This issue started from this comment: https://gitlab.cee.redhat.com/red-hat-3scale-documentation/3scale-documentation/-/merge_requests/1310#note_6453575

With opentracing, APICast generates multiple spans (1 parent span, 3 descendants) with the shared traceID:

• Span 1: Operation name: "apicast"
  • Span 1.1: Operation name: /
  • Span 1.2: Operation name: "@upstream"
  • Span 1.3: Operation name: "@out_of_band_authrep_action"

See opentracing.png image as example

Whereas opentelemetry instrumentation, APICast only generates 1 span (for 1 service and 1 operation)

• Span 1: Operation name: "apicast"

See opentelemetry.png image as example

The main purpose is provide details about time taken to perform upstream and backend actions

Proposed solution (TODO)

• Apicast operation will not generate spans for operations like "/", "@upstream" or "@out_of_band_authrep_action". Each component should generate it's own tracing report.
• The span generated by APIcast should be used as parent span for upstream and backend spans
• APICast will enable opentelemetry_trust_incoming_spans which enables using spans from incoming requests as parent for created ones
• APICast will propagate distributed tracing headers, e.g. traceparent, to upstream (already done) and backend (TODO)
• 3scale Backend should be instrumented (TODO) using opentelemetry SDK. Sintra has instrumentation in place implemented in https://github.com/open-telemetry/opentelemetry-ruby-contrib/tree/main/instrumentation/sinatra
• Upstream, which is not managed by 3scale, should also add instrumentation to add more tracing data

In summary,