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package gensupport
import (
"io"
"net"
"net/http"
"time"
"golang.org/x/net/context"
)
// Retry invokes the given function, retrying it multiple times if the connection failed or
// the HTTP status response indicates the request should be attempted again. ctx may be nil.
func Retry(ctx context.Context, f func() (*http.Response, error), backoff BackoffStrategy) (*http.Response, error) {
for {
resp, err := f()
var status int
if resp != nil {
status = resp.StatusCode
}
// Return if we shouldn't retry.
pause, retry := backoff.Pause()
if !shouldRetry(status, err) || !retry {
return resp, err
}
// Ensure the response body is closed, if any.
if resp != nil && resp.Body != nil {
resp.Body.Close()
}
// Pause, but still listen to ctx.Done if context is not nil.
var done <-chan struct{}
if ctx != nil {
done = ctx.Done()
}
select {
case <-done:
return nil, ctx.Err()
case <-time.After(pause):
}
}
}
// DefaultBackoffStrategy returns a default strategy to use for retrying failed upload requests.
func DefaultBackoffStrategy() BackoffStrategy {
return &ExponentialBackoff{
Base: 250 * time.Millisecond,
Max: 16 * time.Second,
}
}
// shouldRetry returns true if the HTTP response / error indicates that the
// request should be attempted again.
func shouldRetry(status int, err error) bool {
// Retry for 5xx response codes.
if 500 <= status && status < 600 {
return true
}
// Retry on statusTooManyRequests{
if status == statusTooManyRequests {
return true
}
// Retry on unexpected EOFs and temporary network errors.
if err == io.ErrUnexpectedEOF {
return true
}
if err, ok := err.(net.Error); ok {
return err.Temporary()
}
return false
}
|
