Flush the TelemetryChannel when the logger provider is disposed

LOGGING/CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog 
 
+## Version 2.12.0-beta1
+- [ILogger - Flush TelemetryChannel when the ILoggerProvider is Disposed.](https://github.com/microsoft/ApplicationInsights-dotnet/pull/1289)
+
 ## Version 2.11.0
 - Update Base SDK to 2.11.0
 - Update System.Diagnostics.DiagnosticSource to 4.6.0. 

LOGGING/src/ILogger/ApplicationInsightsLoggerOptions.cs

@@ -8,7 +8,6 @@
 namespace Microsoft.Extensions.Logging.ApplicationInsights
 {
     using Microsoft.ApplicationInsights.DataContracts;
-    using Microsoft.Extensions.Logging;
 
     /// <summary>
     /// <see cref="ApplicationInsightsLoggerOptions"/> defines the custom behavior of the tracing information sent to Application Insights.
@@ -26,5 +25,11 @@ public class ApplicationInsightsLoggerOptions
         /// Defaults to true.
         /// </summary>
         public bool IncludeScopes { get; set; } = true;
+
+        /// <summary>
+        /// Gets or sets a value indicating whether to flush telemetry when disposing
+        /// of the logger provider.
+        /// </summary>
+        public bool FlushOnDispose { get; set; } = true;
     }
 }

LOGGING/src/ILogger/ApplicationInsightsLoggerProvider.cs

@@ -8,7 +8,6 @@
 namespace Microsoft.Extensions.Logging.ApplicationInsights
 {
     using System;
-    using System.Collections.Concurrent;
     using Microsoft.ApplicationInsights;
     using Microsoft.ApplicationInsights.Extensibility;
     using Microsoft.ApplicationInsights.Extensibility.Implementation;
@@ -105,7 +104,14 @@ public void SetScopeProvider(IExternalScopeProvider externalScopeProvider)
         /// <param name="releasedManagedResources">Release managed resources.</param>
         protected virtual void Dispose(bool releasedManagedResources)
         {
-            // Nothing to dispose right now.
+            if (releasedManagedResources && this.applicationInsightsLoggerOptions.FlushOnDispose)
+            {
+                this.telemetryClient.Flush();
+
+                // With the ServerTelemetryChannel, Flush pushes buffered telemetry to the Transmitter,
+                // but it doesn't guarantee that all events have been transmitted to the endpoint.
+                // TODO: Should we sleep here? Should that be controlled by options?
+            }
         }
     }
 }

LOGGING/test/ILogger.NetStandard.Tests/ILoggerIntegrationTests.cs

@@ -248,6 +248,39 @@ public void DefaultLoggerOptionsAreCorrectlyRegistered()
             Assert.IsTrue(registeredOptions.Value.IncludeScopes);
         }
 
+        [TestMethod]
+        [TestCategory("ILogger")]
+        public void TelemetryChannelIsFlushedWhenServiceProviderIsDisposed()
+        {
+            TestTelemetryChannel testTelemetryChannel = new TestTelemetryChannel();
+
+            using (ServiceProvider serviceProvider = ILoggerIntegrationTests.SetupApplicationInsightsLoggerIntegration(
+                delegate { },
+                telemetryConfiguration => telemetryConfiguration.TelemetryChannel = testTelemetryChannel))
+            {
+                serviceProvider.GetRequiredService<ILogger<ILoggerIntegrationTests>>();
+            }
+
+            Assert.AreEqual(1, testTelemetryChannel.FlushCount);
+        }
+
+        [TestMethod]
+        [TestCategory("ILogger")]
+        public void TelemetryChannelIsNotFlushedWhenFlushOnDisposeIsFalse()
+        {
+            TestTelemetryChannel testTelemetryChannel = new TestTelemetryChannel();
+
+            using (ServiceProvider serviceProvider = ILoggerIntegrationTests.SetupApplicationInsightsLoggerIntegration(
+                delegate { },
+                telemetryConfiguration => telemetryConfiguration.TelemetryChannel = testTelemetryChannel,
+                applicationInsightsOptions => applicationInsightsOptions.FlushOnDispose = false))
+            {
+                serviceProvider.GetRequiredService<ILogger<ILoggerIntegrationTests>>();
+            }
+
+            Assert.AreEqual(0, testTelemetryChannel.FlushCount);
+        }
+
         /// <summary>
         /// Sets up the Application insights logger.
         /// </summary>
@@ -256,7 +289,7 @@ public void DefaultLoggerOptionsAreCorrectlyRegistered()
         /// <param name="configureApplicationInsightsOptions">Action to configure logger options.</param>
         /// <param name="configureServices">Action to add, configure services to DI container.</param>
         /// <returns>Built DI container.</returns>
-        private static IServiceProvider SetupApplicationInsightsLoggerIntegration(
+        private static ServiceProvider SetupApplicationInsightsLoggerIntegration(
             Action<ITelemetry, ITelemetryProcessor> telemetryActionCallback,
             Action<TelemetryConfiguration> configureTelemetryConfiguration = null,
             Action<ApplicationInsightsLoggerOptions> configureApplicationInsightsOptions = null,
@@ -298,7 +331,7 @@ private static IServiceProvider SetupApplicationInsightsLoggerIntegration(
                 services = configureServices.Invoke(services);
             }
 
-            IServiceProvider serviceProvider = services.BuildServiceProvider();
+            ServiceProvider serviceProvider = services.BuildServiceProvider();
 
             return serviceProvider;
         }

LOGGING/test/ILogger.NetStandard.Tests/TestTelemetryChannel.cs

@@ -0,0 +1,30 @@
+// <copyright file="ILoggerIntegrationTests.cs" company="Microsoft">
+// Copyright © Microsoft. All Rights Reserved.
+// </copyright>
+
+using Microsoft.ApplicationInsights.Channel;
+
+namespace Microsoft.ApplicationInsights
+{
+    internal sealed class TestTelemetryChannel : ITelemetryChannel
+    {
+        public TestTelemetryChannel()
+        {
+        }
+
+        public bool? DeveloperMode { get; set; }
+        public string EndpointAddress { get; set; }
+
+        public void Dispose()
+        {
+        }
+
+        public void Flush() => FlushCount++;
+
+        public void Send(ITelemetry item) => SendCount++;
+
+        public int FlushCount { get; private set; }
+
+        public int SendCount { get; private set; }
+    }
+}