Using OpenTelemetry Sdk with Azure Functions

For using OpenTelemetry Sdk with Azure Functions, AddOpenTelemetryTracing extension method cannot be used. This is because Azure Functions has restrictions on running background hosted services. The right way to configure it for Functions is below:

var openTelemetry = Sdk.CreateTracerProviderBuilder().
                AddSource("MyActivitySourceName")
                .SetSampler(new AlwaysOnSampler())
                .AddConsoleExporter()
                .Build();
            builder.Services.AddSingleton(openTelemetry);

There is also the issue (https://github.com/Azure/azure-functions-host/issues/7135) of Azure Functions not supporting DiagnosticListener callbacks when using System.Diagnostics.DiagnosticSource (> 4.7.0). Therefore, OpenTelemetry instrumentations (like HttpClient, SqlClient etc.) will not work in Azure Functions as the instrumentations use System.Diagnostics.DiagnosticSource (= 5.0.1)

[valdisiljuconoks]

Seems to be working. I’m using the following setup in functions (v4 runtime + in-process):

[assembly: FunctionsStartup(typeof(Startup))]

namespace FunctionApp1;

internal class Startup : FunctionsStartup
{
    public override void Configure(IFunctionsHostBuilder builder)
    {
        builder.Services.AddOpenTelemetryTracing(b =>
        {
            b.AddHttpClientInstrumentation();
            b.AddSource("AzureFunctionsOpenTelemetry");
            b.AddOtlpExporter(options => options.Endpoint = new Uri("http://localhost:4317"));
        });

        builder.AddOpenTelemetry(b =>
        {
            b.IncludeFormattedMessage = true;
            b.IncludeScopes = true;
            b.ParseStateValues = true;
            b.AddOtlpExporter(options => options.Endpoint = new Uri("http://localhost:4317"));
        });
    }
}

public static class OpenTelemetryLoggingExtensions
{
    public static IFunctionsHostBuilder AddOpenTelemetry(
        this IFunctionsHostBuilder builder,
        Action<OpenTelemetryLoggerOptions> configure = null)
    {
        if (builder == null)
        {
            throw new ArgumentNullException(nameof(builder));
        }

        builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, OpenTelemetryLoggerProvider>());

        if (configure != null)
        {
            builder.Services.Configure(configure);
        }

        return builder;
    }
}

[josh-endries]

Just a note that using OpenTelemetry.Trace.TracerProviderBuilderExtensions.AddHttpClientInstrumentation with a .NET 5 isolated runtime Azure Function does seem to work, at least somewhat. If I set the trace ID in an ActivityContext and start my own Activity, then call HttpClient.GetAsync within the activity scope, that outgoing request contains the traceparent header that contains the trace ID.