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badger.go
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badger.go
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/*
* Copyright (C) 2017-2018 GIG Technology NV and Contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package badger
import (
"context"
"errors"
"os"
"time"
dbp "github.com/threefoldtech/0-stor/client/metastor/db"
badgerdb "github.com/dgraph-io/badger"
log "github.com/sirupsen/logrus"
)
const (
// discardRatio represents the discard ratio for the badger GC
// https://godoc.org/github.com/dgraph-io/badger#DB.RunValueLogGC
discardRatio = 0.5
// GC interval
cgInterval = 10 * time.Minute
)
// Config represents badger DB configuration
type Config struct {
// Badger data directory
DataDir string `yaml:"datadir"`
// Badger metadata directory
MetaDir string `yaml:"metadir"`
}
// New creates a new metastor database implementation,
// using badger on the local FS as storage medium.
//
// Both the data and meta dir are required.
// If you want to be able to specify more options than just
// the required data and metadata directory,
// you can make use of the `NewWithOpts` function,
// as this function will use default options for all other badger options.
func New(data, meta string) (*DB, error) {
if len(data) == 0 {
return nil, errors.New("no data directory defined")
}
if len(meta) == 0 {
return nil, errors.New("no meta directory defined")
}
opts := badgerdb.DefaultOptions
opts.SyncWrites = true
opts.Dir, opts.ValueDir = meta, data
return NewWithOpts(opts)
}
// NewWithOpts creates a new metastor database implementation,
// using badger on the local FS as storage medium.
//
// Both the data and meta dir, defined as properties of the given options, are required.
func NewWithOpts(opts badgerdb.Options) (*DB, error) {
if err := os.MkdirAll(opts.Dir, 0774); err != nil {
log.Errorf("meta dir %q couldn't be created: %v", opts.Dir, err)
return nil, err
}
if err := os.MkdirAll(opts.ValueDir, 0774); err != nil {
log.Errorf("data dir %q couldn't be created: %v", opts.ValueDir, err)
return nil, err
}
badgerDB, err := badgerdb.Open(opts)
if err != nil {
return nil, err
}
db := &DB{
badger: badgerDB,
}
db.ctx, db.cancelFunc = context.WithCancel(context.Background())
go db.runGC()
return db, nil
}
// DB defines a metastor database implementation,
// using badger on the local FS as its underlying storage medium.
type DB struct {
badger *badgerdb.DB
ctx context.Context
cancelFunc context.CancelFunc
}
// Set implements db.Set
func (db *DB) Set(namespace, key, metadata []byte) error {
err := db.badger.Update(func(txn *badgerdb.Txn) error {
return txn.Set(badgerKey(namespace, key), metadata)
})
if err != nil {
return mapBadgerError(err)
}
return nil
}
// Get implements db.Get
func (db *DB) Get(namespace, key []byte) (metadata []byte, err error) {
err = db.badger.View(func(txn *badgerdb.Txn) error {
item, err := txn.Get(badgerKey(namespace, key))
if err != nil {
return err
}
value, err := item.Value()
if err != nil {
return err
}
metadata = make([]byte, len(value))
copy(metadata, value)
return nil
})
if err != nil {
return nil, mapBadgerError(err)
}
return metadata, nil
}
// Delete implements db.Delete
func (db *DB) Delete(namespace, key []byte) error {
err := db.badger.Update(func(txn *badgerdb.Txn) error {
return txn.Delete(badgerKey(namespace, key))
})
if err != nil {
return mapBadgerError(err)
}
return nil
}
// Update implements db.Update
func (db *DB) Update(namespace, key []byte, cb dbp.UpdateCallback) error {
bgrKey := badgerKey(namespace, key)
err := badgerdb.ErrConflict
for err == badgerdb.ErrConflict {
err = db.badger.Update(func(txn *badgerdb.Txn) error {
// fetch the original stored and encoded metadata
item, err := txn.Get(bgrKey)
if err != nil {
return mapBadgerError(err)
}
metadata, err := item.Value()
if err != nil {
return mapBadgerError(err)
}
// user-defined update of the metadata
metadata, err = cb(metadata)
if err != nil {
return err // don't map user-specified error
}
// store the updated metadata
err = txn.Set(bgrKey, metadata)
if err != nil {
return mapBadgerError(err)
}
return nil
})
}
return err
}
// ListKeys implements db.ListKeys
func (db *DB) ListKeys(namespace []byte, cb dbp.ListCallback) error {
prefix := badgerPrefix(namespace)
lenPrefix := len(prefix)
err := db.badger.View(func(txt *badgerdb.Txn) error {
opts := badgerdb.DefaultIteratorOptions
opts.PrefetchValues = false
it := txt.NewIterator(opts)
for it.Seek(prefix); it.ValidForPrefix(prefix); it.Next() {
item := it.Item()
key := make([]byte, len(item.Key())-lenPrefix)
copy(key, item.Key()[lenPrefix:])
err := cb(key)
if err != nil {
return err
}
}
return nil
})
return err
}
// Close implements metastor.Client.Close
func (db *DB) Close() error {
// cancel (db) context
db.cancelFunc()
// close db
err := db.badger.Close()
if err != nil {
mapBadgerError(err)
}
return nil
}
// collectGarbage runs the garbage collection for Badger backend db
func (db *DB) collectGarbage() error {
if err := db.badger.PurgeOlderVersions(); err != nil {
return err
}
return db.badger.RunValueLogGC(discardRatio)
}
// runGC triggers the garbage collection for the Badger backend db.
// Should be run as a goroutine
func (db *DB) runGC() {
ticker := time.NewTicker(cgInterval)
for {
select {
case <-ticker.C:
err := db.collectGarbage()
if err != nil {
// don't report error when gc didn't result in any cleanup
if err == badgerdb.ErrNoRewrite {
log.Debugf("Badger GC: %v", err)
} else {
log.Errorf("Badger GC failed: %v", err)
}
}
case <-db.ctx.Done():
return
}
}
}
func badgerPrefix(namespace []byte) []byte {
return []byte(string(namespace) + "/")
}
func badgerKey(namespace, key []byte) []byte {
return append(badgerPrefix(namespace), key...)
}
// map badger errors, if we know about them
func mapBadgerError(err error) error {
switch err {
case badgerdb.ErrKeyNotFound:
return dbp.ErrNotFound
default:
return &dbp.InternalError{Type: databaseType, Err: err}
}
}
const (
databaseType = "Badger"
)
var (
_ dbp.DB = (*DB)(nil)
)