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|
package backoff
import (
"context"
"time"
)
type ExponentialInterval struct {
current float64
maxInterval float64
minInterval float64
multiplier float64
jitter jitter
}
const (
defaultMaxInterval = float64(time.Minute)
defaultMinInterval = float64(500 * time.Millisecond)
defaultMultiplier = 1.5
)
func NewExponentialInterval(options ...ExponentialOption) *ExponentialInterval {
jitterFactor := 0.0
maxInterval := defaultMaxInterval
minInterval := defaultMinInterval
multiplier := defaultMultiplier
var rng Random
for _, option := range options {
switch option.Ident() {
case identJitterFactor{}:
jitterFactor = option.Value().(float64)
case identMaxInterval{}:
maxInterval = float64(option.Value().(time.Duration))
case identMinInterval{}:
minInterval = float64(option.Value().(time.Duration))
case identMultiplier{}:
multiplier = option.Value().(float64)
case identRNG{}:
rng = option.Value().(Random)
}
}
if minInterval > maxInterval {
minInterval = maxInterval
}
if multiplier <= 1 {
multiplier = defaultMultiplier
}
return &ExponentialInterval{
maxInterval: maxInterval,
minInterval: minInterval,
multiplier: multiplier,
jitter: newJitter(jitterFactor, rng),
}
}
func (g *ExponentialInterval) Next() time.Duration {
var next float64
if g.current == 0 {
next = g.minInterval
} else {
next = g.current * g.multiplier
}
if next > g.maxInterval {
next = g.maxInterval
}
if next < g.minInterval {
next = g.minInterval
}
// Apply jitter *AFTER* we calculate the base interval
next = g.jitter.apply(next)
g.current = next
return time.Duration(next)
}
type ExponentialPolicy struct {
cOptions []ControllerOption
igOptions []ExponentialOption
}
func NewExponentialPolicy(options ...ExponentialOption) *ExponentialPolicy {
var cOptions []ControllerOption
var igOptions []ExponentialOption
for _, option := range options {
switch opt := option.(type) {
case ControllerOption:
cOptions = append(cOptions, opt)
default:
igOptions = append(igOptions, opt)
}
}
return &ExponentialPolicy{
cOptions: cOptions,
igOptions: igOptions,
}
}
func (p *ExponentialPolicy) Start(ctx context.Context) Controller {
ig := NewExponentialInterval(p.igOptions...)
return newController(ctx, ig, p.cOptions...)
}
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