4.x MP metrics doc refers to `RegistryFactory` which is package private in 4.x about helidon HOT 2 CLOSED

What you say is true for SE. This issue addresses MP, which still uses separate MP MetricRegistry instances for each scope as in the MP Metrics spec.

Previously, users could invoke RegistryFactory.getInstance().getRegistry(registryType) from SE or MP code to get the MetricRegistry for a particular type (now called scope). RegistryFactory has moved into helidon-microprofile-metrics in 4.0 and is currently package-private.

Currently the developer of an MP app can use injection to get a reference to a MetricRegistry if the scope name is known at compile-time, but there is no way to retrieve a given scope's MetricRegistry programmatically.

There are no public elements on RegistryFactory currently in 4.0, so one way we could allow this use case would be to change the RegistryFactory class to public and add a single static method:

public static MetricRegistry getRegistry(String scopeName) {
    return getInstance().getRegistry(scopeName);
}

This would not expose any of the existing methods or their types publicly while keeping an API close to what Helidon 3 developers had used previously.

from helidon.

What is the use case here?
I thought that we have Metrics.globalRegistry() that supports creating and getting meters for specific scopes...

from helidon.