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restic/backend/s3/s3.go

227 lines
4.8 KiB
Go

package s3
import (
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"strings"
"github.com/mitchellh/goamz/aws"
"github.com/mitchellh/goamz/s3"
"github.com/restic/restic/backend"
)
const maxKeysInList = 1000
const connLimit = 10
func s3path(t backend.Type, name string) string {
if t == backend.Config {
return string(t)
}
return string(t) + "/" + name
}
type S3 struct {
bucket *s3.Bucket
connChan chan struct{}
path string
}
// Open a backend using an S3 bucket object
func OpenS3Bucket(bucket *s3.Bucket, bucketname string) *S3 {
connChan := make(chan struct{}, connLimit)
for i := 0; i < connLimit; i++ {
connChan <- struct{}{}
}
return &S3{bucket: bucket, path: bucketname, connChan: connChan}
}
// Open opens the s3 backend at bucket and region.
func Open(regionname, bucketname string) (backend.Backend, error) {
auth, err := aws.EnvAuth()
if err != nil {
return nil, err
}
client := s3.New(auth, aws.Regions[regionname])
return OpenS3Bucket(client.Bucket(bucketname), bucketname), nil
}
// Location returns this backend's location (the bucket name).
func (b *S3) Location() string {
return b.path
}
type s3Blob struct {
b *S3
buf *bytes.Buffer
final bool
}
func (bb *s3Blob) Write(p []byte) (int, error) {
if bb.final {
return 0, errors.New("blob already closed")
}
n, err := bb.buf.Write(p)
return n, err
}
func (bb *s3Blob) Read(p []byte) (int, error) {
return bb.buf.Read(p)
}
func (bb *s3Blob) Close() error {
bb.final = true
bb.buf.Reset()
return nil
}
func (bb *s3Blob) Size() uint {
return uint(bb.buf.Len())
}
func (bb *s3Blob) Finalize(t backend.Type, name string) error {
if bb.final {
return errors.New("Already finalized")
}
bb.final = true
path := s3path(t, name)
// Check key does not already exist
key, err := bb.b.bucket.GetKey(path)
if err == nil && key.Key == path {
return errors.New("key already exists!")
}
<-bb.b.connChan
err = bb.b.bucket.Put(path, bb.buf.Bytes(), "binary/octet-stream", "private")
bb.b.connChan <- struct{}{}
bb.buf.Reset()
return err
}
// Create creates a new Blob. The data is available only after Finalize()
// has been called on the returned Blob.
func (b *S3) Create() (backend.Blob, error) {
blob := s3Blob{
b: b,
buf: &bytes.Buffer{},
}
return &blob, nil
}
// Get returns a reader that yields the content stored under the given
// name. The reader should be closed after draining it.
func (b *S3) Get(t backend.Type, name string) (io.ReadCloser, error) {
path := s3path(t, name)
return b.bucket.GetReader(path)
}
// GetReader returns an io.ReadCloser for the Blob with the given name of
// type t at offset and length. If length is 0, the reader reads until EOF.
func (b *S3) GetReader(t backend.Type, name string, offset, length uint) (io.ReadCloser, error) {
rc, err := b.Get(t, name)
if err != nil {
return nil, err
}
n, errc := io.CopyN(ioutil.Discard, rc, int64(offset))
if errc != nil {
return nil, errc
} else if n != int64(offset) {
return nil, fmt.Errorf("less bytes read than expected, read: %d, expected: %d", n, offset)
}
if length == 0 {
return rc, nil
}
return backend.LimitReadCloser(rc, int64(length)), nil
}
// Test returns true if a blob of the given type and name exists in the backend.
func (b *S3) Test(t backend.Type, name string) (bool, error) {
found := false
path := s3path(t, name)
key, err := b.bucket.GetKey(path)
if err == nil && key.Key == path {
found = true
}
// If error, then not found
return found, nil
}
// Remove removes the blob with the given name and type.
func (b *S3) Remove(t backend.Type, name string) error {
path := s3path(t, name)
return b.bucket.Del(path)
}
// 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 (b *S3) List(t backend.Type, done <-chan struct{}) <-chan string {
ch := make(chan string)
prefix := string(t) + "/"
listresp, err := b.bucket.List(prefix, "/", "", maxKeysInList)
if err != nil {
close(ch)
return ch
}
matches := make([]string, len(listresp.Contents))
for idx, key := range listresp.Contents {
matches[idx] = strings.TrimPrefix(key.Key, prefix)
}
// Continue making requests to get full list.
for listresp.IsTruncated {
listresp, err = b.bucket.List(prefix, "/", listresp.NextMarker, maxKeysInList)
if err != nil {
close(ch)
return ch
}
for _, key := range listresp.Contents {
matches = append(matches, strings.TrimPrefix(key.Key, prefix))
}
}
go func() {
defer close(ch)
for _, m := range matches {
if m == "" {
continue
}
select {
case ch <- m:
case <-done:
return
}
}
}()
return ch
}
// Delete removes the repository and all files.
func (b *S3) Delete() error {
return b.bucket.DelBucket()
}
// Close does nothing
func (b *S3) Close() error { return nil }