README
¶
backoff
Exponential backoff algorithm with randomized jitter
Example
package main
import (
"context"
"fmt"
"log"
"net/http"
"time"
"github.com/go-tk/backoff"
"github.com/go-tk/optional"
)
func main() {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
_ = cancel
b := backoff.New(backoff.Options{
MinDelay: optional.MakeDuration(100 * time.Millisecond), // default
MaxDelay: optional.MakeDuration(100 * time.Second), // default
DelayFactor: optional.MakeFloat64(2), // default
MaxDelayJitter: optional.MakeFloat64(1), // default
DelayFunc: backoff.DelayWithContext(ctx), // with respect to ctx
MaxNumberOfAttempts: optional.MakeInt(100), // default
})
req, err := http.NewRequestWithContext(ctx, "GET", "http://example.com/", nil)
if err != nil {
log.Fatal(err)
}
for {
resp, err := http.DefaultClient.Do(req)
if err != nil {
if err2 := b.Do(); err2 != nil { // delay
log.Printf("failed to back off; err=%q", err2)
log.Fatal(err)
}
continue // retry
}
resp.Body.Close()
if resp.StatusCode/100 == 5 {
err := fmt.Errorf("http server error; httpStatusCode=%v", resp.StatusCode)
if err2 := b.Do(); err2 != nil { // delay
log.Printf("failed to back off; err=%q", err2)
log.Fatal(err)
}
continue // retry
}
fmt.Println(resp.StatusCode)
return
}
// Output:
// 200
}
Documentation
¶
Overview ¶
Package backoff implements the exponential backoff algorithm with randomized jitter.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
View Source
var ErrTooManyAttempts = errors.New("backoff: too many attempts")
ErrTooManyAttempts is returned when the maximum number of attempts to back off has been reached.
Functions ¶
This section is empty.
Types ¶
type Backoff ¶
type Backoff struct {
// contains filtered or unexported fields
}
Backoff represents an instance of the exponential backoff algorithm.
Example ¶
package main
import (
"context"
"fmt"
"log"
"net/http"
"time"
"github.com/go-tk/backoff"
"github.com/go-tk/optional"
)
func main() {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
_ = cancel
b := backoff.New(backoff.Options{
MinDelay: optional.MakeDuration(100 * time.Millisecond), // default
MaxDelay: optional.MakeDuration(100 * time.Second), // default
DelayFactor: optional.MakeFloat64(2), // default
MaxDelayJitter: optional.MakeFloat64(1), // default
DelayFunc: backoff.DelayWithContext(ctx), // with respect to ctx
MaxNumberOfAttempts: optional.MakeInt(100), // default
})
req, err := http.NewRequestWithContext(ctx, "GET", "http://example.com/", nil)
if err != nil {
log.Fatal(err)
}
for {
resp, err := http.DefaultClient.Do(req)
if err != nil {
if err2 := b.Do(); err2 != nil { // delay
log.Printf("failed to back off; err=%q", err2)
log.Fatal(err)
}
continue // retry
}
resp.Body.Close()
if resp.StatusCode/100 == 5 {
err := fmt.Errorf("http server error; httpStatusCode=%v", resp.StatusCode)
if err2 := b.Do(); err2 != nil { // delay
log.Printf("failed to back off; err=%q", err2)
log.Fatal(err)
}
continue // retry
}
fmt.Println(resp.StatusCode)
return
}
}
Output: 200
type DelayFunc ¶
type DelayFunc func(timedOut <-chan struct{}) (err error)
DelayFunc is the type of the function blocking until the timed-out event happens.
func DelayWithContext ¶
DelayWithContext makes a DelayFunc with respect to the given ctx.
type Options ¶
type Options struct {
// Default value is 100ms.
// Value <= 0 is equivalent to default value.
MinDelay optional.Duration
// Default value is 100s.
// Value <= 0 is equivalent to default value.
MaxDelay optional.Duration
// Default value is 2.
// Value < 1 is equivalent to default value.
DelayFactor optional.Float64
// Default value is 1.
// Value <= 0 means no delay jitter.
// Value > 1 is equivalent to 1.
MaxDelayJitter optional.Float64
// Default value is:
// func(timedOut <-chan struct{}) error {
// <-timedOut
// return nil
// }
DelayFunc DelayFunc
// Default value is 100.
// Value < 0 means no limit on the number of attempts.
MaxNumberOfAttempts optional.Int
}
Options represents options for backoffs.
The pseudo code for the delay calculation:
if delay is not initialized
delay = MIN_DELAY
else
delay = min(delay * DELAY_FACTOR, MAX_DELAY)
delay_jitter = random(-MAX_DELAY_JITTER, MAX_DELAY_JITTER)
delay_with_jitter = delay * (1 + delay_jitter)
Source Files
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