fix: unify rack middleware_args

[sergiofbsilva]

Standalone rack applications need to initialize middlewares explicitly:

Rack::Builder.new do
	use *OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.middleware_args
	run lambda { |_arg| [200, { 'Content-Type' => 'text/plain' }, body] }
 end

However this doesn't take into account the new OTEL_SEMCONV_STABILITY_OPT_IN environment variable.

This PR ensures rack middleware_args are selected consistently based on OTEL_SEMCONV_STABILITY_OPT_IN environment variable.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: sergiofbsilva / name: Sérgio Silva (11584fd, a8c45f2, dabdb87, 2797f5f, 235bdbe)
• ✅ login: kaylareopelle / name: Kayla Reopelle (5b6615b)
• ✅ login: arielvalentin / name: Ariel Valentin (f5e77df)

[ericmustin]

Thanks for opening this @sergiofbsilva . We chatted on this briefly in SIG, just wanted to clarify

• To confirm, the issue here that you're using rack as a standalone app, and the env var OTEL_SEMCONV_STABILITY_OPT_IN isn't being respected because it isn't being by the evaluated by the middleware_args helper method?

cc @hannahramadan

[sergiofbsilva]

Thanks for opening this @sergiofbsilva . We chatted on this briefly in SIG, just wanted to clarify

• To confirm, the issue here that you're using rack as a standalone app, and the env var OTEL_SEMCONV_STABILITY_OPT_IN isn't being respected because it isn't being by the evaluated by the middleware_args helper method?

cc @hannahramadan

Yes, that's right. We want to use middleware_args without all the logic around OTEL_SEMCONV_STABILITY_OPT_IN being on the API client.

[hannahramadan]

Thanks @sergiofbsilva! This looks like a good change, and allows users to continuing using middleware_args vs needing to explicitly add one of the new middleware_args_* methods. We look forward to reviewing when you're ready.

[sergiofbsilva]

Hi @hannahramadan

I just signed the CLA and moved from Draft to Open, I think you can review it, thanks!

[sergiofbsilva]

@hannahramadan updated the tests, CI was failing, updated branch.

[hannahramadan]

🚀

[kaylareopelle]

Thanks, @sergiofbsilva! This is much cleaner.

[kaylareopelle]

@sergiofbsilva - I'm changing the conventional commit prefix to fix so that this triggers a new release. Thanks for your contribution!