minor update: update method name of TraceContext

[wbpcode]

Commit Message: minor update: update method name of TraceContext
Additional Description:

Update authority() of TraceContext to host() as the host is more widely used to represent k8s service name, dns domain, VIP, etc.

Risk Level: n/a.
Testing: n/a.
Docs Changes: n/a.
Release Notes: n/a.
Platform Specific Features: n/a.

[KBaichoo]

/assign-from @envoyproxy/envoy-maintainers

[repokitteh-read-only]

@envoyproxy/envoy-maintainers assignee is @kyessenov

🐱

Caused by: a #24826 (comment) was created by @KBaichoo.

see: more, trace.

[yanavlasov]

I'm unsure this is the right naming. authority represents a well defined term in the HTTP standard and the header map returns the authority per the standard. host does not have this well defined meaning. I understand that host is used more widely in k8s but this code deals with HTTP, not k8s. As such authority is a more appropriate name here.

[yanavlasov]

/wait-any

[kyessenov]

I tend to agree with Yan: authority is internally consistent with the rest of the Envoy codebase, for better or worse. There'll always be a nomenclature gap between the user and the machine APIs, that's why we have so many control planes that do the translation. User APIs are inherently ambiguous to permit options, while machine APIs are precise.

[kyessenov]

/wait-any

[wbpcode]

@yanavlasov yeah, authority is best for HTTP. But the TraceContext is designed as a protocol independent abstraction. It may be implemented by thrift, dubbo or some others third party protocol proxies.
So I want to use host here to represent the meaning of collection of instances (domain, VIP, registered service name, etc) of different protocols. 🤔

Cc @kyessenov

[kyessenov]

I'll leave this one to Yan. I think it makes sense to generalize tracing beyond HTTP and follow https://opentelemetry.io/docs/reference/specification/trace/semantic_conventions/span-general/#nethostname.

[wbpcode]

Friendly ping @yanavlasov

[wbpcode]

friendly ping @yanavlasov

[yanavlasov]

Ok, makes sense. Thanks.