misc: add ability to store the wallet in the remote DB

lnwallet/btcwallet/btcwallet.go

@@ -19,12 +19,14 @@ import (
 	"github.com/btcsuite/btcutil/psbt"
 	"github.com/btcsuite/btcwallet/chain"
 	"github.com/btcsuite/btcwallet/waddrmgr"
+	"github.com/btcsuite/btcwallet/wallet"
 	base "github.com/btcsuite/btcwallet/wallet"
 	"github.com/btcsuite/btcwallet/wallet/txauthor"
 	"github.com/btcsuite/btcwallet/wallet/txrules"
 	"github.com/btcsuite/btcwallet/walletdb"
 	"github.com/btcsuite/btcwallet/wtxmgr"
 	"github.com/lightningnetwork/lnd/blockcache"
+	"github.com/lightningnetwork/lnd/channeldb/kvdb"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
@@ -37,6 +39,13 @@ const (
 	// UnconfirmedHeight is the special case end height that is used to
 	// obtain unconfirmed transactions from ListTransactionDetails.
 	UnconfirmedHeight int32 = -1
+
+	// walletMetaBucket is used to store wallet metadata.
+	walletMetaBucket = "lnwallet"
+
+	// walletReadyKey is used to indicate that the wallet has been
+	// initialized.
+	walletReadyKey = "ready"
 )
 
 var (
@@ -87,9 +96,6 @@ var _ lnwallet.BlockChainIO = (*BtcWallet)(nil)
 // New returns a new fully initialized instance of BtcWallet given a valid
 // configuration struct.
 func New(cfg Config, blockCache *blockcache.BlockCache) (*BtcWallet, error) {
-	// Ensure the wallet exists or create it when the create flag is set.
-	netDir := NetworkDir(cfg.DataDir, cfg.NetParams)
-
 	// Create the key scope for the coin type being managed by this wallet.
 	chainKeyScope := waddrmgr.KeyScope{
 		Purpose: keychain.BIP0043Purpose,
@@ -108,10 +114,13 @@ func New(cfg Config, blockCache *blockcache.BlockCache) (*BtcWallet, error) {
 		} else {
 			pubPass = cfg.PublicPass
 		}
-		loader := base.NewLoader(
-			cfg.NetParams, netDir, cfg.NoFreelistSync,
-			cfg.DBTimeOut, cfg.RecoveryWindow,
+
+		loader, err := NewWalletLoader(
+			cfg.NetParams, cfg.RecoveryWindow, cfg.LoaderOptions...,
 		)
+		if err != nil {
+			return nil, err
+		}
 		walletExists, err := loader.WalletExists()
 		if err != nil {
 			return nil, err
@@ -149,6 +158,104 @@ func New(cfg Config, blockCache *blockcache.BlockCache) (*BtcWallet, error) {
 	}, nil
 }
 
+// loaderCfg holds optional wallet loader configuration.
+type loaderCfg struct {
+	dbDirPath      string
+	noFreelistSync bool
+	dbTimeout      time.Duration
+	useLocalDB     bool
+	externalDB     kvdb.Backend
+}
+
+// LoaderOption is a functional option to update the optional loader config.
+type LoaderOption func(*loaderCfg)
+
+// LoaderWithLocalWalletDB configures the wallet loader to use the local db.
+func LoaderWithLocalWalletDB(dbDirPath string, noFreelistSync bool,
+	dbTimeout time.Duration) LoaderOption {
+
+	return func(cfg *loaderCfg) {
+		cfg.dbDirPath = dbDirPath
+		cfg.noFreelistSync = noFreelistSync
+		cfg.dbTimeout = dbTimeout
+		cfg.useLocalDB = true
+	}
+}
+
+// LoaderWithExternalWalletDB configures the wallet loadr to use an external db.
+func LoaderWithExternalWalletDB(db kvdb.Backend) LoaderOption {
+	return func(cfg *loaderCfg) {
+		cfg.externalDB = db
+	}
+}
+
+// NewWalletLoader constructs a wallet loader.
+func NewWalletLoader(chainParams *chaincfg.Params, recoveryWindow uint32,
+	opts ...LoaderOption) (*wallet.Loader, error) {
+
+	cfg := &loaderCfg{}
+
+	// Apply all functional options.
+	for _, o := range opts {
+		o(cfg)
+	}
+
+	if cfg.externalDB != nil && cfg.useLocalDB {
+		return nil, fmt.Errorf("wallet can either be in the local or " +
+			"an external db")
+	}
+
+	if cfg.externalDB != nil {
+		loader, err := base.NewLoaderWithDB(
+			chainParams, recoveryWindow, cfg.externalDB,
+			func() (bool, error) {
+				return externalWalletExists(cfg.externalDB)
+			},
+		)
+		if err != nil {
+			return nil, err
+		}
+
+		// Decorate wallet db with out own key such that we
+		// can always check whether the wallet exists or not.
+		loader.OnWalletCreated(onWalletCreated)
+		return loader, nil
+	}
+
+	return base.NewLoader(
+		chainParams, cfg.dbDirPath, cfg.noFreelistSync,
+		cfg.dbTimeout, recoveryWindow,
+	), nil
+}
+
+// externalWalletExists is a helper function that we use to template btcwallet's
+// Loader in order to be able check if the wallet database has been initialized
+// in an external DB.
+func externalWalletExists(db kvdb.Backend) (bool, error) {
+	exists := false
+	err := kvdb.View(db, func(tx kvdb.RTx) error {
+		metaBucket := tx.ReadBucket([]byte(walletMetaBucket))
+		if metaBucket != nil {
+			walletReady := metaBucket.Get([]byte(walletReadyKey))
+			exists = string(walletReady) == walletReadyKey
+		}
+
+		return nil
+	}, func() {})
+
+	return exists, err
+}
+
+// onWalletCreated is executed when btcwallet creates the wallet the first time.
+func onWalletCreated(tx kvdb.RwTx) error {
+	metaBucket, err := tx.CreateTopLevelBucket([]byte(walletMetaBucket))
+	if err != nil {
+		return err
+	}
+
+	return metaBucket.Put([]byte(walletReadyKey), []byte(walletReadyKey))
+}
+
 // BackEnd returns the underlying ChainService's name as a string.
 //
 // This is a part of the WalletController interface.

lnwallet/btcwallet/config.go

@@ -28,10 +28,6 @@ var (
 // Config is a struct which houses configuration parameters which modify the
 // instance of BtcWallet generated by the New() function.
 type Config struct {
-	// DataDir is the name of the directory where the wallet's persistent
-	// state should be stored.
-	DataDir string
-
 	// LogDir is the name of the directory which should be used to store
 	// generated log files.
 	LogDir string
@@ -76,14 +72,8 @@ type Config struct {
 	// normally when creating the BtcWallet.
 	Wallet *wallet.Wallet
 
-	// NoFreelistSync, if true, prevents the database from syncing its
-	// freelist to disk, resulting in improved performance at the expense of
-	// increased startup time.
-	NoFreelistSync bool
-
-	// DBTimeOut specifies the timeout value to use when opening the wallet
-	// database.
-	DBTimeOut time.Duration
+	// LoaderOptions holds functional wallet db loader options.
+	LoaderOptions []LoaderOption
 }
 
 // NetworkDir returns the directory name of a network directory to hold wallet

lnwallet/test/test_interface.go

@@ -3427,12 +3427,16 @@ func runTests(t *testing.T, walletDriver *lnwallet.WalletDriver,
 		aliceWalletConfig := &btcwallet.Config{
 			PrivatePass: []byte("alice-pass"),
 			HdSeed:      aliceSeedBytes,
-			DataDir:     tempTestDirAlice,
 			NetParams:   netParams,
 			ChainSource: aliceClient,
 			CoinType:    keychain.CoinTypeTestnet,
 			// wallet starts in recovery mode
 			RecoveryWindow: 2,
+			LoaderOptions: []btcwallet.LoaderOption{
+				btcwallet.LoaderWithLocalWalletDB(
+					tempTestDirAlice, false, time.Minute,
+				),
+			},
 		}
 		aliceWalletController, err = walletDriver.New(
 			aliceWalletConfig, blockCache,
@@ -3454,12 +3458,16 @@ func runTests(t *testing.T, walletDriver *lnwallet.WalletDriver,
 		bobWalletConfig := &btcwallet.Config{
 			PrivatePass: []byte("bob-pass"),
 			HdSeed:      bobSeedBytes,
-			DataDir:     tempTestDirBob,
 			NetParams:   netParams,
 			ChainSource: bobClient,
 			CoinType:    keychain.CoinTypeTestnet,
 			// wallet starts without recovery mode
 			RecoveryWindow: 0,
+			LoaderOptions: []btcwallet.LoaderOption{
+				btcwallet.LoaderWithLocalWalletDB(
+					tempTestDirBob, false, time.Minute,
+				),
+			},
 		}
 		bobWalletController, err = walletDriver.New(
 			bobWalletConfig, blockCache,