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backendmanager.go
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backendmanager.go
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/*
* knoxite
* Copyright (c) 2016-2020, Christian Muehlhaeuser <muesli@gmail.com>
*
* For license see LICENSE
*/
package knoxite
import "errors"
const (
retries = 3
)
// BackendManager stores data on multiple backends.
type BackendManager struct {
Backends []*Backend
lastUsedBackend int
}
// Error declarations.
var (
ErrLoadChunkFailed = errors.New("unable to load chunk from any storage backend")
ErrLoadSnapshotFailed = errors.New("unable to load snapshot from any storage backend")
ErrLoadChunkIndexFailed = errors.New("unable to load chunk-index from any storage backend")
ErrLoadRepositoryFailed = errors.New("unable to load repository from any storage backend")
ErrDeleteChunkFailed = errors.New("unable to delete chunk from any storage backend")
ErrStoreChunkFailed = errors.New("storing chunk failed")
ErrStoreSnapshotFailed = errors.New("storing snapshot failed")
ErrStoreChunkIndexFailed = errors.New("storing chunk-index failed")
ErrStoreRepositoryFailed = errors.New("storing repository failed")
)
// AddBackend adds a backend.
func (backend *BackendManager) AddBackend(be *Backend) {
backend.Backends = append(backend.Backends, be)
}
// Locations returns the urls for all backends.
func (backend *BackendManager) Locations() []string {
paths := []string{}
for _, be := range backend.Backends {
paths = append(paths, (*be).Location())
}
return paths
}
// LoadChunk loads a Chunk from backends.
func (backend *BackendManager) LoadChunk(chunk Chunk, part uint) ([]byte, error) {
for _, be := range backend.Backends {
for i := 0; i < retries; i++ {
b, err := (*be).LoadChunk(chunk.Hash, part, chunk.DataParts)
if err == nil {
return b, err
}
}
}
return []byte{}, ErrLoadChunkFailed
}
// StoreChunk stores a single Chunk on backends.
func (backend *BackendManager) StoreChunk(chunk Chunk) (size uint64, err error) {
for i, data := range *chunk.Data {
// Use storage backends in a round robin fashion to store chunks
backend.lastUsedBackend++
if backend.lastUsedBackend+1 > len(backend.Backends) {
backend.lastUsedBackend = 0
}
be := backend.Backends[backend.lastUsedBackend]
var n uint64
var err error
for j := 0; j < retries; j++ {
n, err = (*be).StoreChunk(chunk.Hash, uint(i), chunk.DataParts, data)
if err != nil {
// retry
continue
}
if n > size {
size = n
}
break
}
if err != nil {
return 0, err
}
}
return size, nil
}
// DeleteChunk deletes a single Chunk.
func (backend *BackendManager) DeleteChunk(shasum string, part, totalParts uint) error {
for _, be := range backend.Backends {
for i := 0; i < retries; i++ {
err := (*be).DeleteChunk(shasum, part, totalParts)
if err == nil {
return nil
}
}
}
return ErrDeleteChunkFailed
}
// LoadSnapshot loads a snapshot.
func (backend *BackendManager) LoadSnapshot(id string) ([]byte, error) {
for _, be := range backend.Backends {
for i := 0; i < retries; i++ {
b, err := (*be).LoadSnapshot(id)
if err == nil {
return b, err
}
}
}
return []byte{}, ErrLoadSnapshotFailed
}
// SaveSnapshot stores a snapshot on all storage backends.
func (backend *BackendManager) SaveSnapshot(id string, b []byte) error {
for _, be := range backend.Backends {
var err error
for i := 0; i < retries; i++ {
err = (*be).SaveSnapshot(id, b)
if err == nil {
break
}
}
if err != nil {
return err
}
}
return nil
}
// LoadChunkIndex loads the chunk-index.
func (backend *BackendManager) LoadChunkIndex() ([]byte, error) {
for _, be := range backend.Backends {
for i := 0; i < retries; i++ {
b, err := (*be).LoadChunkIndex()
if err == nil {
return b, err
}
}
}
return []byte{}, ErrLoadChunkIndexFailed
}
// SaveChunkIndex stores the chunk-index on all storage backends.
func (backend *BackendManager) SaveChunkIndex(b []byte) error {
for _, be := range backend.Backends {
var err error
for i := 0; i < retries; i++ {
err = (*be).SaveChunkIndex(b)
if err == nil {
break
}
}
if err != nil {
return err
}
}
return nil
}
// InitRepository creates a new repository.
func (backend *BackendManager) InitRepository() error {
for _, be := range backend.Backends {
err := (*be).InitRepository()
if err != nil {
return err
}
}
return nil
}
// LoadRepository reads the metadata for a repository.
func (backend *BackendManager) LoadRepository() ([]byte, error) {
for _, be := range backend.Backends {
for i := 0; i < retries; i++ {
b, err := (*be).LoadRepository()
if err == nil {
return b, err
}
}
}
return []byte{}, ErrLoadRepositoryFailed
}
// SaveRepository stores the metadata for a repository.
func (backend *BackendManager) SaveRepository(b []byte) error {
for _, be := range backend.Backends {
var err error
for i := 0; i < retries; i++ {
err = (*be).SaveRepository(b)
if err == nil {
break
}
}
if err != nil {
return err
}
}
return nil
}