mirror of
https://github.com/tailscale/tailscale.git
synced 2024-11-26 03:25:35 +00:00
86a902b201
Updates #1548 Change-Id: Ia55f1b5dc7dfea09a08c90324226fb92cd10fa00 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
83 lines
2.2 KiB
Go
83 lines
2.2 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Package backoff provides a back-off timer type.
|
|
package backoff
|
|
|
|
import (
|
|
"context"
|
|
"math/rand"
|
|
"time"
|
|
|
|
"tailscale.com/types/logger"
|
|
)
|
|
|
|
// Backoff tracks state the history of consecutive failures and sleeps
|
|
// an increasing amount of time, up to a provided limit.
|
|
type Backoff struct {
|
|
n int // number of consecutive failures
|
|
maxBackoff time.Duration
|
|
|
|
// Name is the name of this backoff timer, for logging purposes.
|
|
name string
|
|
// logf is the function used for log messages when backing off.
|
|
logf logger.Logf
|
|
|
|
// NewTimer is the function that acts like time.NewTimer.
|
|
// It's for use in unit tests.
|
|
NewTimer func(time.Duration) *time.Timer
|
|
|
|
// LogLongerThan sets the minimum time of a single backoff interval
|
|
// before we mention it in the log.
|
|
LogLongerThan time.Duration
|
|
}
|
|
|
|
// NewBackoff returns a new Backoff timer with the provided name (for logging), logger,
|
|
// and max backoff time. By default, all failures (calls to BackOff with a non-nil err)
|
|
// are logged unless the returned Backoff.LogLongerThan is adjusted.
|
|
func NewBackoff(name string, logf logger.Logf, maxBackoff time.Duration) *Backoff {
|
|
return &Backoff{
|
|
name: name,
|
|
logf: logf,
|
|
maxBackoff: maxBackoff,
|
|
NewTimer: time.NewTimer,
|
|
}
|
|
}
|
|
|
|
// Backoff sleeps an increasing amount of time if err is non-nil.
|
|
// and the context is not a
|
|
// It resets the backoff schedule once err is nil.
|
|
func (b *Backoff) BackOff(ctx context.Context, err error) {
|
|
if err == nil {
|
|
// No error. Reset number of consecutive failures.
|
|
b.n = 0
|
|
return
|
|
}
|
|
if ctx.Err() != nil {
|
|
// Fast path.
|
|
return
|
|
}
|
|
|
|
b.n++
|
|
// n^2 backoff timer is a little smoother than the
|
|
// common choice of 2^n.
|
|
d := time.Duration(b.n*b.n) * 10 * time.Millisecond
|
|
if d > b.maxBackoff {
|
|
d = b.maxBackoff
|
|
}
|
|
// Randomize the delay between 0.5-1.5 x msec, in order
|
|
// to prevent accidental "thundering herd" problems.
|
|
d = time.Duration(float64(d) * (rand.Float64() + 0.5))
|
|
|
|
if d >= b.LogLongerThan {
|
|
b.logf("%s: [v1] backoff: %d msec", b.name, d.Milliseconds())
|
|
}
|
|
t := b.NewTimer(d)
|
|
select {
|
|
case <-ctx.Done():
|
|
t.Stop()
|
|
case <-t.C:
|
|
}
|
|
}
|