sweep: add sweeper store

This commit adds a store for the sweeper. The sweeper needs minimal
persistent data to be able to recognize its own sweeps.

sweep/store.go

@@ -0,0 +1,247 @@
+package sweep
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/coreos/bbolt"
+	"github.com/lightningnetwork/lnd/channeldb"
+)
+
+var (
+	// lastTxBucketKey is the key that points to a bucket containing a
+	// single item storing the last published tx.
+	//
+	// maps: lastTxKey -> serialized_tx
+	lastTxBucketKey = []byte("sweeper-last-tx")
+
+	// lastTxKey is the fixed key under which the serialized tx is stored.
+	lastTxKey = []byte("last-tx")
+
+	// txHashesBucketKey is the key that points to a bucket containing the
+	// hashes of all sweep txes that were published successfully.
+	//
+	// maps: txHash -> empty slice
+	txHashesBucketKey = []byte("sweeper-tx-hashes")
+
+	// utxnChainPrefix is the bucket prefix for nursery buckets.
+	utxnChainPrefix = []byte("utxn")
+
+	// utxnHeightIndexKey is the sub bucket where the nursery stores the
+	// height index.
+	utxnHeightIndexKey = []byte("height-index")
+
+	// utxnFinalizedKndrTxnKey is a static key that can be used to locate
+	// the nursery finalized kindergarten sweep txn.
+	utxnFinalizedKndrTxnKey = []byte("finalized-kndr-txn")
+
+	byteOrder = binary.BigEndian
+)
+
+// SweeperStore stores published txes.
+type SweeperStore interface {
+	// IsOurTx determines whether a tx is published by us, based on its
+	// hash.
+	IsOurTx(hash chainhash.Hash) (bool, error)
+
+	// NotifyPublishTx signals that we are about to publish a tx.
+	NotifyPublishTx(*wire.MsgTx) error
+
+	// GetLastPublishedTx returns the last tx that we called NotifyPublishTx
+	// for.
+	GetLastPublishedTx() (*wire.MsgTx, error)
+}
+
+type sweeperStore struct {
+	db *channeldb.DB
+}
+
+// NewSweeperStore returns a new store instance.
+func NewSweeperStore(db *channeldb.DB, chainHash *chainhash.Hash) (
+	SweeperStore, error) {
+
+	err := db.Update(func(tx *bbolt.Tx) error {
+		_, err := tx.CreateBucketIfNotExists(
+			lastTxBucketKey,
+		)
+		if err != nil {
+			return err
+		}
+
+		if tx.Bucket(txHashesBucketKey) != nil {
+			return nil
+		}
+
+		txHashesBucket, err := tx.CreateBucket(txHashesBucketKey)
+		if err != nil {
+			return err
+		}
+
+		// Use non-existence of tx hashes bucket as a signal to migrate
+		// nursery finalized txes.
+		err = migrateTxHashes(tx, txHashesBucket, chainHash)
+
+		return err
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return &sweeperStore{
+		db: db,
+	}, nil
+}
+
+// migrateTxHashes migrates nursery finalized txes to the tx hashes bucket. This
+// is not implemented as a database migration, to keep the downgrade path open.
+func migrateTxHashes(tx *bbolt.Tx, txHashesBucket *bbolt.Bucket,
+	chainHash *chainhash.Hash) error {
+
+	log.Infof("Migrating UTXO nursery finalized TXIDs")
+
+	// Compose chain bucket key.
+	var b bytes.Buffer
+	if _, err := b.Write(utxnChainPrefix); err != nil {
+		return err
+	}
+
+	if _, err := b.Write(chainHash[:]); err != nil {
+		return err
+	}
+
+	// Get chain bucket if exists.
+	chainBucket := tx.Bucket(b.Bytes())
+	if chainBucket == nil {
+		return nil
+	}
+
+	// Retrieve the existing height index.
+	hghtIndex := chainBucket.Bucket(utxnHeightIndexKey)
+	if hghtIndex == nil {
+		return nil
+	}
+
+	// Retrieve all heights.
+	err := hghtIndex.ForEach(func(k, v []byte) error {
+		heightBucket := hghtIndex.Bucket(k)
+		if heightBucket == nil {
+			return nil
+		}
+
+		// Get finalized tx for height.
+		txBytes := heightBucket.Get(utxnFinalizedKndrTxnKey)
+		if txBytes == nil {
+			return nil
+		}
+
+		// Deserialize and skip tx if it cannot be deserialized.
+		tx := &wire.MsgTx{}
+		err := tx.Deserialize(bytes.NewReader(txBytes))
+		if err != nil {
+			log.Warnf("Cannot deserialize utxn tx")
+			return nil
+		}
+
+		// Calculate hash.
+		hash := tx.TxHash()
+
+		// Insert utxn tx hash in hashes bucket.
+		log.Debugf("Inserting nursery tx %v in hash list "+
+			"(height=%v)", hash, byteOrder.Uint32(k))
+
+		return txHashesBucket.Put(hash[:], []byte{})
+	})
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// NotifyPublishTx signals that we are about to publish a tx.
+func (s *sweeperStore) NotifyPublishTx(sweepTx *wire.MsgTx) error {
+	return s.db.Update(func(tx *bbolt.Tx) error {
+		lastTxBucket := tx.Bucket(lastTxBucketKey)
+		if lastTxBucket == nil {
+			return errors.New("last tx bucket does not exist")
+		}
+
+		txHashesBucket := tx.Bucket(txHashesBucketKey)
+		if txHashesBucket == nil {
+			return errors.New("tx hashes bucket does not exist")
+		}
+
+		var b bytes.Buffer
+		if err := sweepTx.Serialize(&b); err != nil {
+			return err
+		}
+
+		if err := lastTxBucket.Put(lastTxKey, b.Bytes()); err != nil {
+			return err
+		}
+
+		hash := sweepTx.TxHash()
+
+		return txHashesBucket.Put(hash[:], []byte{})
+	})
+}
+
+// GetLastPublishedTx returns the last tx that we called NotifyPublishTx
+// for.
+func (s *sweeperStore) GetLastPublishedTx() (*wire.MsgTx, error) {
+	var sweepTx *wire.MsgTx
+
+	err := s.db.View(func(tx *bbolt.Tx) error {
+		lastTxBucket := tx.Bucket(lastTxBucketKey)
+		if lastTxBucket == nil {
+			return errors.New("last tx bucket does not exist")
+		}
+
+		sweepTxRaw := lastTxBucket.Get(lastTxKey)
+		if sweepTxRaw == nil {
+			return nil
+		}
+
+		sweepTx = &wire.MsgTx{}
+		txReader := bytes.NewReader(sweepTxRaw)
+		if err := sweepTx.Deserialize(txReader); err != nil {
+			return fmt.Errorf("tx deserialize: %v", err)
+		}
+
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return sweepTx, nil
+}
+
+// IsOurTx determines whether a tx is published by us, based on its
+// hash.
+func (s *sweeperStore) IsOurTx(hash chainhash.Hash) (bool, error) {
+	var ours bool
+
+	err := s.db.View(func(tx *bbolt.Tx) error {
+		txHashesBucket := tx.Bucket(txHashesBucketKey)
+		if txHashesBucket == nil {
+			return errors.New("tx hashes bucket does not exist")
+		}
+
+		ours = txHashesBucket.Get(hash[:]) != nil
+
+		return nil
+	})
+	if err != nil {
+		return false, err
+	}
+
+	return ours, nil
+}
+
+// Compile-time constraint to ensure sweeperStore implements SweeperStore.
+var _ SweeperStore = (*sweeperStore)(nil)