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fs.go
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fs.go
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// Copyright 2018 Francisco Souza. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package backend
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"io"
"io/fs"
"net/url"
"os"
"path/filepath"
"strings"
"sync"
"syscall"
"time"
"github.com/fsouza/fake-gcs-server/internal/checksum"
"github.com/pkg/xattr"
)
// storageFS is an implementation of the backend storage that stores data on disk
//
// The layout is the following:
//
// - rootDir
//
// |- bucket1
// \- bucket2
// |- object1
// \- object2
//
// Bucket and object names are url path escaped, so there's no special meaning of forward slashes.
type storageFS struct {
rootDir string
mtx sync.RWMutex
mh metadataHandler
}
// NewStorageFS creates an instance of the filesystem-backed storage backend.
func NewStorageFS(objects []StreamingObject, rootDir string) (Storage, error) {
if !strings.HasSuffix(rootDir, "/") {
rootDir += "/"
}
err := os.MkdirAll(rootDir, 0o700)
if err != nil {
return nil, err
}
var mh metadataHandler = metadataFile{}
// Use xattr for metadata if rootDir supports it.
if xattr.XATTR_SUPPORTED {
xattrHandler := metadataXattr{}
var xerr *xattr.Error
_, err = xattrHandler.read(rootDir)
if err == nil || (errors.As(err, &xerr) && xerr.Err == xattr.ENOATTR) {
mh = xattrHandler
}
}
s := &storageFS{rootDir: rootDir, mh: mh}
for _, o := range objects {
obj, err := s.CreateObject(o, NoConditions{})
if err != nil {
return nil, err
}
obj.Close()
}
return s, nil
}
// CreateBucket creates a bucket in the fs backend. A bucket is a folder in the
// root directory.
func (s *storageFS) CreateBucket(name string, versioningEnabled bool) error {
if versioningEnabled {
return errors.New("not implemented: fs storage type does not support versioning yet")
}
s.mtx.Lock()
defer s.mtx.Unlock()
return s.createBucket(name)
}
func (s *storageFS) createBucket(name string) error {
return os.MkdirAll(filepath.Join(s.rootDir, url.PathEscape(name)), 0o700)
}
// ListBuckets returns a list of buckets from the list of directories in the
// root directory.
func (s *storageFS) ListBuckets() ([]Bucket, error) {
s.mtx.RLock()
defer s.mtx.RUnlock()
infos, err := os.ReadDir(s.rootDir)
if err != nil {
return nil, err
}
buckets := []Bucket{}
for _, info := range infos {
if info.IsDir() {
unescaped, err := url.PathUnescape(info.Name())
if err != nil {
return nil, fmt.Errorf("failed to unescape object name %s: %w", info.Name(), err)
}
buckets = append(buckets, Bucket{Name: unescaped})
}
}
return buckets, nil
}
func timespecToTime(ts syscall.Timespec) time.Time {
return time.Unix(int64(ts.Sec), int64(ts.Nsec))
}
// GetBucket returns information about the given bucket, or an error if it
// doesn't exist.
func (s *storageFS) GetBucket(name string) (Bucket, error) {
s.mtx.RLock()
defer s.mtx.RUnlock()
dirInfo, err := os.Stat(filepath.Join(s.rootDir, url.PathEscape(name)))
if err != nil {
return Bucket{}, err
}
return Bucket{Name: name, VersioningEnabled: false, TimeCreated: timespecToTime(createTimeFromFileInfo(dirInfo))}, err
}
// DeleteBucket removes the bucket from the backend.
func (s *storageFS) DeleteBucket(name string) error {
objs, err := s.ListObjects(name, "", false)
if err != nil {
return BucketNotFound
}
if len(objs) > 0 {
return BucketNotEmpty
}
s.mtx.Lock()
defer s.mtx.Unlock()
return os.RemoveAll(filepath.Join(s.rootDir, url.PathEscape(name)))
}
// CreateObject stores an object as a regular file on disk. The backing content
// for the object may be in the same file that's being updated, so a temporary
// file is first created and then moved into place. This also makes it so any
// object content readers currently open continue reading from the original
// file instead of the newly created file.
//
// The crc32c checksum and md5 hash of the object content is calculated when
// reading the object content. Any checksum or hash in the passed-in object
// metadata is overwritten.
func (s *storageFS) CreateObject(obj StreamingObject, conditions Conditions) (StreamingObject, error) {
if obj.Generation > 0 {
return StreamingObject{}, errors.New("not implemented: fs storage type does not support objects generation yet")
}
// Note: this was a quick fix for issue #701. Now that we have a way to
// persist object attributes, we should implement versioning in the
// filesystem backend and handle generations outside of the backends.
obj.Generation = time.Now().UnixNano() / 1000
s.mtx.Lock()
defer s.mtx.Unlock()
err := s.createBucket(obj.BucketName)
if err != nil {
return StreamingObject{}, err
}
var activeGeneration int64
existingObj, err := s.getObject(obj.BucketName, obj.Name)
if err != nil {
activeGeneration = 0
} else {
activeGeneration = existingObj.Generation
}
if !conditions.ConditionsMet(activeGeneration) {
return StreamingObject{}, PreConditionFailed
}
path := filepath.Join(s.rootDir, url.PathEscape(obj.BucketName), obj.Name)
if err = os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
return StreamingObject{}, err
}
// Nothing to do if this operation only creates directories
if strings.HasSuffix(obj.Name, "/") {
// TODO: populate Crc32c, Md5Hash, and Etag
return StreamingObject{obj.ObjectAttrs, noopSeekCloser{bytes.NewReader([]byte{})}}, nil
}
var buf bytes.Buffer
hasher := checksum.NewStreamingHasher()
objectContent := io.TeeReader(obj.Content, hasher)
if _, err = io.Copy(&buf, objectContent); err != nil {
return StreamingObject{}, err
}
obj.Crc32c = hasher.EncodedCrc32cChecksum()
obj.Md5Hash = hasher.EncodedMd5Hash()
obj.Etag = fmt.Sprintf("%q", obj.Md5Hash)
// TODO: Handle if metadata is not present more gracefully?
encoded, err := json.Marshal(obj.ObjectAttrs)
if err != nil {
return StreamingObject{}, err
}
if err := writeFile(path, buf.Bytes(), 0o600); err != nil {
return StreamingObject{}, err
}
if err = s.mh.write(path, encoded); err != nil {
return StreamingObject{}, err
}
err = openObjectAndSetSize(&obj, path)
return obj, err
}
// ListObjects lists the objects in a given bucket with a given prefix and
// delimeter.
func (s *storageFS) ListObjects(bucketName string, prefix string, versions bool) ([]ObjectAttrs, error) {
s.mtx.RLock()
defer s.mtx.RUnlock()
objects := []ObjectAttrs{}
// TODO: WalkDir more efficient?
bucketPath := filepath.Join(s.rootDir, url.PathEscape(bucketName))
if err := filepath.Walk(bucketPath, func(path string, info fs.FileInfo, _ error) error {
// Rel() should never return error since path always descend from bucketPath
objName, _ := filepath.Rel(bucketPath, path)
// TODO: should this check path?
if s.mh.isSpecialFile(info.Name()) {
return nil
}
if info.IsDir() {
return nil
}
if prefix != "" && !strings.HasPrefix(objName, prefix) {
return nil
}
object, err := s.getObject(bucketName, objName)
if err != nil {
return err
}
object.Close()
objects = append(objects, object.ObjectAttrs)
return nil
}); err != nil {
return nil, err
}
return objects, nil
}
// GetObject get an object by bucket and name.
func (s *storageFS) GetObject(bucketName, objectName string) (StreamingObject, error) {
s.mtx.RLock()
defer s.mtx.RUnlock()
return s.getObject(bucketName, objectName)
}
// GetObjectWithGeneration retrieves an specific version of the object. Not
// implemented for this backend.
func (s *storageFS) GetObjectWithGeneration(bucketName, objectName string, generation int64) (StreamingObject, error) {
obj, err := s.GetObject(bucketName, objectName)
if err != nil {
return obj, err
}
if obj.Generation != generation {
return obj, fmt.Errorf("generation mismatch, object generation is %v, requested generation is %v (note: filesystem backend does not support versioning)", obj.Generation, generation)
}
return obj, nil
}
func (s *storageFS) getObject(bucketName, objectName string) (StreamingObject, error) {
path := filepath.Join(s.rootDir, url.PathEscape(bucketName), objectName)
encoded, err := s.mh.read(path)
if err != nil {
return StreamingObject{}, err
}
var obj StreamingObject
if err = json.Unmarshal(encoded, &obj.ObjectAttrs); err != nil {
return StreamingObject{}, err
}
obj.Name = filepath.ToSlash(objectName)
obj.BucketName = bucketName
err = openObjectAndSetSize(&obj, path)
return obj, err
}
func openObjectAndSetSize(obj *StreamingObject, path string) error {
info, err := os.Stat(path)
if err != nil {
return err
}
obj.Content = newLazyReader(path)
obj.Size = info.Size()
return nil
}
// DeleteObject deletes an object by bucket and name.
func (s *storageFS) DeleteObject(bucketName, objectName string) error {
s.mtx.Lock()
defer s.mtx.Unlock()
if objectName == "" {
return errors.New("can't delete object with empty name")
}
path := filepath.Join(s.rootDir, url.PathEscape(bucketName), objectName)
if err := s.mh.remove(path); err != nil {
return err
}
return os.Remove(path)
}
// PatchObject patches the given object metadata.
func (s *storageFS) PatchObject(bucketName, objectName string, metadata map[string]string) (StreamingObject, error) {
obj, err := s.GetObject(bucketName, objectName)
if err != nil {
return StreamingObject{}, err
}
defer obj.Close()
if obj.Metadata == nil {
obj.Metadata = map[string]string{}
}
for k, v := range metadata {
obj.Metadata[k] = v
}
obj.Generation = 0 // reset generation id
return s.CreateObject(obj, NoConditions{}) // recreate object
}
// UpdateObject replaces the given object metadata.
func (s *storageFS) UpdateObject(bucketName, objectName string, metadata map[string]string) (StreamingObject, error) {
obj, err := s.GetObject(bucketName, objectName)
if err != nil {
return StreamingObject{}, err
}
defer obj.Close()
obj.Metadata = map[string]string{}
for k, v := range metadata {
obj.Metadata[k] = v
}
obj.Generation = 0 // reset generation id
return s.CreateObject(obj, NoConditions{}) // recreate object
}
type concatenatedContent struct {
io.Reader
}
func (c concatenatedContent) Close() error {
return errors.New("not implemented")
}
func (c concatenatedContent) Seek(offset int64, whence int) (int64, error) {
return 0, errors.New("not implemented")
}
func concatObjectReaders(objects []StreamingObject) io.ReadSeekCloser {
readers := make([]io.Reader, len(objects))
for i := range objects {
readers[i] = objects[i].Content
}
return concatenatedContent{io.MultiReader(readers...)}
}
func (s *storageFS) ComposeObject(bucketName string, objectNames []string, destinationName string, metadata map[string]string, contentType string) (StreamingObject, error) {
var sourceObjects []StreamingObject
for _, n := range objectNames {
obj, err := s.GetObject(bucketName, n)
if err != nil {
return StreamingObject{}, err
}
defer obj.Close()
sourceObjects = append(sourceObjects, obj)
}
dest := StreamingObject{
ObjectAttrs: ObjectAttrs{
BucketName: bucketName,
Name: destinationName,
ContentType: contentType,
Created: time.Now().String(),
},
}
dest.Content = concatObjectReaders(sourceObjects)
dest.Metadata = metadata
result, err := s.CreateObject(dest, NoConditions{})
if err != nil {
return result, err
}
return result, nil
}