[QUERY] How to ignore / drop HealthCheck request samples in Application Insights

[dhayanands]

Library name and version

Azure.Monitor.OpenTelemetry.Exporter 1.3.0

Query/Question

Hi Team,

How to drop the samples of health check requests or ignore them when using Azure Monitor Open Telemetry.

using functions .Net 8 Isolated Model and packages Azure.Monitor.OpenTelemetry.Exporter --version 1.3.0 & Microsoft.ApplicationInsights --version 2.22.0

Below are the configurations updated a bit based on LINK

{
    public class HealthCheck : IHealthCheck
    {
        public static readonly HealthCheck _healthCheck = new HealthCheck();

        public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
        {
            return Task.FromResult(HealthCheckResult.Healthy());
        }

        [Function("HealthCheck")]
        public static async Task<IActionResult> HealthCheckStatus(
                [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "health")] HttpRequest req, FunctionContext context)
        {
            var healthContext = new HealthCheckContext();
            var healthStatus = await _healthCheck.CheckHealthAsync(healthContext);
            return new OkObjectResult(Enum.GetName(typeof(HealthStatus), healthStatus.Status));
        }
    }

    public class CustomTelemetryInitializer : ITelemetryInitializer
    {
        private readonly IHttpContextAccessor _httpContextAccessor;

        public CustomTelemetryInitializer(IHttpContextAccessor httpContextAccessor)
        {
            _httpContextAccessor = httpContextAccessor ?? throw new ArgumentNullException(nameof(httpContextAccessor));
        }

        public void Initialize(ITelemetry telemetry)
        {
            var requestPath = _httpContextAccessor.HttpContext?.Request.Path.Value;

            if (string.IsNullOrWhiteSpace(requestPath))
                return;

            // List of paths to sample out
            var pathsToSampleOut = new[] { "/api/health" };

            if (pathsToSampleOut.Any(path => requestPath.Contains(path, StringComparison.OrdinalIgnoreCase)))
            {
                // We don't want to track these requests in the metrics.
                if (telemetry is ISupportAdvancedSampling advancedSampling)
                    advancedSampling.ProactiveSamplingDecision = SamplingDecision.SampledOut;

                // For the case that we cannot filter out the telemetry, we mark it as synthetic
                if (string.IsNullOrWhiteSpace(telemetry.Context.Operation.SyntheticSource))
                    telemetry.Context.Operation.SyntheticSource = "FilteredRequest";
            }
        }
    }

    public class CustomTelemetryProcessor : ITelemetryProcessor
    {
        private readonly ITelemetryProcessor _next;

        public CustomTelemetryProcessor(ITelemetryProcessor next)
        {
            _next = next ?? throw new ArgumentNullException(nameof(next));
        }

        public void Process(ITelemetry item)
        {
            if (!string.IsNullOrEmpty(item.Context.Operation.SyntheticSource)) { return; }
            _next.Process(item);
        }
    }
}

have initialized the exporters

var resource = ResourceBuilder.CreateDefault().AddAttributes(resourceAttributes);

TracerProvider tracerProvider = Sdk.CreateTracerProviderBuilder()
    .AddSource("GetCatalystOneEvent")
    .AddHttpClientInstrumentation()
    .AddAspNetCoreInstrumentation(options =>
    {
        options.Filter = context => !context.Request.Path.Equals("/api/health");
    })
    .SetResourceBuilder(resource)
    .AddAzureMonitorTraceExporter(options =>
    {
        options.ConnectionString = connectionString;
    })
    .Build();

MeterProvider meterProvider = Sdk.CreateMeterProviderBuilder()
    .SetResourceBuilder(resource)
    .AddHttpClientInstrumentation()
    .AddAspNetCoreInstrumentation()
    .AddRuntimeInstrumentation()
    .AddAzureMonitorMetricExporter(options =>
    {
        options.ConnectionString = connectionString;
    })
    .Build();

var host = Host.CreateDefaultBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureServices(services =>
    {
        services.AddHttpClient();
        services.AddHealthChecks();
        services.AddSingleton(tracerProvider);
        services.AddSingleton(meterProvider);
        services.AddApplicationInsightsTelemetryWorkerService();
        services.AddSingleton<ITelemetryInitializer, CustomTelemetryInitializer>();
        services.AddSingleton<ITelemetryProcessor, CustomTelemetryProcessor>();
    })

Environment

Azure Functions isolated Model with .Net 8

[github-actions]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @cijothomas @rajkumar-rangaraj @reyang @TimothyMothra.

[TimothyMothra]

Hi @dhayanands,
It looks like you're mixing two different telemetry SDKs. This is not recommended.
Please onboard to either one or the other.

Your filtering code looks correct, but I can't begin to troubleshoot your configuration until you switch to using one telemetry SDK or the other.

Application Insights SDK

This is our classic SDK. This is fully supported and feature rich.

• repo: https://github.com/microsoft/ApplicationInsights-dotnet
• nuget: https://www.nuget.org/packages/Microsoft.ApplicationInsights.aspnetcore
• onboarding guide: https://learn.microsoft.com/azure/azure-monitor/app/asp-net-core

services.AddApplicationInsightsTelemetryWorkerService();
services.AddSingleton<ITelemetryInitializer, CustomTelemetryInitializer>();
services.AddSingleton<ITelemetryProcessor, CustomTelemetryProcessor>();

Azure Monitor Exporter & OpenTelemetry

This is our newer SDK which will replace the classic SDK.

• repo: https://github.com/Azure/azure-sdk-for-net/tree/main/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter
• nuget: https://www.nuget.org/packages/Azure.Monitor.OpenTelemetry.Exporter
• onboarding: https://learn.microsoft.com/azure/azure-monitor/app/opentelemetry-enable

.AddAzureMonitorTraceExporter(options =>

.AddAzureMonitorMetricExporter(options =>

Functions

I see that you're using Azure Functions.
Please pay attention to their specific onboarding instructions.

• onboarding guide: https://learn.microsoft.com/azure/azure-functions/opentelemetry-howto?tabs=app-insights&pivots=programming-language-csharp#3-enable-opentelemetry-in-your-app