sweep: use chain notifier instead of chain IO for best block

Because the BestBlock method of ChainIO is not exposed through any
RPC we want to get rid of it so we can use the sweeper outside of
lnd too. Since the chain notifier now also delivers the current best
block we don't need the BestBlock method any more.

server.go

@@ -780,7 +780,6 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 			return time.NewTimer(sweep.DefaultBatchWindowDuration).C
 		},
 		Notifier:             cc.chainNotifier,
-		ChainIO:              cc.chainIO,
 		Store:                sweeperStore,
 		MaxInputsPerTx:       sweep.DefaultMaxInputsPerTx,
 		MaxSweepAttempts:     sweep.DefaultMaxSweepAttempts,

sweep/sweeper.go

@@ -212,9 +212,6 @@ type UtxoSweeperConfig struct {
 	// certain on-chain events.
 	Notifier chainntnfs.ChainNotifier
 
-	// ChainIO is used  to determine the current block height.
-	ChainIO lnwallet.BlockChainIO
-
 	// Store stores the published sweeper txes.
 	Store SweeperStore
 
@@ -323,20 +320,10 @@ func (s *UtxoSweeper) Start() error {
 	// not change from here on.
 	s.relayFeeRate = s.cfg.FeeEstimator.RelayFeePerKW()
 
-	// Register for block epochs to retry sweeping every block.
-	bestHash, bestHeight, err := s.cfg.ChainIO.GetBestBlock()
-	if err != nil {
-		return fmt.Errorf("get best block: %v", err)
-	}
-
-	log.Debugf("Best height: %v", bestHeight)
-
-	blockEpochs, err := s.cfg.Notifier.RegisterBlockEpochNtfn(
-		&chainntnfs.BlockEpoch{
-			Height: bestHeight,
-			Hash:   bestHash,
-		},
-	)
+	// We need to register for block epochs and retry sweeping every block.
+	// We should get a notification with the current best block immediately
+	// if we don't provide any epoch. We'll wait for that in the collector.
+	blockEpochs, err := s.cfg.Notifier.RegisterBlockEpochNtfn(nil)
 	if err != nil {
 		return fmt.Errorf("register block epoch ntfn: %v", err)
 	}
@@ -347,10 +334,7 @@ func (s *UtxoSweeper) Start() error {
 		defer blockEpochs.Cancel()
 		defer s.wg.Done()
 
-		err := s.collector(blockEpochs.Epochs, bestHeight)
-		if err != nil {
-			log.Errorf("sweeper stopped: %v", err)
-		}
+		s.collector(blockEpochs.Epochs)
 	}()
 
 	return nil
@@ -445,8 +429,18 @@ func (s *UtxoSweeper) feeRateForPreference(
 
 // collector is the sweeper main loop. It processes new inputs, spend
 // notifications and counts down to publication of the sweep tx.
-func (s *UtxoSweeper) collector(blockEpochs <-chan *chainntnfs.BlockEpoch,
-	bestHeight int32) error {
+func (s *UtxoSweeper) collector(blockEpochs <-chan *chainntnfs.BlockEpoch) {
+	// We registered for the block epochs with a nil request. The notifier
+	// should send us the current best block immediately. So we need to wait
+	// for it here because we need to know the current best height.
+	var bestHeight int32
+	select {
+	case bestBlock := <-blockEpochs:
+		bestHeight = bestBlock.Height
+
+	case <-s.quit:
+		return
+	}
 
 	for {
 		select {
@@ -622,7 +616,7 @@ func (s *UtxoSweeper) collector(blockEpochs <-chan *chainntnfs.BlockEpoch,
 		// sweep.
 		case epoch, ok := <-blockEpochs:
 			if !ok {
-				return nil
+				return
 			}
 
 			bestHeight = epoch.Height
@@ -635,7 +629,7 @@ func (s *UtxoSweeper) collector(blockEpochs <-chan *chainntnfs.BlockEpoch,
 			}
 
 		case <-s.quit:
-			return nil
+			return
 		}
 	}
 }

sweep/sweeper_test.go

@@ -132,7 +132,6 @@ func createSweeperTestContext(t *testing.T) *sweeperTestContext {
 		},
 		Store:  store,
 		Signer: &mockSigner{},
-		ChainIO: &mockChainIO{},
 		GenSweepScript: func() ([]byte, error) {
 			script := []byte{outputScriptCount}
 			outputScriptCount++

sweep/test_utils.go

@@ -10,12 +10,12 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/input"
-	"github.com/lightningnetwork/lnd/lnwallet"
 )
 
 var (
 	defaultTestTimeout = 5 * time.Second
-	mockChainIOHeight  = int32(100)
+	mockChainHash, _   = chainhash.NewHashFromStr("00aabbccddeeff")
+	mockChainHeight    = int32(100)
 )
 
 type mockSigner struct {
@@ -155,12 +155,22 @@ func (m *MockNotifier) RegisterBlockEpochNtfn(
 	log.Tracef("Mock block ntfn registered")
 
 	m.mutex.Lock()
-	epochChan := make(chan *chainntnfs.BlockEpoch, 0)
-	bestHeight := int32(0)
-	if bestBlock != nil {
-		bestHeight = bestBlock.Height
+	epochChan := make(chan *chainntnfs.BlockEpoch, 1)
+
+	// The real notifier returns a notification with the current block hash
+	// and height immediately if no best block hash or height is specified
+	// in the request. We want to emulate this behaviour as well for the
+	// mock.
+	switch {
+	case bestBlock == nil:
+		epochChan <- &chainntnfs.BlockEpoch{
+			Hash:   mockChainHash,
+			Height: mockChainHeight,
+		}
+		m.epochChan[epochChan] = mockChainHeight
+	default:
+		m.epochChan[epochChan] = bestBlock.Height
 	}
-	m.epochChan[epochChan] = bestHeight
 	m.mutex.Unlock()
 
 	return &chainntnfs.BlockEpochEvent{
@@ -235,25 +245,3 @@ func (m *MockNotifier) RegisterSpendNtfn(outpoint *wire.OutPoint,
 		},
 	}, nil
 }
-
-type mockChainIO struct{}
-
-var _ lnwallet.BlockChainIO = (*mockChainIO)(nil)
-
-func (m *mockChainIO) GetBestBlock() (*chainhash.Hash, int32, error) {
-	return nil, mockChainIOHeight, nil
-}
-
-func (m *mockChainIO) GetUtxo(op *wire.OutPoint, pkScript []byte,
-	heightHint uint32, _ <-chan struct{}) (*wire.TxOut, error) {
-
-	return nil, nil
-}
-
-func (m *mockChainIO) GetBlockHash(blockHeight int64) (*chainhash.Hash, error) {
-	return nil, nil
-}
-
-func (m *mockChainIO) GetBlock(blockHash *chainhash.Hash) (*wire.MsgBlock, error) {
-	return nil, nil
-}