open-consul/lib/cluster.go

62 lines
1.7 KiB
Go

package lib
import (
"math/rand"
"time"
)
const (
// minRate is the minimum rate at which we allow an action to be performed
// across the whole cluster. The value is once a day: 1 / (1 * time.Day)
minRate = 1.0 / 86400
)
// DurationMinusBuffer returns a duration, minus a buffer and jitter
// subtracted from the duration. This function is used primarily for
// servicing Consul TTL Checks in advance of the TTL.
func DurationMinusBuffer(intv time.Duration, buffer time.Duration, jitter int64) time.Duration {
d := intv - buffer
if jitter == 0 {
d -= RandomStagger(d)
} else {
d -= RandomStagger(time.Duration(int64(d) / jitter))
}
return d
}
// DurationMinusBufferDomain returns the domain of valid durations from a
// call to DurationMinusBuffer. This function is used to check user
// specified input values to DurationMinusBuffer.
func DurationMinusBufferDomain(intv time.Duration, buffer time.Duration, jitter int64) (min time.Duration, max time.Duration) {
max = intv - buffer
if jitter == 0 {
min = max
} else {
min = max - time.Duration(int64(max)/jitter)
}
return min, max
}
// RandomStagger returns an interval between 0 and the duration
func RandomStagger(intv time.Duration) time.Duration {
if intv == 0 {
return 0
}
return time.Duration(uint64(rand.Int63()) % uint64(intv))
}
// RateScaledInterval is used to choose an interval to perform an action in
// order to target an aggregate number of actions per second across the whole
// cluster.
func RateScaledInterval(rate float64, min time.Duration, n int) time.Duration {
if rate <= minRate {
return min
}
interval := time.Duration(float64(time.Second) * float64(n) / rate)
if interval < min {
return min
}
return interval
}