How to ignore / drop HealthCheck request samples in Application Insights

[dhayanands]

Hi Team,

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

using .Net 8 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>();
    })

[TimothyMothra]

Hi @dhayanands, This is the wrong repo for issues related to Azure.Monitor.OpenTelemetry.Exporter.
Please open an issue in that SDK's repo: https:/Azure/azure-sdk-for-net/tree/main/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter

[dhayanands]

@TimothyMothra Thank you. I will check on the mentioned repo. Saw that previously but was a bit confused on where to post the query.