vendor: update buildkit to master@ae9d0f5

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/cloud.google.com/go/compute/metadata/retry.go

@@ -0,0 +1,114 @@
+// 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
+}