Selecting multiple exporters via environmental variables

[pellared]

What are you trying to achieve?

The exporter selection environmental variables allow only to select a SINGLE one. It would be handy to allow selecting more than one e.g. otlp,console.

Additional context

An issue where multiple exporters were also mentioned:

• OTEL_EXPORTER not consistent with other variables #1309
• Split OTEL_EXPORTER to OTEL_TRACE_EXPORTER and OTEL_METRICS_EXPORTER #1318

Possible solutions

Allow adding more than one exporter

We can allow adding multiple exporters separated by , via OTEL_TRACES_EXPORTER and OTEL_METRICS_EXPORTER.

The only problem is that it is not a forward-compatible change. However, it is backward-compatible.

Example: OTEL_TRACES_EXPORTER=zipkin,otlp

Add new env vars

We can add new OTEL_TRACES_EXPORTERS and OTEL_METRICS_EXPORTERS env vars which could contain a comma-separated list of exporters.

This change is forward-compatible, however, it makes the API/specs longer. Moreover e,.g. if both OTEL_TRACES_EXPORTER and OTEL_TRACES_EXPORTERS are specified then the "result" should be concatenated.

Example: if OTEL_TRACES_EXPORTER=jaeger and OTEL_TRACES_EXPORTERS=zipkin,otlp then we should add all 3 exporters.

[pellared]

FYI @anuraaga @pjanotti

[carlosalberto]

I'd be up for the first approach. Certainly it won't work with old versions but we keep things simple. Also, adding more environment variables may create a lot of noise.

[ghost]

Same as @carlosalberto with the first approach. Also, I've seen customer requests for this surfacing multiple times already, often to validate what's being sent with logger exporter.

[pellared]

PR for first approach: #1758