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// Copyright 2017 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
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 {
if 500 <= status && status <= 599 {
return true
}
if status == statusTooManyRequests {
return true
}
if err == io.ErrUnexpectedEOF {
return true
}
if err, ok := err.(net.Error); ok {
return err.Temporary()
}
return false
}
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