Automatically remove old tickets and expired transactions

The wallet had no way to remove expired transactions from the internal
memory pool. Tickets that were lower than the current stake difficulty
were also never removed. Automatic pruning of these transactions on a
per block basis has been added, allowing the wallet to recover and
respend these funds. The function removeConflict has also been
renamed to removeUnconfirmed to better describe its activity.

wallet/chainntfns.go

@@ -277,6 +277,16 @@ func (w *Wallet) connectBlock(b wtxmgr.BlockMeta) {
 
 		w.Stop()
 	}
+
+	// Prune all expired transactions and all stake tickets that no longer
+	// meet the minimum stake difficulty.
+	stakeDifficultyInfo := w.GetStakeDifficulty()
+	err = w.TxStore.PruneUnconfirmed(bs.Height,
+		stakeDifficultyInfo.StakeDifficulty)
+	if err != nil {
+		log.Errorf("Failed to prune unconfirmed transactions when "+
+			"connecting block height %v: %v", bs.Height, err.Error())
+	}
 }
 
 // disconnectBlock handles a chain server reorganize by rolling back all

wtxmgr/tx.go

@@ -494,6 +494,83 @@ func (s *Store) getBlockHash(ns walletdb.Bucket, height int32) (chainhash.Hash,
 	return br.Block.Hash, nil
 }
 
+// PruneUnconfirmed prunes old stake tickets that are below the current stake
+// difficulty or any unconfirmed transaction which is expired.
+func (s *Store) PruneUnconfirmed(height int32, stakeDiff int64) error {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	if s.isClosed {
+		str := "tx manager is closed"
+		return storeError(ErrIsClosed, str, nil)
+	}
+
+	var unconfTxRs []*TxRecord
+	var uTxRstoRemove []*TxRecord
+
+	// Open an update transaction in the database and
+	// remove all of the tagged transactions.
+	err := scopedUpdate(s.namespace, func(ns walletdb.Bucket) error {
+		errDb := ns.Bucket(bucketUnmined).ForEach(func(k, v []byte) error {
+			// TODO: Parsing transactions from the db may be a little
+			// expensive.  It's possible the caller only wants the
+			// serialized transactions.
+			var txHash chainhash.Hash
+			errLocal := readRawUnminedHash(k, &txHash)
+			if errLocal != nil {
+				return errLocal
+			}
+
+			var rec TxRecord
+			errLocal = readRawTxRecord(&txHash, v, &rec)
+			if errLocal != nil {
+				return errLocal
+			}
+
+			unconfTxRs = append(unconfTxRs, &rec)
+
+			return nil
+		})
+		if errDb != nil {
+			return errDb
+		}
+
+		for _, uTxR := range unconfTxRs {
+			// Tag all transactions that are expired.
+			if uTxR.MsgTx.Expiry <= uint32(height) &&
+				uTxR.MsgTx.Expiry != wire.NoExpiryValue {
+				log.Debugf("Tagging expired tx %v for removal (expiry %v, "+
+					"height %v)", uTxR.Hash, uTxR.MsgTx.Expiry, height)
+				uTxRstoRemove = append(uTxRstoRemove, uTxR)
+			}
+
+			// Tag all stake tickets which are below
+			// network difficulty.
+			if uTxR.TxType == stake.TxTypeSStx {
+				if uTxR.MsgTx.TxOut[0].Value < stakeDiff {
+					log.Debugf("Tagging low diff ticket %v for removal "+
+						"(stake %v, target %v)", uTxR.Hash,
+						uTxR.MsgTx.TxOut[0].Value, stakeDiff)
+					uTxRstoRemove = append(uTxRstoRemove, uTxR)
+				}
+			}
+		}
+
+		for _, uTxR := range uTxRstoRemove {
+			errLocal := s.removeUnconfirmed(ns, uTxR)
+			if errLocal != nil {
+				return errLocal
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // moveMinedTx moves a transaction record from the unmined buckets to block
 // buckets.
 func (s *Store) moveMinedTx(ns walletdb.Bucket, rec *TxRecord, recKey,
@@ -1422,7 +1499,7 @@ func (s *Store) rollback(ns walletdb.Bucket, height int32) error {
 
 			log.Debugf("Transaction %v spends a removed coinbase "+
 				"output -- removing as well", unminedRec.Hash)
-			err = s.removeConflict(ns, &unminedRec)
+			err = s.removeUnconfirmed(ns, &unminedRec)
 			if err != nil {
 				return err
 			}

wtxmgr/unconfirmed.go

@@ -78,7 +78,7 @@ func (s *Store) removeDoubleSpends(ns walletdb.Bucket, rec *TxRecord) error {
 
 			log.Debugf("Removing double spending transaction %v",
 				doubleSpend.Hash)
-			err = s.removeConflict(ns, &doubleSpend)
+			err = s.removeUnconfirmed(ns, &doubleSpend)
 			if err != nil {
 				return err
 			}
@@ -87,11 +87,13 @@ func (s *Store) removeDoubleSpends(ns walletdb.Bucket, rec *TxRecord) error {
 	return nil
 }
 
-// removeConflict removes an unmined transaction record and all spend chains
+// removeUnconfirmed removes an unmined transaction record and all spend chains
 // deriving from it from the store.  This is designed to remove transactions
 // that would otherwise result in double spend conflicts if left in the store,
-// and to remove transactions that spend coinbase transactions on reorgs.
-func (s *Store) removeConflict(ns walletdb.Bucket, rec *TxRecord) error {
+// and to remove transactions that spend coinbase transactions on reorgs. It
+// can also be used to remove old tickets that do not meet the network difficulty
+// and expired transactions.
+func (s *Store) removeUnconfirmed(ns walletdb.Bucket, rec *TxRecord) error {
 	// For each potential credit for this record, each spender (if any) must
 	// be recursively removed as well.  Once the spenders are removed, the
 	// credit is deleted.
@@ -110,7 +112,7 @@ func (s *Store) removeConflict(ns walletdb.Bucket, rec *TxRecord) error {
 
 			log.Debugf("Transaction %v is part of a removed conflict "+
 				"chain -- removing as well", spender.Hash)
-			err = s.removeConflict(ns, &spender)
+			err = s.removeUnconfirmed(ns, &spender)
 			if err != nil {
 				return err
 			}