micro/util/jitter/ticker.go
Vasiliy Tolstov f47fbb1030 config: add jitter interval for watcher to avoid dos
Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>
2021-08-04 00:37:56 +03:00

66 lines
1.4 KiB
Go

package jitter
import (
"time"
"github.com/unistack-org/micro/v3/util/rand"
)
// Ticker is similar to time.Ticker but ticks at random intervals between
// the min and max duration values (stored internally as int64 nanosecond
// counts).
type Ticker struct {
C chan time.Time
done chan chan struct{}
min int64
max int64
rng rand.Rand
}
// NewTicker returns a pointer to an initialized instance of the Ticker.
// Min and max are durations of the shortest and longest allowed
// ticks. Ticker will run in a goroutine until explicitly stopped.
func NewTicker(min, max time.Duration) *Ticker {
ticker := &Ticker{
C: make(chan time.Time),
done: make(chan chan struct{}),
min: min.Nanoseconds(),
max: max.Nanoseconds(),
}
go ticker.run()
return ticker
}
// Stop terminates the ticker goroutine and closes the C channel.
func (ticker *Ticker) Stop() {
c := make(chan struct{})
ticker.done <- c
<-c
}
func (ticker *Ticker) run() {
defer close(ticker.C)
t := time.NewTimer(ticker.nextInterval())
for {
// either a stop signal or a timeout
select {
case c := <-ticker.done:
t.Stop()
close(c)
return
case <-t.C:
select {
case ticker.C <- time.Now():
t.Stop()
t = time.NewTimer(ticker.nextInterval())
default:
// there could be noone receiving...
}
}
}
}
func (ticker *Ticker) nextInterval() time.Duration {
return time.Duration(ticker.rng.Int63n(ticker.max-ticker.min)+ticker.min) * time.Nanosecond
}