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retry.go
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retry.go
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package backoff
import (
"errors"
"time"
)
// An OperationWithData is executing by RetryWithData() or RetryNotifyWithData().
// The operation will be retried using a backoff policy if it returns an error.
type OperationWithData[T any] func() (T, error)
// An Operation is executing by Retry() or RetryNotify().
// The operation will be retried using a backoff policy if it returns an error.
type Operation func() error
func (o Operation) withEmptyData() OperationWithData[struct{}] {
return func() (struct{}, error) {
return struct{}{}, o()
}
}
// Notify is a notify-on-error function. It receives an operation error and
// backoff delay if the operation failed (with an error).
//
// NOTE that if the backoff policy stated to stop retrying,
// the notify function isn't called.
type Notify func(error, time.Duration)
// Retry the operation o until it does not return error or BackOff stops.
// o is guaranteed to be run at least once.
//
// If o returns a *PermanentError, the operation is not retried, and the
// wrapped error is returned.
//
// Retry sleeps the goroutine for the duration returned by BackOff after a
// failed operation returns.
func Retry(o Operation, b BackOff) error {
return RetryNotify(o, b, nil)
}
// RetryWithData is like Retry but returns data in the response too.
func RetryWithData[T any](o OperationWithData[T], b BackOff) (T, error) {
return RetryNotifyWithData(o, b, nil)
}
// RetryNotify calls notify function with the error and wait duration
// for each failed attempt before sleep.
func RetryNotify(operation Operation, b BackOff, notify Notify) error {
return RetryNotifyWithTimer(operation, b, notify, nil)
}
// RetryNotifyWithData is like RetryNotify but returns data in the response too.
func RetryNotifyWithData[T any](operation OperationWithData[T], b BackOff, notify Notify) (T, error) {
return doRetryNotify(operation, b, notify, nil)
}
// RetryNotifyWithTimer calls notify function with the error and wait duration using the given Timer
// for each failed attempt before sleep.
// A default timer that uses system timer is used when nil is passed.
func RetryNotifyWithTimer(operation Operation, b BackOff, notify Notify, t Timer) error {
_, err := doRetryNotify(operation.withEmptyData(), b, notify, t)
return err
}
// RetryNotifyWithTimerAndData is like RetryNotifyWithTimer but returns data in the response too.
func RetryNotifyWithTimerAndData[T any](operation OperationWithData[T], b BackOff, notify Notify, t Timer) (T, error) {
return doRetryNotify(operation, b, notify, t)
}
func doRetryNotify[T any](operation OperationWithData[T], b BackOff, notify Notify, t Timer) (T, error) {
var (
err error
next time.Duration
res T
)
if t == nil {
t = &defaultTimer{}
}
defer func() {
t.Stop()
}()
ctx := getContext(b)
b.Reset()
for {
res, err = operation()
if err == nil {
return res, nil
}
var permanent *PermanentError
if errors.As(err, &permanent) {
return res, permanent.Err
}
if next = b.NextBackOff(); next == Stop {
if cerr := ctx.Err(); cerr != nil {
return res, cerr
}
return res, err
}
if notify != nil {
notify(err, next)
}
t.Start(next)
select {
case <-ctx.Done():
return res, ctx.Err()
case <-t.C():
}
}
}
// PermanentError signals that the operation should not be retried.
type PermanentError struct {
Err error
}
func (e *PermanentError) Error() string {
return e.Err.Error()
}
func (e *PermanentError) Unwrap() error {
return e.Err
}
func (e *PermanentError) Is(target error) bool {
_, ok := target.(*PermanentError)
return ok
}
// Permanent wraps the given err in a *PermanentError.
func Permanent(err error) error {
if err == nil {
return nil
}
return &PermanentError{
Err: err,
}
}