Time range rounding seems wrong when looking small intervals

[lukester1975]

Hi

Very small time period can miss data points, due to the data source rounding up the from time in getPrometheusTime(). E.g. for a range requested as from=2025-04-14T17:41:49.517Z&to=2025-04-14T17:41:50.503Z can look like:

Using the prometheus data source doesn't exhibit the same behaviour, though I haven't looked in to why (not sure if it sends sub-second timestamps, or rounds differently).

Anyway, a trivial fix still using seconds is to use ceil/floor as appropriate:

  getPrometheusTime(date: string | DateTime, roundUp: boolean) {
    if (typeof date === 'string') {
      date = dateMath.parse(date, roundUp)!;
    }

    if (roundUp) {
      return Math.ceil(date.valueOf() / 1000);
    } else {
      return Math.floor(date.valueOf() / 1000);
    }
  }

Which looks better:

Happy to make a PR but I've no idea if this is the best approach. It was just an obviously quick workaround once I realised where the rounding was happening.

Thanks!