storage/remote/write.go
func (t *timestampTracker) Add(_ labels.Labels, ts int64, v float64) (uint64, error) {
	t.samples++
	if ts > t.highestTimestamp {
		t.highestTimestamp = ts
	}
	return 0, nil
}
func (t *timestampTracker) Add(_ labels.Labels, ts int64, v float64) (uint64, error) {
	t.samples++
	if ts > t.highestTimestamp {
		t.highestTimestamp = ts
	}
	return 0, nil
}
// Add implements storage.Appender.