[SDK] Support OTEL_SDK_DISABLED environment variable

[marcalff]

The SDK spec recently added a new environment variable, OTEL_SDK_DISABLED

See open-telemetry/opentelemetry-specification#2679

Implement support for OTEL_SDK_DISABLED, for all signals.

[github-actions]

This issue was marked as stale due to lack of activity.

[github-actions]

This issue is available for anyone to work on. Make sure to reference this issue in your pull request.
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[RichardChukwu]

Is this available to be worked on @marcalff ?

[divenire05]

If no one is working on this, could I take it up? Feel free to assign it to me. @marcalff

[divenire05]

Thanks, does anyone have any suggestions on getting started with resolving this issue?

[lalitb]

Thanks, does anyone have any suggestions on getting started with resolving this issue?

One approach could be to introduce an disabled flag in the TracerProvider. This flag would be set during the provider's initialization, based on the OTEL_SDK_DISABLED environment variable, and default to false. If the flag is set to true, TracerProvider::GetTracer() would return a NoopTracer. This ensures that any changes to the environment variable are reflected in subsequently created tracer and span through this tracer. A similar mechanism could be implemented for logs and metrics.

[divenire05]

Sounds good. Do you know which files I should focus on editing/where I can find them?

[lalitb]

tracer_provider.cc/h under sdk directory. And similarly logger_provider/meter_provider.

[divenire05]

Got it, thank you!

[divenire05]

Would I access the OTEL_SDK_DISABLED variable with getenv("OTEL_SDK_DISABLED")? I looked at open-telemetry/opentelemetry-specification#2679 but I'm unsure where the environment property is specified in the code.

[lalitb]

You should be using the cross-platform api to access the env variable -

opentelemetry-cpp/sdk/src/common/env_variables.cc

Line 59 in 4998eb1

bool GetBoolEnvironmentVariable(const char *env_var_name, bool &value)