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Instrument your .NET AWS Lambda function for Splunk Observability Cloud 🔗

You can instrument a .NET AWS Lambda function to send traces to Splunk Observability Cloud using the following OpenTelemetry template. The template uses these packages:

To instrument a .NET function in AWS Lambda for Splunk APM, follow these steps:

  1. Integrate your existing AWS Lambda with the following template or start a new function using the template:

using Amazon.Lambda.Core;
using OpenTelemetry;
using OpenTelemetry.Exporter;
using OpenTelemetry.Instrumentation.AWSLambda;
using OpenTelemetry.ResourceDetectors.AWS;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;
using System.Diagnostics;

namespace DotNetInstrumentedLambdaExample;

public class Function
{
   public static readonly TracerProvider TracerProvider;

   static Function()
   {
      TracerProvider = ConfigureSplunkTelemetry()!;
   }

   // Note: Do not forget to point function handler to here.
   public string TracingFunctionHandler(string input, ILambdaContext context)
      => AWSLambdaWrapper.Trace(TracerProvider, FunctionHandler, input, context);

   public string FunctionHandler(string input, ILambdaContext context)
   {
      // TODO: Your function handler code here
   }

   private static TracerProvider ConfigureSplunkTelemetry()
   {
      var serviceName = Environment.GetEnvironmentVariable("AWS_LAMBDA_FUNCTION_NAME") ?? "Unknown";
      var accessToken = Environment.GetEnvironmentVariable("SPLUNK_ACCESS_TOKEN")?.Trim();
      var realm = Environment.GetEnvironmentVariable("SPLUNK_REALM")?.Trim();

      ArgumentNullException.ThrowIfNull(accessToken, "SPLUNK_ACCESS_TOKEN");
      ArgumentNullException.ThrowIfNull(realm, "SPLUNK_REALM");

      var builder = Sdk.CreateTracerProviderBuilder()
            // Use Add[instrumentation-name]Instrumentation to instrument missing services
            // Use Nuget to find different instrumentation libraries
            .AddHttpClientInstrumentation()
            .AddAWSInstrumentation()
            // Use AddSource to add your custom DiagnosticSource source names
            //.AddSource("My.Source.Name")
            .SetSampler(new AlwaysOnSampler())
            .AddAWSLambdaConfigurations(opts => opts.DisableAwsXRayContextExtraction = true)
            .ConfigureResource(configure => configure
                  .AddService(serviceName, serviceVersion: "1.0.0")
                  // Different resource detectors can be found at
                  // https://github.com/open-telemetry/opentelemetry-dotnet-contrib/tree/main/src/OpenTelemetry.ResourceDetectors.AWS#usage
                  .AddDetector(new AWSEBSResourceDetector()))
            .AddOtlpExporter(opts =>
            {
               opts.Endpoint = new Uri($"https://ingest.{realm}.signalfx.com/v2/trace/otlp");
               opts.Protocol = OtlpExportProtocol.HttpProtobuf;
               opts.Headers = $"X-SF-TOKEN={accessToken}";
            });

      return builder.Build()!;
   }
}

  1. Make sure that the new function handler TracingFunctionHandler is configured as the main entry point by editing the aws-lambda-tools-defaults.json file and changing the function-handler entry. You can also do this using the AWS web console, changing the handler in Runtime settings.

  2. The template expects the following environment variables:

    • AWS_LAMBDA_FUNCTION_NAME: Name of your AWS Lambda function

    • SPLUNK_ACCESS_TOKEN: Your Splunk ingest access token

    • SPLUNK_REALM: Your Splunk ingest realm, for example us0

  3. The template also contains the following customization points in ConfigureSplunkTelemetry():

    • Add a custom instrumentation library to support other third-party libraries. You can search for libraries using NuGet and strings starting with OpenTelemetry.Instrumentation..

    • Some libraries already have the System.Diagnostics.DiagnosticSource module built in. Use the .AddSource() method to include a custom DiagnosticSource name.

    • The AWS package contains multiple ResourceDetectors elements that help describe your environment. Select a detector for your use case.

  4. Add your code to the FunctionHandler function as the default AWS template expects.