Allow setting custom scoring parameters

The ProbabilisticScorer and DefaultRouter were always initialized with
hardcoded defaults. If you wanted different fee penalties or decay
behavior, you had to edit the source.

This adds a ProbabilisticScoringParameters struct and exposes it through
the builder API so both fee and decay parameters are configurable. Ported
from cequals#5; the prober module from the original does not
exist on this branch so that part was dropped.

Author: amackillop

src/builder.rs

@@ -73,6 +73,7 @@ use crate::payment::asynchronous::om_mailbox::OnionMessageMailbox;
 use crate::peer_store::PeerStore;
 use crate::router::{LSPS4BlindedPathConfig, LSPS4Router};
 use crate::runtime::Runtime;
+use crate::scoring::ProbabilisticScoringParameters;
 use crate::tx_broadcaster::TransactionBroadcaster;
 use crate::types::{
 	ChainMonitor, ChannelManager, DynStore, GossipSync, Graph, KeysManager, MessageRouter,
@@ -620,6 +621,14 @@ impl NodeBuilder {
 		Ok(self)
 	}
 
+	/// Sets the parameters for the scoring algorithm.
+	pub fn set_scoring_params(
+		&mut self, scoring_params: ProbabilisticScoringParameters,
+	) -> &mut Self {
+		self.config.scoring_parameters = scoring_params;
+		self
+	}
+
 	/// Builds a [`Node`] instance with a [`SqliteStore`] backend and according to the options
 	/// previously configured.
 	pub fn build(&self) -> Result<Node, BuildError> {
@@ -1133,6 +1142,11 @@ impl ArcedNodeBuilder {
 		self.inner.write().unwrap().set_async_payments_role(role).map(|_| ())
 	}
 
+	/// Sets the parameters for the scoring algorithm.
+	pub fn set_scoring_params(&self, scoring_params: ProbabilisticScoringParameters) {
+		self.inner.write().unwrap().set_scoring_params(scoring_params);
+	}
+
 	/// Builds a [`Node`] instance with a [`SqliteStore`] backend and according to the options
 	/// previously configured.
 	pub fn build(&self) -> Result<Arc<Node>, BuildError> {
@@ -1577,8 +1591,12 @@ fn build_with_store_internal(
 		Ok(scorer) => scorer,
 		Err(e) => {
 			if e.kind() == std::io::ErrorKind::NotFound {
-				let params = ProbabilisticScoringDecayParameters::default();
-				ProbabilisticScorer::new(params, Arc::clone(&network_graph), Arc::clone(&logger))
+				let decay_params = config.scoring_parameters.decay_params;
+				ProbabilisticScorer::new(
+					decay_params,
+					Arc::clone(&network_graph),
+					Arc::clone(&logger),
+				)
 			} else {
 				log_error!(logger, "Failed to read scoring data from store: {}", e);
 				return Err(BuildError::ReadFailed);
@@ -1606,7 +1624,7 @@ fn build_with_store_internal(
 		},
 	}
 
-	let scoring_fee_params = ProbabilisticScoringFeeParameters::default();
+	let scoring_fee_params = config.scoring_parameters.fee_params.clone();
 	let inner_router = DefaultRouter::new(
 		Arc::clone(&network_graph),
 		Arc::clone(&logger),

src/config.rs

@@ -20,6 +20,7 @@ use lightning::util::config::{
 };
 
 use crate::logger::LogLevel;
+use crate::scoring::ProbabilisticScoringParameters;
 
 // Config defaults
 const DEFAULT_NETWORK: Network = Network::Bitcoin;
@@ -184,6 +185,9 @@ pub struct Config {
 	/// **Note:** If unset, default parameters will be used, and you will be able to override the
 	/// parameters on a per-payment basis in the corresponding method calls.
 	pub route_parameters: Option<RouteParametersConfig>,
+	/// The parameters used to configure the [`lightning::routing::scoring::ProbabilisticScorer`]
+	/// used by the node.
+	pub scoring_parameters: ProbabilisticScoringParameters,
 }
 
 impl Default for Config {
@@ -198,6 +202,7 @@ impl Default for Config {
 			anchor_channels_config: Some(AnchorChannelsConfig::default()),
 			route_parameters: None,
 			node_alias: None,
+			scoring_parameters: ProbabilisticScoringParameters::default(),
 		}
 	}
 }

src/scoring.rs

@@ -2,10 +2,22 @@ use std::io::Cursor;
 use std::sync::{Arc, Mutex, RwLock};
 use std::time::{Duration, SystemTime};
 
-use lightning::routing::scoring::ChannelLiquidities;
+use lightning::routing::scoring::{
+	ChannelLiquidities, ProbabilisticScoringDecayParameters, ProbabilisticScoringFeeParameters,
+};
 use lightning::util::ser::Readable;
 use lightning::{log_error, log_info, log_trace};
 
+/// The parameters used to configure the [`lightning::routing::scoring::ProbabilisticScorer`]
+/// used by the node.
+#[derive(Debug, Clone, Default)]
+pub struct ProbabilisticScoringParameters {
+	/// The fee parameters used by the router to compute path penalties.
+	pub fee_params: ProbabilisticScoringFeeParameters,
+	/// The decay parameters used by the scorer to reduce certainty of liquidity information.
+	pub decay_params: ProbabilisticScoringDecayParameters,
+}
+
 use crate::config::{
 	EXTERNAL_PATHFINDING_SCORES_SYNC_INTERVAL, EXTERNAL_PATHFINDING_SCORES_SYNC_TIMEOUT_SECS,
 };