open-consul/command/agent/util.go

package agent

import (
	"math"
	"math/rand"
	"time"
)

const (
	// This scale factor means we will add a minute after we
	// cross 128 nodes, another at 256, another at 512, etc.
	// By 8192 nodes, we will scale up by a factor of 8
	aeScaleThreshold = 128
)

// aeScale is used to scale the time interval at which anti-entropy
// take place. It is used to prevent saturation as the cluster size grows
func aeScale(interval time.Duration, n int) time.Duration {
	// Don't scale until we cross the threshold
	if n <= aeScaleThreshold {
		return interval
	}

	multiplier := math.Ceil(math.Log2(float64(n))-math.Log2(aeScaleThreshold)) + 1.0
	return time.Duration(multiplier) * interval
}

// Returns a random stagger interval between 0 and the duration
func randomStagger(intv time.Duration) time.Duration {
	return time.Duration(uint64(rand.Int63()) % uint64(intv))
}