125 lines
3 KiB
Go
125 lines
3 KiB
Go
|
package aws
|
||
|
|
|
||
|
|
import (
|
||
|
|
"math"
|
||
|
|
"net"
|
||
|
|
"net/http"
|
||
|
|
"time"
|
||
|
|
)
|
||
|
|
|
||
|
|
type RetryableFunc func(*http.Request, *http.Response, error) bool
|
||
|
|
type WaitFunc func(try int)
|
||
|
|
type DeadlineFunc func() time.Time
|
||
|
|
|
||
|
|
type ResilientTransport struct {
|
||
|
|
// Timeout is the maximum amount of time a dial will wait for
|
||
|
|
// a connect to complete.
|
||
|
|
//
|
||
|
|
// The default is no timeout.
|
||
|
|
//
|
||
|
|
// With or without a timeout, the operating system may impose
|
||
|
|
// its own earlier timeout. For instance, TCP timeouts are
|
||
|
|
// often around 3 minutes.
|
||
|
|
DialTimeout time.Duration
|
||
|
|
|
||
|
|
// MaxTries, if non-zero, specifies the number of times we will retry on
|
||
|
|
// failure. Retries are only attempted for temporary network errors or known
|
||
|
|
// safe failures.
|
||
|
|
MaxTries int
|
||
|
|
Deadline DeadlineFunc
|
||
|
|
ShouldRetry RetryableFunc
|
||
|
|
Wait WaitFunc
|
||
|
|
transport *http.Transport
|
||
|
|
}
|
||
|
|
|
||
|
|
// Convenience method for creating an http client
|
||
|
|
func NewClient(rt *ResilientTransport) *http.Client {
|
||
|
|
rt.transport = &http.Transport{
|
||
|
|
Dial: func(netw, addr string) (net.Conn, error) {
|
||
|
|
c, err := net.DialTimeout(netw, addr, rt.DialTimeout)
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
c.SetDeadline(rt.Deadline())
|
||
|
|
return c, nil
|
||
|
|
},
|
||
|
|
Proxy: http.ProxyFromEnvironment,
|
||
|
|
}
|
||
|
|
// TODO: Would be nice is ResilientTransport allowed clients to initialize
|
||
|
|
// with http.Transport attributes.
|
||
|
|
return &http.Client{
|
||
|
|
Transport: rt,
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
var retryingTransport = &ResilientTransport{
|
||
|
|
Deadline: func() time.Time {
|
||
|
|
return time.Now().Add(5 * time.Second)
|
||
|
|
},
|
||
|
|
DialTimeout: 10 * time.Second,
|
||
|
|
MaxTries: 3,
|
||
|
|
ShouldRetry: awsRetry,
|
||
|
|
Wait: ExpBackoff,
|
||
|
|
}
|
||
|
|
|
||
|
|
// Exported default client
|
||
|
|
var RetryingClient = NewClient(retryingTransport)
|
||
|
|
|
||
|
|
func (t *ResilientTransport) RoundTrip(req *http.Request) (*http.Response, error) {
|
||
|
|
return t.tries(req)
|
||
|
|
}
|
||
|
|
|
||
|
|
// Retry a request a maximum of t.MaxTries times.
|
||
|
|
// We'll only retry if the proper criteria are met.
|
||
|
|
// If a wait function is specified, wait that amount of time
|
||
|
|
// In between requests.
|
||
|
|
func (t *ResilientTransport) tries(req *http.Request) (res *http.Response, err error) {
|
||
|
|
for try := 0; try < t.MaxTries; try += 1 {
|
||
|
|
res, err = t.transport.RoundTrip(req)
|
||
|
|
|
||
|
|
if !t.ShouldRetry(req, res, err) {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
if res != nil {
|
||
|
|
res.Body.Close()
|
||
|
|
}
|
||
|
|
if t.Wait != nil {
|
||
|
|
t.Wait(try)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
func ExpBackoff(try int) {
|
||
|
|
time.Sleep(100 * time.Millisecond *
|
||
|
|
time.Duration(math.Exp2(float64(try))))
|
||
|
|
}
|
||
|
|
|
||
|
|
func LinearBackoff(try int) {
|
||
|
|
time.Sleep(time.Duration(try*100) * time.Millisecond)
|
||
|
|
}
|
||
|
|
|
||
|
|
// Decide if we should retry a request.
|
||
|
|
// In general, the criteria for retrying a request is described here
|
||
|
|
// http://docs.aws.amazon.com/general/latest/gr/api-retries.html
|
||
|
|
func awsRetry(req *http.Request, res *http.Response, err error) bool {
|
||
|
|
retry := false
|
||
|
|
|
||
|
|
// Retry if there's a temporary network error.
|
||
|
|
if neterr, ok := err.(net.Error); ok {
|
||
|
|
if neterr.Temporary() {
|
||
|
|
retry = true
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Retry if we get a 5xx series error.
|
||
|
|
if res != nil {
|
||
|
|
if res.StatusCode >= 500 && res.StatusCode < 600 {
|
||
|
|
retry = true
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return retry
|
||
|
|
}
|