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// Package strategy provides a way to change the way that retry is performed.
//
// Copyright © 2016 Trevor N. Suarez (Rican7)
package strategy
import (
"time"
"github.com/Rican7/retry/backoff"
"github.com/Rican7/retry/jitter"
)
// Strategy defines a function that Retry calls before every successive attempt
// to determine whether it should make the next attempt or not. Returning `true`
// allows for the next attempt to be made. Returning `false` halts the retrying
// process and returns the last error returned by the called Action.
//
// The strategy will be passed an "attempt" number before each successive retry
// iteration, starting with a `0` value before the first attempt is actually
// made. This allows for a pre-action, such as a delay, etc.
type Strategy func(attempt uint) bool
// Limit creates a Strategy that limits the number of attempts that Retry will
// make.
func Limit(attemptLimit uint) Strategy {
return func(attempt uint) bool {
return (attempt < attemptLimit)
}
}
// Delay creates a Strategy that waits the given duration before the first
// attempt is made.
func Delay(duration time.Duration) Strategy {
return func(attempt uint) bool {
if attempt == 0 {
time.Sleep(duration)
}
return true
}
}
// Wait creates a Strategy that waits the given durations for each attempt after
// the first. If the number of attempts is greater than the number of durations
// provided, then the strategy uses the last duration provided.
func Wait(durations ...time.Duration) Strategy {
return func(attempt uint) bool {
if attempt > 0 && len(durations) > 0 {
durationIndex := int(attempt - 1)
if len(durations) <= durationIndex {
durationIndex = len(durations) - 1
}
time.Sleep(durations[durationIndex])
}
return true
}
}
// Backoff creates a Strategy that waits before each attempt, with a duration as
// defined by the given backoff.Algorithm.
func Backoff(algorithm backoff.Algorithm) Strategy {
return BackoffWithJitter(algorithm, noJitter())
}
// BackoffWithJitter creates a Strategy that waits before each attempt, with a
// duration as defined by the given backoff.Algorithm and jitter.Transformation.
func BackoffWithJitter(algorithm backoff.Algorithm, transformation jitter.Transformation) Strategy {
return func(attempt uint) bool {
if attempt > 0 {
time.Sleep(transformation(algorithm(attempt)))
}
return true
}
}
// noJitter creates a jitter.Transformation that simply returns the input.
func noJitter() jitter.Transformation {
return func(duration time.Duration) time.Duration {
return duration
}
}
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