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// Copyright 2021 Google LLC
//
// 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 metadata
import (
"context"
"io"
"math/rand"
"net/http"
"time"
)
const (
maxRetryAttempts = 5
)
var (
syscallRetryable = func(err error) bool { return false }
)
// defaultBackoff is basically equivalent to gax.Backoff without the need for
// the dependency.
type defaultBackoff struct {
max time.Duration
mul float64
cur time.Duration
}
func (b *defaultBackoff) Pause() time.Duration {
d := time.Duration(1 + rand.Int63n(int64(b.cur)))
b.cur = time.Duration(float64(b.cur) * b.mul)
if b.cur > b.max {
b.cur = b.max
}
return d
}
// sleep is the equivalent of gax.Sleep without the need for the dependency.
func sleep(ctx context.Context, d time.Duration) error {
t := time.NewTimer(d)
select {
case <-ctx.Done():
t.Stop()
return ctx.Err()
case <-t.C:
return nil
}
}
func newRetryer() *metadataRetryer {
return &metadataRetryer{bo: &defaultBackoff{
cur: 100 * time.Millisecond,
max: 30 * time.Second,
mul: 2,
}}
}
type backoff interface {
Pause() time.Duration
}
type metadataRetryer struct {
bo backoff
attempts int
}
func (r *metadataRetryer) Retry(status int, err error) (time.Duration, bool) {
if status == http.StatusOK {
return 0, false
}
retryOk := shouldRetry(status, err)
if !retryOk {
return 0, false
}
if r.attempts == maxRetryAttempts {
return 0, false
}
r.attempts++
return r.bo.Pause(), true
}
func shouldRetry(status int, err error) bool {
if 500 <= status && status <= 599 {
return true
}
if err == io.ErrUnexpectedEOF {
return true
}
// Transient network errors should be retried.
if syscallRetryable(err) {
return true
}
if err, ok := err.(interface{ Temporary() bool }); ok {
if err.Temporary() {
return true
}
}
if err, ok := err.(interface{ Unwrap() error }); ok {
return shouldRetry(status, err.Unwrap())
}
return false
}
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