Support for OTLP/UDP Span Exporter

[jj22ee]

What are you trying to achieve?

We want to mitigate some of the performance issues in an AWS Lambda Environment when using the OTel Lambda Layers to send spans to AWS X-Ray. One mitigation involves avoid deploying the OTel Collector during a Lambda Function invocation to reduce cold start time and memory allocated. As a workaround for having no Collector, we are trying to send Spans to a UDP endpoint (AWS_XRAY_DAEMON_ADDRESS) in an AWS Lambda Environment. This UDP endpoint was originally designed for the X-Ray SDKs to send X-Ray Trace Segments to AWS X-Ray. Today in AWS Lambda, this UDP endpoint also supports receiving OTel Spans and send them to AWS X-Ray.

What did you expect to see?

We expect the OTel SDKs to provide a Span Exporter that can export spans via UDP protocol.

• This exporter can be configured via OTEL_EXPORTER_OTLP_TRACES_PROTOCOL=udp.
• The endpoint is configurable when instantiating the UDP Exporter or via OTEL_EXPORTER_OTLP_TRACES_ENDPOINT env var.

Additional context.

• Slow start-up? opentelemetry-lambda#263 - issue summarizes the OTel performance impact in Lambda that we want to mitigate
• While the purpose of this UDP Exporter was originally for this Lambda Performance mitigation use case to vend to AWS X-Ray, it is quite generic w/ configurable endpoints. As such, what are the thoughts of the OTel community on the addition of this UDP Exporter?
• Today, AWS Observability's JS instrumentation is leveraging a UDP Exporter to export traces to Lambda's UDP endpoint to send traces to AWS X-Ray. This is the UDP Exporter's implementation in JavaScript.
• Related issue opened in opentelemetry-lambda

[dmathieu]

While there could always be hacky ways to do this, OTLP relies on protobuf and gRPC, and the gRPC folks have explicitly said support for UDP is not on their roadmap.
grpc/grpc#9493