[API Proposal]: Allow to delete an instrument inside a Meter instance

[LGouellec]

Background and motivation

For now, when you create an instance of Meter you can create multiple types of instrument (Histogram, Counter, ObservableGauge or ObservableCounter).

But you can't delete one observable gauge (for instance) previously created. The only way is to dispose the Meter instance and recreate from scratch with all instruments minus the instrument supposed to remove. It's not efficient at all.

API Proposal

 public class Meter : IDisposable
{
       private List<Instrument> _instruments = new List<Instrument>();
       // ....

      public void Remove(Instrument instrument) {
           _instruments.Remove(instrument)
     }
}

API Usage

var meter = new Meter("ServiceName");
var gauge =  meter.CreateObservableGauge(
                        key, 
                        () => new[]
                        {
                            new Measurement<double>(
                                value,
                                tags)
                        },
                        description: summary);           

meter.Remove(gauge);

Alternative Designs

No response

Risks

No response

[tommcdon]

@noahfalk @tarekgh

[asasine]

I would think that having Instrument implement IDisposable is the canonical way to indicate that instruments are disposable. Stealing from the Observer design pattern, the instances of Instrument can hold references to their Meter and remove themself from the meter's collection when disposed. This further supports the DI model as types only need to depend on the appropriate instrument, not the meter, to accurately dispose of the instrument when the DI container disposes them.