Method Advance

modules/generator/registry/cardinality.go:107–142

Advance should be called by an external ticker every sketchDuration to advance the ring. It advances at least 1 step per call.

()

// Advance should be called by an external ticker every sketchDuration to advance the ring.
// It advances at least 1 step per call.
func (c *Cardinality) Advance() {
	c.mu.Lock()
	delta := time.Since(c.lastAdvance)
	steps := 0
	if delta < c.sketchDuration {
		steps = 1
	} else {
		steps = int(delta / c.sketchDuration)
	}
	// Cap steps so we don't loop excessively after very long pauses.
	if steps > c.sketchesLength {
		steps = c.sketchesLength
	}

	for i := 0; i < steps; i++ {
		// advance ring
		c.current++
		if c.current >= c.sketchesLength {
			c.current = 0
		}
		// reset new current sketch
		c.sketches[c.current], _ = hll.NewSketch(c.precision, true)
		c.lastAdvance = c.lastAdvance.Add(c.sketchDuration)
	}

	// Recompute cached merge of all non-current sketches
	cachedMerge, _ := hll.NewSketch(c.precision, true)
	for i := 0; i < c.sketchesLength; i++ {
		if i == c.current {
			continue
		}
		_ = cachedMerge.Merge(c.sketches[i])
	}
	c.cachedMerge = cachedMerge
	c.mu.Unlock()
}