Initial sampling rate from applicationHost.config fix (#1048)

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 This changelog will be used to generate documentation on [release notes page](http://azure.microsoft.com/documentation/articles/app-insights-release-notes-dotnet/).
 
+## Version next:
+- InitialSamplingRate is now correctly applied if set in applicationInsights.config (https://github.com/Microsoft/ApplicationInsights-dotnet/pull/1048)
+
 ## Version 2.9.0-beta3
 - [Flatten IExtension and Unknown ITelemetry implementations for Rich Payload Event Source consumption](https://github.com/Microsoft/ApplicationInsights-dotnet/pull/1017)
 - [Fix: Start/StopOperation with W3C distributed tracing enabled does not track telemetry](https://github.com/Microsoft/ApplicationInsights-dotnet/pull/1031)

Test/ServerTelemetryChannel.Test/Shared.Tests/AdaptiveSamplingTelemetryProcessorTest.cs

@@ -3,6 +3,7 @@
     using System;
     using System.Collections.Generic;
     using System.Diagnostics;
+    using System.Linq;
     using System.Reflection;
     using System.Threading;
 
@@ -13,7 +14,8 @@
     using Microsoft.ApplicationInsights.TestFramework;
     using Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel;
     using Microsoft.VisualStudio.TestTools.UnitTesting;
-
+    using Moq;
+
     [TestClass]
     public class AdaptiveSamplingTelemetryProcessorTest
     {
@@ -295,6 +297,44 @@ public void AdaptiveSamplingSetsExcludedTypesOnInternalSamplingProcessor()
             Assert.AreEqual("request;", internalProcessor.ExcludedTypes);
         }
 
+        [TestMethod]
+        public void CurrentSamplingRateResetsOnInitialSamplingRateChange()
+        {
+            var nextMock = new Mock<ITelemetryProcessor>();
+            var next = nextMock.Object;
+            var adaptiveSamplingProcessor = new AdaptiveSamplingTelemetryProcessor(
+                new Channel.Implementation.SamplingPercentageEstimatorSettings
+                {
+                    InitialSamplingPercentage = 20,
+                },
+                null,
+                next);
+
+            Assert.AreEqual(20, adaptiveSamplingProcessor.InitialSamplingPercentage);
+            Assert.AreEqual(100 / 20, adaptiveSamplingProcessor.SamplingPercentageEstimatorTelemetryProcessor.CurrentSamplingRate);
+
+            // change in InitialSamplingPercentage should change the CurrentSamplingPercentage:
+            adaptiveSamplingProcessor.InitialSamplingPercentage = 50;
+            Assert.AreEqual(50, adaptiveSamplingProcessor.InitialSamplingPercentage);
+            Assert.AreEqual(100 / 50, adaptiveSamplingProcessor.SamplingPercentageEstimatorTelemetryProcessor.CurrentSamplingRate);
+        }
+
+        [TestMethod]
+        public void SettingsFromPassedInTelemetryProcessorsAreAppliedToSamplingTelemetryProcessor()
+        {
+            var nextMock = new Mock<ITelemetryProcessor>();
+            var next = nextMock.Object;
+            var adaptiveSamplingProcessor = new AdaptiveSamplingTelemetryProcessor(
+                new Channel.Implementation.SamplingPercentageEstimatorSettings
+                {
+                    InitialSamplingPercentage = 25,
+                },
+                null,
+                next);
+            var percentageEstimatorProcessor = adaptiveSamplingProcessor.SamplingTelemetryProcessor;
+            Assert.AreEqual(25, percentageEstimatorProcessor.SamplingPercentage);
+        }
+
         private void TraceSamplingPercentageEvaluation(
             double afterSamplingTelemetryItemRatePerSecond,
             double currentSamplingPercentage,

src/ServerTelemetryChannel/AdaptiveSamplingTelemetryProcessor.cs

@@ -57,7 +57,10 @@ public AdaptiveSamplingTelemetryProcessor(
 
             // make estimator telemetry processor  work after sampling was done
             this.estimatorProcessor = new SamplingPercentageEstimatorTelemetryProcessor(settings, this.SamplingPercentageChanged, next);
-            this.samplingProcessor = new SamplingTelemetryProcessor(next, this.estimatorProcessor);
+            this.samplingProcessor = new SamplingTelemetryProcessor(next, this.estimatorProcessor)
+            {
+                SamplingPercentage = this.estimatorSettings.InitialSamplingPercentage
+            };
         }
 
         /// <summary>
@@ -99,6 +102,7 @@ public double InitialSamplingPercentage
                 // note: 'initial' percentage will affect sampling even 
                 // if it was running for a while
                 this.estimatorSettings.InitialSamplingPercentage = value;
+                this.estimatorProcessor.CurrentSamplingRate = this.estimatorSettings.EffectiveInitialSamplingRate;
                 this.samplingProcessor.SamplingPercentage = value;
             }
         }
@@ -221,6 +225,16 @@ public double MovingAverageRatio
             }
         }
 
+        /// <summary>
+        /// Gets sampling telemetry processor.
+        /// </summary>
+        internal SamplingTelemetryProcessor SamplingTelemetryProcessor => this.samplingProcessor;
+
+        /// <summary>
+        /// Gets sampling percentage estimator telemetry processor.
+        /// </summary>
+        internal SamplingPercentageEstimatorTelemetryProcessor SamplingPercentageEstimatorTelemetryProcessor => this.estimatorProcessor;
+
         /// <summary>
         /// Processes telemetry item.
         /// </summary>

src/ServerTelemetryChannel/Implementation/SamplingPercentageEstimatorTelemetryProcessor.cs

@@ -120,6 +120,15 @@ public SamplingPercentageEstimatorTelemetryProcessor(
                 this.evaluationInterval);
         }
 
+        /// <summary>
+        /// Gets or sets current sampling rate.
+        /// </summary>
+        internal int CurrentSamplingRate
+        {
+            get => this.currenSamplingRate;
+            set => this.currenSamplingRate = value;
+        }
+
         /// <summary>
         /// Processes telemetry item.
         /// </summary>