metrics collecting middleware

HttpMetricsMiddleware.cs

public class HttpMetricsMiddleware
{
    private readonly RequestDelegate next;
    private static readonly Gauge httpInProgress = Prometheus.Metrics.CreateGauge("http_requests_in_progress", "Number or requests in progress", "system");
    private static readonly Histogram httpRequestsDuration = Prometheus.Metrics.CreateHistogram("http_requests_duration_seconds", "Duration of http requests per tracking system", "system");
    
    public HttpMetricsMiddleware(RequestDelegate next)
    {
        this.next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        string[] subsystem = new string[1];
        var path = context.Request.Path;

        // will not track request to diagnostics endpoints
        if (path.StartsWithSegments("/metrics"))
        {
            await next(context);
            return;
        }

        using var inprogress = httpInProgress.TrackInProgress();
        using var timer = httpRequestsDuration.NewTimer();

        try
        {
            await next(context);
        }
        catch (Exception)
        {
            CommonMetrics.ExceptionsOccur.Inc();
            throw;
        }
    }
}