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db.go
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db.go
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package badgerdb
import (
"bytes"
"context"
"encoding/csv"
"errors"
"os"
"path/filepath"
"strconv"
"sync"
"sync/atomic"
"github.com/opzlabs/cosmos-sdk/db"
dbutil "github.com/opzlabs/cosmos-sdk/db/internal"
"github.com/dgraph-io/badger/v3"
bpb "github.com/dgraph-io/badger/v3/pb"
"github.com/dgraph-io/ristretto/z"
)
var (
versionsFilename = "versions.csv"
)
var (
_ db.DBConnection = (*BadgerDB)(nil)
_ db.DBReader = (*badgerTxn)(nil)
_ db.DBWriter = (*badgerWriter)(nil)
_ db.DBReadWriter = (*badgerWriter)(nil)
)
// BadgerDB is a connection to a BadgerDB key-value database.
type BadgerDB struct {
db *badger.DB
vmgr *versionManager
mtx sync.RWMutex
openWriters int32
}
type badgerTxn struct {
txn *badger.Txn
db *BadgerDB
}
type badgerWriter struct {
badgerTxn
discarded bool
}
type badgerIterator struct {
reverse bool
start, end []byte
iter *badger.Iterator
lastErr error
// Whether iterator has been advanced to the first element (is fully initialized)
primed bool
}
// Map our versions to Badger timestamps.
//
// A badger Txn's commit timestamp must be strictly greater than a record's "last-read"
// timestamp in order to detect conflicts, and a Txn must be read at a timestamp after last
// commit to see current state. So we must use commit increments that are more
// granular than our version interval, and map versions to the corresponding timestamp.
type versionManager struct {
*db.VersionManager
vmap map[uint64]uint64
lastTs uint64
}
// NewDB creates or loads a BadgerDB key-value database inside the given directory.
// If dir does not exist, it will be created.
func NewDB(dir string) (*BadgerDB, error) {
// Since Badger doesn't support database names, we join both to obtain
// the final directory to use for the database.
if err := os.MkdirAll(dir, 0755); err != nil {
return nil, err
}
opts := badger.DefaultOptions(dir)
opts.SyncWrites = false // note that we have Sync methods
opts.Logger = nil // badger is too chatty by default
return NewDBWithOptions(opts)
}
// NewDBWithOptions creates a BadgerDB key-value database with the specified Options
// (https://pkg.go.dev/github.com/dgraph-io/badger/v3#Options)
func NewDBWithOptions(opts badger.Options) (*BadgerDB, error) {
d, err := badger.OpenManaged(opts)
if err != nil {
return nil, err
}
vmgr, err := readVersionsFile(filepath.Join(opts.Dir, versionsFilename))
if err != nil {
return nil, err
}
return &BadgerDB{
db: d,
vmgr: vmgr,
}, nil
}
// Load metadata CSV file containing valid versions
func readVersionsFile(path string) (*versionManager, error) {
file, err := os.OpenFile(path, os.O_RDONLY|os.O_CREATE, 0644)
if err != nil {
return nil, err
}
defer file.Close()
r := csv.NewReader(file)
r.FieldsPerRecord = 2
rows, err := r.ReadAll()
if err != nil {
return nil, err
}
var (
versions []uint64
lastTs uint64
)
vmap := map[uint64]uint64{}
for _, row := range rows {
version, err := strconv.ParseUint(row[0], 10, 64)
if err != nil {
return nil, err
}
ts, err := strconv.ParseUint(row[1], 10, 64)
if err != nil {
return nil, err
}
if version == 0 { // 0 maps to the latest timestamp
lastTs = ts
}
versions = append(versions, version)
vmap[version] = ts
}
vmgr := db.NewVersionManager(versions)
return &versionManager{
VersionManager: vmgr,
vmap: vmap,
lastTs: lastTs,
}, nil
}
// Write version metadata to CSV file
func writeVersionsFile(vm *versionManager, path string) error {
file, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE, 0644)
if err != nil {
return err
}
defer file.Close()
w := csv.NewWriter(file)
rows := [][]string{
[]string{"0", strconv.FormatUint(vm.lastTs, 10)},
}
for it := vm.Iterator(); it.Next(); {
version := it.Value()
ts, ok := vm.vmap[version]
if !ok {
panic("version not mapped to ts")
}
rows = append(rows, []string{
strconv.FormatUint(it.Value(), 10),
strconv.FormatUint(ts, 10),
})
}
return w.WriteAll(rows)
}
func (b *BadgerDB) Reader() db.DBReader {
b.mtx.RLock()
ts := b.vmgr.lastTs
b.mtx.RUnlock()
return &badgerTxn{txn: b.db.NewTransactionAt(ts, false), db: b}
}
func (b *BadgerDB) ReaderAt(version uint64) (db.DBReader, error) {
b.mtx.RLock()
defer b.mtx.RUnlock()
ts, has := b.vmgr.versionTs(version)
if !has {
return nil, db.ErrVersionDoesNotExist
}
return &badgerTxn{txn: b.db.NewTransactionAt(ts, false), db: b}, nil
}
func (b *BadgerDB) ReadWriter() db.DBReadWriter {
atomic.AddInt32(&b.openWriters, 1)
b.mtx.RLock()
ts := b.vmgr.lastTs
b.mtx.RUnlock()
return &badgerWriter{badgerTxn{txn: b.db.NewTransactionAt(ts, true), db: b}, false}
}
func (b *BadgerDB) Writer() db.DBWriter {
// Badger has a WriteBatch, but it doesn't support conflict detection
return b.ReadWriter()
}
func (b *BadgerDB) Close() error {
b.mtx.Lock()
defer b.mtx.Unlock()
writeVersionsFile(b.vmgr, filepath.Join(b.db.Opts().Dir, versionsFilename))
return b.db.Close()
}
// Versions implements DBConnection.
// Returns a VersionSet that is valid until the next call to SaveVersion or DeleteVersion.
func (b *BadgerDB) Versions() (db.VersionSet, error) {
b.mtx.RLock()
defer b.mtx.RUnlock()
return b.vmgr, nil
}
func (b *BadgerDB) save(target uint64) (uint64, error) {
b.mtx.Lock()
defer b.mtx.Unlock()
if b.openWriters > 0 {
return 0, db.ErrOpenTransactions
}
b.vmgr = b.vmgr.Copy()
return b.vmgr.Save(target)
}
// SaveNextVersion implements DBConnection.
func (b *BadgerDB) SaveNextVersion() (uint64, error) {
return b.save(0)
}
// SaveVersion implements DBConnection.
func (b *BadgerDB) SaveVersion(target uint64) error {
if target == 0 {
return db.ErrInvalidVersion
}
_, err := b.save(target)
return err
}
func (b *BadgerDB) DeleteVersion(target uint64) error {
b.mtx.Lock()
defer b.mtx.Unlock()
if !b.vmgr.Exists(target) {
return db.ErrVersionDoesNotExist
}
b.vmgr = b.vmgr.Copy()
b.vmgr.Delete(target)
return nil
}
func (b *BadgerDB) Revert() error {
b.mtx.RLock()
defer b.mtx.RUnlock()
if b.openWriters > 0 {
return db.ErrOpenTransactions
}
// Revert from latest commit timestamp to last "saved" timestamp
// if no versions exist, use 0 as it precedes any possible commit timestamp
var target uint64
last := b.vmgr.Last()
if last == 0 {
target = 0
} else {
var has bool
if target, has = b.vmgr.versionTs(last); !has {
return errors.New("bad version history")
}
}
lastTs := b.vmgr.lastTs
if target == lastTs {
return nil
}
// Badger provides no way to rollback committed data, so we undo all changes
// since the target version using the Stream API
stream := b.db.NewStreamAt(lastTs)
// Skips unchanged keys
stream.ChooseKey = func(item *badger.Item) bool { return item.Version() > target }
// Scans for value at target version
stream.KeyToList = func(key []byte, itr *badger.Iterator) (*bpb.KVList, error) {
kv := bpb.KV{Key: key}
// advance down to <= target version
itr.Next() // we have at least one newer version
for itr.Valid() && bytes.Equal(key, itr.Item().Key()) && itr.Item().Version() > target {
itr.Next()
}
if itr.Valid() && bytes.Equal(key, itr.Item().Key()) && !itr.Item().IsDeletedOrExpired() {
var err error
kv.Value, err = itr.Item().ValueCopy(nil)
if err != nil {
return nil, err
}
}
return &bpb.KVList{Kv: []*bpb.KV{&kv}}, nil
}
txn := b.db.NewTransactionAt(lastTs, true)
defer txn.Discard()
stream.Send = func(buf *z.Buffer) error {
kvl, err := badger.BufferToKVList(buf)
if err != nil {
return err
}
// nil Value indicates a deleted entry
for _, kv := range kvl.Kv {
if kv.Value == nil {
err = txn.Delete(kv.Key)
if err != nil {
return err
}
} else {
err = txn.Set(kv.Key, kv.Value)
if err != nil {
return err
}
}
}
return nil
}
err := stream.Orchestrate(context.Background())
if err != nil {
return err
}
return txn.CommitAt(lastTs, nil)
}
func (b *BadgerDB) Stats() map[string]string { return nil }
func (tx *badgerTxn) Get(key []byte) ([]byte, error) {
if len(key) == 0 {
return nil, db.ErrKeyEmpty
}
item, err := tx.txn.Get(key)
if err == badger.ErrKeyNotFound {
return nil, nil
} else if err != nil {
return nil, err
}
val, err := item.ValueCopy(nil)
if err == nil && val == nil {
val = []byte{}
}
return val, err
}
func (tx *badgerTxn) Has(key []byte) (bool, error) {
if len(key) == 0 {
return false, db.ErrKeyEmpty
}
_, err := tx.txn.Get(key)
if err != nil && err != badger.ErrKeyNotFound {
return false, err
}
return (err != badger.ErrKeyNotFound), nil
}
func (tx *badgerWriter) Set(key, value []byte) error {
if err := dbutil.ValidateKv(key, value); err != nil {
return err
}
return tx.txn.Set(key, value)
}
func (tx *badgerWriter) Delete(key []byte) error {
if len(key) == 0 {
return db.ErrKeyEmpty
}
return tx.txn.Delete(key)
}
func (tx *badgerWriter) Commit() (err error) {
if tx.discarded {
return errors.New("transaction has been discarded")
}
defer func() { err = dbutil.CombineErrors(err, tx.Discard(), "Discard also failed") }()
// Commit to the current commit timestamp, after ensuring it is > ReadTs
tx.db.mtx.RLock()
tx.db.vmgr.updateCommitTs(tx.txn.ReadTs())
ts := tx.db.vmgr.lastTs
tx.db.mtx.RUnlock()
err = tx.txn.CommitAt(ts, nil)
return
}
func (tx *badgerTxn) Discard() error {
tx.txn.Discard()
return nil
}
func (tx *badgerWriter) Discard() error {
if !tx.discarded {
defer atomic.AddInt32(&tx.db.openWriters, -1)
tx.discarded = true
}
return tx.badgerTxn.Discard()
}
func (tx *badgerTxn) iteratorOpts(start, end []byte, opts badger.IteratorOptions) (*badgerIterator, error) {
if (start != nil && len(start) == 0) || (end != nil && len(end) == 0) {
return nil, db.ErrKeyEmpty
}
iter := tx.txn.NewIterator(opts)
iter.Rewind()
iter.Seek(start)
if opts.Reverse && iter.Valid() && bytes.Equal(iter.Item().Key(), start) {
// If we're going in reverse, our starting point was "end", which is exclusive.
iter.Next()
}
return &badgerIterator{
reverse: opts.Reverse,
start: start,
end: end,
iter: iter,
primed: false,
}, nil
}
func (tx *badgerTxn) Iterator(start, end []byte) (db.Iterator, error) {
opts := badger.DefaultIteratorOptions
return tx.iteratorOpts(start, end, opts)
}
func (tx *badgerTxn) ReverseIterator(start, end []byte) (db.Iterator, error) {
opts := badger.DefaultIteratorOptions
opts.Reverse = true
return tx.iteratorOpts(end, start, opts)
}
func (i *badgerIterator) Close() error {
i.iter.Close()
return nil
}
func (i *badgerIterator) Domain() (start, end []byte) { return i.start, i.end }
func (i *badgerIterator) Error() error { return i.lastErr }
func (i *badgerIterator) Next() bool {
if !i.primed {
i.primed = true
} else {
i.iter.Next()
}
return i.Valid()
}
func (i *badgerIterator) Valid() bool {
if !i.iter.Valid() {
return false
}
if len(i.end) > 0 {
key := i.iter.Item().Key()
if c := bytes.Compare(key, i.end); (!i.reverse && c >= 0) || (i.reverse && c < 0) {
// We're at the end key, or past the end.
return false
}
}
return true
}
func (i *badgerIterator) Key() []byte {
if !i.Valid() {
panic("iterator is invalid")
}
return i.iter.Item().KeyCopy(nil)
}
func (i *badgerIterator) Value() []byte {
if !i.Valid() {
panic("iterator is invalid")
}
val, err := i.iter.Item().ValueCopy(nil)
if err != nil {
i.lastErr = err
}
return val
}
func (vm *versionManager) versionTs(ver uint64) (uint64, bool) {
ts, has := vm.vmap[ver]
return ts, has
}
// updateCommitTs increments the lastTs if equal to readts.
func (vm *versionManager) updateCommitTs(readts uint64) {
if vm.lastTs == readts {
vm.lastTs++
}
}
// Atomically accesses the last commit timestamp used as a version marker.
func (vm *versionManager) lastCommitTs() uint64 {
return atomic.LoadUint64(&vm.lastTs)
}
func (vm *versionManager) Copy() *versionManager {
vmap := map[uint64]uint64{}
for ver, ts := range vm.vmap {
vmap[ver] = ts
}
return &versionManager{
VersionManager: vm.VersionManager.Copy(),
vmap: vmap,
lastTs: vm.lastCommitTs(),
}
}
func (vm *versionManager) Save(target uint64) (uint64, error) {
id, err := vm.VersionManager.Save(target)
if err != nil {
return 0, err
}
vm.vmap[id] = vm.lastTs // non-atomic, already guarded by the vmgr mutex
return id, nil
}
func (vm *versionManager) Delete(target uint64) {
vm.VersionManager.Delete(target)
delete(vm.vmap, target)
}