KVConfig. MetricsRegisterer looks an anti-pattern

[pracucci]

The KVConfig defined in kv/memberlist/memberlist_client.go includes MetricsRegisterer prometheus.Registerer:

dskit/kv/memberlist/memberlist_client.go

Lines 157 to 159 in a48e5b8

	// Where to put custom metrics. Metrics are not registered, if this is nil.
	MetricsRegisterer prometheus.Registerer `yaml:"-"`
	MetricsNamespace string `yaml:"-"`

This looks an anti-pattern to me. The registerer is typically specified in the NewXXX() function. In this case, I'm wondering if we could remove the registered from there and take it in input in the NewKV() function.

Any reason why not doing it?

[pstibrany]

Sounds good to me. I am pretty sure I've added this to Cortex before we started to pass registrerer via New function, and we just used default registrerer everywhere, which I thought is ugly. Let's fix it.

[pstibrany]

I would suggest dropping MetricsNamespace too, this is better solved by using registrerer with prefix.