retry.go

// Copyright (c) 2015-2016 Jeevanandam M (jeeva@myjeeva.com), All rights reserved.
// resty source code and usage is governed by a MIT style
// license that can be found in the LICENSE file.

package resty

import (
	"math"
	"math/rand"
	"time"
)

type function func() error

// Option ...
type Option func(*Options)

// Options to hold go-resty retry values
type Options struct {
	maxRetries  int
	waitTime    int
	maxWaitTime int
}

// Retries sets the max number of retries
func Retries(value int) Option {
	return func(o *Options) {
		o.maxRetries = value
	}
}

// WaitTime sets the default wait time to sleep between requests
func WaitTime(value int) Option {
	return func(o *Options) {
		o.waitTime = value
	}
}

// MaxWaitTime sets the max wait time to sleep between requests
func MaxWaitTime(value int) Option {
	return func(o *Options) {
		o.maxWaitTime = value
	}
}

// Backoff retries with increasing timeout duration up until X amount of retries
// (Default is 3 attempts, Override with option Retries(n))
func Backoff(operation function, options ...Option) error {
	// Defaults
	opts := Options{maxRetries: 3, waitTime: 100, maxWaitTime: 2000}
	for _, o := range options {
		o(&opts)
	}

	var err error
	base := float64(opts.waitTime)        // Time to wait between each attempt
	capLevel := float64(opts.maxWaitTime) // Maximum amount of wait time for the retry
	for attempt := 0; attempt < opts.maxRetries; attempt++ {
		err = operation()
		if err == nil {
			return nil
		}

		// Adding capped exponential backup with jitter
		// See the following article...
		// http://www.awsarchitectureblog.com/2015/03/backoff.html
		temp := math.Min(capLevel, base*math.Exp2(float64(attempt)))
		sleepTime := int(temp/2) + rand.Intn(int(temp/2))

		sleepDuration := time.Duration(sleepTime) * time.Millisecond
		time.Sleep(sleepDuration)
	}

	return err
}