Track the last time we received new information about a channel

In the next commit we'll enable users to assign a penalty to
channels which we don't have any recent information for to better
enable probing diversity. In order to do so, we need to actually
track the last time we received new information for a channel,
which we do here.

Author: TheBlueMatt

lightning/src/routing/scoring.rs

@@ -779,6 +779,7 @@ struct DummyLiquidity {
 	c: HistoricalLiquidityTracker,
 	d: Duration,
 	e: Duration,
+	f: Duration,
 }
 
 /// The amount of padding required to make [`ChannelLiquidity`] (plus a u64) a full 4 cache lines.
@@ -806,6 +807,10 @@ struct ChannelLiquidity {
 	/// epoch.
 	offset_history_last_updated: Duration,
 
+	/// The last time when the liquidity bounds were updated with new payment information (i.e.
+	/// ignoring decays).
+	last_datapoint: Duration,
+
 	_padding: [u64; LIQ_PADDING_LEN],
 }
 
@@ -821,7 +826,7 @@ struct ChannelLiquidity {
 //
 // The next two cache lines will have the historical points, which we only access last during
 // scoring, followed by the last_updated `Duration`s (which we do not need during scoring). The
-// extra padding brings us up to a clean four cache lines.
+// `last_datapoint` `Duration` and extra padding bring us up to a clean 4 cache lines.
 const _LIQUIDITY_MAP_SIZING_CHECK: usize = 256 - ::core::mem::size_of::<(u64, ChannelLiquidity)>();
 const _LIQUIDITY_MAP_SIZING_CHECK_2: usize = ::core::mem::size_of::<(u64, ChannelLiquidity)>() - 256;
 
@@ -833,6 +838,7 @@ struct DirectedChannelLiquidity<L: Deref<Target = u64>, HT: Deref<Target = Histo
 	capacity_msat: u64,
 	last_updated: T,
 	offset_history_last_updated: T,
+	last_datapoint: T,
 }
 
 impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ProbabilisticScorer<G, L> where L::Target: Logger {
@@ -1009,6 +1015,7 @@ impl ChannelLiquidity {
 			liquidity_history: HistoricalLiquidityTracker::new(),
 			last_updated,
 			offset_history_last_updated: last_updated,
+			last_datapoint: last_updated,
 			_padding: [0; LIQ_PADDING_LEN],
 		}
 	}
@@ -1033,6 +1040,7 @@ impl ChannelLiquidity {
 			capacity_msat,
 			last_updated: &self.last_updated,
 			offset_history_last_updated: &self.offset_history_last_updated,
+			last_datapoint: &self.last_datapoint,
 		}
 	}
 
@@ -1056,6 +1064,7 @@ impl ChannelLiquidity {
 			capacity_msat,
 			last_updated: &mut self.last_updated,
 			offset_history_last_updated: &mut self.offset_history_last_updated,
+			last_datapoint: &mut self.last_datapoint,
 		}
 	}
 
@@ -1335,6 +1344,7 @@ DirectedChannelLiquidity<L, HT, T> {
 			*self.max_liquidity_offset_msat = 0;
 		}
 		*self.last_updated = duration_since_epoch;
+		*self.last_datapoint = duration_since_epoch;
 	}
 
 	/// Adjusts the upper bound of the channel liquidity balance in this direction.
@@ -1344,6 +1354,7 @@ DirectedChannelLiquidity<L, HT, T> {
 			*self.min_liquidity_offset_msat = 0;
 		}
 		*self.last_updated = duration_since_epoch;
+		*self.last_datapoint = duration_since_epoch;
 	}
 }
 
@@ -1953,6 +1964,7 @@ impl Writeable for ChannelLiquidity {
 			(5, self.liquidity_history.writeable_min_offset_history(), required),
 			(7, self.liquidity_history.writeable_max_offset_history(), required),
 			(9, self.offset_history_last_updated, required),
+			(11, self.last_datapoint, required),
 		});
 		Ok(())
 	}
@@ -1969,6 +1981,7 @@ impl Readable for ChannelLiquidity {
 		let mut max_liquidity_offset_history: Option<HistoricalBucketRangeTracker> = None;
 		let mut last_updated = Duration::from_secs(0);
 		let mut offset_history_last_updated = None;
+		let mut last_datapoint = None;
 		read_tlv_fields!(r, {
 			(0, min_liquidity_offset_msat, required),
 			(1, legacy_min_liq_offset_history, option),
@@ -1978,6 +1991,7 @@ impl Readable for ChannelLiquidity {
 			(5, min_liquidity_offset_history, option),
 			(7, max_liquidity_offset_history, option),
 			(9, offset_history_last_updated, option),
+			(11, last_datapoint, option),
 		});
 
 		if min_liquidity_offset_history.is_none() {
@@ -2002,6 +2016,7 @@ impl Readable for ChannelLiquidity {
 			),
 			last_updated,
 			offset_history_last_updated: offset_history_last_updated.unwrap_or(last_updated),
+			last_datapoint: last_datapoint.unwrap_or(last_updated),
 			_padding: [0; LIQ_PADDING_LEN],
 		})
 	}
@@ -2175,20 +2190,21 @@ mod tests {
 		let logger = TestLogger::new();
 		let last_updated = Duration::ZERO;
 		let offset_history_last_updated = Duration::ZERO;
+		let last_datapoint = Duration::ZERO;
 		let network_graph = network_graph(&logger);
 		let decay_params = ProbabilisticScoringDecayParameters::default();
 		let mut scorer = ProbabilisticScorer::new(decay_params, &network_graph, &logger)
 			.with_channel(42,
 				ChannelLiquidity {
 					min_liquidity_offset_msat: 700, max_liquidity_offset_msat: 100,
-					last_updated, offset_history_last_updated,
+					last_updated, offset_history_last_updated, last_datapoint,
 					liquidity_history: HistoricalLiquidityTracker::new(),
 					_padding: [0; LIQ_PADDING_LEN],
 				})
 			.with_channel(43,
 				ChannelLiquidity {
 					min_liquidity_offset_msat: 700, max_liquidity_offset_msat: 100,
-					last_updated, offset_history_last_updated,
+					last_updated, offset_history_last_updated, last_datapoint,
 					liquidity_history: HistoricalLiquidityTracker::new(),
 					_padding: [0; LIQ_PADDING_LEN],
 				});
@@ -2256,13 +2272,14 @@ mod tests {
 		let logger = TestLogger::new();
 		let last_updated = Duration::ZERO;
 		let offset_history_last_updated = Duration::ZERO;
+		let last_datapoint = Duration::ZERO;
 		let network_graph = network_graph(&logger);
 		let decay_params = ProbabilisticScoringDecayParameters::default();
 		let mut scorer = ProbabilisticScorer::new(decay_params, &network_graph, &logger)
 			.with_channel(42,
 				ChannelLiquidity {
 					min_liquidity_offset_msat: 200, max_liquidity_offset_msat: 400,
-					last_updated, offset_history_last_updated,
+					last_updated, offset_history_last_updated, last_datapoint,
 					liquidity_history: HistoricalLiquidityTracker::new(),
 					_padding: [0; LIQ_PADDING_LEN],
 				});
@@ -2317,13 +2334,14 @@ mod tests {
 		let logger = TestLogger::new();
 		let last_updated = Duration::ZERO;
 		let offset_history_last_updated = Duration::ZERO;
+		let last_datapoint = Duration::ZERO;
 		let network_graph = network_graph(&logger);
 		let decay_params = ProbabilisticScoringDecayParameters::default();
 		let mut scorer = ProbabilisticScorer::new(decay_params, &network_graph, &logger)
 			.with_channel(42,
 				ChannelLiquidity {
 					min_liquidity_offset_msat: 200, max_liquidity_offset_msat: 400,
-					last_updated, offset_history_last_updated,
+					last_updated, offset_history_last_updated, last_datapoint,
 					liquidity_history: HistoricalLiquidityTracker::new(),
 					_padding: [0; LIQ_PADDING_LEN],
 				});
@@ -2430,6 +2448,7 @@ mod tests {
 		let logger = TestLogger::new();
 		let last_updated = Duration::ZERO;
 		let offset_history_last_updated = Duration::ZERO;
+		let last_datapoint = Duration::ZERO;
 		let network_graph = network_graph(&logger);
 		let params = ProbabilisticScoringFeeParameters {
 			liquidity_penalty_multiplier_msat: 1_000,
@@ -2443,7 +2462,7 @@ mod tests {
 			.with_channel(42,
 				ChannelLiquidity {
 					min_liquidity_offset_msat: 40, max_liquidity_offset_msat: 40,
-					last_updated, offset_history_last_updated,
+					last_updated, offset_history_last_updated, last_datapoint,
 					liquidity_history: HistoricalLiquidityTracker::new(),
 					_padding: [0; LIQ_PADDING_LEN],
 				});