mirror of
https://github.com/cloudflare/cloudflared
synced 2026-06-08 13:33:07 +00:00
Miguel da Costa Martins Marcelino
a9b6f703f0
This introduces the main precheck logic. This will follow concurrency model, timeout handling, and retry logic established in the SPEC. We will follow the decision flow in the [connectivity pre-checks SPEC](https://wiki.cfdata.org/spaces/TUN/pages/1374967685/Connectivity+Pre-checks+for+cloudflared). You can find an attached image of what the decision flow should look like. {width=900 height=235}
84 lines
2.3 KiB
Markdown
84 lines
2.3 KiB
Markdown
# backoff
|
|
## Go implementation of "Exponential Backoff And Jitter"
|
|
|
|
This package implements the backoff strategy described in the AWS
|
|
Architecture Blog article
|
|
["Exponential Backoff And Jitter"](http://www.awsarchitectureblog.com/2015/03/backoff.html). Essentially,
|
|
the backoff has an interval `time.Duration`; the *n<sup>th</sup>* call
|
|
to backoff will return an a `time.Duration` that is *2 <sup>n</sup> *
|
|
interval*. If jitter is enabled (which is the default behaviour), the
|
|
duration is a random value between 0 and *2 <sup>n</sup> * interval*.
|
|
The backoff is configured with a maximum duration that will not be
|
|
exceeded; e.g., by default, the longest duration returned is
|
|
`backoff.DefaultMaxDuration`.
|
|
|
|
## Usage
|
|
|
|
A `Backoff` is initialised with a call to `New`. Using zero values
|
|
causes it to use `DefaultMaxDuration` and `DefaultInterval` as the
|
|
maximum duration and interval.
|
|
|
|
```
|
|
package something
|
|
|
|
import "github.com/cloudflare/backoff"
|
|
|
|
func retryable() {
|
|
b := backoff.New(0, 0)
|
|
for {
|
|
err := someOperation()
|
|
if err == nil {
|
|
break
|
|
}
|
|
|
|
log.Printf("error in someOperation: %v", err)
|
|
<-time.After(b.Duration())
|
|
}
|
|
|
|
log.Printf("succeeded after %d tries", b.Tries()+1)
|
|
b.Reset()
|
|
}
|
|
```
|
|
|
|
It can also be used to rate limit code that should retry infinitely, but which does not
|
|
use `Backoff` itself.
|
|
|
|
```
|
|
package something
|
|
|
|
import (
|
|
"time"
|
|
|
|
"github.com/cloudflare/backoff"
|
|
)
|
|
|
|
func retryable() {
|
|
b := backoff.New(0, 0)
|
|
b.SetDecay(30 * time.Second)
|
|
|
|
for {
|
|
// b will reset if someOperation returns later than
|
|
// the last call to b.Duration() + 30s.
|
|
err := someOperation()
|
|
if err == nil {
|
|
break
|
|
}
|
|
|
|
log.Printf("error in someOperation: %v", err)
|
|
<-time.After(b.Duration())
|
|
}
|
|
}
|
|
```
|
|
|
|
## Tunables
|
|
|
|
* `NewWithoutJitter` creates a Backoff that doesn't use jitter.
|
|
|
|
The default behaviour is controlled by two variables:
|
|
|
|
* `DefaultInterval` sets the base interval for backoffs created with
|
|
the zero `time.Duration` value in the `Interval` field.
|
|
* `DefaultMaxDuration` sets the maximum duration for backoffs created
|
|
with the zero `time.Duration` value in the `MaxDuration` field.
|
|
|