packer-cn/common/retry.go

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package common
import (
"fmt"
"math"
"time"
)
var RetryExhaustedError error = fmt.Errorf("Function never succeeded in Retry")
// 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 func() (bool, error)) 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()
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
}