Usage of unspecified environment variables? OTEL_SPAN_ATTRIBUTE_PER_LINK/EVENT_COUNT_LIMIT

[vekunz]

Hi, more or less by chance, I found two environment variables in the @opentelemetry/sdk-node package that I can't find in the OpenTelemetry specs.

The file experimental/packages/opentelemetry-sdk-node/src/create-from-env.ts uses these two env variables:

• OTEL_SPAN_ATTRIBUTE_PER_EVENT_COUNT_LIMIT
• OTEL_SPAN_ATTRIBUTE_PER_LINK_COUNT_LIMIT

In the specs I can't find a reference to them.

But what I found in the specs were these two variables that are not used by this SDK:

• OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT
• OTEL_LINK_ATTRIBUTE_COUNT_LIMIT

I was wondering if this SDK might use the wrong variables for these two settings. Or maybe I'm missing something?

[pacocartones]

Thanks for tracking this down. I can confirm the mismatch is still present on main:

• createSpanLimitsFromEnv() reads OTEL_SPAN_ATTRIBUTE_PER_EVENT_COUNT_LIMIT and OTEL_SPAN_ATTRIBUTE_PER_LINK_COUNT_LIMIT.
• The SDK environment-variable specification defines the corresponding standard names as OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT and OTEL_LINK_ATTRIBUTE_COUNT_LIMIT.

Would it make sense to turn this into an issue with a regression test that exercises the standard names? The implementation decision could then be explicit: either replace the non-standard names, or continue accepting them as documented deprecated aliases for compatibility. That would avoid silently changing existing deployments while bringing the SDK into line with the specification.