# retry
[](https://github.com/avast/retry-go/releases/latest)
[](LICENSE.md)
[](https://goreportcard.com/report/github.com/avast/retry-go)
[](http://godoc.org/github.com/avast/retry-go)
[](https://codecov.io/github/avast/retry-go?branch=master)
[](https://sourcegraph.com/github.com/avast/retry-go?badge)
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
},
)
fmt.Println(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
- 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`)
## Usage
#### func BackOffDelay
```go
func BackOffDelay(n uint, _ error, config *Config) time.Duration
```
BackOffDelay is a DelayType which increases delay between consecutive retries
#### func Do
```go
func Do(retryableFunc RetryableFunc, opts ...Option) error
```
#### func FixedDelay
```go
func FixedDelay(_ uint, _ error, config *Config) time.Duration
```
FixedDelay is a DelayType which keeps delay the same through all iterations
#### func IsRecoverable
```go
func IsRecoverable(err error) bool
```
IsRecoverable checks if error is an instance of `unrecoverableError`
#### func RandomDelay
```go
func RandomDelay(_ uint, _ error, config *Config) time.Duration
```
RandomDelay is a DelayType which picks a random delay up to config.maxJitter
#### func Unrecoverable
```go
func Unrecoverable(err error) error
```
Unrecoverable wraps an error in `unrecoverableError` struct
#### type Config
```go
type Config struct {
}
```
#### type DelayTypeFunc
```go
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
```go
func CombineDelay(delays ...DelayTypeFunc) DelayTypeFunc
```
CombineDelay is a DelayType the combines all of the specified delays into a new
DelayTypeFunc
#### type Error
```go
type Error []error
```
Error type represents list of errors in retry
#### func (Error) As
```go
func (e Error) As(target interface{}) bool
```
#### func (Error) Error
```go
func (e Error) Error() string
```
Error method return string representation of Error It is an implementation of
error interface
#### func (Error) Is
```go
func (e Error) Is(target error) bool
```
#### func (Error) Unwrap
```go
func (e Error) Unwrap() error
```
Unwrap the last error for compatible with the `errors.Unwrap()` when you need
unwrap all erros, 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
```go
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
```go
type OnRetryFunc func(n uint, err error)
```
Function signature of OnRetry function n = count of attempts
#### type Option
```go
type Option func(*Config)
```
Option represents an option for retry.
#### func Attempts
```go
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
```go
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
```go
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
```go
func Delay(delay time.Duration) Option
```
Delay set delay between retry default is 100ms
#### func DelayType
```go
func DelayType(delayType DelayTypeFunc) Option
```
DelayType set type of the delay between retries default is BackOff
#### func LastErrorOnly
```go
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
```go
func MaxDelay(maxDelay time.Duration) Option
```
MaxDelay set maximum delay between retry does not apply by default
#### func MaxJitter
```go
func MaxJitter(maxJitter time.Duration) Option
```
MaxJitter sets the maximum random Jitter between retries for RandomDelay
#### func OnRetry
```go
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
```go
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
```go
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{})
)
#### type RetryIfFunc
```go
type RetryIfFunc func(error) bool
```
Function signature of retry if function
#### type RetryableFunc
```go
type RetryableFunc func() error
```
Function signature of retryable function
#### type Timer
```go
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](.godocdown.tmpl) and code documentation via [godocdown](https://github.com/robertkrimen/godocdown).
Never edit README.md direct, because your change will be lost.