Splunk Observability Cloud 用 .NET Azure WebJobs をインストルメンテーションする

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host;
using Microsoft.Extensions.DependencyInjection;
using OpenTelemetry.Exporter;
using OpenTelemetry.Metrics;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;
using System.Diagnostics;

namespace <YourNamespaceHere>.Helpers;

internal static class SplunkOpenTelemetry
{
    private static readonly string AccessToken;
    private static readonly string Realm;

    static SplunkOpenTelemetry()
    {
        AccessToken = Environment.GetEnvironmentVariable("SPLUNK_ACCESS_TOKEN")?.Trim()
            ?? throw new ArgumentNullException("SPLUNK_ACCESS_TOKEN");

        Realm = Environment.GetEnvironmentVariable("SPLUNK_REALM")?.Trim()
            ?? throw new ArgumentNullException("SPLUNK_REALM");
    }

    public static IWebJobsBuilder AddSplunkOpenTelemetry(this IWebJobsBuilder builder)
    {
        // Get environment variables from function configuration
        // You need a valid Splunk Observability Cloud access token and realm
        var serviceName = Environment.GetEnvironmentVariable("WEBSITE_SITE_NAME") ?? "Unknown";
        var enableTraceResponseHeaderValue = Environment.GetEnvironmentVariable("SPLUNK_TRACE_RESPONSE_HEADER_ENABLED")?.Trim();

        builder.Services.AddOpenTelemetry()
            .ConfigureResource(cfg => cfg
                // See https://github.com/open-telemetry/opentelemetry-dotnet-contrib/tree/main/src/OpenTelemetry.Resources.Azure
                // for other types of Azure detectors
                .AddAzureAppServiceDetector()
                .AddService(serviceName: serviceName, serviceVersion: "1.0.0"))
            .WithTracing(t => t
                // Use Add[instrumentation-name]Instrumentation to instrument missing services
                // Use Nuget to find different instrumentation libraries
                .AddHttpClientInstrumentation(opts =>
                {
                    // This filter prevents background (parent-less) http client activity
                    opts.FilterHttpWebRequest = req => Activity.Current?.Parent != null;
                    opts.FilterHttpRequestMessage = req => Activity.Current?.Parent != null;
                })
                // Use AddSource to add your custom DiagnosticSource source names
                //.AddSource("My.Source.Name")
                // Automatically creates the root span with function start
                .AddSource(SplunkFunctionAttribute.ActivitySourceName)
                .SetSampler(new AlwaysOnSampler())
                .AddOtlpExporter(opts =>
                {
                    opts.Endpoint = new Uri($"https://ingest.{Realm}.signalfx.com/v2/trace/otlp");
                    opts.Protocol = OtlpExportProtocol.HttpProtobuf;
                    opts.Headers = $"X-SF-TOKEN={AccessToken}";
                }))
            .WithMetrics(m => m
                // Use Add[instrumentation-name]Instrumentation to instrument missing services
                // Use Nuget to find different instrumentation libraries
                .AddHttpClientInstrumentation()
                .AddRuntimeInstrumentation()
                .AddProcessInstrumentation()
                .AddOtlpExporter(opts =>
                {
                    opts.Endpoint = new Uri($"https://ingest.{Realm}.signalfx.com/v2/datapoint/otlp");
                    opts.Headers = $"X-SF-TOKEN={AccessToken}";
                }));

        return builder;
    }
}

internal class SplunkFunctionAttribute : FunctionInvocationFilterAttribute
{
    public const string ActivitySourceName = "Splunk.Azure.WebJob";

    private static readonly ActivitySource ActivitySource = new(ActivitySourceName);

    private Activity? _currentActivity;

    public override Task OnExecutingAsync(FunctionExecutingContext executingContext, CancellationToken cancellationToken)
    {
        _currentActivity = ActivitySource.StartActivity(executingContext.FunctionName, ActivityKind.Server);
        _currentActivity?.AddTag("faas.name", executingContext.FunctionName);
        _currentActivity?.AddTag("faas.instance", executingContext.FunctionInstanceId);

        return base.OnExecutingAsync(executingContext, cancellationToken);
    }

    public override Task OnExecutedAsync(FunctionExecutedContext executedContext, CancellationToken cancellationToken)
    {
        if (!executedContext.FunctionResult.Succeeded)
        {
            if (executedContext.FunctionResult.Exception != null)
            {
                _currentActivity?.SetStatus(Status.Error.WithDescription(executedContext.FunctionResult.Exception.Message));
                _currentActivity?.RecordException(executedContext.FunctionResult.Exception);
            }
            else
            {
                _currentActivity?.SetStatus(Status.Error);
            }
        }

        _currentActivity?.Stop();

        return base.OnExecutedAsync(executedContext, cancellationToken);
    }
}

var builder = new HostBuilder()
.ConfigureWebJobs(context =>
{
    context.AddSplunkOpenTelemetry();
})

public class Functions
{
    [SplunkFunction]
    public void ProcessTimer([TimerTrigger("1/5 * * * * *")] TimerInfo timerInfo, ILogger logger)
    {
        logger.LogInformation("Hello World!");
    }
}