[Metrics] Example for filtering which metrics we want to export

[bsarden]

I'm trying to build a user application that exposes which metrics we want to export via regex. For example:

# Export all metrics under the foo.bar namespace
$ ./my-application --metrics_filter="foo\.bar.*"

Is this possible to do? IIUC, the InstrumentSelector, MetricSelector, and Predicate classes indicate that this functionality is achievable. However, I can't find any pointers into how we expose the ability to configure which metrics to export to the user. Happy to convert this into an example and send a PR after completing!

[bsarden]

FWIW, it looks like filtering is possible on the otel-collector. Still, I'd like to filter before logs are sent to the otel-collector to avoid paying the runtime cost for observing View's that I don't intend to consume downstream.

Thanks in advance!