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boltdb.go
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boltdb.go
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package boltdb
import (
"bytes"
"encoding/binary"
"errors"
"os"
"path/filepath"
"sync"
"sync/atomic"
"time"
store "github.com/docker/docker/libnetwork/internal/kvstore"
bolt "go.etcd.io/bbolt"
)
var (
// ErrMultipleEndpointsUnsupported is thrown when multiple endpoints specified for
// BoltDB. Endpoint has to be a local file path
ErrMultipleEndpointsUnsupported = errors.New("boltdb supports one endpoint and should be a file path")
// ErrBoltBucketOptionMissing is thrown when boltBcuket config option is missing
ErrBoltBucketOptionMissing = errors.New("boltBucket config option missing")
)
const filePerm = 0o644
// BoltDB type implements the Store interface
type BoltDB struct {
mu sync.Mutex
client *bolt.DB
boltBucket []byte
dbIndex uint64
path string
timeout time.Duration
// By default libkv opens and closes the bolt DB connection for every
// get/put operation. This allows multiple apps to use a Bolt DB at the
// same time.
// PersistConnection flag provides an option to override ths behavior.
// ie: open the connection in New and use it till Close is called.
PersistConnection bool
}
const (
libkvmetadatalen = 8
transientTimeout = time.Duration(10) * time.Second
)
// New opens a new BoltDB connection to the specified path and bucket
func New(endpoints []string, options *store.Config) (store.Store, error) {
if len(endpoints) > 1 {
return nil, ErrMultipleEndpointsUnsupported
}
if (options == nil) || (len(options.Bucket) == 0) {
return nil, ErrBoltBucketOptionMissing
}
dir, _ := filepath.Split(endpoints[0])
if err := os.MkdirAll(dir, 0o750); err != nil {
return nil, err
}
var db *bolt.DB
if options.PersistConnection {
var err error
db, err = bolt.Open(endpoints[0], filePerm, &bolt.Options{
Timeout: options.ConnectionTimeout,
})
if err != nil {
return nil, err
}
}
timeout := transientTimeout
if options.ConnectionTimeout != 0 {
timeout = options.ConnectionTimeout
}
b := &BoltDB{
client: db,
path: endpoints[0],
boltBucket: []byte(options.Bucket),
timeout: timeout,
PersistConnection: options.PersistConnection,
}
return b, nil
}
func (b *BoltDB) reset() {
b.path = ""
b.boltBucket = []byte{}
}
func (b *BoltDB) getDBhandle() (*bolt.DB, error) {
if !b.PersistConnection {
db, err := bolt.Open(b.path, filePerm, &bolt.Options{Timeout: b.timeout})
if err != nil {
return nil, err
}
b.client = db
}
return b.client, nil
}
func (b *BoltDB) releaseDBhandle() {
if !b.PersistConnection {
b.client.Close()
}
}
// Put the key, value pair. index number metadata is prepended to the value
func (b *BoltDB) Put(key string, value []byte) error {
b.mu.Lock()
defer b.mu.Unlock()
db, err := b.getDBhandle()
if err != nil {
return err
}
defer b.releaseDBhandle()
return db.Update(func(tx *bolt.Tx) error {
bucket, err := tx.CreateBucketIfNotExists(b.boltBucket)
if err != nil {
return err
}
dbIndex := atomic.AddUint64(&b.dbIndex, 1)
dbval := make([]byte, libkvmetadatalen)
binary.LittleEndian.PutUint64(dbval, dbIndex)
dbval = append(dbval, value...)
return bucket.Put([]byte(key), dbval)
})
}
// Exists checks if the key exists inside the store
func (b *BoltDB) Exists(key string) (bool, error) {
b.mu.Lock()
defer b.mu.Unlock()
db, err := b.getDBhandle()
if err != nil {
return false, err
}
defer b.releaseDBhandle()
var exists bool
err = db.View(func(tx *bolt.Tx) error {
bucket := tx.Bucket(b.boltBucket)
if bucket == nil {
return store.ErrKeyNotFound
}
exists = len(bucket.Get([]byte(key))) > 0
return nil
})
if err != nil {
return false, err
}
if !exists {
return false, store.ErrKeyNotFound
}
return true, nil
}
// List returns the range of keys starting with the passed in prefix
func (b *BoltDB) List(keyPrefix string) ([]*store.KVPair, error) {
b.mu.Lock()
defer b.mu.Unlock()
db, err := b.getDBhandle()
if err != nil {
return nil, err
}
defer b.releaseDBhandle()
var kv []*store.KVPair
err = db.View(func(tx *bolt.Tx) error {
bucket := tx.Bucket(b.boltBucket)
if bucket == nil {
return store.ErrKeyNotFound
}
cursor := bucket.Cursor()
prefix := []byte(keyPrefix)
for key, v := cursor.Seek(prefix); bytes.HasPrefix(key, prefix); key, v = cursor.Next() {
dbIndex := binary.LittleEndian.Uint64(v[:libkvmetadatalen])
v = v[libkvmetadatalen:]
val := make([]byte, len(v))
copy(val, v)
kv = append(kv, &store.KVPair{
Key: string(key),
Value: val,
LastIndex: dbIndex,
})
}
return nil
})
if err != nil {
return nil, err
}
if len(kv) == 0 {
return nil, store.ErrKeyNotFound
}
return kv, nil
}
// AtomicDelete deletes a value at "key" if the key
// has not been modified in the meantime, throws an
// error if this is the case
func (b *BoltDB) AtomicDelete(key string, previous *store.KVPair) error {
b.mu.Lock()
defer b.mu.Unlock()
if previous == nil {
return store.ErrPreviousNotSpecified
}
db, err := b.getDBhandle()
if err != nil {
return err
}
defer b.releaseDBhandle()
return db.Update(func(tx *bolt.Tx) error {
bucket := tx.Bucket(b.boltBucket)
if bucket == nil {
return store.ErrKeyNotFound
}
val := bucket.Get([]byte(key))
if val == nil {
return store.ErrKeyNotFound
}
dbIndex := binary.LittleEndian.Uint64(val[:libkvmetadatalen])
if dbIndex != previous.LastIndex {
return store.ErrKeyModified
}
return bucket.Delete([]byte(key))
})
}
// AtomicPut puts a value at "key" if the key has not been
// modified since the last Put, throws an error if this is the case
func (b *BoltDB) AtomicPut(key string, value []byte, previous *store.KVPair) (*store.KVPair, error) {
b.mu.Lock()
defer b.mu.Unlock()
db, err := b.getDBhandle()
if err != nil {
return nil, err
}
defer b.releaseDBhandle()
var dbIndex uint64
dbval := make([]byte, libkvmetadatalen)
err = db.Update(func(tx *bolt.Tx) error {
bucket := tx.Bucket(b.boltBucket)
if bucket == nil {
if previous != nil {
return store.ErrKeyNotFound
}
var err error
bucket, err = tx.CreateBucket(b.boltBucket)
if err != nil {
return err
}
}
// AtomicPut is equivalent to Put if previous is nil and the Ky
// doesn't exist in the DB.
val := bucket.Get([]byte(key))
if previous == nil && len(val) != 0 {
return store.ErrKeyExists
}
if previous != nil {
if len(val) == 0 {
return store.ErrKeyNotFound
}
dbIndex = binary.LittleEndian.Uint64(val[:libkvmetadatalen])
if dbIndex != previous.LastIndex {
return store.ErrKeyModified
}
}
dbIndex = atomic.AddUint64(&b.dbIndex, 1)
binary.LittleEndian.PutUint64(dbval, b.dbIndex)
dbval = append(dbval, value...)
return bucket.Put([]byte(key), dbval)
})
if err != nil {
return nil, err
}
return &store.KVPair{Key: key, Value: value, LastIndex: dbIndex}, nil
}
// Close the db connection to the BoltDB
func (b *BoltDB) Close() {
b.mu.Lock()
defer b.mu.Unlock()
if !b.PersistConnection {
b.reset()
} else {
b.client.Close()
}
}