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package client
import (
"math"
"strconv"
"time"
"github.com/aws/aws-sdk-go/aws/request"
"github.com/aws/aws-sdk-go/internal/sdkrand"
)
// DefaultRetryer implements basic retry logic using exponential backoff for
// most services. If you want to implement custom retry logic, you can implement the
// request.Retryer interface.
//
type DefaultRetryer struct {
// Num max Retries is the number of max retries that will be performed.
// By default, this is zero.
NumMaxRetries int
// MinRetryDelay is the minimum retry delay after which retry will be performed.
// If not set, the value is 0ns.
MinRetryDelay time.Duration
// MinThrottleRetryDelay is the minimum retry delay when throttled.
// If not set, the value is 0ns.
MinThrottleDelay time.Duration
// MaxRetryDelay is the maximum retry delay before which retry must be performed.
// If not set, the value is 0ns.
MaxRetryDelay time.Duration
// MaxThrottleDelay is the maximum retry delay when throttled.
// If not set, the value is 0ns.
MaxThrottleDelay time.Duration
}
const (
// DefaultRetryerMaxNumRetries sets maximum number of retries
DefaultRetryerMaxNumRetries = 3
// DefaultRetryerMinRetryDelay sets minimum retry delay
DefaultRetryerMinRetryDelay = 30 * time.Millisecond
// DefaultRetryerMinThrottleDelay sets minimum delay when throttled
DefaultRetryerMinThrottleDelay = 500 * time.Millisecond
// DefaultRetryerMaxRetryDelay sets maximum retry delay
DefaultRetryerMaxRetryDelay = 300 * time.Second
// DefaultRetryerMaxThrottleDelay sets maximum delay when throttled
DefaultRetryerMaxThrottleDelay = 300 * time.Second
)
// MaxRetries returns the number of maximum returns the service will use to make
// an individual API request.
func (d DefaultRetryer) MaxRetries() int {
return d.NumMaxRetries
}
// setRetryerDefaults sets the default values of the retryer if not set
func (d *DefaultRetryer) setRetryerDefaults() {
if d.MinRetryDelay == 0 {
d.MinRetryDelay = DefaultRetryerMinRetryDelay
}
if d.MaxRetryDelay == 0 {
d.MaxRetryDelay = DefaultRetryerMaxRetryDelay
}
if d.MinThrottleDelay == 0 {
d.MinThrottleDelay = DefaultRetryerMinThrottleDelay
}
if d.MaxThrottleDelay == 0 {
d.MaxThrottleDelay = DefaultRetryerMaxThrottleDelay
}
}
// RetryRules returns the delay duration before retrying this request again
func (d DefaultRetryer) RetryRules(r *request.Request) time.Duration {
// if number of max retries is zero, no retries will be performed.
if d.NumMaxRetries == 0 {
return 0
}
// Sets default value for retryer members
d.setRetryerDefaults()
// minDelay is the minimum retryer delay
minDelay := d.MinRetryDelay
var initialDelay time.Duration
isThrottle := r.IsErrorThrottle()
if isThrottle {
if delay, ok := getRetryAfterDelay(r); ok {
initialDelay = delay
}
minDelay = d.MinThrottleDelay
}
retryCount := r.RetryCount
// maxDelay the maximum retryer delay
maxDelay := d.MaxRetryDelay
if isThrottle {
maxDelay = d.MaxThrottleDelay
}
var delay time.Duration
// Logic to cap the retry count based on the minDelay provided
actualRetryCount := int(math.Log2(float64(minDelay))) + 1
if actualRetryCount < 63-retryCount {
delay = time.Duration(1<<uint64(retryCount)) * getJitterDelay(minDelay)
if delay > maxDelay {
delay = getJitterDelay(maxDelay / 2)
}
} else {
delay = getJitterDelay(maxDelay / 2)
}
return delay + initialDelay
}
// getJitterDelay returns a jittered delay for retry
func getJitterDelay(duration time.Duration) time.Duration {
return time.Duration(sdkrand.SeededRand.Int63n(int64(duration)) + int64(duration))
}
// ShouldRetry returns true if the request should be retried.
func (d DefaultRetryer) ShouldRetry(r *request.Request) bool {
// ShouldRetry returns false if number of max retries is 0.
if d.NumMaxRetries == 0 {
return false
}
// If one of the other handlers already set the retry state
// we don't want to override it based on the service's state
if r.Retryable != nil {
return *r.Retryable
}
return r.IsErrorRetryable() || r.IsErrorThrottle()
}
// This will look in the Retry-After header, RFC 7231, for how long
// it will wait before attempting another request
func getRetryAfterDelay(r *request.Request) (time.Duration, bool) {
if !canUseRetryAfterHeader(r) {
return 0, false
}
delayStr := r.HTTPResponse.Header.Get("Retry-After")
if len(delayStr) == 0 {
return 0, false
}
delay, err := strconv.Atoi(delayStr)
if err != nil {
return 0, false
}
return time.Duration(delay) * time.Second, true
}
// Will look at the status code to see if the retry header pertains to
// the status code.
func canUseRetryAfterHeader(r *request.Request) bool {
switch r.HTTPResponse.StatusCode {
case 429:
case 503:
default:
return false
}
return true
}
|
