sweepbatcher: fix some minor bugs

sweepbatcher/sweep_batch.go

@@ -214,10 +214,6 @@ type batch struct {
 	// currentHeight is the current block height.
 	currentHeight int32
 
-	// blockEpochChan is the channel over which block epoch notifications
-	// are received.
-	blockEpochChan chan int32
-
 	// spendChan is the channel over which spend notifications are received.
 	spendChan chan *chainntnfs.SpendDetail
 
@@ -362,7 +358,6 @@ func NewBatch(cfg batchConfig, bk batchKit) *batch {
 		id:                  -1,
 		state:               Open,
 		sweeps:              make(map[lntypes.Hash]sweep),
-		blockEpochChan:      make(chan int32),
 		spendChan:           make(chan *chainntnfs.SpendDetail),
 		confChan:            make(chan *chainntnfs.TxConfirmation, 1),
 		reorgChan:           make(chan struct{}, 1),
@@ -407,7 +402,6 @@ func NewBatchFromDB(cfg batchConfig, bk batchKit) (*batch, error) {
 		state:               bk.state,
 		primarySweepID:      bk.primaryID,
 		sweeps:              bk.sweeps,
-		blockEpochChan:      make(chan int32),
 		spendChan:           make(chan *chainntnfs.SpendDetail),
 		confChan:            make(chan *chainntnfs.TxConfirmation, 1),
 		reorgChan:           make(chan struct{}, 1),
@@ -626,6 +620,16 @@ func (b *batch) Run(ctx context.Context) error {
 		return err
 	}
 
+	// Set currentHeight here, because it may be needed in monitorSpend.
+	select {
+	case b.currentHeight = <-blockChan:
+		b.log.Debugf("initial height for the batch is %v",
+			b.currentHeight)
+
+	case <-runCtx.Done():
+		return runCtx.Err()
+	}
+
 	// If a primary sweep exists we immediately start monitoring for its
 	// spend.
 	if b.primarySweepID != lntypes.ZeroHash {
@@ -642,9 +646,9 @@ func (b *batch) Run(ctx context.Context) error {
 	skipBefore := clock.Now().Add(b.cfg.initialDelay)
 
 	// initialDelayChan is a timer which fires upon initial delay end.
-	// If initialDelay is 0, it does not fire to prevent race with
-	// blockChan which also fires immediately with current tip. Such a race
-	// may result in double publishing if batchPublishDelay is also 0.
+	// If initialDelay is set to 0, it will not trigger to avoid setting up
+	// timerChan twice, which could lead to double publishing if
+	// batchPublishDelay is also 0.
 	var initialDelayChan <-chan time.Time
 	if b.cfg.initialDelay > 0 {
 		initialDelayChan = clock.TickAfter(b.cfg.initialDelay)
@@ -653,9 +657,10 @@ func (b *batch) Run(ctx context.Context) error {
 	// We use a timer in order to not publish new transactions at the same
 	// time as the block epoch notification. This is done to prevent
 	// unnecessary transaction publishments when a spend is detected on that
-	// block. This timer starts after new block arrives or initialDelay
+	// block. This timer starts after new block arrives (including the
+	// current tip which we read from blockChan above) or when initialDelay
 	// completes.
-	var timerChan <-chan time.Time
+	timerChan := clock.TickAfter(b.cfg.batchPublishDelay)
 
 	b.log.Infof("started, primary %x, total sweeps %v",
 		b.primarySweepID[0:6], len(b.sweeps))
@@ -1872,7 +1877,10 @@ func (b *batch) monitorConfirmations(ctx context.Context) error {
 func getFeePortionForSweep(spendTx *wire.MsgTx, numSweeps int,
 	totalSweptAmt btcutil.Amount) (btcutil.Amount, btcutil.Amount) {
 
-	totalFee := int64(totalSweptAmt) - spendTx.TxOut[0].Value
+	totalFee := int64(totalSweptAmt)
+	if len(spendTx.TxOut) > 0 {
+		totalFee -= spendTx.TxOut[0].Value
+	}
 	feePortionPerSweep := totalFee / int64(numSweeps)
 	roundingDiff := totalFee - (int64(numSweeps) * feePortionPerSweep)
 
@@ -1900,7 +1908,11 @@ func (b *batch) handleSpend(ctx context.Context, spendTx *wire.MsgTx) error {
 		notifyList = make([]sweep, 0, len(b.sweeps))
 	)
 	b.batchTxid = &txHash
-	b.batchPkScript = spendTx.TxOut[0].PkScript
+	if len(spendTx.TxOut) > 0 {
+		b.batchPkScript = spendTx.TxOut[0].PkScript
+	} else {
+		b.log.Warnf("transaction %v has no outputs", txHash)
+	}
 
 	// As a previous version of the batch transaction may get confirmed,
 	// which does not contain the latest sweeps, we need to detect the