// Blueflood will use the finest-grained resolution which doesn't exceed the slot limit.
// Thus, if you request too many points, it will automatically reduce the resolution.
func (b *Blueflood) ChooseResolution(requested api.Timerange, smallestResolution time.Duration) time.Duration {
// In some cases, coarser-resolution data may have a shorter TTL.
// To accomodate these cases, it must be verified that the requested timerange will
// actually be present for the chosen resolution.
// TODO: figure out how to make this work with moving averages and timeshifts
requiredAge := b.timeSource().Sub(requested.StartTime())
for _, resolution := range Resolutions {
survivesFor := b.config.oldestViableDataForResolution(resolution)
if survivesFor < requiredAge {
// The data probably won't be around for the earliest part of the timerange,
// so don't use this resolution
continue
}
if resolution.duration < requested.Resolution() {
// Skip this timerange, it is finer than the one requested.
continue
}
// Check that the timerange is large enough
if resolution.duration >= smallestResolution {
return resolution.duration
}
}
// Leave it alone, since a better one can't be found
return requested.Resolution()
}
