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// Package cloud provides utilities to implement a petrific storage using a cloud-based object-storage (S3/Openstack Swift style)
package cloud
import (
"bytes"
"code.laria.me/petrific/config"
"code.laria.me/petrific/objects"
"code.laria.me/petrific/storage"
"errors"
"fmt"
"math/rand"
)
type CloudStorage interface {
Get(key string) ([]byte, error)
Has(key string) (bool, error)
Put(key string, content []byte) error
Delete(key string) error
List(prefix string) ([]string, error)
Close() error
}
var (
NotFoundErr = errors.New("Object not found") // Cloud object could not be found
)
type CloudBasedObjectStorage struct {
CS CloudStorage
Prefix string
index storage.Index
}
func (cbos CloudBasedObjectStorage) objidToKey(id objects.ObjectId) string {
return cbos.Prefix + "obj/" + id.String()
}
func (cbos CloudBasedObjectStorage) readIndex(name string) (storage.Index, error) {
index := storage.NewIndex()
b, err := cbos.CS.Get(name)
if err != nil {
return index, err
}
err = index.Load(bytes.NewReader(b))
return index, err
}
func (cbos *CloudBasedObjectStorage) Init() error {
cbos.index = storage.NewIndex()
// Load and combine all indexes, keep only the one with the "largest" name (see also Close())
index_names, err := cbos.CS.List(cbos.Prefix + "index/")
if err != nil {
return err
}
max_index := ""
for _, index_name := range index_names {
index, err := cbos.readIndex(index_name)
if err != nil {
return err
}
cbos.index.Combine(index)
}
for _, index_name := range index_names {
if index_name != max_index {
if err := cbos.CS.Delete(index_name); err != nil {
return err
}
}
}
return nil
}
func (cbos CloudBasedObjectStorage) Get(id objects.ObjectId) ([]byte, error) {
return cbos.CS.Get(cbos.objidToKey(id))
}
func (cbos CloudBasedObjectStorage) Has(id objects.ObjectId) (bool, error) {
return cbos.CS.Has(cbos.objidToKey(id))
}
func (cbos CloudBasedObjectStorage) Set(id objects.ObjectId, typ objects.ObjectType, b []byte) error {
if err := cbos.CS.Put(cbos.objidToKey(id), b); err != nil {
return err
}
// could be used to repopulate the index (not implemented yet)
if err := cbos.CS.Put(cbos.Prefix+"typeof/"+id.String(), []byte(typ)); err != nil {
return err
}
cbos.index.Set(id, typ)
return nil
}
func (cbos CloudBasedObjectStorage) List(typ objects.ObjectType) ([]objects.ObjectId, error) {
return cbos.index.List(typ), nil
}
func (cbos CloudBasedObjectStorage) Close() (outerr error) {
defer func() {
err := cbos.CS.Close()
if outerr == nil {
outerr = err
}
}()
// We need to adress the problem of parallel index creation here.
// We handle this by adding a random hex number to the index name.
// When loading the index, all "index/*" objects will be read and combined
// and all but the one with the largest number will be deleted.
buf := new(bytes.Buffer)
if outerr = cbos.index.Save(buf); outerr != nil {
return outerr
}
index_name := fmt.Sprintf("%sindex/%016x", cbos.Prefix, rand.Int63())
return cbos.CS.Put(index_name, buf.Bytes())
}
type cloudObjectStorageCreator func(conf config.Config, name string) (CloudStorage, error)
func cloudStorageCreator(cloudCreator cloudObjectStorageCreator) storage.CreateStorageFromConfig {
return func(conf config.Config, name string) (storage.Storage, error) {
var cbos CloudBasedObjectStorage
var storageconf struct {
Prefix string `toml:"prefix,omitempty"`
}
if err := conf.GetStorageConfData(name, &storageconf); err != nil {
return nil, err
}
cbos.Prefix = storageconf.Prefix
var err error
if cbos.CS, err = cloudCreator(conf, name); err != nil {
return nil, err
}
err = cbos.Init()
return cbos, err
}
}
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