Support the OTEL_BSP_* environment variables

[MrAlias]

Add support for the following environment variables as defined in the specification.

• OTEL_BSP_SCHEDULE_DELAY
• OTEL_BSP_EXPORT_TIMEOUT
• OTEL_BSP_MAX_QUEUE_SIZE
• OTEL_BSP_MAX_EXPORT_BATCH_SIZE

Part of #1698

[hanyuancheung]

This is already done: https://github.com/open-telemetry/opentelemetry-go/blob/main/sdk/trace/batch_span_processor.go#L29-L32, I'll change the status of otel-specification.

[MrAlias]

The link provided is to code that defines defaults for the batch span processor, not parsing of the listed environment variables. A search of the project also does not return any use of the mentioned variables names. It does not appear that this is complete.

[ianzhang1988]

Can someone elaborate how actually these OTEL_BSP_* work.

In my test, It show that at every OTEL_BSP_EXPORT_TIMEOUT sdk send OTEL_BSP_MAX_EXPORT_BATCH_SIZE spans. Then some spans got droped(I guess it used up OTEL_BSP_MAX_QUEUE_SIZE).

Is OTEL_BSP_EXPORT_TIMEOUT interval for sending spans?

[MrAlias]

@ianzhang1988 please take a look at the related batch span processor docs (https://pkg.go.dev/go.opentelemetry.io/otel/sdk/trace#BatchSpanProcessorOption) and the specification info on the environment variables (https://github.com/open-telemetry/opentelemetry-specification/blob/08a15efd4c43336ae31d14809aaa1acce07c9a0a/specification/sdk-environment-variables.md#batch-span-processor).

If these do not answer your question, please open an new issue for your question.

[ianzhang1988]

@MrAlias After some digging, I found that It's my server end (jaeger) do not send http 202, then block otel upload. Sorry for the false alarm.