server+lncfg: make sweepr batch window duration configurable

config.go

@@ -41,6 +41,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/routing"
 	"github.com/lightningnetwork/lnd/signal"
+	"github.com/lightningnetwork/lnd/sweep"
 	"github.com/lightningnetwork/lnd/tor"
 )
 
@@ -439,6 +440,8 @@ type Config struct {
 
 	RemoteSigner *lncfg.RemoteSigner `group:"remotesigner" namespace:"remotesigner"`
 
+	Sweeper *lncfg.Sweeper `group:"sweeper" namespace:"sweeper"`
+
 	// LogWriter is the root logger that all of the daemon's subloggers are
 	// hooked up to.
 	LogWriter *build.RotatingLogWriter
@@ -635,6 +638,9 @@ func DefaultConfig() Config {
 		RemoteSigner: &lncfg.RemoteSigner{
 			Timeout: lncfg.DefaultRemoteSignerRPCTimeout,
 		},
+		Sweeper: &lncfg.Sweeper{
+			BatchWindowDuration: sweep.DefaultBatchWindowDuration,
+		},
 	}
 }
 
@@ -1651,6 +1657,7 @@ func ValidateConfig(cfg Config, interceptor signal.Interceptor, fileParser,
 		cfg.HealthChecks,
 		cfg.RPCMiddleware,
 		cfg.RemoteSigner,
+		cfg.Sweeper,
 	)
 	if err != nil {
 		return nil, err

lncfg/sweeper.go

@@ -0,0 +1,19 @@
+package lncfg
+
+import (
+	"fmt"
+	"time"
+)
+
+type Sweeper struct {
+	BatchWindowDuration time.Duration `long:"batchwindowduration" description:"Duration of the sweep batch window. The sweep is held back during the batch window to allow more inputs to be added and thereby lower the fee per input."`
+}
+
+// Validate checks the values configured for the sweeper.
+func (s *Sweeper) Validate() error {
+	if s.BatchWindowDuration < 0 {
+		return fmt.Errorf("batchwindowduration must be positive")
+	}
+
+	return nil
+}

sample-lnd.conf

@@ -1415,3 +1415,10 @@ litecoin.node=ltcd
 ; for neutrino nodes as it means they'll only maintain edges where both nodes are
 ; seen as being live from it's PoV.
 ; routing.strictgraphpruning=true
+
+[sweeper]
+
+; Duration of the sweep batch window. The sweep is held back during the batch
+; window to allow more inputs to be added and thereby lower the fee per input.
+; sweeper.batchwindowduration=30s
+

server.go

@@ -1004,7 +1004,7 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 		Signer:         cc.Wallet.Cfg.Signer,
 		Wallet:         cc.Wallet,
 		NewBatchTimer: func() <-chan time.Time {
-			return time.NewTimer(sweep.DefaultBatchWindowDuration).C
+			return time.NewTimer(cfg.Sweeper.BatchWindowDuration).C
 		},
 		Notifier:             cc.ChainNotifier,
 		Store:                sweeperStore,