Fix GCS

Signed-off-by: Olivier Gambier <olivier@docker.com>

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

@@ -0,0 +1,46 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gensupport
+
+import (
+	"math/rand"
+	"time"
+)
+
+type BackoffStrategy interface {
+	// Pause returns the duration of the next pause and true if the operation should be
+	// retried, or false if no further retries should be attempted.
+	Pause() (time.Duration, bool)
+
+	// Reset restores the strategy to its initial state.
+	Reset()
+}
+
+// ExponentialBackoff performs exponential backoff as per https://en.wikipedia.org/wiki/Exponential_backoff.
+// The initial pause time is given by Base.
+// Once the total pause time exceeds Max, Pause will indicate no further retries.
+type ExponentialBackoff struct {
+	Base  time.Duration
+	Max   time.Duration
+	total time.Duration
+	n     uint
+}
+
+func (eb *ExponentialBackoff) Pause() (time.Duration, bool) {
+	if eb.total > eb.Max {
+		return 0, false
+	}
+
+	// The next pause is selected from randomly from [0, 2^n * Base).
+	d := time.Duration(rand.Int63n((1 << eb.n) * int64(eb.Base)))
+	eb.total += d
+	eb.n++
+	return d, true
+}
+
+func (eb *ExponentialBackoff) Reset() {
+	eb.n = 0
+	eb.total = 0
+}

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

@@ -0,0 +1,77 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gensupport
+
+import (
+	"bytes"
+	"io"
+
+	"google.golang.org/api/googleapi"
+)
+
+// ResumableBuffer buffers data from an io.Reader to support uploading media in retryable chunks.
+type ResumableBuffer struct {
+	media io.Reader
+
+	chunk []byte // The current chunk which is pending upload.  The capacity is the chunk size.
+	err   error  // Any error generated when populating chunk by reading media.
+
+	// The absolute position of chunk in the underlying media.
+	off int64
+}
+
+func NewResumableBuffer(media io.Reader, chunkSize int) *ResumableBuffer {
+	return &ResumableBuffer{media: media, chunk: make([]byte, 0, chunkSize)}
+}
+
+// Chunk returns the current buffered chunk, the offset in the underlying media
+// from which the chunk is drawn, and the size of the chunk.
+// Successive calls to Chunk return the same chunk between calls to Next.
+func (rb *ResumableBuffer) Chunk() (chunk io.Reader, off int64, size int, err error) {
+	// There may already be data in chunk if Next has not been called since the previous call to Chunk.
+	if rb.err == nil && len(rb.chunk) == 0 {
+		rb.err = rb.loadChunk()
+	}
+	return bytes.NewReader(rb.chunk), rb.off, len(rb.chunk), rb.err
+}
+
+// loadChunk will read from media into chunk, up to the capacity of chunk.
+func (rb *ResumableBuffer) loadChunk() error {
+	bufSize := cap(rb.chunk)
+	rb.chunk = rb.chunk[:bufSize]
+
+	read := 0
+	var err error
+	for err == nil && read < bufSize {
+		var n int
+		n, err = rb.media.Read(rb.chunk[read:])
+		read += n
+	}
+	rb.chunk = rb.chunk[:read]
+	return err
+}
+
+// Next advances to the next chunk, which will be returned by the next call to Chunk.
+// Calls to Next without a corresponding prior call to Chunk will have no effect.
+func (rb *ResumableBuffer) Next() {
+	rb.off += int64(len(rb.chunk))
+	rb.chunk = rb.chunk[0:0]
+}
+
+type readerTyper struct {
+	io.Reader
+	googleapi.ContentTyper
+}
+
+// ReaderAtToReader adapts a ReaderAt to be used as a Reader.
+// If ra implements googleapi.ContentTyper, then the returned reader
+// will also implement googleapi.ContentTyper, delegating to ra.
+func ReaderAtToReader(ra io.ReaderAt, size int64) io.Reader {
+	r := io.NewSectionReader(ra, 0, size)
+	if typer, ok := ra.(googleapi.ContentTyper); ok {
+		return readerTyper{r, typer}
+	}
+	return r
+}

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

@@ -0,0 +1,10 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gensupport is an internal implementation detail used by code
+// generated by the google-api-go-generator tool.
+//
+// This package may be modified at any time without regard for backwards
+// compatibility. It should not be used directly by API users.
+package gensupport

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

@@ -0,0 +1,172 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gensupport
+
+import (
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// MarshalJSON returns a JSON encoding of schema containing only selected fields.
+// A field is selected if:
+//   * it has a non-empty value, or
+//     * its field name is present in forceSendFields, and
+//     * it is not a nil pointer or nil interface.
+// The JSON key for each selected field is taken from the field's json: struct tag.
+func MarshalJSON(schema interface{}, forceSendFields []string) ([]byte, error) {
+	if len(forceSendFields) == 0 {
+		return json.Marshal(schema)
+	}
+
+	mustInclude := make(map[string]struct{})
+	for _, f := range forceSendFields {
+		mustInclude[f] = struct{}{}
+	}
+
+	dataMap, err := schemaToMap(schema, mustInclude)
+	if err != nil {
+		return nil, err
+	}
+	return json.Marshal(dataMap)
+}
+
+func schemaToMap(schema interface{}, mustInclude map[string]struct{}) (map[string]interface{}, error) {
+	m := make(map[string]interface{})
+	s := reflect.ValueOf(schema)
+	st := s.Type()
+
+	for i := 0; i < s.NumField(); i++ {
+		jsonTag := st.Field(i).Tag.Get("json")
+		if jsonTag == "" {
+			continue
+		}
+		tag, err := parseJSONTag(jsonTag)
+		if err != nil {
+			return nil, err
+		}
+		if tag.ignore {
+			continue
+		}
+
+		v := s.Field(i)
+		f := st.Field(i)
+		if !includeField(v, f, mustInclude) {
+			continue
+		}
+
+		// nil maps are treated as empty maps.
+		if f.Type.Kind() == reflect.Map && v.IsNil() {
+			m[tag.apiName] = map[string]string{}
+			continue
+		}
+
+		// nil slices are treated as empty slices.
+		if f.Type.Kind() == reflect.Slice && v.IsNil() {
+			m[tag.apiName] = []bool{}
+			continue
+		}
+
+		if tag.stringFormat {
+			m[tag.apiName] = formatAsString(v, f.Type.Kind())
+		} else {
+			m[tag.apiName] = v.Interface()
+		}
+	}
+	return m, nil
+}
+
+// formatAsString returns a string representation of v, dereferencing it first if possible.
+func formatAsString(v reflect.Value, kind reflect.Kind) string {
+	if kind == reflect.Ptr && !v.IsNil() {
+		v = v.Elem()
+	}
+
+	return fmt.Sprintf("%v", v.Interface())
+}
+
+// jsonTag represents a restricted version of the struct tag format used by encoding/json.
+// It is used to describe the JSON encoding of fields in a Schema struct.
+type jsonTag struct {
+	apiName      string
+	stringFormat bool
+	ignore       bool
+}
+
+// parseJSONTag parses a restricted version of the struct tag format used by encoding/json.
+// The format of the tag must match that generated by the Schema.writeSchemaStruct method
+// in the api generator.
+func parseJSONTag(val string) (jsonTag, error) {
+	if val == "-" {
+		return jsonTag{ignore: true}, nil
+	}
+
+	var tag jsonTag
+
+	i := strings.Index(val, ",")
+	if i == -1 || val[:i] == "" {
+		return tag, fmt.Errorf("malformed json tag: %s", val)
+	}
+
+	tag = jsonTag{
+		apiName: val[:i],
+	}
+
+	switch val[i+1:] {
+	case "omitempty":
+	case "omitempty,string":
+		tag.stringFormat = true
+	default:
+		return tag, fmt.Errorf("malformed json tag: %s", val)
+	}
+
+	return tag, nil
+}
+
+// Reports whether the struct field "f" with value "v" should be included in JSON output.
+func includeField(v reflect.Value, f reflect.StructField, mustInclude map[string]struct{}) bool {
+	// The regular JSON encoding of a nil pointer is "null", which means "delete this field".
+	// Therefore, we could enable field deletion by honoring pointer fields' presence in the mustInclude set.
+	// However, many fields are not pointers, so there would be no way to delete these fields.
+	// Rather than partially supporting field deletion, we ignore mustInclude for nil pointer fields.
+	// Deletion will be handled by a separate mechanism.
+	if f.Type.Kind() == reflect.Ptr && v.IsNil() {
+		return false
+	}
+
+	// The "any" type is represented as an interface{}.  If this interface
+	// is nil, there is no reasonable representation to send.  We ignore
+	// these fields, for the same reasons as given above for pointers.
+	if f.Type.Kind() == reflect.Interface && v.IsNil() {
+		return false
+	}
+
+	_, ok := mustInclude[f.Name]
+	return ok || !isEmptyValue(v)
+}
+
+// isEmptyValue reports whether v is the empty value for its type.  This
+// implementation is based on that of the encoding/json package, but its
+// correctness does not depend on it being identical. What's important is that
+// this function return false in situations where v should not be sent as part
+// of a PATCH operation.
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+	}
+	return false
+}

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

@@ -0,0 +1,200 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gensupport
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"mime/multipart"
+	"net/http"
+	"net/textproto"
+
+	"google.golang.org/api/googleapi"
+)
+
+const sniffBuffSize = 512
+
+func newContentSniffer(r io.Reader) *contentSniffer {
+	return &contentSniffer{r: r}
+}
+
+// contentSniffer wraps a Reader, and reports the content type determined by sniffing up to 512 bytes from the Reader.
+type contentSniffer struct {
+	r     io.Reader
+	start []byte // buffer for the sniffed bytes.
+	err   error  // set to any error encountered while reading bytes to be sniffed.
+
+	ctype   string // set on first sniff.
+	sniffed bool   // set to true on first sniff.
+}
+
+func (cs *contentSniffer) Read(p []byte) (n int, err error) {
+	// Ensure that the content type is sniffed before any data is consumed from Reader.
+	_, _ = cs.ContentType()
+
+	if len(cs.start) > 0 {
+		n := copy(p, cs.start)
+		cs.start = cs.start[n:]
+		return n, nil
+	}
+
+	// We may have read some bytes into start while sniffing, even if the read ended in an error.
+	// We should first return those bytes, then the error.
+	if cs.err != nil {
+		return 0, cs.err
+	}
+
+	// Now we have handled all bytes that were buffered while sniffing.  Now just delegate to the underlying reader.
+	return cs.r.Read(p)
+}
+
+// ContentType returns the sniffed content type, and whether the content type was succesfully sniffed.
+func (cs *contentSniffer) ContentType() (string, bool) {
+	if cs.sniffed {
+		return cs.ctype, cs.ctype != ""
+	}
+	cs.sniffed = true
+	// If ReadAll hits EOF, it returns err==nil.
+	cs.start, cs.err = ioutil.ReadAll(io.LimitReader(cs.r, sniffBuffSize))
+
+	// Don't try to detect the content type based on possibly incomplete data.
+	if cs.err != nil {
+		return "", false
+	}
+
+	cs.ctype = http.DetectContentType(cs.start)
+	return cs.ctype, true
+}
+
+// DetermineContentType determines the content type of the supplied reader.
+// If the content type is already known, it can be specified via ctype.
+// Otherwise, the content of media will be sniffed to determine the content type.
+// If media implements googleapi.ContentTyper (deprecated), this will be used
+// instead of sniffing the content.
+// After calling DetectContentType the caller must not perform further reads on
+// media, but rather read from the Reader that is returned.
+func DetermineContentType(media io.Reader, ctype string) (io.Reader, string) {
+	// Note: callers could avoid calling DetectContentType if ctype != "",
+	// but doing the check inside this function reduces the amount of
+	// generated code.
+	if ctype != "" {
+		return media, ctype
+	}
+
+	// For backwards compatability, allow clients to set content
+	// type by providing a ContentTyper for media.
+	if typer, ok := media.(googleapi.ContentTyper); ok {
+		return media, typer.ContentType()
+	}
+
+	sniffer := newContentSniffer(media)
+	if ctype, ok := sniffer.ContentType(); ok {
+		return sniffer, ctype
+	}
+	// If content type could not be sniffed, reads from sniffer will eventually fail with an error.
+	return sniffer, ""
+}
+
+type typeReader struct {
+	io.Reader
+	typ string
+}
+
+// multipartReader combines the contents of multiple readers to creat a multipart/related HTTP body.
+// Close must be called if reads from the multipartReader are abandoned before reaching EOF.
+type multipartReader struct {
+	pr       *io.PipeReader
+	pipeOpen bool
+	ctype    string
+}
+
+func newMultipartReader(parts []typeReader) *multipartReader {
+	mp := &multipartReader{pipeOpen: true}
+	var pw *io.PipeWriter
+	mp.pr, pw = io.Pipe()
+	mpw := multipart.NewWriter(pw)
+	mp.ctype = "multipart/related; boundary=" + mpw.Boundary()
+	go func() {
+		for _, part := range parts {
+			w, err := mpw.CreatePart(typeHeader(part.typ))
+			if err != nil {
+				mpw.Close()
+				pw.CloseWithError(fmt.Errorf("googleapi: CreatePart failed: %v", err))
+				return
+			}
+			_, err = io.Copy(w, part.Reader)
+			if err != nil {
+				mpw.Close()
+				pw.CloseWithError(fmt.Errorf("googleapi: Copy failed: %v", err))
+				return
+			}
+		}
+
+		mpw.Close()
+		pw.Close()
+	}()
+	return mp
+}
+
+func (mp *multipartReader) Read(data []byte) (n int, err error) {
+	return mp.pr.Read(data)
+}
+
+func (mp *multipartReader) Close() error {
+	if !mp.pipeOpen {
+		return nil
+	}
+	mp.pipeOpen = false
+	return mp.pr.Close()
+}
+
+// CombineBodyMedia combines a json body with media content to create a multipart/related HTTP body.
+// It returns a ReadCloser containing the combined body, and the overall "multipart/related" content type, with random boundary.
+//
+// The caller must call Close on the returned ReadCloser if reads are abandoned before reaching EOF.
+func CombineBodyMedia(body io.Reader, bodyContentType string, media io.Reader, mediaContentType string) (io.ReadCloser, string) {
+	mp := newMultipartReader([]typeReader{
+		{body, bodyContentType},
+		{media, mediaContentType},
+	})
+	return mp, mp.ctype
+}
+
+func typeHeader(contentType string) textproto.MIMEHeader {
+	h := make(textproto.MIMEHeader)
+	if contentType != "" {
+		h.Set("Content-Type", contentType)
+	}
+	return h
+}
+
+// PrepareUpload determines whether the data in the supplied reader should be
+// uploaded in a single request, or in sequential chunks.
+// chunkSize is the size of the chunk that media should be split into.
+// If chunkSize is non-zero and the contents of media do not fit in a single
+// chunk (or there is an error reading media), then media will be returned as a
+// ResumableBuffer.  Otherwise, media will be returned as a Reader.
+//
+// After PrepareUpload has been called, media should no longer be used: the
+// media content should be accessed via one of the return values.
+func PrepareUpload(media io.Reader, chunkSize int) (io.Reader,
+	*ResumableBuffer) {
+	if chunkSize == 0 { // do not chunk
+		return media, nil
+	}
+
+	rb := NewResumableBuffer(media, chunkSize)
+	rdr, _, _, err := rb.Chunk()
+
+	if err == io.EOF { // we can upload this in a single request
+		return rdr, nil
+	}
+	// err might be a non-EOF error. If it is, the next call to rb.Chunk will
+	// return the same error. Returning a ResumableBuffer ensures that this error
+	// will be handled at some point.
+
+	return nil, rb
+}

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

@@ -0,0 +1,50 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gensupport
+
+import (
+	"net/url"
+
+	"google.golang.org/api/googleapi"
+)
+
+// URLParams is a simplified replacement for url.Values
+// that safely builds up URL parameters for encoding.
+type URLParams map[string][]string
+
+// Get returns the first value for the given key, or "".
+func (u URLParams) Get(key string) string {
+	vs := u[key]
+	if len(vs) == 0 {
+		return ""
+	}
+	return vs[0]
+}
+
+// Set sets the key to value.
+// It replaces any existing values.
+func (u URLParams) Set(key, value string) {
+	u[key] = []string{value}
+}
+
+// SetMulti sets the key to an array of values.
+// It replaces any existing values.
+// Note that values must not be modified after calling SetMulti
+// so the caller is responsible for making a copy if necessary.
+func (u URLParams) SetMulti(key string, values []string) {
+	u[key] = values
+}
+
+// Encode encodes the values into ``URL encoded'' form
+// ("bar=baz&foo=quux") sorted by key.
+func (u URLParams) Encode() string {
+	return url.Values(u).Encode()
+}
+
+func SetOptions(u URLParams, opts ...googleapi.CallOption) {
+	for _, o := range opts {
+		u.Set(o.Get())
+	}
+}

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

@@ -0,0 +1,198 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gensupport
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/context/ctxhttp"
+)
+
+const (
+	// statusResumeIncomplete is the code returned by the Google uploader
+	// when the transfer is not yet complete.
+	statusResumeIncomplete = 308
+
+	// statusTooManyRequests is returned by the storage API if the
+	// per-project limits have been temporarily exceeded. The request
+	// should be retried.
+	// https://cloud.google.com/storage/docs/json_api/v1/status-codes#standardcodes
+	statusTooManyRequests = 429
+)
+
+// ResumableUpload is used by the generated APIs to provide resumable uploads.
+// It is not used by developers directly.
+type ResumableUpload struct {
+	Client *http.Client
+	// URI is the resumable resource destination provided by the server after specifying "&uploadType=resumable".
+	URI       string
+	UserAgent string // User-Agent for header of the request
+	// Media is the object being uploaded.
+	Media *ResumableBuffer
+	// MediaType defines the media type, e.g. "image/jpeg".
+	MediaType string
+
+	mu       sync.Mutex // guards progress
+	progress int64      // number of bytes uploaded so far
+
+	// Callback is an optional function that will be periodically called with the cumulative number of bytes uploaded.
+	Callback func(int64)
+
+	// If not specified, a default exponential backoff strategy will be used.
+	Backoff BackoffStrategy
+}
+
+// Progress returns the number of bytes uploaded at this point.
+func (rx *ResumableUpload) Progress() int64 {
+	rx.mu.Lock()
+	defer rx.mu.Unlock()
+	return rx.progress
+}
+
+// doUploadRequest performs a single HTTP request to upload data.
+// off specifies the offset in rx.Media from which data is drawn.
+// size is the number of bytes in data.
+// final specifies whether data is the final chunk to be uploaded.
+func (rx *ResumableUpload) doUploadRequest(ctx context.Context, data io.Reader, off, size int64, final bool) (*http.Response, error) {
+	req, err := http.NewRequest("POST", rx.URI, data)
+	if err != nil {
+		return nil, err
+	}
+
+	req.ContentLength = size
+	var contentRange string
+	if final {
+		if size == 0 {
+			contentRange = fmt.Sprintf("bytes */%v", off)
+		} else {
+			contentRange = fmt.Sprintf("bytes %v-%v/%v", off, off+size-1, off+size)
+		}
+	} else {
+		contentRange = fmt.Sprintf("bytes %v-%v/*", off, off+size-1)
+	}
+	req.Header.Set("Content-Range", contentRange)
+	req.Header.Set("Content-Type", rx.MediaType)
+	req.Header.Set("User-Agent", rx.UserAgent)
+	return ctxhttp.Do(ctx, rx.Client, req)
+
+}
+
+// reportProgress calls a user-supplied callback to report upload progress.
+// If old==updated, the callback is not called.
+func (rx *ResumableUpload) reportProgress(old, updated int64) {
+	if updated-old == 0 {
+		return
+	}
+	rx.mu.Lock()
+	rx.progress = updated
+	rx.mu.Unlock()
+	if rx.Callback != nil {
+		rx.Callback(updated)
+	}
+}
+
+// transferChunk performs a single HTTP request to upload a single chunk from rx.Media.
+func (rx *ResumableUpload) transferChunk(ctx context.Context) (*http.Response, error) {
+	chunk, off, size, err := rx.Media.Chunk()
+
+	done := err == io.EOF
+	if !done && err != nil {
+		return nil, err
+	}
+
+	res, err := rx.doUploadRequest(ctx, chunk, off, int64(size), done)
+	if err != nil {
+		return res, err
+	}
+
+	if res.StatusCode == statusResumeIncomplete || res.StatusCode == http.StatusOK {
+		rx.reportProgress(off, off+int64(size))
+	}
+
+	if res.StatusCode == statusResumeIncomplete {
+		rx.Media.Next()
+	}
+	return res, nil
+}
+
+func contextDone(ctx context.Context) bool {
+	select {
+	case <-ctx.Done():
+		return true
+	default:
+		return false
+	}
+}
+
+// Upload starts the process of a resumable upload with a cancellable context.
+// It retries using the provided back off strategy until cancelled or the
+// strategy indicates to stop retrying.
+// It is called from the auto-generated API code and is not visible to the user.
+// rx is private to the auto-generated API code.
+// Exactly one of resp or err will be nil.  If resp is non-nil, the caller must call resp.Body.Close.
+func (rx *ResumableUpload) Upload(ctx context.Context) (resp *http.Response, err error) {
+	var pause time.Duration
+	backoff := rx.Backoff
+	if backoff == nil {
+		backoff = DefaultBackoffStrategy()
+	}
+
+	for {
+		// Ensure that we return in the case of cancelled context, even if pause is 0.
+		if contextDone(ctx) {
+			return nil, ctx.Err()
+		}
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case <-time.After(pause):
+		}
+
+		resp, err = rx.transferChunk(ctx)
+
+		var status int
+		if resp != nil {
+			status = resp.StatusCode
+		}
+
+		// Check if we should retry the request.
+		if shouldRetry(status, err) {
+			var retry bool
+			pause, retry = backoff.Pause()
+			if retry {
+				if resp != nil && resp.Body != nil {
+					resp.Body.Close()
+				}
+				continue
+			}
+		}
+
+		// If the chunk was uploaded successfully, but there's still
+		// more to go, upload the next chunk without any delay.
+		if status == statusResumeIncomplete {
+			pause = 0
+			backoff.Reset()
+			resp.Body.Close()
+			continue
+		}
+
+		// It's possible for err and resp to both be non-nil here, but we expose a simpler
+		// contract to our callers: exactly one of resp and err will be non-nil.  This means
+		// that any response body must be closed here before returning a non-nil error.
+		if err != nil {
+			if resp != nil && resp.Body != nil {
+				resp.Body.Close()
+			}
+			return nil, err
+		}
+
+		return resp, nil
+	}
+}

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

@@ -0,0 +1,77 @@
+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 {
+	// Retry for 5xx response codes.
+	if 500 <= status && status < 600 {
+		return true
+	}
+
+	// Retry on statusTooManyRequests{
+	if status == statusTooManyRequests {
+		return true
+	}
+
+	// Retry on unexpected EOFs and temporary network errors.
+	if err == io.ErrUnexpectedEOF {
+		return true
+	}
+	if err, ok := err.(net.Error); ok {
+		return err.Temporary()
+	}
+
+	return false
+}