Simple library for retry mechanism
Slightly inspired by Try::Tiny::Retry
HTTP GET with retry:
url := "http://example.com"
var body []byte
err := retry.Do(
func() error {
resp, err := http.Get(url)
if err != nil {
return err
}
defer resp.Body.Close()
body, err = ioutil.ReadAll(resp.Body)
if err != nil {
return err
}
return nil
},
)
if err != nil {
// handle error
}
fmt.Println(string(body))
HTTP GET with retry with data:
url := "http://example.com"
body, err := retry.DoWithData(
func() ([]byte, error) {
resp, err := http.Get(url)
if err != nil {
return nil, err
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
return body, nil
},
)
if err != nil {
// handle error
}
fmt.Println(string(body))
-
giantswarm/retry-go - slightly complicated interface.
-
sethgrid/pester - only http retry for http calls with retries and backoff
-
cenkalti/backoff - Go port of the exponential backoff algorithm from Google's HTTP Client Library for Java. Really complicated interface.
-
rafaeljesus/retry-go - looks good, slightly similar as this package, don't have 'simple'
Retrymethod -
matryer/try - very popular package, nonintuitive interface (for me)
-
4.0.0
- infinity retry is possible by set
Attempts(0)by PR #49
- infinity retry is possible by set
-
3.0.0
DelayTypeFuncaccepts a new parametererr- this breaking change affects only your custom Delay Functions. This change allow make delay functions based on error.
-
1.0.2 -> 2.0.0
- argument of
retry.Delayis final delay (no multiplication byretry.Unitsanymore) - function
retry.Unitsare removed - more about this breaking change
- argument of
-
0.3.0 -> 1.0.0
retry.Retryfunction are changed toretry.Dofunctionretry.RetryCustom(OnRetry) andretry.RetryCustomWithOptsfunctions are now implement via functions produces Options (akaretry.OnRetry)
func BackOffDelay(n uint, _ error, config *Config) time.DurationBackOffDelay is a DelayType which increases delay between consecutive retries
func Do(retryableFunc RetryableFunc, opts ...Option) errorfunc DoWithData[T any](retryableFunc RetryableFuncWithData[T], opts ...Option) (T, error)func FixedDelay(_ uint, _ error, config *Config) time.DurationFixedDelay is a DelayType which keeps delay the same through all iterations
func IsRecoverable(err error) boolIsRecoverable checks if error is an instance of unrecoverableError
func RandomDelay(_ uint, _ error, config *Config) time.DurationRandomDelay is a DelayType which picks a random delay up to config.maxJitter
func Unrecoverable(err error) errorUnrecoverable wraps an error in unrecoverableError struct
type Config struct {
}type DelayTypeFunc func(n uint, err error, config *Config) time.DurationDelayTypeFunc is called to return the next delay to wait after the retriable
function fails on err after n attempts.
func CombineDelay(delays ...DelayTypeFunc) DelayTypeFuncCombineDelay is a DelayType the combines all of the specified delays into a new DelayTypeFunc
type Error []errorError type represents list of errors in retry
func (e Error) As(target interface{}) boolfunc (e Error) Error() stringError method return string representation of Error It is an implementation of error interface
func (e Error) Is(target error) boolfunc (e Error) Unwrap() errorUnwrap the last error for compatibility with errors.Unwrap(). When you need to
unwrap all errors, you should use WrappedErrors() instead.
err := Do(
func() error {
return errors.New("original error")
},
Attempts(1),
)
fmt.Println(errors.Unwrap(err)) # "original error" is printed
Added in version 4.2.0.
func (e Error) WrappedErrors() []errorWrappedErrors returns the list of errors that this Error is wrapping. It is an
implementation of the errwrap.Wrapper interface in package
errwrap so that retry.Error can be
used with that library.
type OnRetryFunc func(attempt uint, err error)Function signature of OnRetry function
type Option func(*Config)Option represents an option for retry.
func Attempts(attempts uint) OptionAttempts set count of retry. Setting to 0 will retry until the retried function succeeds. default is 10
func AttemptsForError(attempts uint, err error) OptionAttemptsForError sets count of retry in case execution results in given err
Retries for the given err are also counted against total retries. The retry
will stop if any of given retries is exhausted.
added in 4.3.0
func Context(ctx context.Context) OptionContext allow to set context of retry default are Background context
example of immediately cancellation (maybe it isn't the best example, but it describes behavior enough; I hope)
ctx, cancel := context.WithCancel(context.Background())
cancel()
retry.Do(
func() error {
...
},
retry.Context(ctx),
)
func Delay(delay time.Duration) OptionDelay set delay between retry default is 100ms
func DelayType(delayType DelayTypeFunc) OptionDelayType set type of the delay between retries default is BackOff
func LastErrorOnly(lastErrorOnly bool) Optionreturn the direct last error that came from the retried function default is false (return wrapped errors with everything)
func MaxDelay(maxDelay time.Duration) OptionMaxDelay set maximum delay between retry does not apply by default
func MaxJitter(maxJitter time.Duration) OptionMaxJitter sets the maximum random Jitter between retries for RandomDelay
func OnRetry(onRetry OnRetryFunc) OptionOnRetry function callback are called each retry
log each retry example:
retry.Do(
func() error {
return errors.New("some error")
},
retry.OnRetry(func(n uint, err error) {
log.Printf("#%d: %s\n", n, err)
}),
)
func RetryIf(retryIf RetryIfFunc) OptionRetryIf controls whether a retry should be attempted after an error (assuming there are any retry attempts remaining)
skip retry if special error example:
retry.Do(
func() error {
return errors.New("special error")
},
retry.RetryIf(func(err error) bool {
if err.Error() == "special error" {
return false
}
return true
})
)
By default RetryIf stops execution if the error is wrapped using
retry.Unrecoverable, so above example may also be shortened to:
retry.Do(
func() error {
return retry.Unrecoverable(errors.New("special error"))
}
)
func UntilSucceeded() OptionUntilSucceeded will retry until the retried function succeeds. Equivalent to setting Attempts(0).
func WithTimer(t Timer) OptionWithTimer provides a way to swap out timer module implementations. This primarily is useful for mocking/testing, where you may not want to explicitly wait for a set duration for retries.
example of augmenting time.After with a print statement
type struct MyTimer {}
func (t *MyTimer) After(d time.Duration) <- chan time.Time {
fmt.Print("Timer called!")
return time.After(d)
}
retry.Do(
func() error { ... },
retry.WithTimer(&MyTimer{})
)
func WrapContextErrorWithLastError(wrapContextErrorWithLastError bool) OptionWrapContextErrorWithLastError allows the context error to be returned wrapped with the last error that the retried function returned. This is only applicable when Attempts is set to 0 to retry indefinitly and when using a context to cancel / timeout
default is false
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
retry.Do(
func() error {
...
},
retry.Context(ctx),
retry.Attempts(0),
retry.WrapContextErrorWithLastError(true),
)
type RetryIfFunc func(error) boolFunction signature of retry if function
type RetryableFunc func() errorFunction signature of retryable function
type RetryableFuncWithData[T any] func() (T, error)Function signature of retryable function with data
type Timer interface {
After(time.Duration) <-chan time.Time
}Timer represents the timer used to track time for a retry.
Contributions are very much welcome.
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