Adaptive Sampler not working as expected

[vishweshbankwar]

• List of NuGet packages and version that you are using:
• "Microsoft.ApplicationInsights.WorkerService" Version="2.21.0"

Describe the bug

Adaptive sampler when used with activities with Recorded flag set to true (in case of OpenTelemetry this could be set via AlwaysOnSampler) results in high number of telemetry records to be ingested compared to activities with the flag set to false
A clear and concise description of what the bug is.

To Reproduce

internal class Program
    {
        static void Main(string[] args)
        {
            TelemetryConfiguration configuration = TelemetryConfiguration.CreateDefault();
            configuration.TelemetryInitializers.Add(new OperationCorrelationTelemetryInitializer());
            configuration.TelemetryChannel = new CustomChannel();
            configuration.InstrumentationKey = "ikey";
            var telemetryClient = new TelemetryClient(configuration);

            // Sampling
            var builder = configuration.DefaultTelemetrySink.TelemetryProcessorChainBuilder;
            builder.UseAdaptiveSampling();
            builder.Build();

            while (true)
            {
                for (int i = 0; i < 10000; i++)
                {
                    Activity act = new Activity("Parent");
                    // uncomment the following line to see more telemetryitems
                    // act.ActivityTraceFlags |= ActivityTraceFlags.Recorded;
                    act.Start();
                    var startTime = DateTime.UtcNow;
                    var timer = System.Diagnostics.Stopwatch.StartNew();
                    timer.Stop();
                    telemetryClient.TrackDependency("myDependencyType", "myDependencyCall", "myDependencyData", startTime, timer.Elapsed, true);

                    act.Stop();
                }
                telemetryClient.Flush();
                Thread.Sleep(1000);
            }
        }
    }

CustomChannel

internal class CustomChannel : ITelemetryChannel
    {
        public bool? DeveloperMode { get; set; } = true;
        public string EndpointAddress { get; set; } = "endpoint";

        static long telemetryCount = 0;

        public void Dispose()
        {
        }

        public void Flush()
        {
            Console.WriteLine("TelemetryCount: " + telemetryCount);
        }

        public void Send(ITelemetry item)
        {
            telemetryCount++;
        }
    }

[vishweshbankwar]

For anyone encountering this, the workaround is to use Fixed rate sampling instead of Adaptive.

[vishweshbankwar]

Beta package is now available with the fix https://www.nuget.org/packages/Microsoft.ApplicationInsights/2.22.0-beta3

[OsmondJiang]

@vishweshbankwar do you know when will this fix be shipped to a stable version?

[TimothyMothra]

Hi @OsmondJiang, we're targeting end of May for the next stable release.

[cijothomas]

Closing as the issue is fixed #2742 (comment)