retry

package module
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 Go to latest Published: Sep 5, 2023 License: MIT Imports: 8 Imported by: 0

README

retry

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Simple library for retry mechanism

slightly inspired by Try::Tiny::Retry

SYNOPSIS

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))

next examples

SEE ALSO

  • 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' Retry method

  • matryer/try - very popular package, nonintuitive interface (for me)

BREAKING CHANGES

  • 4.0.0

    • infinity retry is possible by set Attempts(0) by PR #49

  • 3.0.0

  • 1.0.2 -> 2.0.0

  • 0.3.0 -> 1.0.0

    • retry.Retry function are changed to retry.Do function
    • retry.RetryCustom (OnRetry) and retry.RetryCustomWithOpts functions are now implement via functions produces Options (aka retry.OnRetry)

Usage

func BackOffDelay
func BackOffDelay(n uint, _ error, config *Config) time.Duration

BackOffDelay is a DelayType which increases delay between consecutive retries

func Do
func Do(retryableFunc RetryableFunc, opts ...Option) error
func DoWithData
func DoWithData[T any](retryableFunc RetryableFuncWithData[T], opts ...Option) (T, error)
func FixedDelay
func FixedDelay(_ uint, _ error, config *Config) time.Duration

FixedDelay is a DelayType which keeps delay the same through all iterations

func IsRecoverable
func IsRecoverable(err error) bool

IsRecoverable checks if error is an instance of unrecoverableError

func RandomDelay
func RandomDelay(_ uint, _ error, config *Config) time.Duration

RandomDelay is a DelayType which picks a random delay up to config.maxJitter

func Unrecoverable
func Unrecoverable(err error) error

Unrecoverable wraps an error in unrecoverableError struct

type Config
type Config struct {
}
type DelayTypeFunc
type DelayTypeFunc func(n uint, err error, config *Config) time.Duration

DelayTypeFunc is called to return the next delay to wait after the retriable function fails on err after n attempts.

func CombineDelay
func CombineDelay(delays ...DelayTypeFunc) DelayTypeFunc

CombineDelay is a DelayType the combines all of the specified delays into a new DelayTypeFunc

type Error
type Error []error

Error type represents list of errors in retry

func (Error) As
func (e Error) As(target interface{}) bool
func (Error) Error
func (e Error) Error() string

Error method return string representation of Error It is an implementation of error interface

func (Error) Is
func (e Error) Is(target error) bool
func (Error) Unwrap
func (e Error) Unwrap() error

Unwrap 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 (Error) WrappedErrors
func (e Error) WrappedErrors() []error

WrappedErrors 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
type OnRetryFunc func(n uint, err error)

Function signature of OnRetry function n = count of attempts

type Option
type Option func(*Config)

Option represents an option for retry.

func Attempts
func Attempts(attempts uint) Option

Attempts set count of retry. Setting to 0 will retry until the retried function succeeds. default is 10

func AttemptsForError
func AttemptsForError(attempts uint, err error) Option

AttemptsForError 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
func Context(ctx context.Context) Option

Context 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
func Delay(delay time.Duration) Option

Delay set delay between retry default is 100ms

func DelayType
func DelayType(delayType DelayTypeFunc) Option

DelayType set type of the delay between retries default is BackOff

func LastErrorOnly
func LastErrorOnly(lastErrorOnly bool) Option

return the direct last error that came from the retried function default is false (return wrapped errors with everything)

func MaxDelay
func MaxDelay(maxDelay time.Duration) Option

MaxDelay set maximum delay between retry does not apply by default

func MaxJitter
func MaxJitter(maxJitter time.Duration) Option

MaxJitter sets the maximum random Jitter between retries for RandomDelay

func OnRetry
func OnRetry(onRetry OnRetryFunc) Option

OnRetry 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
func RetryIf(retryIf RetryIfFunc) Option

RetryIf 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 WithTimer
func WithTimer(t Timer) Option

WithTimer 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
func WrapContextErrorWithLastError(wrapContextErrorWithLastError bool) Option

WrapContextErrorWithLastError 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
type RetryIfFunc func(error) bool

Function signature of retry if function

type RetryableFunc
type RetryableFunc func() error

Function signature of retryable function

type RetryableFuncWithData
type RetryableFuncWithData[T any] func() (T, error)

Function signature of retryable function with data

type Timer
type Timer interface {
	After(time.Duration) <-chan time.Time
}

Timer represents the timer used to track time for a retry.

Contributing

Contributions are very much welcome.

Makefile

Makefile provides several handy rules, like README.md generator , setup for prepare build/dev environment, test, cover, etc...

Try make help for more information.

Before pull request

maybe you need make setup in order to setup environment

please try:

  • run tests (make test)
  • run linter (make lint)
  • if your IDE don't automaticaly do go fmt, run go fmt (make fmt)
README

README.md are generate from template .godocdown.tmpl and code documentation via godocdown.

Never edit README.md direct, because your change will be lost.

Documentation

Overview

Simple library for retry mechanism

slightly inspired by [Try::Tiny::Retry](https://metacpan.org/pod/Try::Tiny::Retry)

SYNOPSIS

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))

[next examples](https://github.com/avast/retry-go/tree/master/examples)

SEE ALSO

* giantswarm/retry-go(https://github.com/giantswarm/retry-go) - slightly complicated interface.

* sethgrid/pester(https://github.com/sethgrid/pester) - only http retry for http calls with retries and backoff

* cenkalti/backoff(https://github.com/cenkalti/backoff) - Go port of the exponential backoff algorithm from Google's HTTP Client Library for Java. Really complicated interface.

* rafaeljesus/retry-go(https://github.com/rafaeljesus/retry-go) - looks good, slightly similar as this package, don't have 'simple' `Retry` method

* matryer/try(https://github.com/matryer/try) - very popular package, nonintuitive interface (for me)

BREAKING CHANGES

* 4.0.0

* 3.0.0

  • `DelayTypeFunc` accepts a new parameter `err` - this breaking change affects only your custom Delay Functions. This change allow [make delay functions based on error](examples/delay_based_on_error_test.go).

* 1.0.2 -> 2.0.0

* 0.3.0 -> 1.0.0

  • `retry.Retry` function are changed to `retry.Do` function
  • `retry.RetryCustom` (OnRetry) and `retry.RetryCustomWithOpts` functions are now implement via functions produces Options (aka `retry.OnRetry`)

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func BackOffDelay 

func BackOffDelay(n uint, _ error, config *Config) time.Duration

BackOffDelay is a DelayType which increases delay between consecutive retries

func Do 

func Do(retryableFunc RetryableFunc, opts ...Option) error

func DoWithData 

func DoWithData[T any](retryableFunc RetryableFuncWithData[T], opts ...Option) (T, error)

func FixedDelay 

func FixedDelay(_ uint, _ error, config *Config) time.Duration

FixedDelay is a DelayType which keeps delay the same through all iterations

func IsRecoverable 

func IsRecoverable(err error) bool

IsRecoverable checks if error is an instance of `unrecoverableError`

func RandomDelay 

func RandomDelay(_ uint, _ error, config *Config) time.Duration

RandomDelay is a DelayType which picks a random delay up to config.maxJitter

func Unrecoverable 

func Unrecoverable(err error) error

Unrecoverable wraps an error in `unrecoverableError` struct

Types

type Config 

type Config struct {
	// contains filtered or unexported fields
}

type DelayTypeFunc 

type DelayTypeFunc func(n uint, err error, config *Config) time.Duration

DelayTypeFunc is called to return the next delay to wait after the retriable function fails on `err` after `n` attempts.

func CombineDelay 

func CombineDelay(delays ...DelayTypeFunc) DelayTypeFunc

CombineDelay is a DelayType the combines all of the specified delays into a new DelayTypeFunc

type Error 

type Error []error

Error type represents list of errors in retry

func (Error) As 

func (e Error) As(target interface{}) bool

func (Error) Error 

func (e Error) Error() string

Error method return string representation of Error It is an implementation of error interface

func (Error) Is 

func (e Error) Is(target error) bool

func (Error) Unwrap 

func (e Error) Unwrap() error

Unwrap 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 (Error) WrappedErrors 

func (e Error) WrappedErrors() []error

WrappedErrors returns the list of errors that this Error is wrapping. It is an implementation of the `errwrap.Wrapper` interface in package [errwrap](https://github.com/hashicorp/errwrap) so that `retry.Error` can be used with that library.

type OnRetryFunc 

type OnRetryFunc func(n uint, err error)

Function signature of OnRetry function n = count of attempts

type Option 

type Option func(*Config)

Option represents an option for retry.

func Attempts 

func Attempts(attempts uint) Option

Attempts set count of retry. Setting to 0 will retry until the retried function succeeds. default is 10

func AttemptsForError 

func AttemptsForError(attempts uint, err error) Option

AttemptsForError 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 

func Context(ctx context.Context) Option

Context 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 

func Delay(delay time.Duration) Option

Delay set delay between retry default is 100ms

func DelayType 

func DelayType(delayType DelayTypeFunc) Option

DelayType set type of the delay between retries default is BackOff

func LastErrorOnly 

func LastErrorOnly(lastErrorOnly bool) Option

return the direct last error that came from the retried function default is false (return wrapped errors with everything)

func MaxDelay 

func MaxDelay(maxDelay time.Duration) Option

MaxDelay set maximum delay between retry does not apply by default

func MaxJitter 

func MaxJitter(maxJitter time.Duration) Option

MaxJitter sets the maximum random Jitter between retries for RandomDelay

func OnRetry 

func OnRetry(onRetry OnRetryFunc) Option

OnRetry 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 

func RetryIf(retryIf RetryIfFunc) Option

RetryIf 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 WithTimer 

func WithTimer(t Timer) Option

WithTimer 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 

func WrapContextErrorWithLastError(wrapContextErrorWithLastError bool) Option

WrapContextErrorWithLastError 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 

type RetryIfFunc func(error) bool

Function signature of retry if function

type RetryableFunc 

type RetryableFunc func() error

Function signature of retryable function

type RetryableFuncWithData 

type RetryableFuncWithData[T any] func() (T, error)

Function signature of retryable function with data

type Timer 

type Timer interface {
	After(time.Duration) <-chan time.Time
}

Timer represents the timer used to track time for a retry.

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