fix!: total order constraint on span.status=

[fbogsany]

See open-telemetry/opentelemetry-specification#1685

BREAKING CHANGES

• The OpenTelemetry::Trace::Util::HttpToStatus module has been removed. It previously contributed the http_to_status class method to the Status class. That method incorrectly set the span status to OK for response codes in the range 100..399. Calls to that method should be changed as follows:

# change:
span.status = OpenTelemetry::Trace::Status.http_to_status(response_code)
# to:
span.status = OpenTelemetry::Trace::Status.error unless (100..399).include?(response_code.to_i)

• The Status.new(code, description:) initializer has been hidden in favour of simpler constructors for each status code: Status.ok, Status.error and Status.unset. Each constructor takes an optional description.

[robertlaurin]

Excon is doing something fishy with span status here, probably needs to be updated.

opentelemetry-ruby/instrumentation/excon/lib/opentelemetry/instrumentation/excon/middlewares/tracer_middleware.rb

Lines 82 to 84 in 353c381

	span.status = OpenTelemetry::Trace::Status.http_to_status(
	response[:status]
	)

[robertlaurin]

If instrumentation is not supposed to set an OK status anymore we probably need to look for uses of this too

opentelemetry-ruby/api/lib/opentelemetry/trace/util/http_to_status.rb

Lines 11 to 24 in 353c381

	module HttpToStatus
	# Maps numeric HTTP status codes to Trace::Status. This module is a mixin for Trace::Status
	# and is not intended for standalone use.
	#
	# @param code Numeric HTTP status
	# @return Status
	def http_to_status(code)
	case code.to_i
	when 100..399
	new(const_get(:OK))
	else
	new(const_get(:ERROR))
	end
	end

[fbogsany]

I think we need to 👀 the semantic conventions for HTTP instrumentation - I think there was a requirement to set the span status based on the response code.

[robertlaurin]

Span Status MUST be left unset if HTTP status code was in the 1xx, 2xx or 3xx ranges, unless there was another error (e.g., network error receiving the response body; or 3xx codes with max redirects exceeded), in which case status MUST be set to Error.

For HTTP status codes in the 4xx and 5xx ranges, as well as any other code the client failed to interpret, status MUST be set to Error.

Don't set the span status description if the reason can be inferred from http.status_code.

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#status

Updated since review

[ahayworth]

LGTM!