Support OTEL_EXPORTER_OTLP_*PROTOCOL environment variables from otel spec

[johnbley]

Steps to reproduce
Set, e.g., OTEL_TRACES_EXPORTER to otlp and OTEL_EXPORTER_OTLP_TRACES_PROTOCOL to http/protobuf per the specification at https://opentelemetry.io/docs/specs/otel/protocol/exporter/#configuration-options.

What is the expected behavior?
http/protobuf in use.

What is the actual behavior?
grpc in use. (if otlp_proto_grpc is not installed, an error message and failure to initialize the sdk)

Additional context
A workaround is to set OTEL_TRACES_EXPORTER=otlp_proto_http - this works correctly, but is against specification.

[srikanthccv]

These should be supported already if I am not wrong #2893

[johnbley]

I apologize, you are correct. I had some custom code that was manipulating these environment variables and that appears to be the source of my problem. Closing.