sweep: start tracking inputs spent by unknown tx

This commit adds a new field `InputsSpent` to the `BumpResult` so they
can be used to track inputs spent by txns not recoginized by the fee
bumper.

sweep/fee_bumper.go

@@ -273,6 +273,10 @@ type BumpResult struct {
 	// Err is the error that occurred during the broadcast.
 	Err error
 
+	// SpentInputs are the inputs spent by another tx which caused the
+	// current tx to be failed.
+	SpentInputs map[wire.OutPoint]*wire.MsgTx
+
 	// requestID is the ID of the request that created this record.
 	requestID uint64
 }
@@ -812,6 +816,10 @@ type monitorRecord struct {
 
 	// outpointToTxIndex is a map of outpoint to tx index.
 	outpointToTxIndex map[wire.OutPoint]int
+
+	// spentInputs are the inputs spent by another tx which caused the
+	// current tx failed.
+	spentInputs map[wire.OutPoint]*wire.MsgTx
 }
 
 // Start starts the publisher by subscribing to block epoch updates and kicking
@@ -910,6 +918,9 @@ func (t *TxPublisher) processRecords() {
 		// If the any of the inputs has been spent, the record will be
 		// marked as failed or confirmed.
 		if len(spends) != 0 {
+			// Attach the spending txns.
+			r.spentInputs = spends
+
 			// When tx is nil, it means we haven't tried the initial
 			// broadcast yet the input is already spent. This could
 			// happen when the node shuts down, a previous sweeping
@@ -1159,16 +1170,71 @@ func (t *TxPublisher) handleUnknownSpent(r *monitorRecord) {
 		"bumper, failing it now:\n%v", r.requestID,
 		inputTypeSummary(r.req.Inputs))
 
-	// Create a result that will be sent to the resultChan which is
-	// listened by the caller.
+	// Create a result that will be sent to the resultChan which is listened
+	// by the caller.
 	result := &BumpResult{
-		Event:     TxUnknownSpend,
-		Tx:        r.tx,
-		requestID: r.requestID,
-		Err:       ErrUnknownSpent,
+		Event:       TxUnknownSpend,
+		Tx:          r.tx,
+		requestID:   r.requestID,
+		Err:         ErrUnknownSpent,
+		SpentInputs: r.spentInputs,
 	}
 
-	// Notify that this tx is confirmed and remove the record from the map.
+	// Get the fee function, which will be used to decided the next fee rate
+	// to use if the sweeper decides to retry sweeping this input.
+	feeFunc := r.feeFunction
+
+	// When the record is failed before the initial broadcast is attempted,
+	// it will have a nil fee func. In this case, we'll create the fee func
+	// here.
+	//
+	// NOTE: Since the current record is failed and will be deleted, we
+	// don't need to update the record on this fee function. We only need
+	// the fee rate data so the sweeper can pick up where we left off.
+	if feeFunc == nil {
+		f, err := t.initializeFeeFunction(r.req)
+		// TODO(yy): The only error we would receive here is when the
+		// pkScript is not recognized by the weightEstimator. What we
+		// should do instead is to check the pkScript immediately after
+		// receiving a sweep request so we don't need to check it again,
+		// which will also save us from error checking from several
+		// callsites.
+		if err != nil {
+			log.Errorf("Failed to create fee func for record %v: "+
+				"%v", r.requestID, err)
+
+			// Overwrite the event and error so the sweeper will
+			// remove this input.
+			result.Event = TxFatal
+			result.Err = err
+
+			// Notify the sweeper about this result in the end.
+			t.handleResult(result)
+
+			return
+		}
+
+		feeFunc = f
+	}
+
+	// Since the sweeping tx has been replaced by another party's tx, we
+	// missed this block window to increase its fee rate. To make sure the
+	// fee rate stays in the initial line, we now ask the fee function to
+	// give us the next fee rate as if the sweeping tx were RBFed. This new
+	// fee rate will be used as the starting fee rate if the upper system
+	// decides to continue sweeping the rest of the inputs.
+	_, err := feeFunc.Increment()
+	if err != nil {
+		// The fee function has reached its max position - nothing we
+		// can do here other than letting the user increase the budget.
+		log.Errorf("Failed to calculate the next fee rate for "+
+			"Record(%v): %v", r.requestID, err)
+	}
+
+	// Attach the new fee rate to be used for the next sweeping attempt.
+	result.FeeRate = feeFunc.FeeRate()
+
+	// Notify the sweeper about this result in the end.
 	t.handleResult(result)
 }
 

sweep/fee_bumper_test.go

@@ -1772,6 +1772,13 @@ func TestProcessRecordsSpent(t *testing.T) {
 	tp.subscriberChans.Store(requestID, subscriber)
 	tp.records.Store(requestID, recordConfirmed)
 
+	// Mock the fee function to increase feerate.
+	m.feeFunc.On("Increment").Return(true, nil).Once()
+
+	// Create a test feerate and return it from the mock fee function.
+	feerate := chainfee.SatPerKWeight(1000)
+	m.feeFunc.On("FeeRate").Return(feerate)
+
 	// Call processRecords and expect the results are notified back.
 	tp.processRecords()
 
@@ -1785,6 +1792,9 @@ func TestProcessRecordsSpent(t *testing.T) {
 		require.Equal(t, TxUnknownSpend, result.Event)
 		require.Equal(t, tx, result.Tx)
 
+		// We expect the fee rate to be updated.
+		require.Equal(t, feerate, result.FeeRate)
+
 		// No error should be set.
 		require.ErrorIs(t, result.Err, ErrUnknownSpent)
 		require.Equal(t, requestID, result.requestID)