restic/internal/backend/gs/gs.go

459 lines
11 KiB
Go

// Package gs provides a restic backend for Google Cloud Storage.
package gs
import (
"context"
"fmt"
"io"
"os"
"path"
"strings"
"github.com/pkg/errors"
"github.com/restic/restic/internal/backend"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/restic"
"io/ioutil"
"golang.org/x/oauth2/google"
"google.golang.org/api/googleapi"
storage "google.golang.org/api/storage/v1"
)
// Backend stores data in a GCS bucket.
//
// The service account used to access the bucket must have these permissions:
// * storage.objects.create
// * storage.objects.delete
// * storage.objects.get
// * storage.objects.list
type Backend struct {
service *storage.Service
projectID string
sem *backend.Semaphore
bucketName string
prefix string
listMaxItems int
backend.Layout
}
// Ensure that *Backend implements restic.Backend.
var _ restic.Backend = &Backend{}
func getStorageService(jsonKeyPath string) (*storage.Service, error) {
raw, err := ioutil.ReadFile(jsonKeyPath)
if err != nil {
return nil, errors.Wrap(err, "ReadFile")
}
conf, err := google.JWTConfigFromJSON(raw, storage.DevstorageReadWriteScope)
if err != nil {
return nil, err
}
client := conf.Client(context.TODO())
service, err := storage.New(client)
if err != nil {
return nil, err
}
return service, nil
}
const defaultListMaxItems = 1000
func open(cfg Config) (*Backend, error) {
debug.Log("open, config %#v", cfg)
service, err := getStorageService(cfg.JSONKeyPath)
if err != nil {
return nil, errors.Wrap(err, "getStorageService")
}
sem, err := backend.NewSemaphore(cfg.Connections)
if err != nil {
return nil, err
}
be := &Backend{
service: service,
projectID: cfg.ProjectID,
sem: sem,
bucketName: cfg.Bucket,
prefix: cfg.Prefix,
Layout: &backend.DefaultLayout{
Path: cfg.Prefix,
Join: path.Join,
},
listMaxItems: defaultListMaxItems,
}
return be, nil
}
// Open opens the gs backend at the specified bucket.
func Open(cfg Config) (restic.Backend, error) {
return open(cfg)
}
// Create opens the gs backend at the specified bucket and attempts to creates
// the bucket if it does not exist yet.
//
// The service account must have the "storage.buckets.create" permission to
// create a bucket the does not yet exist.
func Create(cfg Config) (restic.Backend, error) {
be, err := open(cfg)
if err != nil {
return nil, errors.Wrap(err, "open")
}
// Try to determine if the bucket exists. If it does not, try to create it.
//
// A Get call has three typical error cases:
//
// * nil: Bucket exists and we have access to the metadata (returned).
//
// * 403: Bucket exists and we do not have access to the metadata. We
// don't have storage.buckets.get permission to the bucket, but we may
// still be able to access objects in the bucket.
//
// * 404: Bucket doesn't exist.
//
// Determining if the bucket is accessible is best-effort because the
// 403 case is ambiguous.
if _, err := be.service.Buckets.Get(be.bucketName).Do(); err != nil {
gerr, ok := err.(*googleapi.Error)
if !ok {
// Don't know what to do with this error.
return nil, errors.Wrap(err, "service.Buckets.Get")
}
switch gerr.Code {
case 403:
// Bucket exists, but we don't know if it is
// accessible. Optimistically assume it is; if not,
// future Backend calls will fail.
debug.Log("Unable to determine if bucket %s is accessible (err %v). Continuing as if it is.", be.bucketName, err)
case 404:
// Bucket doesn't exist, try to create it.
bucket := &storage.Bucket{
Name: be.bucketName,
}
if _, err := be.service.Buckets.Insert(be.projectID, bucket).Do(); err != nil {
// Always an error, as the bucket definitely
// doesn't exist.
return nil, errors.Wrap(err, "service.Buckets.Insert")
}
default:
// Don't know what to do with this error.
return nil, errors.Wrap(err, "service.Buckets.Get")
}
}
return be, nil
}
// SetListMaxItems sets the number of list items to load per request.
func (be *Backend) SetListMaxItems(i int) {
be.listMaxItems = i
}
// IsNotExist returns true if the error is caused by a not existing file.
func (be *Backend) IsNotExist(err error) bool {
debug.Log("IsNotExist(%T, %#v)", err, err)
if os.IsNotExist(err) {
return true
}
if er, ok := err.(*googleapi.Error); ok {
if er.Code == 404 {
return true
}
}
return false
}
// Join combines path components with slashes.
func (be *Backend) Join(p ...string) string {
return path.Join(p...)
}
// Location returns this backend's location (the bucket name).
func (be *Backend) Location() string {
return be.Join(be.bucketName, be.prefix)
}
// Path returns the path in the bucket that is used for this backend.
func (be *Backend) Path() string {
return be.prefix
}
// Save stores data in the backend at the handle.
func (be *Backend) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err error) {
if err := h.Valid(); err != nil {
return err
}
objName := be.Filename(h)
debug.Log("Save %v at %v", h, objName)
be.sem.GetToken()
// Check key does not already exist
if _, err := be.service.Objects.Get(be.bucketName, objName).Do(); err == nil {
debug.Log("%v already exists", h)
be.sem.ReleaseToken()
return errors.New("key already exists")
}
debug.Log("InsertObject(%v, %v)", be.bucketName, objName)
// Set chunk size to zero to disable resumable uploads.
//
// With a non-zero chunk size (the default is
// googleapi.DefaultUploadChunkSize, 8MB), Insert will buffer data from
// rd in chunks of this size so it can upload these chunks in
// individual requests.
//
// This chunking allows the library to automatically handle network
// interruptions and re-upload only the last chunk rather than the full
// file.
//
// Unfortunately, this buffering doesn't play nicely with
// --limit-upload, which applies a rate limit to rd. This rate limit
// ends up only limiting the read from rd into the buffer rather than
// the network traffic itself. This results in poor network rate limit
// behavior, where individual chunks are written to the network at full
// bandwidth for several seconds, followed by several seconds of no
// network traffic as the next chunk is read through the rate limiter.
//
// By disabling chunking, rd is passed further down the request stack,
// where there is less (but some) buffering, which ultimately results
// in better rate limiting behavior.
//
// restic typically writes small blobs (4MB-30MB), so the resumable
// uploads are not providing significant benefit anyways.
cs := googleapi.ChunkSize(0)
info, err := be.service.Objects.Insert(be.bucketName,
&storage.Object{
Name: objName,
}).Media(rd, cs).Do()
be.sem.ReleaseToken()
if err != nil {
debug.Log("%v: err %#v: %v", objName, err, err)
return errors.Wrap(err, "service.Objects.Insert")
}
debug.Log("%v -> %v bytes", objName, info.Size)
return nil
}
// wrapReader wraps an io.ReadCloser to run an additional function on Close.
type wrapReader struct {
io.ReadCloser
f func()
}
func (wr wrapReader) Close() error {
err := wr.ReadCloser.Close()
wr.f()
return err
}
// Load returns a reader that yields the contents of the file at h at the
// given offset. If length is nonzero, only a portion of the file is
// returned. rd must be closed after use.
func (be *Backend) Load(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
debug.Log("Load %v, length %v, offset %v from %v", h, length, offset, be.Filename(h))
if err := h.Valid(); err != nil {
return nil, err
}
if offset < 0 {
return nil, errors.New("offset is negative")
}
if length < 0 {
return nil, errors.Errorf("invalid length %d", length)
}
objName := be.Filename(h)
be.sem.GetToken()
var byteRange string
if length > 0 {
byteRange = fmt.Sprintf("bytes=%d-%d", offset, offset+int64(length-1))
} else {
byteRange = fmt.Sprintf("bytes=%d-", offset)
}
req := be.service.Objects.Get(be.bucketName, objName)
// https://cloud.google.com/storage/docs/json_api/v1/parameters#range
req.Header().Set("Range", byteRange)
res, err := req.Download()
if err != nil {
be.sem.ReleaseToken()
return nil, err
}
closeRd := wrapReader{
ReadCloser: res.Body,
f: func() {
debug.Log("Close()")
be.sem.ReleaseToken()
},
}
return closeRd, err
}
// Stat returns information about a blob.
func (be *Backend) Stat(ctx context.Context, h restic.Handle) (bi restic.FileInfo, err error) {
debug.Log("%v", h)
objName := be.Filename(h)
be.sem.GetToken()
obj, err := be.service.Objects.Get(be.bucketName, objName).Do()
be.sem.ReleaseToken()
if err != nil {
debug.Log("GetObject() err %v", err)
return restic.FileInfo{}, errors.Wrap(err, "service.Objects.Get")
}
return restic.FileInfo{Size: int64(obj.Size)}, nil
}
// Test returns true if a blob of the given type and name exists in the backend.
func (be *Backend) Test(ctx context.Context, h restic.Handle) (bool, error) {
found := false
objName := be.Filename(h)
be.sem.GetToken()
_, err := be.service.Objects.Get(be.bucketName, objName).Do()
be.sem.ReleaseToken()
if err == nil {
found = true
}
// If error, then not found
return found, nil
}
// Remove removes the blob with the given name and type.
func (be *Backend) Remove(ctx context.Context, h restic.Handle) error {
objName := be.Filename(h)
be.sem.GetToken()
err := be.service.Objects.Delete(be.bucketName, objName).Do()
be.sem.ReleaseToken()
if er, ok := err.(*googleapi.Error); ok {
if er.Code == 404 {
err = nil
}
}
debug.Log("Remove(%v) at %v -> err %v", h, objName, err)
return errors.Wrap(err, "client.RemoveObject")
}
// List returns a channel that yields all names of blobs of type t. A
// goroutine is started for this. If the channel done is closed, sending
// stops.
func (be *Backend) List(ctx context.Context, t restic.FileType) <-chan string {
debug.Log("listing %v", t)
ch := make(chan string)
prefix, _ := be.Basedir(t)
// make sure prefix ends with a slash
if prefix[len(prefix)-1] != '/' {
prefix += "/"
}
go func() {
defer close(ch)
listReq := be.service.Objects.List(be.bucketName).Prefix(prefix).MaxResults(int64(be.listMaxItems))
for {
be.sem.GetToken()
obj, err := listReq.Do()
be.sem.ReleaseToken()
if err != nil {
fmt.Fprintf(os.Stderr, "error listing %v: %v\n", prefix, err)
return
}
debug.Log("returned %v items", len(obj.Items))
for _, item := range obj.Items {
m := strings.TrimPrefix(item.Name, prefix)
if m == "" {
continue
}
select {
case ch <- path.Base(m):
case <-ctx.Done():
return
}
}
if obj.NextPageToken == "" {
break
}
listReq.PageToken(obj.NextPageToken)
}
}()
return ch
}
// Remove keys for a specified backend type.
func (be *Backend) removeKeys(ctx context.Context, t restic.FileType) error {
for key := range be.List(ctx, restic.DataFile) {
err := be.Remove(ctx, restic.Handle{Type: restic.DataFile, Name: key})
if err != nil {
return err
}
}
return nil
}
// Delete removes all restic keys in the bucket. It will not remove the bucket itself.
func (be *Backend) Delete(ctx context.Context) error {
alltypes := []restic.FileType{
restic.DataFile,
restic.KeyFile,
restic.LockFile,
restic.SnapshotFile,
restic.IndexFile}
for _, t := range alltypes {
err := be.removeKeys(ctx, t)
if err != nil {
return nil
}
}
return be.Remove(ctx, restic.Handle{Type: restic.ConfigFile})
}
// Close does nothing.
func (be *Backend) Close() error { return nil }