vendor/google.golang.org/api/gensupport/retry.go

   1 // Copyright 2017 Google LLC
   2 //
   3 // Licensed under the Apache License, Version 2.0 (the "License");
   4 // you may not use this file except in compliance with the License.
   5 // You may obtain a copy of the License at
   6 //
   7 //      http://www.apache.org/licenses/LICENSE-2.0
   8 //
   9 // Unless required by applicable law or agreed to in writing, software
  10 // distributed under the License is distributed on an "AS IS" BASIS,
  11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 // See the License for the specific language governing permissions and
  13 // limitations under the License.
  14
  15 package gensupport
  16
  17 import (
  18         "context"
  19         "io"
  20         "net"
  21         "net/http"
  22         "time"
  23 )
  24
  25 // Retry invokes the given function, retrying it multiple times if the connection failed or
  26 // the HTTP status response indicates the request should be attempted again. ctx may be nil.
  27 func Retry(ctx context.Context, f func() (*http.Response, error), backoff BackoffStrategy) (*http.Response, error) {
  28         for {
  29                 resp, err := f()
  30
  31                 var status int
  32                 if resp != nil {
  33                         status = resp.StatusCode
  34                 }
  35
  36                 // Return if we shouldn't retry.
  37                 pause, retry := backoff.Pause()
  38                 if !shouldRetry(status, err) || !retry {
  39                         return resp, err
  40                 }
  41
  42                 // Ensure the response body is closed, if any.
  43                 if resp != nil && resp.Body != nil {
  44                         resp.Body.Close()
  45                 }
  46
  47                 // Pause, but still listen to ctx.Done if context is not nil.
  48                 var done <-chan struct{}
  49                 if ctx != nil {
  50                         done = ctx.Done()
  51                 }
  52                 select {
  53                 case <-done:
  54                         return nil, ctx.Err()
  55                 case <-time.After(pause):
  56                 }
  57         }
  58 }
  59
  60 // DefaultBackoffStrategy returns a default strategy to use for retrying failed upload requests.
  61 func DefaultBackoffStrategy() BackoffStrategy {
  62         return &ExponentialBackoff{
  63                 Base: 250 * time.Millisecond,
  64                 Max:  16 * time.Second,
  65         }
  66 }
  67
  68 // shouldRetry returns true if the HTTP response / error indicates that the
  69 // request should be attempted again.
  70 func shouldRetry(status int, err error) bool {
  71         if 500 <= status && status <= 599 {
  72                 return true
  73         }
  74         if status == statusTooManyRequests {
  75                 return true
  76         }
  77         if err == io.ErrUnexpectedEOF {
  78                 return true
  79         }
  80         if err, ok := err.(net.Error); ok {
  81                 return err.Temporary()
  82         }
  83         return false
  84 }