Add ScoreProducer trait

This allows users to create their own structs that implement scoring
methods. When these methods receive updates or called, they execute
the user's customized function and update metadata in a customized way.

Author: sourabhmarathe

lightning/src/routing/network_graph.rs

@@ -13,7 +13,6 @@ use chain::chaininterface::{ChainError, ChainWatchInterface};
 use ln::features::{ChannelFeatures, NodeFeatures};
 use ln::msgs::{DecodeError,ErrorAction,LightningError,RoutingMessageHandler,NetAddress};
 use ln::msgs;
-use routing::router::RouteHop;
 use util::ser::{Writeable, Readable, Writer};
 use util::logger::Logger;
 
@@ -428,15 +427,30 @@ impl Readable for NodeInfo {
 	}
 }
 
-/// Users store custom channel metadata separately. This trait is implemented by users, so that NetworkGraph
-/// objects can call into them to update the metadata and retrieve a minimum fee penalty when doing the
-/// route-finding algorithm.
+/// Represents custom methods used to update channel scores based on user stored metadata. By
+/// default, these methods do nothing. Users may customize these methods.
+pub trait ScoreProducer {
+	/// Default method for tracking PaymentFailed events
+	fn score_payment_failure(&self) {}
+	/// Default method for tracking PaymentSent events
+	fn score_payment_success(&self) {}
+}
+
+/// Users store custom channel metadata separately. This trait is implemented by users, who may use
+/// the NetworkGraph to update whatever metadata they are storing about their view of the network.
 pub trait ChannelScorer {
 	/// Holds information about a given channel that is to be updated when the user wishes to update
 	/// the metadata they are tracking (eg metrics for reliability, uptime, floppiness, etc.)
 	type Metadata;
-	/// Returns penalty fee for a given channel ID based on user's channel metadata
-	fn calculate_minimum_fee_penalty(&self, _channel_id: u64) -> u64 { 0 }
+	/// Any struct that implements the ScoreProducer trait. By default, these methods do not do
+	/// anything, but a user could create a list of customized ScorerProducers that implement select
+	/// methods of a given trait.
+	type ScorerProducer: ScoreProducer;
+	/// Return score for a given channel by using user-defined channel_scorers
+	fn calculate_minimum_fee_penalty(&self, channel_scorers: Vec<Self::ScorerProducer>, channel: Self::Metadata) -> u64;
+	/// Adds a ScoreProducer struct to user metadata. These are overriden customizations of the
+	/// default methods provided by rust-lightning.
+	fn add_scorer_producer(&self, score_producer: Self::ScorerProducer);
 }
 
 /// Represents the network as nodes and channels between them

lightning/src/routing/router.rs

@@ -9,7 +9,7 @@ use chain::chaininterface::ChainWatchInterface;
 use ln::channelmanager;
 use ln::features::{ChannelFeatures, NodeFeatures};
 use ln::msgs::{DecodeError,ErrorAction,LightningError};
-use routing::network_graph::{NetGraphMsgHandler, RoutingFees, ChannelScorer};
+use routing::network_graph::{NetGraphMsgHandler, RoutingFees};
 use util::ser::{Writeable, Readable};
 use util::logger::Logger;
 
@@ -104,12 +104,6 @@ impl Readable for Route {
 	}
 }
 
-/// Another default implementation of ChannelScorer. The use case is a user processing the
-/// success/failure of a given Route. They can implement these functions to fit their needs.
-impl ChannelScorer for Route {
-	type Metadata = Option<u8>;
-}
-
 /// A channel descriptor which provides a last-hop route to get_route
 pub struct RouteHint {
 	/// The node_id of the non-target end of the route