axum-otlp example not working out of the box?

[xmo-odoo]

Trying to better understand what the repository provides I decided to run the "axum-otlp" example to see how it fared. Now the readme does suggest OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317 and that works (so does OTEL_EXPORTER_OTLP_PROTOCOL=grpc), however it doesn't seem to work using the protobuf exporter (to the endpoint http://localhost:4318), which is the default configuration, even though it's not saying anything and the DEBUG reporting for the otel configuration seems happy with everything.

The odd part is the corresponding example from open-telemetry/opentelemetry-rust (the somewhat ill named tracing-jaeger) does work with no issue, it seems to send trace with either OTEL_EXPORTER_OTLP_PROTOCOL (although I've not found a way to confirm that it was taking that key into account as it does not report anything).

I'm not sure what gives.

In both cases, my collector is CtrlSpice/otel-desktop-viewer

[davidB]

Thanks for reporting, there is an issue in the computation of OTEL_EXPORTER_OTLP_TRACES_ENDPOINT from OTEL_EXPORTER_OTLP_PROTOCOL when protocol is http/protobuf.

As a workaround, you can set explicitly

export OTEL_EXPORTER_OTLP_TRACES_ENDPOINT="http://127.0.0.1:4318/v1/traces"

(see https://opentelemetry.io/docs/languages/sdk-configuration/otlp-exporter/)

I'll release a patched version (and maybe later another version without the code related to environment variables as now, it seems to be handled by the crate opentelemetry)

FIX in 0f45ecb