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package resource
import (
"sync"
"time"
)
// Retry is a basic wrapper around StateChangeConf that will just retry
// a function until it no longer returns an error.
func Retry(timeout time.Duration, f RetryFunc) error {
// These are used to pull the error out of the function; need a mutex to
// avoid a data race.
var resultErr error
var resultErrMu sync.Mutex
c := &StateChangeConf{
Pending: []string{"retryableerror"},
Target: []string{"success"},
Timeout: timeout,
MinTimeout: 500 * time.Millisecond,
Refresh: func() (interface{}, string, error) {
rerr := f()
resultErrMu.Lock()
defer resultErrMu.Unlock()
if rerr == nil {
resultErr = nil
return 42, "success", nil
}
resultErr = rerr.Err
if rerr.Retryable {
return 42, "retryableerror", nil
}
return nil, "quit", rerr.Err
},
}
_, waitErr := c.WaitForState()
// Need to acquire the lock here to be able to avoid race using resultErr as
// the return value
resultErrMu.Lock()
defer resultErrMu.Unlock()
// resultErr may be nil because the wait timed out and resultErr was never
// set; this is still an error
if resultErr == nil {
return waitErr
}
// resultErr takes precedence over waitErr if both are set because it is
// more likely to be useful
return resultErr
}
// RetryFunc is the function retried until it succeeds.
type RetryFunc func() *RetryError
// RetryError is the required return type of RetryFunc. It forces client code
// to choose whether or not a given error is retryable.
type RetryError struct {
Err error
Retryable bool
}
// RetryableError is a helper to create a RetryError that's retryable from a
// given error.
func RetryableError(err error) *RetryError {
if err == nil {
return nil
}
return &RetryError{Err: err, Retryable: true}
}
// NonRetryableError is a helper to create a RetryError that's _not)_ retryable
// from a given error.
func NonRetryableError(err error) *RetryError {
if err == nil {
return nil
}
return &RetryError{Err: err, Retryable: false}
}
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