()
+    {
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+        {
+            var singleton = MetricEtwDataTransport.Instance;
+            this.EmitMetrics("one");
+            Assert.Equal(singleton, MetricEtwDataTransport.Instance);
+            this.EmitMetrics("two");
+            Assert.Equal(singleton, MetricEtwDataTransport.Instance);
+        }
+    }
+
+    private void EmitMetrics(string attempt)
+    {
+        using var meterProviderBuilder = Sdk.CreateMeterProviderBuilder()
+            .AddMeter("*")
+            .AddGenevaMetricExporter(x =>
+            {
+                x.MetricExportIntervalMilliseconds = 1000;
+                x.ConnectionString = "Account=OTelGeneva;Namespace=MeteringSample";
+            })
+            .Build();
+
+        using var meter = new Meter("MeterName", "0.0.1");
+        var counter = meter.CreateCounter<long>("counter_" + attempt);
+        counter.Add(1);
+    }
+
     [Theory]
     [InlineData(true)]
     [InlineData(false)]