OpenTelemetry.Shims.OpenTracing Invalid 'SpanContext' when not sampled

[konczykl]

Bug Report

List of [all OpenTelemetry NuGet packages]:

<PackageReference Include="OpenTelemetry" Version="1.4.0-rc.1" />
<PackageReference Include="OpenTelemetry.Exporter.Console" Version="1.4.0-rc.1" />
<PackageReference Include="OpenTelemetry.Exporter.Jaeger" Version="1.4.0-rc.1" />
<PackageReference Include="OpenTelemetry.Exporter.Prometheus.AspNetCore" Version="1.4.0-rc.1" />
<PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.4.0-rc.1" />
<PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.0.0-rc9.10" />
<PackageReference Include="OpenTelemetry.Instrumentation.Hangfire" Version="1.0.0-beta.4" />
<PackageReference Include="OpenTelemetry.Instrumentation.SqlClient" Version="1.0.0-rc9.10" />
<PackageReference Include="OpenTelemetry.Shims.OpenTracing" Version="1.0.0-rc9.11" />

Runtime version:

• net7.0

Symptom

When using shim package

What is the expected behavior?
Return some noop instance.

What is the actual behavior?
ArgumentException thrown from SpanShim ctor.

Reproduce

Reproduced error:
https:/konczykl/OpenTracingShimError

Additional Context

Problem exists if we are not sampling spans - underlying activity is not created resulting in default SpanContext.

using (var parent = tracer.BuildSpan("parent").StartActive())
using (var child = tracer.BuildSpan("child").StartActive())
{

}

Parent span's activity is set as PropagationData and gets created but child's activity is null.

 public SpanShim(TelemetrySpan span)
{
    Guard.ThrowIfNull(span);

    if (!span.Context.IsValid) // here Context is default -> not valid
    {
        throw new ArgumentException($"Invalid '{nameof(SpanContext)}'", nameof(span.Context));
    }

    this.Span = span;
    this.spanContextShim = new SpanContextShim(this.Span.Context);
}

[TimothyMothra]

I spent some time today digging into this.

First, I put together a smaller repro sample as a unit test for easier debugging:

using System.Diagnostics;
using Microsoft.Extensions.DependencyInjection;
using OpenTelemetry.Context.Propagation;
using OpenTelemetry.Shims.OpenTracing;
using OpenTelemetry.Trace;
using OpenTracing;
using Xunit;


[Fact]
public void Investigate4087_AlwaysOff()
{
	string serviceName = "Investigate4087";

	var exportedItems = new List<Activity>();

	var services = new ServiceCollection();

	services.AddOpenTelemetry()
		.WithTracing(b => b
			.AddSource(serviceName)
			.AddInMemoryExporter(exportedItems)
			.SetSampler(new AlwaysOffSampler())); // this fails
			//.SetSampler(new AlwaysOnSampler())); // this works

	services.AddSingleton<ITracer>(sp =>
	{
		var tracerProvider = sp.GetRequiredService<TracerProvider>();
		var tracer = new TracerShim(tracerProvider.GetTracer(serviceName), Propagators.DefaultTextMapPropagator);
		return tracer;
	});

	IServiceProvider serviceProvider = services.BuildServiceProvider();
	var tracer = serviceProvider.GetRequiredService<ITracer>();

	using (var parent = tracer.BuildSpan("parent").StartActive())
	using (var child = tracer.BuildSpan("child").StartActive())
	{
	}
}        

Part of the cause is in StartSpanHelper(), this method tries to start a new activity and return a TelemetrySpan.
This method is failing to create an activity and instead returns the TelemetrySpan.NoopInstance.

opentelemetry-dotnet/src/OpenTelemetry.Api/Trace/Tracer.cs

Lines 176 to 180 in d0829ff

	var activity = this.ActivitySource.StartActivity(name, activityKind, parentContext.ActivityContext, initialAttributes?.Attributes ?? null, activityLinks, startTime);
	if (activity == null)
	{
	return TelemetrySpan.NoopInstance;
	}

The TelemetrySpan.NoopInstance uses all default values including:

• TraceId {00000000000000000000000000000000}
• SpanId {0000000000000000}

Here, the Span Context is Invalid because of the default values and fails here:

opentelemetry-dotnet/src/OpenTelemetry.Api/Trace/SpanContext.cs

Line 104 in d0829ff

public bool IsValid => IsTraceIdValid(this.TraceId) && IsSpanIdValid(this.SpanId);

opentelemetry-dotnet/src/OpenTelemetry.Shims.OpenTracing/SpanShim.cs

Lines 44 to 51 in d0829ff

	public SpanShim(TelemetrySpan span)
	{
	Guard.ThrowIfNull(span);
	if (!span.Context.IsValid)
	{
	throw new ArgumentException($"Invalid '{nameof(SpanContext)}'", nameof(span.Context));
	}

[TimothyMothra]

While digging into the relationship between Samplers and StartActivity I found this:

opentelemetry-dotnet/src/OpenTelemetry/Trace/TracerProviderSdk.cs

Lines 234 to 245 in d0829ff

	if (this.sampler is AlwaysOnSampler)
	{
	listener.Sample = (ref ActivityCreationOptions<ActivityContext> options) =>
	!Sdk.SuppressInstrumentation ? ActivitySamplingResult.AllDataAndRecorded : ActivitySamplingResult.None;
	this.getRequestedDataAction = this.RunGetRequestedDataAlwaysOnSampler;
	}
	else if (this.sampler is AlwaysOffSampler)
	{
	listener.Sample = (ref ActivityCreationOptions<ActivityContext> options) =>
	!Sdk.SuppressInstrumentation ? PropagateOrIgnoreData(options.Parent) : ActivitySamplingResult.None;
	this.getRequestedDataAction = this.RunGetRequestedDataAlwaysOffSampler;
	}

In summary, when using the AlwaysOffSampler, the PropogateOrIgnoreData() is effectively determining to not create a new Activity.
This eventually results in the ArgumentException detailed above.

--
This sounds related to #3290. I'll follow up.

[pjanotti]

@TimothyMothra @open-telemetry/dotnet-maintainers While some other aspects are mentioned on this issue it seems that we can close it as fixed via #4668

[TimothyMothra]

@pjanotti Confirmed!

@open-telemetry/dotnet-maintainers I think this Issue could be assigned to the current milestone and closed. :)