mirror of
https://github.com/tailscale/tailscale.git
synced 2024-11-26 03:25:35 +00:00
64db026c8b
Some programs use frequent short-duration backoffs even under non-error conditions. They can set this to avoid logging short backoffs when things are operating normally, but still get messages when longer backoffs kick in. Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>
59 lines
1.4 KiB
Go
59 lines
1.4 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
|
|
|
|
import (
|
|
"context"
|
|
"log"
|
|
"math/rand"
|
|
"time"
|
|
)
|
|
|
|
const MAX_BACKOFF_MSEC = 30000
|
|
|
|
type Backoff struct {
|
|
n int
|
|
// Name is the name of this backoff timer, for logging purposes.
|
|
Name string
|
|
// NewTimer is the function that acts like time.NewTimer().
|
|
// You can override this in unit tests.
|
|
NewTimer func(d time.Duration) *time.Timer
|
|
// LogLongerThan sets the minimum time of a single backoff interval
|
|
// before we mention it in the log.
|
|
LogLongerThan time.Duration
|
|
}
|
|
|
|
func (b *Backoff) BackOff(ctx context.Context, err error) {
|
|
if ctx.Err() == nil && err != nil {
|
|
b.n++
|
|
// n^2 backoff timer is a little smoother than the
|
|
// common choice of 2^n.
|
|
msec := b.n * b.n * 10
|
|
if msec > MAX_BACKOFF_MSEC {
|
|
msec = MAX_BACKOFF_MSEC
|
|
}
|
|
// Randomize the delay between 0.5-1.5 x msec, in order
|
|
// to prevent accidental "thundering herd" problems.
|
|
msec = rand.Intn(msec) + msec/2
|
|
dur := time.Duration(msec) * time.Millisecond
|
|
if dur >= b.LogLongerThan {
|
|
log.Printf("%s: backoff: %d msec\n", b.Name, msec)
|
|
}
|
|
newTimer := b.NewTimer
|
|
if newTimer == nil {
|
|
newTimer = time.NewTimer
|
|
}
|
|
t := newTimer(dur)
|
|
select {
|
|
case <-ctx.Done():
|
|
t.Stop()
|
|
case <-t.C:
|
|
}
|
|
} else {
|
|
// not a regular error
|
|
b.n = 0
|
|
}
|
|
}
|