NLog Target support ConnectionString with isolated TelemetryClient

.publicApi/Microsoft.ApplicationInsights.NLogTarget.dll/net452/PublicAPI.Shipped.txt

@@ -3,6 +3,8 @@ Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ApplicationIn
 Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ContextProperties.get -> System.Collections.Generic.IList<Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext>
 Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.InstrumentationKey.get -> string
 Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.InstrumentationKey.set -> void
+Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ConnectionString.get -> string
+Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ConnectionString.set -> void
 Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext
 Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext.Layout.get -> NLog.Layouts.Layout
 Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext.Layout.set -> void

.publicApi/Microsoft.ApplicationInsights.NLogTarget.dll/netstandard2.0/PublicAPI.Shipped.txt

@@ -3,6 +3,8 @@ Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ApplicationIn
 Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ContextProperties.get -> System.Collections.Generic.IList<Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext>
 Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.InstrumentationKey.get -> string
 Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.InstrumentationKey.set -> void
+Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ConnectionString.get -> string
+Microsoft.ApplicationInsights.NLogTarget.ApplicationInsightsTarget.ConnectionString.set -> void
 Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext
 Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext.Layout.get -> NLog.Layouts.Layout
 Microsoft.ApplicationInsights.NLogTarget.TargetPropertyWithContext.Layout.set -> void

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## VNext
 - [Populate required field Message with "n/a" if it is empty](https://github.com/microsoft/ApplicationInsights-dotnet/issues/1066)
+- [NLog Target with support for specifying ConnectionString](https://github.com/microsoft/ApplicationInsights-dotnet/issues/2897)
 
 ## Version 2.22.0
 - no changes since beta.

LOGGING/README.md

@@ -37,7 +37,26 @@ Application Insights NLog Target nuget package adds ApplicationInsights target i
 
 If your application does not have web.config then it can also be configured manually.
 
- * **Configure ApplicationInsightsTarget using NLog.config** :
+* **Configure ApplicationInsightsTarget with ConnectionString using NLog.config** :
+ConnectionString is the preferred approach to write logs into Application Insights. If the NLog Application Insights target has connectionString in the config file then TelemetryClient will use it, otherwise it will use the instrumentationKey.
+
+```xml
+<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <extensions>
+		<add assembly="Microsoft.ApplicationInsights.NLogTarget" />
+    </extensions>
+	<targets>
+		<target xsi:type="ApplicationInsightsTarget" name="aiTarget">
+			<connectionString>Your_ApplicationInsights_ConnectionString</connectionString>	<!-- Only required if not using ApplicationInsights.config -->
+			<contextproperty name="threadid" layout="${threadid}" />	<!-- Can be repeated with more context -->
+		</target>
+	</targets>
+	<rules>
+		<logger name="*" minlevel="Trace" writeTo="aiTarget" />
+	</rules>
+</nlog>
+```
+  * **Configure ApplicationInsightsTarget using NLog.config** :
 
 ```xml
 <nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
@@ -70,6 +89,10 @@ For more information see:
 
 
 ```csharp
+// You need this only if you did not define ConnectionString or InstrumentationKey in ApplicationInsights.config (Or in the NLog.config)
+TelemetryConfiguration.Active.ConnectionString = "Your_ApplicationInsights_ConnectionString";
+
+or 
 // You need this only if you did not define InstrumentationKey in ApplicationInsights.config (Or in the NLog.config)
 TelemetryConfiguration.Active.InstrumentationKey = "Your_Resource_Key";
 
@@ -85,6 +108,9 @@ If you configure NLog programmatically with the [NLog Config API](https://github
 var config = new LoggingConfiguration();
 
 ApplicationInsightsTarget target = new ApplicationInsightsTarget();
+// You need this only if you did not define Application Insights ConnectionString in ApplicationInsights.config or want to use different connectionstring
+target.ConnectionString = "Your_ApplicationInsights_ConnectionString";
+or
 // You need this only if you did not define InstrumentationKey in ApplicationInsights.config or want to use different instrumentation key
 target.InstrumentationKey = "Your_Resource_Key";
 

LOGGING/src/NLogTarget/ApplicationInsightsTarget.cs

@@ -13,6 +13,7 @@ namespace Microsoft.ApplicationInsights.NLogTarget
 
     using Microsoft.ApplicationInsights.Channel;
     using Microsoft.ApplicationInsights.DataContracts;
+    using Microsoft.ApplicationInsights.Extensibility;
     using Microsoft.ApplicationInsights.Extensibility.Implementation;
     using Microsoft.ApplicationInsights.Implementation;
 
@@ -29,8 +30,9 @@ namespace Microsoft.ApplicationInsights.NLogTarget
     public sealed class ApplicationInsightsTarget : TargetWithLayout
     {
         private TelemetryClient telemetryClient;
-        private DateTime lastLogEventTime;
+        private TelemetryConfiguration telemetryConfiguration;
         private NLog.Layouts.Layout instrumentationKeyLayout = string.Empty;
+        private NLog.Layouts.Layout connectionStringLayout = string.Empty;
 
         /// <summary>
         /// Initializers a new instance of ApplicationInsightsTarget type.
@@ -50,19 +52,25 @@ public string InstrumentationKey
             set => this.instrumentationKeyLayout = value ?? string.Empty;
         }
 
+        /// <summary>
+        /// Gets or sets the Application Insights connectionstring for your application.
+        /// </summary>
+        public string ConnectionString
+        {
+            get => (this.connectionStringLayout as NLog.Layouts.SimpleLayout)?.Text ?? null;
+            set => this.connectionStringLayout = value ?? string.Empty;
+        }
+
         /// <summary>
         /// Gets the array of custom attributes to be passed into the logevent context.
         /// </summary>
         [ArrayParameter(typeof(TargetPropertyWithContext), "contextproperty")]
         public IList<TargetPropertyWithContext> ContextProperties { get; } = new List<TargetPropertyWithContext>();
 
         /// <summary>
-        /// Gets the logging controller we will be using.
+        /// Gets or sets the factory for creating TelemetryConfiguration, so unit-tests can override in-memory-channel.
         /// </summary>
-        internal TelemetryClient TelemetryClient
-        {
-            get { return this.telemetryClient; }
-        }
+        internal Func<TelemetryConfiguration> TelemetryConfigurationFactory { get; set; }
 
         internal void BuildPropertyBag(LogEventInfo logEvent, ITelemetry trace)
         {
@@ -108,25 +116,49 @@ internal void BuildPropertyBag(LogEventInfo logEvent, ITelemetry trace)
         }
 
         /// <summary>
-        /// Initializes the Target and perform instrumentationKey validation.
+        /// Initializes the Target and configures TelemetryClient.
         /// </summary>
-        /// <exception cref="NLogConfigurationException">Will throw when <see cref="InstrumentationKey"/> is not set.</exception>
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Reliability", "CA2000:DisposeObjectsBeforeLosingScope", Justification = "ApplicationInsightsTarget class handles ownership of TelemetryConfiguration with Dispose.")]
         protected override void InitializeTarget()
         {
             base.InitializeTarget();
-#pragma warning disable CS0618 // Type or member is obsolete: TelemtryConfiguration.Active is used in TelemetryClient constructor.
-            this.telemetryClient = new TelemetryClient();
-#pragma warning restore CS0618 // Type or member is obsolete
 
-            string instrumentationKey = this.instrumentationKeyLayout.Render(LogEventInfo.CreateNullEvent());
-            if (!string.IsNullOrWhiteSpace(instrumentationKey))
+            string connectionString = this.connectionStringLayout.Render(LogEventInfo.CreateNullEvent());
+
+            // Check if nlog application insights target has connectionstring in config file then
+            // configure new telemetryclient with the connectionstring otherwise using legacy instrumentationkey.
+            if (!string.IsNullOrWhiteSpace(connectionString))
             {
-                this.telemetryClient.Context.InstrumentationKey = instrumentationKey;
+                this.telemetryConfiguration = this.TelemetryConfigurationFactory?.Invoke() ?? TelemetryConfiguration.CreateDefault();
+                this.telemetryConfiguration.ConnectionString = connectionString;
+                this.telemetryClient = new TelemetryClient(this.telemetryConfiguration);
+            }
+            else
+            {
+#pragma warning disable CS0618 // Type or member is obsolete: TelemtryConfiguration.Active is used in TelemetryClient constructor.
+                this.telemetryClient = new TelemetryClient();
+#pragma warning restore CS0618 // Type or member is obsolete
+                string instrumentationKey = this.instrumentationKeyLayout.Render(LogEventInfo.CreateNullEvent());
+                if (!string.IsNullOrWhiteSpace(instrumentationKey))
+                {
+                    this.telemetryClient.Context.InstrumentationKey = instrumentationKey;
+                }
             }
 
             this.telemetryClient.Context.GetInternalContext().SdkVersion = SdkVersionUtils.GetSdkVersion("nlog:");
         }
 
+        /// <summary>
+        /// Closes the target and releases resources used by the current instance of the <see cref="ApplicationInsightsTarget"/> class.
+        /// </summary>
+        protected override void CloseTarget()
+        {
+            this.telemetryConfiguration?.Dispose();
+            this.telemetryConfiguration = null;
+
+            base.CloseTarget();
+        }
+
         /// <summary>
         /// Send the log message to Application Insights.
         /// </summary>
@@ -138,8 +170,6 @@ protected override void Write(LogEventInfo logEvent)
                 throw new ArgumentNullException(nameof(logEvent));
             }
 
-            this.lastLogEventTime = DateTime.UtcNow;
-
             if (logEvent.Exception != null)
             {
                 this.SendException(logEvent);
@@ -163,25 +193,29 @@ protected override void FlushAsync(AsyncContinuation asyncContinuation)
 
             try
             {
-                this.TelemetryClient.Flush();
-                if (DateTime.UtcNow.AddSeconds(-30) > this.lastLogEventTime)
-                {
-                    // Nothing has been written, so nothing to wait for
-                    asyncContinuation(null);
-                }
-                else
-                {
-                    // Documentation says it is important to wait after flush, else nothing will happen
-                    // https://docs.microsoft.com/azure/application-insights/app-insights-api-custom-events-metrics#flushing-data
-                    System.Threading.Tasks.Task.Delay(TimeSpan.FromMilliseconds(500)).ContinueWith((task) => asyncContinuation(null));
-                }
+                this.telemetryClient.FlushAsync(System.Threading.CancellationToken.None).ContinueWith(t => asyncContinuation(t.Exception));
             }
             catch (Exception ex)
             {
                 asyncContinuation(ex);
             }
         }
 
+        /// <summary>
+        /// Releases resources used by the current instance of the <see cref="ApplicationInsightsTarget"/> class.
+        /// </summary>
+        /// <param name="disposing">Dispose managed state (managed objects).</param>
+        protected override void Dispose(bool disposing)
+        {
+            base.Dispose(disposing);
+
+            if (disposing)
+            {
+                this.telemetryConfiguration?.Dispose();
+                this.telemetryConfiguration = null;
+            }
+        }
+
         private static void LoadLogEventProperties(LogEventInfo logEvent, IDictionary<string, string> propertyBag)
         {
             if (logEvent.Properties?.Count > 0)

LOGGING/test/NLogTarget.Tests/NLogTargetTests.cs

@@ -230,7 +230,7 @@ public void TraceHasCustomProperties()
         }
 
 
-    [TestMethod]
+        [TestMethod]
         [TestCategory("NLogTarget")]
         public void GlobalDiagnosticContextPropertiesAreAddedToProperties()
         {
@@ -455,8 +455,14 @@ public void NLogTargetFlushesTelemetryClient()
             NLog.Common.AsyncContinuation asyncContinuation = (ex) => { flushException = ex; flushEvent.Set(); };
             aiLogger.Factory.Flush(asyncContinuation, 5000);
             Assert.IsTrue(flushEvent.WaitOne(5000));
-            Assert.IsNotNull(flushException);
-            Assert.AreEqual("Flush called", flushException.Message);
+        }
+
+        [TestMethod]
+        [TestCategory("NLogTarget")]
+        public void NLogTargetWithConnectionString()
+        {
+            var aiLogger = this.CreateTargetWithGivenConnectionString("TestAI");
+            VerifyMessagesInMockChannel(aiLogger, "TestAI");
         }
 
         private void VerifyMessagesInMockChannel(Logger aiLogger, string instrumentationKey)
@@ -504,5 +510,34 @@ private Logger CreateTargetWithGivenInstrumentationKey(
 
             return aiLogger;
         }
+
+        private Logger CreateTargetWithGivenConnectionString(
+            string instrumentationKey = "TEST",
+            Action<Logger> loggerAction = null)
+        {
+            ApplicationInsightsTarget target = new ApplicationInsightsTarget
+            {
+                ConnectionString = $"InstrumentationKey={instrumentationKey};IngestionEndpoint=https://localhost/;LiveEndpoint=https://localhost/"
+            };
+
+            target.TelemetryConfigurationFactory = () => new TelemetryConfiguration() { TelemetryChannel = this.adapterHelper.Channel };
+
+            LoggingRule rule = new LoggingRule("*", LogLevel.Trace, target);
+            LoggingConfiguration config = new LoggingConfiguration();
+            config.AddTarget("AITarget", target);
+            config.LoggingRules.Add(rule);
+
+            LogManager.Configuration = config;
+            Logger aiLogger = LogManager.GetLogger("AITarget");
+
+            if (loggerAction != null)
+            {
+                loggerAction(aiLogger);
+                target.Dispose();
+                return null;
+            }
+
+            return aiLogger;
+        }
     }
 }