Using X-Ray UDP Exporter with `TracingProvider`'s resource

[daniel-ferguson]

I'd like to be able to use the X-Ray UDP Exporter on AWS lambda, and have traces emitted with rich resource info inferred from the lambda environment (e.g. lambda ARN, memory & CPU available).

I'm struggling to get this working and I suspect it could be due to how the exporter works with Resources. When constructing it, it seems necessary to pass in a fully-built Resource, and I'm not sure how to build a resource that will have all the lambda properties I'm interested in having recorded on my traces. Here's the TracerProviderBuilder setup as shown in the README for this project:

var tracerProvider = Sdk.CreateTracerProviderBuilder()
    // ...
    .AddProcessor(
        new SimpleActivityExportProcessor(
            // Add the X-Ray UDP Exporter
            new XrayUdpExporter(resourceBuilder.Build())
        )
    )

This contrasts with the way I'd add a console or OLTP exporter:

var tracerProvider = Sdk.CreateTracerProviderBuilder()
  .AddOtlpExporter()

I've had a go at reading how AddOtlpExporter works, and it seems to fetch the Resource from its parent provider at runtime: https://github.com/open-telemetry/opentelemetry-dotnet/blob/5f5b6bce4087ef5e76539ed44e93efb53107202d/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpTraceExporter.cs#L63

I'd hope for something similar from XrayUdpExporter. I'm not too familiar with the ecosystem here, so if I'm missing something really obvious about how I can use XrayUdpExporter with the auto-configured resource that .AddAWSLambdaConfigurations attaches to the TracerProvider please let me know.

What else have I tried?

I've also tried building a resource that has all the data I'm interested in - just as AddAWSLambdaConfigurations does (https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/2642fc886e9220f7ccc113f16da82d4813f1fff8/src/OpenTelemetry.Instrumentation.AWSLambda/TracerProviderBuilderExtensions.cs#L46). Unfortunately AWSLambdaResourceDetector is private. If and when open-telemetry/opentelemetry-dotnet-contrib#3411 gets merged and released I might be able work around this issue.

---

I'm not an expert when it comes to the OpenTelemetry ecosystem in general, nor the dotnet side of it, so here are some assumptions I'm making:

• Resources represent a thing that traces relate to (a piece of infrastructure, an AWS lambda function, etc.)
• resource detectors can be registered with a ResourceBuilder, and describe a process for populating information on that resource
• resource information gets recorded with traces, when those traces are emitted
• the fact that I'm using a very plain Resource, rather than the one built by calling .AddAWSLambdaConfigurations is the cause of the traces my system records being
• XrayUdpExporter is fine to use (I'm really hoping this is the case, since at least at first glance it looks like a really good workaround for the 400ms, startup latencies we're seeing when we try to run the OTel collector as a lambda layer)