Merge pull request #838 from starius/loopout-retarget-feerate-ever-block

loopout: re-target sweep's feerate every block

Author: starius

client.go

@@ -62,8 +62,14 @@ var (
 	// probeTimeout is the maximum time until a probe is allowed to take.
 	probeTimeout = 3 * time.Minute
 
+	// repushDelay is the delay of (re)adding a sweep to sweepbatcher after
+	// a block is mined.
 	repushDelay = 1 * time.Second
 
+	// additionalDelay is the delay added on top of repushDelay inside the
+	// sweepbatcher to publish a sweep transaction.
+	additionalDelay = 1 * time.Second
+
 	// MinerFeeEstimationFailed is a magic number that is returned in a
 	// quote call as the miner fee if the fee estimation in lnd's wallet
 	// failed because of insufficient funds.
@@ -185,13 +191,52 @@ func NewClient(dbDir string, loopDB loopdb.SwapStore,
 			"NewSweepFetcherFromSwapStore failed: %w", err)
 	}
 
+	// There is circular dependency between executor and sweepbatcher, as
+	// executor stores sweepbatcher and sweepbatcher depends on
+	// executor.height() though loopOutSweepFeerateProvider.
+	var executor *executor
+
+	// getHeight returns current height, according to executor.
+	getHeight := func() int32 {
+		if executor == nil {
+			// This must not happen, because executor is set in this
+			// function, before sweepbatcher.Run is called.
+			log.Errorf("getHeight called when executor is nil")
+
+			return 0
+		}
+
+		return executor.height()
+	}
+
+	loopOutSweepFeerateProvider := newLoopOutSweepFeerateProvider(
+		sweeper, loopDB, cfg.Lnd.ChainParams, getHeight,
+	)
+
 	batcher := sweepbatcher.NewBatcher(
 		cfg.Lnd.WalletKit, cfg.Lnd.ChainNotifier, cfg.Lnd.Signer,
 		swapServerClient.MultiMuSig2SignSweep, verifySchnorrSig,
 		cfg.Lnd.ChainParams, sweeperDb, sweepStore,
+
+		// Disable 100 sats/kw fee bump every block and retarget feerate
+		// every block according to the current mempool condition.
+		sweepbatcher.WithCustomFeeRate(
+			loopOutSweepFeerateProvider.GetMinFeeRate,
+		),
+
+		// Upon new block arrival, republishing is triggered in both
+		// loopout.go code (waitForHtlcSpendConfirmedV2/ <-timerChan)
+		// and in sweepbatcher code (batch.Run/case <-timerChan). The
+		// former updates the fee rate which is used by the later by
+		// calling AddSweep. Make sure they are ordered, add additional
+		// delay time to sweepbatcher's handling. The delay used in
+		// loopout.go is repushDelay.
+		sweepbatcher.WithPublishDelay(
+			repushDelay+additionalDelay,
+		),
 	)
 
-	executor := newExecutor(&executorConfig{
+	executor = newExecutor(&executorConfig{
 		lnd:                 cfg.Lnd,
 		store:               loopDB,
 		sweeper:             sweeper,
@@ -570,8 +615,11 @@ func (s *Client) getLoopOutSweepFee(ctx context.Context, confTarget int32) (
 		htlc = swap.QuoteHtlcP2WSH
 	}
 
+	label := "loopout-quote"
+
 	return s.sweeper.GetSweepFee(
 		ctx, htlc.AddSuccessToEstimator, p2wshAddress, confTarget,
+		label,
 	)
 }
 

liquidity/liquidity.go

@@ -106,13 +106,13 @@ const (
 	// time we reach timeout. We set this to a high estimate so that we can
 	// account for worst-case fees, (1250 * 4 / 1000) = 50 sat/byte.
 	defaultLoopInSweepFee = chainfee.SatPerKWeight(1250)
-)
 
-var (
 	// defaultHtlcConfTarget is the default confirmation target we use for
 	// loop in swap htlcs, set to the same default at the client.
 	defaultHtlcConfTarget = loop.DefaultHtlcConfTarget
+)
 
+var (
 	// defaultBudget is the default autoloop budget we set. This budget will
 	// only be used for automatically dispatched swaps if autoloop is
 	// explicitly enabled, so we are happy to set a non-zero value here. The

loopd/log.go

@@ -11,6 +11,7 @@ import (
 	"github.com/lightninglabs/loop/liquidity"
 	"github.com/lightninglabs/loop/loopdb"
 	"github.com/lightninglabs/loop/notifications"
+	"github.com/lightninglabs/loop/sweep"
 	"github.com/lightninglabs/loop/sweepbatcher"
 	"github.com/lightningnetwork/lnd"
 	"github.com/lightningnetwork/lnd/build"
@@ -52,6 +53,9 @@ func SetupLoggers(root *build.RotatingLogWriter, intercept signal.Interceptor) {
 	lnd.AddSubLogger(
 		root, notifications.Subsystem, intercept, notifications.UseLogger,
 	)
+	lnd.AddSubLogger(
+		root, sweep.Subsystem, intercept, sweep.UseLogger,
+	)
 }
 
 // genSubLogger creates a logger for a subsystem. We provide an instance of

loopin.go

@@ -1077,10 +1077,12 @@ func (s *loopInSwap) publishTimeoutTx(ctx context.Context,
 		}
 	}
 
+	label := fmt.Sprintf("loopin-timeout-%x", s.hash[:6])
+
 	// Calculate sweep tx fee.
 	fee, err := s.sweeper.GetSweepFee(
 		ctx, s.htlc.AddTimeoutToEstimator, s.timeoutAddr,
-		TimeoutTxConfTarget,
+		TimeoutTxConfTarget, label,
 	)
 	if err != nil {
 		return 0, err

loopin_test.go

@@ -312,11 +312,13 @@ func handleHtlcExpiry(t *testing.T, ctx *loopInTestContext, inSwap *loopInSwap,
 	// Expect timeout tx to be published.
 	timeoutTx := <-ctx.lnd.TxPublishChannel
 
+	label := fmt.Sprintf("loopin-timeout-%x", inSwap.hash[:6])
+
 	// We can just get our sweep fee as we would in the swap code because
 	// our estimate is static.
 	fee, err := inSwap.sweeper.GetSweepFee(
 		context.Background(), inSwap.htlc.AddTimeoutToEstimator,
-		inSwap.timeoutAddr, TimeoutTxConfTarget,
+		inSwap.timeoutAddr, TimeoutTxConfTarget, label,
 	)
 	require.NoError(t, err)
 	cost.Onchain += fee

loopout.go

@@ -38,27 +38,33 @@ const (
 	// We'll try to sweep with MuSig2 at most 10 times. If that fails we'll
 	// fail back to using standard scriptspend sweep.
 	maxMusigSweepRetries = 10
-)
 
-var (
 	// MinLoopOutPreimageRevealDelta configures the minimum number of
 	// remaining blocks before htlc expiry required to reveal preimage.
-	MinLoopOutPreimageRevealDelta int32 = 20
+	MinLoopOutPreimageRevealDelta = 20
 
 	// DefaultSweepConfTarget is the default confirmation target we'll use
 	// when sweeping on-chain HTLCs.
-	DefaultSweepConfTarget int32 = 9
+	DefaultSweepConfTarget = 9
 
 	// DefaultHtlcConfTarget is the default confirmation target we'll use
 	// for on-chain htlcs published by the swap client for Loop In.
-	DefaultHtlcConfTarget int32 = 6
+	DefaultHtlcConfTarget = 6
 
 	// DefaultSweepConfTargetDelta is the delta of blocks from a Loop Out
-	// swap's expiration height at which we begin to use the default sweep
-	// confirmation target.
-	//
-	// TODO(wilmer): tune?
-	DefaultSweepConfTargetDelta = DefaultSweepConfTarget * 2
+	// swap's expiration height at which we begin to cap the sweep
+	// confirmation target with urgentSweepConfTarget and multiply feerate
+	// by factor urgentSweepConfTargetFactor.
+	DefaultSweepConfTargetDelta = 10
+
+	// urgentSweepConfTarget is the confirmation target we'll use when the
+	// loop-out swap is about to expire (<= DefaultSweepConfTargetDelta
+	// blocks to expire).
+	urgentSweepConfTarget = 3
+
+	// urgentSweepConfTargetFactor is the factor we apply to feerate of
+	// loop-out sweep if it is about to expire.
+	urgentSweepConfTargetFactor = 1.1
 )
 
 // loopOutSwap contains all the in-memory state related to a pending loop out
@@ -1169,12 +1175,12 @@ func (s *loopOutSwap) waitForHtlcSpendConfirmedV2(globalCtx context.Context,
 			timerChan = s.timerFactory(repushDelay)
 
 		case <-timerChan:
-			// sweepConfTarget will return false if the preimage is
+			// canSweep will return false if the preimage is
 			// not revealed yet but the conf target is closer than
 			// 20 blocks. In this case to be sure we won't attempt
 			// to sweep at all and we won't reveal the preimage
 			// either.
-			_, canSweep := s.sweepConfTarget()
+			canSweep := s.canSweep()
 			if !canSweep {
 				s.log.Infof("Aborting swap, timed " +
 					"out on-chain")
@@ -1375,9 +1381,9 @@ func validateLoopOutContract(lnd *lndclient.LndServices, request *OutRequest,
 	return nil
 }
 
-// sweepConfTarget returns the confirmation target for the htlc sweep or false
-// if we're too late.
-func (s *loopOutSwap) sweepConfTarget() (int32, bool) {
+// canSweep will return false if the preimage is not revealed yet but the conf
+// target is closer than 20 blocks (i.e. it is too late to reveal the preimage).
+func (s *loopOutSwap) canSweep() bool {
 	remainingBlocks := s.CltvExpiry - s.height
 	blocksToLastReveal := remainingBlocks - MinLoopOutPreimageRevealDelta
 	preimageRevealed := s.state == loopdb.StatePreimageRevealed
@@ -1393,20 +1399,8 @@ func (s *loopOutSwap) sweepConfTarget() (int32, bool) {
 			s.height)
 
 		s.state = loopdb.StateFailTimeout
-		return 0, false
-	}
-
-	// Calculate the transaction fee based on the confirmation target
-	// required to sweep the HTLC before the timeout. We'll use the
-	// confirmation target provided by the client unless we've come too
-	// close to the expiration height, in which case we'll use the default
-	// if it is better than what the client provided.
-	confTarget := s.SweepConfTarget
-	if remainingBlocks <= DefaultSweepConfTargetDelta &&
-		confTarget > DefaultSweepConfTarget {
-
-		confTarget = DefaultSweepConfTarget
+		return false
 	}
 
-	return confTarget, true
+	return true
 }