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package client
import (
"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, implement the
// request.Retryer interface or create a structure type that composes this
// struct and override the specific methods. For example, to override only
// the MaxRetries method:
//
// type retryer struct {
// client.DefaultRetryer
// }
//
// // This implementation always has 100 max retries
// func (d retryer) MaxRetries() int { return 100 }
type DefaultRetryer struct {
NumMaxRetries int
}
// 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
}
// RetryRules returns the delay duration before retrying this request again
func (d DefaultRetryer) RetryRules(r *request.Request) time.Duration {
// Set the upper limit of delay in retrying at ~five minutes
minTime := 30
throttle := d.shouldThrottle(r)
if throttle {
if delay, ok := getRetryDelay(r); ok {
return delay
}
minTime = 500
}
retryCount := r.RetryCount
if throttle && retryCount > 8 {
retryCount = 8
} else if retryCount > 13 {
retryCount = 13
}
delay := (1 << uint(retryCount)) * (sdkrand.SeededRand.Intn(minTime) + minTime)
return time.Duration(delay) * time.Millisecond
}
// ShouldRetry returns true if the request should be retried.
func (d DefaultRetryer) ShouldRetry(r *request.Request) bool {
// 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
}
if r.HTTPResponse.StatusCode >= 500 && r.HTTPResponse.StatusCode != 501 {
return true
}
return r.IsErrorRetryable() || d.shouldThrottle(r)
}
// ShouldThrottle returns true if the request should be throttled.
func (d DefaultRetryer) shouldThrottle(r *request.Request) bool {
switch r.HTTPResponse.StatusCode {
case 429:
case 502:
case 503:
case 504:
default:
return r.IsErrorThrottle()
}
return true
}
// This will look in the Retry-After header, RFC 7231, for how long
// it will wait before attempting another request
func getRetryDelay(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
}
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