packer-cn/common/retry.go

55 lines
1.6 KiB
Go

package common
import (
"fmt"
"math"
"time"
)
var RetryExhaustedError error = fmt.Errorf("Function never succeeded in Retry")
// RetryableFunc performs an action and returns a bool indicating whether the
// function is done, or if it should keep retrying, and an error which will
// abort the retry and be returned by the Retry function. The 0-indexed attempt
// is passed with each call.
type RetryableFunc func(uint) (bool, error)
/*
Retry retries a function up to numTries times with exponential backoff.
If numTries == 0, retry indefinitely.
If interval == 0, Retry will not delay retrying and there will be no
exponential backoff.
If maxInterval == 0, maxInterval is set to +Infinity.
Intervals are in seconds.
Returns an error if initial > max intervals, if retries are exhausted, or if the passed function returns
an error.
*/
func Retry(initialInterval float64, maxInterval float64, numTries uint, function RetryableFunc) error {
if maxInterval == 0 {
maxInterval = math.Inf(1)
} else if initialInterval < 0 || initialInterval > maxInterval {
return fmt.Errorf("Invalid retry intervals (negative or initial < max). Initial: %f, Max: %f.", initialInterval, maxInterval)
}
var err error
done := false
interval := initialInterval
for i := uint(0); !done && (numTries == 0 || i < numTries); i++ {
done, err = function(i)
if err != nil {
return err
}
if !done {
// Retry after delay. Calculate next delay.
time.Sleep(time.Duration(interval) * time.Second)
interval = math.Min(interval*2, maxInterval)
}
}
if !done {
return RetryExhaustedError
}
return nil
}