Allow setting custom scoring parameters (#23)

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/lib.rs

@@ -103,6 +103,8 @@ mod tx_broadcaster;
 mod types;
 mod wallet;
 
+pub use scoring::ProbabilisticScoringParameters;
+
 use std::default::Default;
 use std::net::ToSocketAddrs;
 use std::sync::{Arc, Mutex, RwLock};

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,
 };