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

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+// Copyright 2017 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 gensupport
+
+import (
+	"context"
+	"io"
+	"net"
+	"net/http"
+	"time"
+)
+
+// 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
+}