Handling "none" value in OTEL_PROPAGATORS, OTEL_TRACES_EXPORTER, OTEL_METRICS_EXPORTER and OTEL_LOGS_EXPORTER

[robsunday]

What are you trying to achieve?
I need to understand how SDK is supposed to behave if value "none" is specified together with other value(s) in any of the following environment variables:

• OTEL_PROPAGATORS
• OTEL_TRACES_EXPORTER
• OTEL_METRICS_EXPORTER
• OTEL_LOGS_EXPORTER

Additional context.

sdk-environment-variables.md file metions that value "none" indicates that no propagator or appropriate exporter should be configured.
The issue is that these environment variables can hold a list of values.
In current specification I did not find any information what should happen if for example OTEL_PROPAGATORS has value "baggage, none". I think such a specification would be worth adding.

In this case Java SDK throws an exception (see PropagatorConfiguration.java), but is it the right approach?

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[pellared]

In this case Java SDK throws an exception (see PropagatorConfiguration.java), but is it the right approach?

I don’t think that’s the right approach. "none" should represent a no-op configuration instead of causing an error.

[robsunday]

So to be clear - do you suggest that all propagators should be silently skipped if "none" is specified as one of the items in the propagator list ?

[pellared]

It is good that you are asking. For OTEL_PROPAGATORS=baggage,none the W3C Baggage Propagator is set. The none acts as a "NullValue".

[jkwatson]

It is good that you are asking. For OTEL_PROPAGATORS=baggage,none the W3C Baggage Propagator is set. The none acts as a "NullValue".

Java considers this an error because it doesn't make any sense, and probably means that the user has made a mistake in their env var setting.

[dmathieu]

I would tend to agree with the reasoning that having "none" among other propagators doesn't make sense and looks like a config mistake.

[pellared]

@robsunday, can you check how different languages are handling this already?