OTEL_EXPORTER_OTLP_HEADERS not honored by gRPC exporter

[vreynolds]

• This only affects the JavaScript OpenTelemetry library
• This may affect other libraries, but I would like to get opinions here first

I noticed that the gRPC exporter does not honor OTEL_EXPORTER_OTLP_HEADERS (or variants) when setting up metadata, which makes it impossible to configure the gRPC exporter through env vars, if you need authentication metadata.

Based on the spec, I expected that environment variable to apply to the gRPC exporter:

Key-value pairs to be used as headers associated with gRPC or HTTP requests.

Am I misreading the spec, or is this an oversight?

[vmarchaud]

I believe this is indeed an oversight, i implemented OTEL_EXPORTER_OTLP_HEADERS for http but i don't remember seeing that it was applicable to grpc too. Do you want to tackle this ?

[vreynolds]

Yep, I will work on a PR. Thanks for confirming!