Support env variable configuration for OTLP exporter

[codeboten]

The spec describes environment variables that should be supported to configure the OTLP exporter, this feature request is to add support in the current implementation.

Spec PR:
https://github.com/open-telemetry/opentelemetry-specification/pull/699/files

[jan25]

@codeboten can i help fix this?

[jan25]

Looks like current OTLP exporter code doesn't cover all the cases covered in spec.

These seem like can be immediately supported:

• OTEL_EXPORTER_OTLP_SPAN_ENDPOINT OTEL_EXPORTER_OTLP_METRIC_ENDPOINT
• OTEL_EXPORTER_OTLP_SPAN_INSECURE OTEL_EXPORTER_OTLP_METRIC_INSECURE
• OTEL_EXPORTER_OTLP_SPAN_CERTIFICATE OTEL_EXPORTER_OTLP_METRIC_CERTIFICATE

These require the cases to be implemented(for e.g. moving to trace/metric experimental API) before adding support for ENV based configuration:

• OTEL_EXPORTER_OTLP_SPAN_PROTOCOL OTEL_EXPORTER_OTLP_METRIC_PROTOCOL
• OTEL_EXPORTER_OTLP_SPAN_HEADERS OTEL_EXPORTER_OTLP_METRIC_HEADERS
• OTEL_EXPORTER_OTLP_SPAN_COMPRESSION OTEL_EXPORTER_OTLP_METRIC_COMPRESSION
• OTEL_EXPORTER_OTLP_SPAN_TIMEOUT OTEL_EXPORTER_OTLP_METRIC_TIMEOUT

Would you recommend we cover the top 3 cases and have a way to work with ENV variables, and for later cases the support can be added as they are implemented?

[owais]

I think add env var based support to existing options makes sense. Adding new the missing options can be a different stream of work.

[codeboten]

I agree, supporting the ones that are already present seems like a good first step. Also worth implementing the case where a general config option is set instead of SPAN/METRIC specific ones:

OTEL_EXPORTER_OTLP_ENDPOINT
OTEL_EXPORTER_OTLP_INSECURE
OTEL_EXPORTER_OTLP_CERTIFICATE
OTEL_EXPORTER_OTLP_HEADERS

Worth noting that the current OTLP exporter calls headers metadata: https://github.com/open-telemetry/opentelemetry-python/blob/master/exporter/opentelemetry-exporter-otlp/src/opentelemetry/exporter/otlp/exporter.py#L110

[jan25]

I opened a WIP PR. Any feedback early on would be helpful :)

[jan25]

Also, I think we can clarify few things in exporter spec:

• Mention that OTEL_EXPORTER_OTLP_CERTIFICATE and related vars take path to certificate file.
• Clarify on format of OTEL_EXPORTER_OTLP_HEADERS . For e.g. is it JSON string?
• Add sample examples for above flags in same spec file.
• OTEL_EXPORTER_OTLP_INSECURE can take true for default. That way supplying certificates is 'not' mandatory.

wdyt?

[codeboten]

Sure, I think it makes sense to clarify this in the spec. I would expect the format for OTLP_HEADERS to be a list of key/value pairs like the the resource attributes env variable: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/sdk-environment-variables.md#general-sdk-configuration

[jan25]

Cool. I'll find some time soon to open a PR in spec repo to discuss more and also to finalize this current issue