chainntnfs/bitcoindnotify: rescan blocks manually instead of rewinding

chainntnfs/bitcoindnotify/bitcoind.go

@@ -15,6 +15,7 @@ import (
 	"github.com/roasbeef/btcd/wire"
 	"github.com/roasbeef/btcutil"
 	"github.com/roasbeef/btcwallet/chain"
+	"github.com/roasbeef/btcwallet/wtxmgr"
 )
 
 const (
@@ -44,14 +45,6 @@ type chainUpdate struct {
 	blockHeight int32
 }
 
-// txUpdate encapsulates a transaction related notification sent from bitcoind
-// to the registered RPC client. This struct is used as an element within an
-// unbounded queue in order to avoid blocking the main rpc dispatch rule.
-type txUpdate struct {
-	tx      *btcutil.Tx
-	details *btcjson.BlockDetails
-}
-
 // TODO(roasbeef): generalize struct below:
 //  * move chans to config, allow outside callers to handle send conditions
 
@@ -65,9 +58,6 @@ type BitcoindNotifier struct {
 	started int32 // To be used atomically.
 	stopped int32 // To be used atomically.
 
-	heightMtx  sync.RWMutex
-	bestHeight int32
-
 	chainConn *chain.BitcoindClient
 
 	notificationCancels  chan interface{}
@@ -139,15 +129,11 @@ func (b *BitcoindNotifier) Start() error {
 		return err
 	}
 
-	b.heightMtx.Lock()
-	b.bestHeight = currentHeight
-	b.heightMtx.Unlock()
-
 	b.txConfNotifier = chainntnfs.NewTxConfNotifier(
 		uint32(currentHeight), reorgSafetyLimit)
 
 	b.wg.Add(1)
-	go b.notificationDispatcher()
+	go b.notificationDispatcher(currentHeight)
 
 	return nil
 }
@@ -193,7 +179,7 @@ type blockNtfn struct {
 
 // notificationDispatcher is the primary goroutine which handles client
 // notification registrations, as well as notification dispatches.
-func (b *BitcoindNotifier) notificationDispatcher() {
+func (b *BitcoindNotifier) notificationDispatcher(bestHeight int32) {
 out:
 	for {
 		select {
@@ -260,34 +246,31 @@ out:
 				if err != nil {
 					chainntnfs.Log.Error(err)
 				}
-				b.heightMtx.RLock()
 				err = b.txConfNotifier.Register(&msg.ConfNtfn, txConf)
 				if err != nil {
 					chainntnfs.Log.Error(err)
 				}
-				b.heightMtx.RUnlock()
 			case *blockEpochRegistration:
 				chainntnfs.Log.Infof("New block epoch subscription")
 				b.blockEpochClients[msg.epochID] = msg
+			case chain.RelevantTx:
+				b.handleRelevantTx(msg, bestHeight)
 			}
 
 		case ntfn := <-b.chainConn.Notifications():
 			switch item := ntfn.(type) {
 			case chain.BlockConnected:
-				b.heightMtx.Lock()
-				if item.Height != b.bestHeight+1 {
+				if item.Height != bestHeight+1 {
 					chainntnfs.Log.Warnf("Received blocks out of order: "+
 						"current height=%d, new height=%d",
-						b.bestHeight, item.Height)
-					b.heightMtx.Unlock()
+						bestHeight, item.Height)
 					continue
 				}
-				b.bestHeight = item.Height
+				bestHeight = item.Height
 
 				rawBlock, err := b.chainConn.GetBlock(&item.Hash)
 				if err != nil {
 					chainntnfs.Log.Errorf("Unable to get block: %v", err)
-					b.heightMtx.Unlock()
 					continue
 				}
 
@@ -302,20 +285,17 @@ out:
 				if err != nil {
 					chainntnfs.Log.Error(err)
 				}
-				b.heightMtx.Unlock()
 				continue
 
 			case chain.BlockDisconnected:
-				b.heightMtx.Lock()
-				if item.Height != b.bestHeight {
+				if item.Height != bestHeight {
 					chainntnfs.Log.Warnf("Received blocks "+
 						"out of order: current height="+
 						"%d, disconnected height=%d",
-						b.bestHeight, item.Height)
-					b.heightMtx.Unlock()
+						bestHeight, item.Height)
 					continue
 				}
-				b.bestHeight = item.Height - 1
+				bestHeight = item.Height - 1
 
 				chainntnfs.Log.Infof("Block disconnected from "+
 					"main chain: height=%v, sha=%v",
@@ -326,53 +306,9 @@ out:
 				if err != nil {
 					chainntnfs.Log.Error(err)
 				}
-				b.heightMtx.Unlock()
 
 			case chain.RelevantTx:
-				tx := item.TxRecord.MsgTx
-				// First, check if this transaction spends an output
-				// that has an existing spend notification for it.
-				for i, txIn := range tx.TxIn {
-					prevOut := txIn.PreviousOutPoint
-
-					// If this transaction indeed does spend an
-					// output which we have a registered
-					// notification for, then create a spend
-					// summary, finally sending off the details to
-					// the notification subscriber.
-					if clients, ok := b.spendNotifications[prevOut]; ok {
-						spenderSha := tx.TxHash()
-						spendDetails := &chainntnfs.SpendDetail{
-							SpentOutPoint:     &prevOut,
-							SpenderTxHash:     &spenderSha,
-							SpendingTx:        &tx,
-							SpenderInputIndex: uint32(i),
-						}
-						// TODO(roasbeef): after change to
-						// loadfilter, only notify on block
-						// inclusion?
-						if item.Block != nil {
-							spendDetails.SpendingHeight = item.Block.Height
-						} else {
-							b.heightMtx.RLock()
-							spendDetails.SpendingHeight = b.bestHeight + 1
-							b.heightMtx.RUnlock()
-						}
-
-						for _, ntfn := range clients {
-							chainntnfs.Log.Infof("Dispatching "+
-								"spend notification for "+
-								"outpoint=%v", ntfn.targetOutpoint)
-							ntfn.spendChan <- spendDetails
-
-							// Close spendChan to ensure that any calls to Cancel will not
-							// block. This is safe to do since the channel is buffered, and the
-							// message can still be read by the receiver.
-							close(ntfn.spendChan)
-						}
-						delete(b.spendNotifications, prevOut)
-					}
-				}
+				b.handleRelevantTx(item, bestHeight)
 			}
 
 		case <-b.quit:
@@ -382,6 +318,52 @@ out:
 	b.wg.Done()
 }
 
+// handleRelevantTx notifies any clients of a relevant transaction.
+func (b *BitcoindNotifier) handleRelevantTx(tx chain.RelevantTx, bestHeight int32) {
+	msgTx := tx.TxRecord.MsgTx
+	// First, check if this transaction spends an output
+	// that has an existing spend notification for it.
+	for i, txIn := range msgTx.TxIn {
+		prevOut := txIn.PreviousOutPoint
+
+		// If this transaction indeed does spend an
+		// output which we have a registered
+		// notification for, then create a spend
+		// summary, finally sending off the details to
+		// the notification subscriber.
+		if clients, ok := b.spendNotifications[prevOut]; ok {
+			spenderSha := msgTx.TxHash()
+			spendDetails := &chainntnfs.SpendDetail{
+				SpentOutPoint:     &prevOut,
+				SpenderTxHash:     &spenderSha,
+				SpendingTx:        &msgTx,
+				SpenderInputIndex: uint32(i),
+			}
+			// TODO(roasbeef): after change to
+			// loadfilter, only notify on block
+			// inclusion?
+			if tx.Block != nil {
+				spendDetails.SpendingHeight = tx.Block.Height
+			} else {
+				spendDetails.SpendingHeight = bestHeight + 1
+			}
+
+			for _, ntfn := range clients {
+				chainntnfs.Log.Infof("Dispatching "+
+					"spend notification for "+
+					"outpoint=%v", ntfn.targetOutpoint)
+				ntfn.spendChan <- spendDetails
+
+				// Close spendChan to ensure that any calls to Cancel will not
+				// block. This is safe to do since the channel is buffered, and the
+				// message can still be read by the receiver.
+				close(ntfn.spendChan)
+			}
+			delete(b.spendNotifications, prevOut)
+		}
+	}
+}
+
 // historicalConfDetails looks up whether a transaction is already included in a
 // block in the active chain and, if so, returns details about the confirmation.
 func (b *BitcoindNotifier) historicalConfDetails(txid *chainhash.Hash,
@@ -523,40 +505,66 @@ func (b *BitcoindNotifier) RegisterSpendNtfn(outpoint *wire.OutPoint,
 			}
 		}
 
-		// We'll only request a rescan if the transaction has actually
+		// We'll only scan old blocks if the transaction has actually
 		// been included within a block. Otherwise, we'll encounter an
 		// error when scanning for blocks. This can happens in the case
 		// of a race condition, wherein the output itself is unspent,
 		// and only arrives in the mempool after the getxout call.
 		if transaction != nil && transaction.BlockHash != "" {
-			blockhash, err := chainhash.NewHashFromStr(transaction.BlockHash)
+			startHash, err := chainhash.NewHashFromStr(transaction.BlockHash)
 			if err != nil {
 				return nil, err
 			}
 
-			// Rewind the rescan, since the btcwallet bitcoind
-			// back-end doesn't support that.
-			blockHeight, err := b.chainConn.GetBlockHeight(blockhash)
+			// Rescan all the blocks until the current one.
+			startHeight, err := b.chainConn.GetBlockHeight(startHash)
 			if err != nil {
 				return nil, err
 			}
-			b.heightMtx.Lock()
-			currentHeight := b.bestHeight
-			b.bestHeight = blockHeight
-			for i := currentHeight; i > blockHeight; i-- {
-				err = b.txConfNotifier.DisconnectTip(uint32(i))
+
+			_, endHeight, err := b.chainConn.GetBestBlock()
+			if err != nil {
+				return nil, err
+			}
+
+		out:
+			for i := startHeight; i <= endHeight; i++ {
+				blockHash, err := b.chainConn.GetBlockHash(int64(i))
 				if err != nil {
 					return nil, err
 				}
+				block, err := b.chainConn.GetBlock(blockHash)
+				if err != nil {
+					return nil, err
+				}
+				for _, tx := range block.Transactions {
+					for _, in := range tx.TxIn {
+						if in.PreviousOutPoint == *outpoint {
+							relTx := chain.RelevantTx{
+								TxRecord: &wtxmgr.TxRecord{
+									MsgTx:    *tx,
+									Hash:     tx.TxHash(),
+									Received: block.Header.Timestamp,
+								},
+								Block: &wtxmgr.BlockMeta{
+									Block: wtxmgr.Block{
+										Hash:   block.BlockHash(),
+										Height: i,
+									},
+									Time: block.Header.Timestamp,
+								},
+							}
+							select {
+							case <-b.quit:
+								return nil, ErrChainNotifierShuttingDown
+							case b.notificationRegistry <- relTx:
+							}
+							break out
+						}
+					}
+				}
 			}
-			b.heightMtx.Unlock()
 
-			ops := []*wire.OutPoint{outpoint}
-			if err := b.chainConn.Rescan(blockhash, nil, ops); err != nil {
-				chainntnfs.Log.Errorf("Rescan for spend "+
-					"notification txout failed: %v", err)
-				return nil, err
-			}
 		}
 	}