Specify how exporters should deal with invalid instrumentation library names

[Oberon00]

Since #1534 / #1472, we pass on invalid (i.e. null/empty) instrumentation library names to the exporter. We should specify how specific exporters should deal with it. In my opinion, the goal should be to alert users that they are making a mistake when they decline (not forget: the null/empty string has to be explicitly passed) to specify an instrumentation library name. So I would suggest:

• OTLP: Probably pass it on as-is, but add SHOULD/MUST-requirement for consumers (e.g. collector when translating to other protocol) to alert users somehow.
• Jaeger/Zipkin: Replace with "<INSTRUMENTATION LIBRARY NAME MISSING>" or similarly screaming string.

[carlosalberto]

@yurishkuro @anuraaga do you have any opinion about Jaeger and Zipkin handling of this, respectively?

[yurishkuro]

Jaeger has no requirements on instrumentation library name, it only requires service name. I assume the same holds for Zipkin. So I am not clear what value a long screaming string would provide. I would simply omit setting this on the spans.

[Oberon00]

Jaeger has no requirements on instrumentation library name,

But OpenTelemetry has. And in #1534 / #1472 it was decided that the backend is responsible for showing the error message to the user. Since I don't think Jaeger/Zipkin will add special support for the OTel library names, the last point in the chain where we can add the error message is the exporter.

So I am not clear what value a long screaming string would provide.

It will urge users to put in place an instrumentation library name, therefore stop calling the OpenTelemetry getTracer API with invalid arguments.

[yurishkuro]

backend is responsible for showing the error message to the user

I don't think this is stated anywhere as a requirement. Most users won't even care about this value, I think the main persona who cares is someone who's investigating instrumentation issues, and for them the absence of this value tells as much as a long screaming string.