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mirror of https://github.com/octoleo/restic.git synced 2024-11-30 08:44:02 +00:00
restic/internal/backend/b2/b2.go
Michael Eischer 257740b0cc b2: Successful delete if file does not exist
When deleting a file, B2 sometimes returns a "500 Service Unavailable"
error but nevertheless correctly deletes the file. Due to retries in
the B2 library blazer, we sometimes also see a "400 File not present"
error. The retries of restic for the delete request then fail with
"404 File with such name does not exist.".

As we have to rely on request retries in a distributed system to handle
temporary errors, also consider a delete request to be successful if the
file is reported as not existing. This should be safe as B2 claims to
provide a strongly consistent bucket listing and thus a missing file
shouldn't mysteriously show up again later on.
2021-10-09 23:51:12 +02:00

351 lines
8.2 KiB
Go

package b2
import (
"context"
"hash"
"io"
"net/http"
"path"
"github.com/restic/restic/internal/backend"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/restic"
"github.com/cenkalti/backoff/v4"
"github.com/kurin/blazer/b2"
)
// b2Backend is a backend which stores its data on Backblaze B2.
type b2Backend struct {
client *b2.Client
bucket *b2.Bucket
cfg Config
listMaxItems int
backend.Layout
sem *backend.Semaphore
}
const defaultListMaxItems = 1000
// ensure statically that *b2Backend implements restic.Backend.
var _ restic.Backend = &b2Backend{}
func newClient(ctx context.Context, cfg Config, rt http.RoundTripper) (*b2.Client, error) {
opts := []b2.ClientOption{b2.Transport(rt)}
c, err := b2.NewClient(ctx, cfg.AccountID, cfg.Key, opts...)
if err != nil {
return nil, errors.Wrap(err, "b2.NewClient")
}
return c, nil
}
// Open opens a connection to the B2 service.
func Open(ctx context.Context, cfg Config, rt http.RoundTripper) (restic.Backend, error) {
debug.Log("cfg %#v", cfg)
ctx, cancel := context.WithCancel(ctx)
defer cancel()
client, err := newClient(ctx, cfg, rt)
if err != nil {
return nil, err
}
bucket, err := client.Bucket(ctx, cfg.Bucket)
if err != nil {
return nil, errors.Wrap(err, "Bucket")
}
sem, err := backend.NewSemaphore(cfg.Connections)
if err != nil {
return nil, err
}
be := &b2Backend{
client: client,
bucket: bucket,
cfg: cfg,
Layout: &backend.DefaultLayout{
Join: path.Join,
Path: cfg.Prefix,
},
listMaxItems: defaultListMaxItems,
sem: sem,
}
return be, nil
}
// Create opens a connection to the B2 service. If the bucket does not exist yet,
// it is created.
func Create(ctx context.Context, cfg Config, rt http.RoundTripper) (restic.Backend, error) {
debug.Log("cfg %#v", cfg)
ctx, cancel := context.WithCancel(ctx)
defer cancel()
client, err := newClient(ctx, cfg, rt)
if err != nil {
return nil, err
}
attr := b2.BucketAttrs{
Type: b2.Private,
}
bucket, err := client.NewBucket(ctx, cfg.Bucket, &attr)
if err != nil {
return nil, errors.Wrap(err, "NewBucket")
}
sem, err := backend.NewSemaphore(cfg.Connections)
if err != nil {
return nil, err
}
be := &b2Backend{
client: client,
bucket: bucket,
cfg: cfg,
Layout: &backend.DefaultLayout{
Join: path.Join,
Path: cfg.Prefix,
},
listMaxItems: defaultListMaxItems,
sem: sem,
}
present, err := be.Test(ctx, restic.Handle{Type: restic.ConfigFile})
if err != nil {
return nil, err
}
if present {
return nil, errors.New("config already exists")
}
return be, nil
}
// SetListMaxItems sets the number of list items to load per request.
func (be *b2Backend) SetListMaxItems(i int) {
be.listMaxItems = i
}
// Location returns the location for the backend.
func (be *b2Backend) Location() string {
return be.cfg.Bucket
}
// Hasher may return a hash function for calculating a content hash for the backend
func (be *b2Backend) Hasher() hash.Hash {
return nil
}
// IsNotExist returns true if the error is caused by a non-existing file.
func (be *b2Backend) IsNotExist(err error) bool {
return b2.IsNotExist(errors.Cause(err))
}
// Load runs fn with a reader that yields the contents of the file at h at the
// given offset.
func (be *b2Backend) Load(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error {
return backend.DefaultLoad(ctx, h, length, offset, be.openReader, fn)
}
func (be *b2Backend) openReader(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, backoff.Permanent(err)
}
if offset < 0 {
return nil, errors.New("offset is negative")
}
if length < 0 {
return nil, errors.Errorf("invalid length %d", length)
}
ctx, cancel := context.WithCancel(ctx)
be.sem.GetToken()
name := be.Layout.Filename(h)
obj := be.bucket.Object(name)
if offset == 0 && length == 0 {
rd := obj.NewReader(ctx)
return be.sem.ReleaseTokenOnClose(rd, cancel), nil
}
// pass a negative length to NewRangeReader so that the remainder of the
// file is read.
if length == 0 {
length = -1
}
rd := obj.NewRangeReader(ctx, offset, int64(length))
return be.sem.ReleaseTokenOnClose(rd, cancel), nil
}
// Save stores data in the backend at the handle.
func (be *b2Backend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
ctx, cancel := context.WithCancel(ctx)
defer cancel()
if err := h.Valid(); err != nil {
return backoff.Permanent(err)
}
be.sem.GetToken()
defer be.sem.ReleaseToken()
name := be.Filename(h)
debug.Log("Save %v, name %v", h, name)
obj := be.bucket.Object(name)
// b2 always requires sha1 checksums for uploaded file parts
w := obj.NewWriter(ctx)
n, err := io.Copy(w, rd)
debug.Log(" saved %d bytes, err %v", n, err)
if err != nil {
_ = w.Close()
return errors.Wrap(err, "Copy")
}
// sanity check
if n != rd.Length() {
return errors.Errorf("wrote %d bytes instead of the expected %d bytes", n, rd.Length())
}
return errors.Wrap(w.Close(), "Close")
}
// Stat returns information about a blob.
func (be *b2Backend) Stat(ctx context.Context, h restic.Handle) (bi restic.FileInfo, err error) {
debug.Log("Stat %v", h)
be.sem.GetToken()
defer be.sem.ReleaseToken()
name := be.Filename(h)
obj := be.bucket.Object(name)
info, err := obj.Attrs(ctx)
if err != nil {
debug.Log("Attrs() err %v", err)
return restic.FileInfo{}, errors.Wrap(err, "Stat")
}
return restic.FileInfo{Size: info.Size, Name: h.Name}, nil
}
// Test returns true if a blob of the given type and name exists in the backend.
func (be *b2Backend) Test(ctx context.Context, h restic.Handle) (bool, error) {
debug.Log("Test %v", h)
be.sem.GetToken()
defer be.sem.ReleaseToken()
found := false
name := be.Filename(h)
obj := be.bucket.Object(name)
info, err := obj.Attrs(ctx)
if err == nil && info != nil && info.Status == b2.Uploaded {
found = true
}
return found, nil
}
// Remove removes the blob with the given name and type.
func (be *b2Backend) Remove(ctx context.Context, h restic.Handle) error {
debug.Log("Remove %v", h)
be.sem.GetToken()
defer be.sem.ReleaseToken()
obj := be.bucket.Object(be.Filename(h))
err := obj.Delete(ctx)
// consider a file as removed if b2 informs us that it does not exist
if b2.IsNotExist(err) {
return nil
}
return errors.Wrap(err, "Delete")
}
type semLocker struct {
*backend.Semaphore
}
func (sm semLocker) Lock() { sm.GetToken() }
func (sm semLocker) Unlock() { sm.ReleaseToken() }
// List returns a channel that yields all names of blobs of type t.
func (be *b2Backend) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
debug.Log("List %v", t)
ctx, cancel := context.WithCancel(ctx)
defer cancel()
prefix, _ := be.Basedir(t)
iter := be.bucket.List(ctx, b2.ListPrefix(prefix), b2.ListPageSize(be.listMaxItems), b2.ListLocker(semLocker{be.sem}))
for iter.Next() {
obj := iter.Object()
attrs, err := obj.Attrs(ctx)
if err != nil {
return err
}
fi := restic.FileInfo{
Name: path.Base(obj.Name()),
Size: attrs.Size,
}
if err := fn(fi); err != nil {
return err
}
}
if err := iter.Err(); err != nil {
debug.Log("List: %v", err)
return err
}
return nil
}
// Remove keys for a specified backend type.
func (be *b2Backend) removeKeys(ctx context.Context, t restic.FileType) error {
debug.Log("removeKeys %v", t)
return be.List(ctx, t, func(fi restic.FileInfo) error {
return be.Remove(ctx, restic.Handle{Type: t, Name: fi.Name})
})
}
// Delete removes all restic keys in the bucket. It will not remove the bucket itself.
func (be *b2Backend) Delete(ctx context.Context) error {
alltypes := []restic.FileType{
restic.PackFile,
restic.KeyFile,
restic.LockFile,
restic.SnapshotFile,
restic.IndexFile}
for _, t := range alltypes {
err := be.removeKeys(ctx, t)
if err != nil {
return nil
}
}
err := be.Remove(ctx, restic.Handle{Type: restic.ConfigFile})
if err != nil && b2.IsNotExist(errors.Cause(err)) {
err = nil
}
return err
}
// Close does nothing
func (be *b2Backend) Close() error { return nil }