mulit: use kvdb.Backend for the kv payment db

diff --git a/channeldb/db.go b/channeldb/db.go
index 793eb70..715b906 100644
--- a/channeldb/db.go
+++ b/channeldb/db.go
@@ -352,7 +352,6 @@ type DB struct {
 	dbPath                    string
 	clock                     clock.Clock
 	dryRun                    bool
-	keepFailedPaymentAttempts bool
 	storeFinalHtlcResolutions bool
 
 	// noRevLogAmtData if true, means that commitment transaction amount
@@ -413,7 +412,6 @@ func CreateWithBackend(backend kvdb.Backend, modifiers ...OptionModifier) (*DB,
 		},
 		clock:                     opts.clock,
 		dryRun:                    opts.dryRun,
-		keepFailedPaymentAttempts: opts.keepFailedPaymentAttempts,
 		storeFinalHtlcResolutions: opts.storeFinalHtlcResolutions,
 		noRevLogAmtData:           opts.NoRevLogAmtData,
 	}
diff --git a/channeldb/options.go b/channeldb/options.go
index b00ba1f..a8ec8cf 100644
--- a/channeldb/options.go
+++ b/channeldb/options.go
@@ -68,10 +68,6 @@ type Options struct {
 	// database if set to true.
 	dryRun bool
 
-	// keepFailedPaymentAttempts determines whether failed htlc attempts
-	// are kept on disk or removed to save space.
-	keepFailedPaymentAttempts bool
-
 	// storeFinalHtlcResolutions determines whether to persistently store
 	// the final resolution of incoming htlcs.
 	storeFinalHtlcResolutions bool
@@ -120,14 +116,6 @@ func OptionDryRunMigration(dryRun bool) OptionModifier {
 	}
 }
 
-// OptionKeepFailedPaymentAttempts controls whether failed payment attempts are
-// kept on disk after a payment settles.
-func OptionKeepFailedPaymentAttempts(keepFailedPaymentAttempts bool) OptionModifier {
-	return func(o *Options) {
-		o.keepFailedPaymentAttempts = keepFailedPaymentAttempts
-	}
-}
-
 // OptionStoreFinalHtlcResolutions controls whether to persistently store the
 // final resolution of incoming htlcs.
 func OptionStoreFinalHtlcResolutions(
diff --git a/channeldb/payments_kv_store.go b/channeldb/payments_kv_store.go
index 4c1880a..5474f60 100644
--- a/channeldb/payments_kv_store.go
+++ b/channeldb/payments_kv_store.go
@@ -119,17 +119,66 @@ var (
 
 // KVPaymentsDB implements persistence for payments and payment attempts.
 type KVPaymentsDB struct {
+	// Sequence management for the kv store.
 	paymentSeqMx     sync.Mutex
 	currPaymentSeq   uint64
 	storedPaymentSeq uint64
-	db               *DB
+
+	// db is the underlying database implementation.
+	db kvdb.Backend
+
+	keepFailedPaymentAttempts bool
 }
 
-// NewKVPaymentsDB creates a new instance of the KVPaymentsDB.
-func NewKVPaymentsDB(db *DB) *KVPaymentsDB {
+// defaultKVStoreOptions returns the default options for the KV store.
+func defaultKVStoreOptions() *paymentsdb.StoreOptions {
+	return &paymentsdb.StoreOptions{
+		KeepFailedPaymentAttempts: false,
+	}
+}
+
+// NewKVPaymentsDB creates a new KVStore for payments.
+func NewKVPaymentsDB(db kvdb.Backend,
+	options ...paymentsdb.OptionModifier) (*KVPaymentsDB, error) {
+
+	opts := defaultKVStoreOptions()
+	for _, applyOption := range options {
+		applyOption(opts)
+	}
+
+	if !opts.NoMigration {
+		if err := initKVStore(db); err != nil {
+			return nil, err
+		}
+	}
+
 	return &KVPaymentsDB{
-		db: db,
+		db:                        db,
+		keepFailedPaymentAttempts: opts.KeepFailedPaymentAttempts,
+	}, nil
+}
+
+var paymentsTopLevelBuckets = [][]byte{
+	paymentsRootBucket,
+	paymentsIndexBucket,
+}
+
+// initKVStore creates and initializes the top-level buckets for the payment db.
+func initKVStore(db kvdb.Backend) error {
+	err := kvdb.Update(db, func(tx kvdb.RwTx) error {
+		for _, tlb := range paymentsTopLevelBuckets {
+			if _, err := tx.CreateTopLevelBucket(tlb); err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}, func() {})
+	if err != nil {
+		return fmt.Errorf("unable to create new payments db: %w", err)
 	}
+
+	return nil
 }
 
 // InitPayment checks or records the given PaymentCreationInfo with the DB,
@@ -154,7 +203,7 @@ func (p *KVPaymentsDB) InitPayment(paymentHash lntypes.Hash,
 	infoBytes := b.Bytes()
 
 	var updateErr error
-	err = kvdb.Batch(p.db.Backend, func(tx kvdb.RwTx) error {
+	err = kvdb.Batch(p.db, func(tx kvdb.RwTx) error {
 		// Reset the update error, to avoid carrying over an error
 		// from a previous execution of the batched db transaction.
 		updateErr = nil
@@ -241,7 +290,7 @@ func (p *KVPaymentsDB) InitPayment(paymentHash lntypes.Hash,
 // DeleteFailedAttempts deletes all failed htlcs for a payment if configured
 // by the KVPaymentsDB db.
 func (p *KVPaymentsDB) DeleteFailedAttempts(hash lntypes.Hash) error {
-	if !p.db.keepFailedPaymentAttempts {
+	if !p.keepFailedPaymentAttempts {
 		const failedHtlcsOnly = true
 		err := p.DeletePayment(hash, failedHtlcsOnly)
 		if err != nil {
@@ -322,7 +371,7 @@ func (p *KVPaymentsDB) RegisterAttempt(paymentHash lntypes.Hash,
 	binary.BigEndian.PutUint64(htlcIDBytes, attempt.AttemptID)
 
 	var payment *MPPayment
-	err = kvdb.Batch(p.db.Backend, func(tx kvdb.RwTx) error {
+	err = kvdb.Batch(p.db, func(tx kvdb.RwTx) error {
 		prefetchPayment(tx, paymentHash)
 		bucket, err := fetchPaymentBucketUpdate(tx, paymentHash)
 		if err != nil {
@@ -490,7 +539,7 @@ func (p *KVPaymentsDB) updateHtlcKey(paymentHash lntypes.Hash,
 	binary.BigEndian.PutUint64(aid, attemptID)
 
 	var payment *MPPayment
-	err := kvdb.Batch(p.db.Backend, func(tx kvdb.RwTx) error {
+	err := kvdb.Batch(p.db, func(tx kvdb.RwTx) error {
 		payment = nil
 
 		prefetchPayment(tx, paymentHash)
@@ -562,7 +611,7 @@ func (p *KVPaymentsDB) Fail(paymentHash lntypes.Hash,
 		updateErr error
 		payment   *MPPayment
 	)
-	err := kvdb.Batch(p.db.Backend, func(tx kvdb.RwTx) error {
+	err := kvdb.Batch(p.db, func(tx kvdb.RwTx) error {
 		// Reset the update error, to avoid carrying over an error
 		// from a previous execution of the batched db transaction.
 		updateErr = nil
@@ -715,7 +764,7 @@ func (p *KVPaymentsDB) nextPaymentSequence() ([]byte, error) {
 	// conflicts on the sequence when using etcd.
 	if p.currPaymentSeq == p.storedPaymentSeq {
 		var currPaymentSeq, newUpperBound uint64
-		if err := kvdb.Update(p.db.Backend, func(tx kvdb.RwTx) error {
+		if err := kvdb.Update(p.db, func(tx kvdb.RwTx) error {
 			paymentsBucket, err := tx.CreateTopLevelBucket(
 				paymentsRootBucket,
 			)
diff --git a/channeldb/payments_kv_store_test.go b/channeldb/payments_kv_store_test.go
index 4083fa3..d1953fa 100644
--- a/channeldb/payments_kv_store_test.go
+++ b/channeldb/payments_kv_store_test.go
@@ -67,7 +67,8 @@ func TestKVPaymentsDBSwitchFail(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err, "unable to init db")
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	info, attempt, preimg, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
@@ -207,7 +208,8 @@ func TestKVPaymentsDBSwitchDoubleSend(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err, "unable to init db")
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	info, attempt, preimg, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
@@ -283,7 +285,8 @@ func TestKVPaymentsDBSuccessesWithoutInFlight(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err, "unable to init db")
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	info, _, preimg, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
@@ -306,7 +309,8 @@ func TestKVPaymentsDBFailsWithoutInFlight(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err, "unable to init db")
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	info, _, _, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
@@ -329,7 +333,8 @@ func TestKVPaymentsDBDeleteNonInFlight(t *testing.T) {
 	// start at 1, so 9999 is a safe bet for this test.
 	var duplicateSeqNr = 9999
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	payments := []struct {
 		failed       bool
@@ -547,7 +552,8 @@ func TestKVPaymentsDBDeletePayments(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err, "unable to init db")
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	// Register three payments:
 	// 1. A payment with two failed attempts.
@@ -608,7 +614,8 @@ func TestKVPaymentsDBDeleteSinglePayment(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err, "unable to init db")
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	// Register four payments:
 	// All payments will have one failed HTLC attempt and one HTLC attempt
@@ -714,7 +721,8 @@ func TestKVPaymentsDBMultiShard(t *testing.T) {
 			t.Fatalf("unable to init db: %v", err)
 		}
 
-		paymentDB := NewKVPaymentsDB(db)
+		paymentDB, err := NewKVPaymentsDB(db)
+		require.NoError(t, err)
 
 		info, attempt, preimg, err := genInfo(t)
 		if err != nil {
@@ -995,7 +1003,8 @@ func TestKVPaymentsDBMPPRecordValidation(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err, "unable to init db")
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	info, attempt, _, err := genInfo(t)
 	require.NoError(t, err, "unable to generate htlc message")
@@ -1076,11 +1085,15 @@ func TestDeleteFailedAttempts(t *testing.T) {
 
 func testDeleteFailedAttempts(t *testing.T, keepFailedPaymentAttempts bool) {
 	db, err := MakeTestDB(t)
-
 	require.NoError(t, err, "unable to init db")
-	db.keepFailedPaymentAttempts = keepFailedPaymentAttempts
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(
+		db,
+		paymentsdb.WithKeepFailedPaymentAttempts(
+			keepFailedPaymentAttempts,
+		),
+	)
+	require.NoError(t, err)
 
 	// Register three payments:
 	// All payments will have one failed HTLC attempt and one HTLC attempt
@@ -1577,7 +1590,8 @@ func TestFetchPaymentWithSequenceNumber(t *testing.T) {
 	db, err := MakeTestDB(t)
 	require.NoError(t, err)
 
-	paymentDB := NewKVPaymentsDB(db)
+	paymentDB, err := NewKVPaymentsDB(db)
+	require.NoError(t, err)
 
 	// Generate a test payment which does not have duplicates.
 	noDuplicates, _, _, err := genInfo(t)
@@ -1703,8 +1717,8 @@ func TestFetchPaymentWithSequenceNumber(t *testing.T) {
 //
 // This code is *only* intended to replicate legacy duplicate payments in lnd,
 // our current schema does not allow duplicates.
-func appendDuplicatePayment(t *testing.T, db *DB, paymentHash lntypes.Hash,
-	seqNr uint64, preImg lntypes.Preimage) {
+func appendDuplicatePayment(t *testing.T, db kvdb.Backend,
+	paymentHash lntypes.Hash, seqNr uint64, preImg lntypes.Preimage) {
 
 	err := kvdb.Update(db, func(tx walletdb.ReadWriteTx) error {
 		bucket, err := fetchPaymentBucketUpdate(
diff --git a/channeldb/payments_test.go b/channeldb/payments_test.go
index 727bd91..dce993f 100644
--- a/channeldb/payments_test.go
+++ b/channeldb/payments_test.go
@@ -358,7 +358,8 @@ func TestQueryPayments(t *testing.T) {
 			require.NoError(t, err)
 
 			// Initialize the payment database.
-			paymentDB := NewKVPaymentsDB(db)
+			paymentDB, err := NewKVPaymentsDB(db)
+			require.NoError(t, err)
 
 			// Make a preliminary query to make sure it's ok to
 			// query when we have no payments.
diff --git a/config_builder.go b/config_builder.go
index 35a44e2..47eb96b 100644
--- a/config_builder.go
+++ b/config_builder.go
@@ -48,6 +48,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/rpcwallet"
 	"github.com/lightningnetwork/lnd/macaroons"
 	"github.com/lightningnetwork/lnd/msgmux"
+	paymentsdb "github.com/lightningnetwork/lnd/payments/db"
 	"github.com/lightningnetwork/lnd/rpcperms"
 	"github.com/lightningnetwork/lnd/signal"
 	"github.com/lightningnetwork/lnd/sqldb"
@@ -1052,9 +1053,6 @@ func (d *DefaultDatabaseBuilder) BuildDatabase(
 
 	dbOptions := []channeldb.OptionModifier{
 		channeldb.OptionDryRunMigration(cfg.DryRunMigration),
-		channeldb.OptionKeepFailedPaymentAttempts(
-			cfg.KeepFailedPaymentAttempts,
-		),
 		channeldb.OptionStoreFinalHtlcResolutions(
 			cfg.StoreFinalHtlcResolutions,
 		),
@@ -1222,9 +1220,24 @@ func (d *DefaultDatabaseBuilder) BuildDatabase(
 	// Mount the payments DB which is only KV for now.
 	//
 	// TODO(ziggie): Add support for SQL payments DB.
-	kvPaymentsDB := channeldb.NewKVPaymentsDB(
+	// Mount the payments DB for the KV store.
+	paymentsDBOptions := []paymentsdb.OptionModifier{
+		paymentsdb.WithKeepFailedPaymentAttempts(
+			cfg.KeepFailedPaymentAttempts,
+		),
+	}
+	kvPaymentsDB, err := channeldb.NewKVPaymentsDB(
 		dbs.ChanStateDB,
+		paymentsDBOptions...,
 	)
+	if err != nil {
+		cleanUp()
+
+		err = fmt.Errorf("unable to open payments DB: %w", err)
+		d.logger.Error(err)
+
+		return nil, nil, err
+	}
 	dbs.KVPaymentsDB = kvPaymentsDB
 
 	// Wrap the watchtower client DB and make sure we clean up.
diff --git a/payments/db/options.go b/payments/db/options.go
new file mode 100644
index 0000000..4f6fa57
--- /dev/null
+++ b/payments/db/options.go
@@ -0,0 +1,30 @@
+package paymentsdb
+
+// StoreOptions holds parameters for the KVStore.
+type StoreOptions struct {
+	// NoMigration allows to open the database in readonly mode
+	NoMigration bool
+
+	// KeepFailedPaymentAttempts is a flag that determines whether to keep
+	// failed payment attempts for a settled payment in the db.
+	KeepFailedPaymentAttempts bool
+}
+
+// OptionModifier is a function signature for modifying the default
+// StoreOptions.
+type OptionModifier func(*StoreOptions)
+
+// WithKeepFailedPaymentAttempts sets the KeepFailedPaymentAttempts to n.
+func WithKeepFailedPaymentAttempts(n bool) OptionModifier {
+	return func(o *StoreOptions) {
+		o.KeepFailedPaymentAttempts = n
+	}
+}
+
+// WithNoMigration allows the database to be opened in read only mode by
+// disabling migrations.
+func WithNoMigration(b bool) OptionModifier {
+	return func(o *StoreOptions) {
+		o.NoMigration = b
+	}
+}
diff --git a/routing/control_tower_test.go b/routing/control_tower_test.go
index ceb5cb6..f45c2de 100644
--- a/routing/control_tower_test.go
+++ b/routing/control_tower_test.go
@@ -48,12 +48,18 @@ var (
 func TestControlTowerSubscribeUnknown(t *testing.T) {
 	t.Parallel()
 
-	db := initDB(t, false)
+	db := initDB(t)
 
-	pControl := NewControlTower(channeldb.NewKVPaymentsDB(db))
+	paymentDB, err := channeldb.NewKVPaymentsDB(
+		db,
+		paymentsdb.WithKeepFailedPaymentAttempts(true),
+	)
+	require.NoError(t, err)
+
+	pControl := NewControlTower(paymentDB)
 
 	// Subscription should fail when the payment is not known.
-	_, err := pControl.SubscribePayment(lntypes.Hash{1})
+	_, err = pControl.SubscribePayment(lntypes.Hash{1})
 	require.ErrorIs(t, err, paymentsdb.ErrPaymentNotInitiated)
 }
 
@@ -62,9 +68,12 @@ func TestControlTowerSubscribeUnknown(t *testing.T) {
 func TestControlTowerSubscribeSuccess(t *testing.T) {
 	t.Parallel()
 
-	db := initDB(t, false)
+	db := initDB(t)
 
-	pControl := NewControlTower(channeldb.NewKVPaymentsDB(db))
+	paymentDB, err := channeldb.NewKVPaymentsDB(db)
+	require.NoError(t, err)
+
+	pControl := NewControlTower(paymentDB)
 
 	// Initiate a payment.
 	info, attempt, preimg, err := genInfo()
@@ -181,9 +190,15 @@ func TestKVPaymentsDBSubscribeFail(t *testing.T) {
 func TestKVPaymentsDBSubscribeAllSuccess(t *testing.T) {
 	t.Parallel()
 
-	db := initDB(t, true)
+	db := initDB(t)
 
-	pControl := NewControlTower(channeldb.NewKVPaymentsDB(db))
+	paymentDB, err := channeldb.NewKVPaymentsDB(
+		db,
+		paymentsdb.WithKeepFailedPaymentAttempts(true),
+	)
+	require.NoError(t, err)
+
+	pControl := NewControlTower(paymentDB)
 
 	// Initiate a payment.
 	info1, attempt1, preimg1, err := genInfo()
@@ -294,9 +309,15 @@ func TestKVPaymentsDBSubscribeAllSuccess(t *testing.T) {
 func TestKVPaymentsDBSubscribeAllImmediate(t *testing.T) {
 	t.Parallel()
 
-	db := initDB(t, true)
+	db := initDB(t)
+
+	paymentDB, err := channeldb.NewKVPaymentsDB(
+		db,
+		paymentsdb.WithKeepFailedPaymentAttempts(true),
+	)
+	require.NoError(t, err)
 
-	pControl := NewControlTower(channeldb.NewKVPaymentsDB(db))
+	pControl := NewControlTower(paymentDB)
 
 	// Initiate a payment.
 	info, attempt, _, err := genInfo()
@@ -331,9 +352,15 @@ func TestKVPaymentsDBSubscribeAllImmediate(t *testing.T) {
 func TestKVPaymentsDBUnsubscribeSuccess(t *testing.T) {
 	t.Parallel()
 
-	db := initDB(t, true)
+	db := initDB(t)
 
-	pControl := NewControlTower(channeldb.NewKVPaymentsDB(db))
+	paymentDB, err := channeldb.NewKVPaymentsDB(
+		db,
+		paymentsdb.WithKeepFailedPaymentAttempts(true),
+	)
+	require.NoError(t, err)
+
+	pControl := NewControlTower(paymentDB)
 
 	subscription1, err := pControl.SubscribeAllPayments()
 	require.NoError(t, err, "expected subscribe to succeed, but got: %v")
@@ -400,9 +427,17 @@ func TestKVPaymentsDBUnsubscribeSuccess(t *testing.T) {
 func testKVPaymentsDBSubscribeFail(t *testing.T, registerAttempt,
 	keepFailedPaymentAttempts bool) {
 
-	db := initDB(t, keepFailedPaymentAttempts)
+	db := initDB(t)
+
+	paymentDB, err := channeldb.NewKVPaymentsDB(
+		db,
+		paymentsdb.WithKeepFailedPaymentAttempts(
+			keepFailedPaymentAttempts,
+		),
+	)
+	require.NoError(t, err)
 
-	pControl := NewControlTower(channeldb.NewKVPaymentsDB(db))
+	pControl := NewControlTower(paymentDB)
 
 	// Initiate a payment.
 	info, attempt, _, err := genInfo()
@@ -518,11 +553,9 @@ func testKVPaymentsDBSubscribeFail(t *testing.T, registerAttempt,
 	}
 }
 
-func initDB(t *testing.T, keepFailedPaymentAttempts bool) *channeldb.DB {
+func initDB(t *testing.T) *channeldb.DB {
 	return channeldb.OpenForTesting(
-		t, t.TempDir(), channeldb.OptionKeepFailedPaymentAttempts(
-			keepFailedPaymentAttempts,
-		),
+		t, t.TempDir(),
 	)
 }