godot-host-test/Game/Metrics/MetricsHandler.cs

using System;
using System.Diagnostics.Metrics;
using GodotHostTest.Interfaces;
using Microsoft.Extensions.Logging;
using OwofGames.GodotHost;
using OwofGames.GodotHost.Observability;
using OwofGames.GodotLume;
using R3;

namespace GodotHostTest.Game.Metrics;

public class MetricsHandler(
    ILogger<MetricsHandler> logger,
    IOptional<IMeterFactory> meterFactoryWrapper,
    ITargetEventBus targetEventBus) : IHostLifetime
{
    private IDisposable? _disposables;

    public void Startup()
    {
        if (!meterFactoryWrapper.TryGet(out var meterFactory))
        {
            logger.LogWarning("Metrics not enabled, cannot start local metrics");
            return;
        }

        // create meter
        var meter = meterFactory.Create();

        // create instruments
        var hitTargetsCounter =
            meter.CreateCounter<int>("targets.hit", description: "number of targets hit");
        var missedTargetsCounter =
            meter.CreateCounter<int>("targets.missed", description: "number of targets missed");

        // feed instruments data, and contextually create the disposable to clean up at shutdown time
        _disposables = Disposable.Combine(
            targetEventBus.Hit.Subscribe(_ => hitTargetsCounter.Add(1)),
            targetEventBus.TimedOut.Subscribe(_ => missedTargetsCounter.Add(1)),
            meter
        );
    }

    public void Shutdown()
    {
        _disposables?.Dispose();
    }
}