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retry.go
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retry.go
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/*
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))
[More 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
- infinity retry is possible by set `Attempts(0)` by PR [#49](https://github.com/avast/retry-go/pull/49)
* 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
- argument of `retry.Delay` is final delay (no multiplication by `retry.Units` anymore)
- function `retry.Units` are removed
- [more about this breaking change](https://github.com/avast/retry-go/issues/7)
* 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`)
*/
package retry
import (
"context"
"errors"
"fmt"
"strings"
"time"
)
// Function signature of retryable function
type RetryableFunc func() error
// Function signature of retryable function with data
type RetryableFuncWithData[T any] func() (T, error)
// Default timer is a wrapper around time.After
type timerImpl struct{}
func (t *timerImpl) After(d time.Duration) <-chan time.Time {
return time.After(d)
}
func Do(retryableFunc RetryableFunc, opts ...Option) error {
retryableFuncWithData := func() (any, error) {
return nil, retryableFunc()
}
_, err := DoWithData(retryableFuncWithData, opts...)
return err
}
func DoWithData[T any](retryableFunc RetryableFuncWithData[T], opts ...Option) (T, error) {
var n uint
var emptyT T
// default
config := newDefaultRetryConfig()
// apply opts
for _, opt := range opts {
opt(config)
}
if err := config.context.Err(); err != nil {
return emptyT, err
}
// Setting attempts to 0 means we'll retry until we succeed
var lastErr error
if config.attempts == 0 {
for {
t, err := retryableFunc()
if err == nil {
return t, nil
}
if !IsRecoverable(err) {
return emptyT, err
}
if !config.retryIf(err) {
return emptyT, err
}
lastErr = err
config.onRetry(n, err)
n++
select {
case <-config.timer.After(delay(config, n, err)):
case <-config.context.Done():
if config.wrapContextErrorWithLastError {
return emptyT, Error{config.context.Err(), lastErr}
}
return emptyT, config.context.Err()
}
}
}
errorLog := Error{}
attemptsForError := make(map[error]uint, len(config.attemptsForError))
for err, attempts := range config.attemptsForError {
attemptsForError[err] = attempts
}
shouldRetry := true
for shouldRetry {
t, err := retryableFunc()
if err == nil {
return t, nil
}
errorLog = append(errorLog, unpackUnrecoverable(err))
if !config.retryIf(err) {
break
}
config.onRetry(n, err)
for errToCheck, attempts := range attemptsForError {
if errors.Is(err, errToCheck) {
attempts--
attemptsForError[errToCheck] = attempts
shouldRetry = shouldRetry && attempts > 0
}
}
// if this is last attempt - don't wait
if n == config.attempts-1 {
break
}
select {
case <-config.timer.After(delay(config, n, err)):
case <-config.context.Done():
if config.lastErrorOnly {
return emptyT, config.context.Err()
}
return emptyT, append(errorLog, config.context.Err())
}
n++
shouldRetry = shouldRetry && n < config.attempts
}
if config.lastErrorOnly {
return emptyT, errorLog.Unwrap()
}
return emptyT, errorLog
}
func newDefaultRetryConfig() *Config {
return &Config{
attempts: uint(10),
attemptsForError: make(map[error]uint),
delay: 100 * time.Millisecond,
maxJitter: 100 * time.Millisecond,
onRetry: func(n uint, err error) {},
retryIf: IsRecoverable,
delayType: CombineDelay(BackOffDelay, RandomDelay),
lastErrorOnly: false,
context: context.Background(),
timer: &timerImpl{},
}
}
// Error type represents list of errors in retry
type Error []error
// Error method return string representation of Error
// It is an implementation of error interface
func (e Error) Error() string {
logWithNumber := make([]string, len(e))
for i, l := range e {
if l != nil {
logWithNumber[i] = fmt.Sprintf("#%d: %s", i+1, l.Error())
}
}
return fmt.Sprintf("All attempts fail:\n%s", strings.Join(logWithNumber, "\n"))
}
func (e Error) Is(target error) bool {
for _, v := range e {
if errors.Is(v, target) {
return true
}
}
return false
}
func (e Error) As(target interface{}) bool {
for _, v := range e {
if errors.As(v, target) {
return true
}
}
return false
}
/*
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 (e Error) Unwrap() error {
return e[len(e)-1]
}
// 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.
func (e Error) WrappedErrors() []error {
return e
}
type unrecoverableError struct {
error
}
func (e unrecoverableError) Error() string {
if e.error == nil {
return "unrecoverable error"
}
return e.error.Error()
}
func (e unrecoverableError) Unwrap() error {
return e.error
}
// Unrecoverable wraps an error in `unrecoverableError` struct
func Unrecoverable(err error) error {
return unrecoverableError{err}
}
// IsRecoverable checks if error is an instance of `unrecoverableError`
func IsRecoverable(err error) bool {
return !errors.Is(err, unrecoverableError{})
}
// Adds support for errors.Is usage on unrecoverableError
func (unrecoverableError) Is(err error) bool {
_, isUnrecoverable := err.(unrecoverableError)
return isUnrecoverable
}
func unpackUnrecoverable(err error) error {
if unrecoverable, isUnrecoverable := err.(unrecoverableError); isUnrecoverable {
return unrecoverable.error
}
return err
}
func delay(config *Config, n uint, err error) time.Duration {
delayTime := config.delayType(n, err, config)
if config.maxDelay > 0 && delayTime > config.maxDelay {
delayTime = config.maxDelay
}
return delayTime
}