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restic/backend/s3/s3.go

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package s3
import (
"bytes"
"errors"
"fmt"
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"io"
"io/ioutil"
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"strings"
"github.com/mitchellh/goamz/aws"
"github.com/mitchellh/goamz/s3"
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"github.com/restic/restic/backend"
)
const maxKeysInList = 1000
const connLimit = 10
const backendPrefix = "restic"
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func s3path(t backend.Type, name string) string {
if t == backend.Config {
return backendPrefix + "/" + string(t)
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}
return backendPrefix + "/" + string(t) + "/" + name
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}
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type S3Backend struct {
bucket *s3.Bucket
connChan chan struct{}
path string
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}
// Open a backend using an S3 bucket object
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func OpenS3Bucket(bucket *s3.Bucket, bucketname string) *S3Backend {
connChan := make(chan struct{}, connLimit)
for i := 0; i < connLimit; i++ {
connChan <- struct{}{}
}
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return &S3Backend{bucket: bucket, path: bucketname, connChan: connChan}
}
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// Open opens the S3 backend at bucket and region.
func Open(regionname, bucketname string) (backend.Backend, error) {
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auth, err := aws.EnvAuth()
if err != nil {
return nil, err
}
client := s3.New(auth, aws.Regions[regionname])
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return OpenS3Bucket(client.Bucket(bucketname), bucketname), nil
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}
// Location returns this backend's location (the bucket name).
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func (be *S3Backend) Location() string {
return be.path
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}
type s3Blob struct {
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b *S3Backend
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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.PutReader(path, bb.buf, int64(bb.buf.Len()), "binary/octet-stream", "private")
bb.b.connChan <- struct{}{}
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bb.buf.Reset()
return err
}
// Create creates a new Blob. The data is available only after Finalize()
// has been called on the returned Blob.
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func (be *S3Backend) Create() (backend.Blob, error) {
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blob := s3Blob{
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b: be,
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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.
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func (be *S3Backend) Get(t backend.Type, name string) (io.ReadCloser, error) {
path := s3path(t, name)
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return be.bucket.GetReader(path)
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}
// 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.
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func (be *S3Backend) GetReader(t backend.Type, name string, offset, length uint) (io.ReadCloser, error) {
rc, err := be.Get(t, name)
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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)
}
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if length == 0 {
return rc, nil
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}
return backend.LimitReadCloser(rc, int64(length)), nil
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}
// Test returns true if a blob of the given type and name exists in the backend.
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func (be *S3Backend) Test(t backend.Type, name string) (bool, error) {
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found := false
path := s3path(t, name)
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key, err := be.bucket.GetKey(path)
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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.
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func (be *S3Backend) Remove(t backend.Type, name string) error {
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path := s3path(t, name)
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return be.bucket.Del(path)
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}
// 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.
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func (be *S3Backend) List(t backend.Type, done <-chan struct{}) <-chan string {
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ch := make(chan string)
prefix := s3path(t, "")
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listresp, err := be.bucket.List(prefix, "/", "", maxKeysInList)
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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 {
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listresp, err = be.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))
}
}
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go func() {
defer close(ch)
for _, m := range matches {
if m == "" {
continue
}
select {
case ch <- m:
case <-done:
return
}
}
}()
return ch
}
// Remove keys for a specified backend type
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func (be *S3Backend) removeKeys(t backend.Type) {
doneChan := make(chan struct{})
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for key := range be.List(backend.Data, doneChan) {
be.Remove(backend.Data, key)
}
doneChan <- struct{}{}
}
// Delete removes all restic keys
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func (be *S3Backend) Delete() error {
be.removeKeys(backend.Data)
be.removeKeys(backend.Key)
be.removeKeys(backend.Lock)
be.removeKeys(backend.Snapshot)
be.removeKeys(backend.Index)
be.removeKeys(backend.Config)
return nil
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}
// Close does nothing
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func (be *S3Backend) Close() error { return nil }