[component] Review component.Host.GetFactory

[mx-psi]

component.Host.GetFactory is used by a single component: the receivercreator. While it may not be possible it would be great to consider if we can remove this or maybe make it optional (by having an optional interface that the service can implement). This would simplify the Host interface

[mx-psi]

One example where we do the optional interface thingie

opentelemetry-collector/extension/zpagesextension/zpagesextension.go

Lines 58 to 66 in 91f13c3

	hostZPages, ok := host.(interface {
	RegisterZPages(mux *http.ServeMux, pathPrefix string)
	})
	if ok {
	hostZPages.RegisterZPages(zPagesMux, "/debug")
	zpe.telemetry.Logger.Info("Registered Host's zPages")
	} else {
	zpe.telemetry.Logger.Warn("Host's zPages not available")
	}

[TylerHelmuth]

Removing it from the component.Host interface and leaving it implemented on our implementation of component.Host seems fine to me.

On the other hand, the functionality is interesting and simple for any component.Host to implement, since it should already have all the component factories it is managing. Unlike #7370 where connectors were the clear solution to components needing to call GetExporters, this method is the only way for 1 component to create another.

Since we only have 1 use case that utilizes this feature, I am in favor of the optional interface approach, but would be ok if we choose to keep it on the interface.

[atoulme]

I think we could change the behavior so that the GetFactory method is available as a func as a receiver factory option. I'll try and draft something for review.

[atoulme]

Here is the draft PR with a design experiment: #10679

I changed the design a bit so you can only get access to receiver factories, hopefully that's fine given the only use case we have is about creating receivers.

[mx-psi]

I think #10679 is interesting, but it also seems like something we can do after 1.0. If we are okay with removing this from component.Host and keeping on service, I think that's the bare minimum we can do now and we can look into something like #10679 afterwards