X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Frouting%2Fscorer.rs;h=df744ce686b55bc4777e7ddceb824625653af0ee;hb=6f053e48b021d516b562a449c91f977397502e73;hp=e3f5c8679b68d6b57ca418b70befdc0ff34e35d7;hpb=2d102a3065d7a438d5c88fffcad36545a0822bfa;p=rust-lightning

diff --git a/lightning/src/routing/scorer.rs b/lightning/src/routing/scorer.rs
index e3f5c867..df744ce6 100644
--- a/lightning/src/routing/scorer.rs
+++ b/lightning/src/routing/scorer.rs
@@ -19,7 +19,7 @@
 //! #
 //! # use lightning::routing::network_graph::NetworkGraph;
 //! # use lightning::routing::router::{RouteParameters, find_route};
-//! # use lightning::routing::scorer::Scorer;
+//! # use lightning::routing::scorer::{Scorer, ScoringParameters};
 //! # use lightning::util::logger::{Logger, Record};
 //! # use secp256k1::key::PublicKey;
 //! #
@@ -30,52 +30,523 @@
 //! # fn find_scored_route(payer: PublicKey, params: RouteParameters, network_graph: NetworkGraph) {
 //! # let logger = FakeLogger {};
 //! #
-//! // Use the default channel penalty.
+//! // Use the default channel penalties.
 //! let scorer = Scorer::default();
 //!
-//! // Or use a custom channel penalty.
-//! let scorer = Scorer::new(1_000);
+//! // Or use custom channel penalties.
+//! let scorer = Scorer::new(ScoringParameters {
+//!     base_penalty_msat: 1000,
+//!     failure_penalty_msat: 2 * 1024 * 1000,
+//!     ..ScoringParameters::default()
+//! });
 //!
 //! let route = find_route(&payer, &params, &network_graph, None, &logger, &scorer);
 //! # }
 //! ```
 //!
+//! # Note
+//!
+//! If persisting [`Scorer`], it must be restored using the same [`Time`] parameterization. Using a
+//! different type results in undefined behavior. Specifically, persisting when built with feature
+//! `no-std` and restoring without it, or vice versa, uses different types and thus is undefined.
+//!
 //! [`find_route`]: crate::routing::router::find_route
 
 use routing;
 
+use ln::msgs::DecodeError;
 use routing::network_graph::NodeId;
+use routing::router::RouteHop;
+use util::ser::{Readable, Writeable, Writer};
+
+use prelude::*;
+use core::ops::Sub;
+use core::time::Duration;
+use io::{self, Read};
 
 /// [`routing::Score`] implementation that provides reasonable default behavior.
 ///
 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
-/// slightly higher fees are available.
+/// slightly higher fees are available. Will further penalize channels that fail to relay payments.
 ///
 /// See [module-level documentation] for usage.
 ///
 /// [module-level documentation]: crate::routing::scorer
-pub struct Scorer {
-	base_penalty_msat: u64,
+pub type Scorer = ScorerUsingTime::<DefaultTime>;
+
+/// Time used by [`Scorer`].
+#[cfg(not(feature = "no-std"))]
+pub type DefaultTime = std::time::Instant;
+
+/// Time used by [`Scorer`].
+#[cfg(feature = "no-std")]
+pub type DefaultTime = Eternity;
+
+/// [`routing::Score`] implementation parameterized by [`Time`].
+///
+/// See [`Scorer`] for details.
+///
+/// # Note
+///
+/// Mixing [`Time`] types between serialization and deserialization results in undefined behavior.
+pub struct ScorerUsingTime<T: Time> {
+	params: ScoringParameters,
+	// TODO: Remove entries of closed channels.
+	channel_failures: HashMap<u64, ChannelFailure<T>>,
+}
+
+/// Parameters for configuring [`Scorer`].
+pub struct ScoringParameters {
+	/// A fixed penalty in msats to apply to each channel.
+	pub base_penalty_msat: u64,
+
+	/// A penalty in msats to apply to a channel upon failing to relay a payment.
+	///
+	/// This accumulates for each failure but may be reduced over time based on
+	/// [`failure_penalty_half_life`].
+	///
+	/// [`failure_penalty_half_life`]: Self::failure_penalty_half_life
+	pub failure_penalty_msat: u64,
+
+	/// The time required to elapse before any accumulated [`failure_penalty_msat`] penalties are
+	/// cut in half.
+	///
+	/// # Note
+	///
+	/// When time is an [`Eternity`], as is default when enabling feature `no-std`, it will never
+	/// elapse. Therefore, this penalty will never decay.
+	///
+	/// [`failure_penalty_msat`]: Self::failure_penalty_msat
+	pub failure_penalty_half_life: Duration,
+}
+
+impl_writeable_tlv_based!(ScoringParameters, {
+	(0, base_penalty_msat, required),
+	(2, failure_penalty_msat, required),
+	(4, failure_penalty_half_life, required),
+});
+
+/// Accounting for penalties against a channel for failing to relay any payments.
+///
+/// Penalties decay over time, though accumulate as more failures occur.
+struct ChannelFailure<T: Time> {
+	/// Accumulated penalty in msats for the channel as of `last_failed`.
+	undecayed_penalty_msat: u64,
+
+	/// Last time the channel failed. Used to decay `undecayed_penalty_msat`.
+	last_failed: T,
+}
+
+/// A measurement of time.
+pub trait Time: Sub<Duration, Output = Self> where Self: Sized {
+	/// Returns an instance corresponding to the current moment.
+	fn now() -> Self;
+
+	/// Returns the amount of time elapsed since `self` was created.
+	fn elapsed(&self) -> Duration;
+
+	/// Returns the amount of time passed since the beginning of [`Time`].
+	///
+	/// Used during (de-)serialization.
+	fn duration_since_epoch() -> Duration;
 }
 
-impl Scorer {
-	/// Creates a new scorer using `base_penalty_msat` as the channel penalty.
-	pub fn new(base_penalty_msat: u64) -> Self {
-		Self { base_penalty_msat }
+impl<T: Time> ScorerUsingTime<T> {
+	/// Creates a new scorer using the given scoring parameters.
+	pub fn new(params: ScoringParameters) -> Self {
+		Self {
+			params,
+			channel_failures: HashMap::new(),
+		}
+	}
+
+	/// Creates a new scorer using `penalty_msat` as a fixed channel penalty.
+	#[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
+	pub fn with_fixed_penalty(penalty_msat: u64) -> Self {
+		Self::new(ScoringParameters {
+			base_penalty_msat: penalty_msat,
+			failure_penalty_msat: 0,
+			failure_penalty_half_life: Duration::from_secs(0),
+		})
 	}
 }
 
-impl Default for Scorer {
-	/// Creates a new scorer using 500 msat as the channel penalty.
+impl<T: Time> ChannelFailure<T> {
+	fn new(failure_penalty_msat: u64) -> Self {
+		Self {
+			undecayed_penalty_msat: failure_penalty_msat,
+			last_failed: T::now(),
+		}
+	}
+
+	fn add_penalty(&mut self, failure_penalty_msat: u64, half_life: Duration) {
+		self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) + failure_penalty_msat;
+		self.last_failed = T::now();
+	}
+
+	fn decayed_penalty_msat(&self, half_life: Duration) -> u64 {
+		let decays = self.last_failed.elapsed().as_secs().checked_div(half_life.as_secs());
+		match decays {
+			Some(decays) => self.undecayed_penalty_msat >> decays,
+			None => 0,
+		}
+	}
+}
+
+impl<T: Time> Default for ScorerUsingTime<T> {
 	fn default() -> Self {
-		Scorer::new(500)
+		Self::new(ScoringParameters::default())
 	}
 }
 
-impl routing::Score for Scorer {
+impl Default for ScoringParameters {
+	fn default() -> Self {
+		Self {
+			base_penalty_msat: 500,
+			failure_penalty_msat: 1024 * 1000,
+			failure_penalty_half_life: Duration::from_secs(3600),
+		}
+	}
+}
+
+impl<T: Time> routing::Score for ScorerUsingTime<T> {
 	fn channel_penalty_msat(
-		&self, _short_channel_id: u64, _source: &NodeId, _target: &NodeId
+		&self, short_channel_id: u64, _source: &NodeId, _target: &NodeId
 	) -> u64 {
-		self.base_penalty_msat
+		let failure_penalty_msat = self.channel_failures
+			.get(&short_channel_id)
+			.map_or(0, |value| value.decayed_penalty_msat(self.params.failure_penalty_half_life));
+
+		self.params.base_penalty_msat + failure_penalty_msat
+	}
+
+	fn payment_path_failed(&mut self, _path: &[&RouteHop], short_channel_id: u64) {
+		let failure_penalty_msat = self.params.failure_penalty_msat;
+		let half_life = self.params.failure_penalty_half_life;
+		self.channel_failures
+			.entry(short_channel_id)
+			.and_modify(|failure| failure.add_penalty(failure_penalty_msat, half_life))
+			.or_insert_with(|| ChannelFailure::new(failure_penalty_msat));
+	}
+}
+
+#[cfg(not(feature = "no-std"))]
+impl Time for std::time::Instant {
+	fn now() -> Self {
+		std::time::Instant::now()
+	}
+
+	fn duration_since_epoch() -> Duration {
+		use std::time::SystemTime;
+		SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap()
+	}
+
+	fn elapsed(&self) -> Duration {
+		std::time::Instant::elapsed(self)
+	}
+}
+
+/// A state in which time has no meaning.
+#[derive(Debug, PartialEq, Eq)]
+pub struct Eternity;
+
+impl Time for Eternity {
+	fn now() -> Self {
+		Self
+	}
+
+	fn duration_since_epoch() -> Duration {
+		Duration::from_secs(0)
+	}
+
+	fn elapsed(&self) -> Duration {
+		Duration::from_secs(0)
+	}
+}
+
+impl Sub<Duration> for Eternity {
+	type Output = Self;
+
+	fn sub(self, _other: Duration) -> Self {
+		self
+	}
+}
+
+impl<T: Time> Writeable for ScorerUsingTime<T> {
+	#[inline]
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		self.params.write(w)?;
+		self.channel_failures.write(w)?;
+		write_tlv_fields!(w, {});
+		Ok(())
+	}
+}
+
+impl<T: Time> Readable for ScorerUsingTime<T> {
+	#[inline]
+	fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
+		let res = Ok(Self {
+			params: Readable::read(r)?,
+			channel_failures: Readable::read(r)?,
+		});
+		read_tlv_fields!(r, {});
+		res
+	}
+}
+
+impl<T: Time> Writeable for ChannelFailure<T> {
+	#[inline]
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		let duration_since_epoch = T::duration_since_epoch() - self.last_failed.elapsed();
+		write_tlv_fields!(w, {
+			(0, self.undecayed_penalty_msat, required),
+			(2, duration_since_epoch, required),
+		});
+		Ok(())
+	}
+}
+
+impl<T: Time> Readable for ChannelFailure<T> {
+	#[inline]
+	fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
+		let mut undecayed_penalty_msat = 0;
+		let mut duration_since_epoch = Duration::from_secs(0);
+		read_tlv_fields!(r, {
+			(0, undecayed_penalty_msat, required),
+			(2, duration_since_epoch, required),
+		});
+		Ok(Self {
+			undecayed_penalty_msat,
+			last_failed: T::now() - (T::duration_since_epoch() - duration_since_epoch),
+		})
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::{Eternity, ScoringParameters, ScorerUsingTime, Time};
+
+	use routing::Score;
+	use routing::network_graph::NodeId;
+	use util::ser::{Readable, Writeable};
+
+	use bitcoin::secp256k1::PublicKey;
+	use core::cell::Cell;
+	use core::ops::Sub;
+	use core::time::Duration;
+	use io;
+
+	/// Time that can be advanced manually in tests.
+	#[derive(Debug, PartialEq, Eq)]
+	struct SinceEpoch(Duration);
+
+	impl SinceEpoch {
+		thread_local! {
+			static ELAPSED: Cell<Duration> = core::cell::Cell::new(Duration::from_secs(0));
+		}
+
+		fn advance(duration: Duration) {
+			Self::ELAPSED.with(|elapsed| elapsed.set(elapsed.get() + duration))
+		}
+	}
+
+	impl Time for SinceEpoch {
+		fn now() -> Self {
+			Self(Self::duration_since_epoch())
+		}
+
+		fn duration_since_epoch() -> Duration {
+			Self::ELAPSED.with(|elapsed| elapsed.get())
+		}
+
+		fn elapsed(&self) -> Duration {
+			Self::duration_since_epoch() - self.0
+		}
+	}
+
+	impl Sub<Duration> for SinceEpoch {
+		type Output = Self;
+
+		fn sub(self, other: Duration) -> Self {
+			Self(self.0 - other)
+		}
+	}
+
+	#[test]
+	fn time_passes_when_advanced() {
+		let now = SinceEpoch::now();
+		assert_eq!(now.elapsed(), Duration::from_secs(0));
+
+		SinceEpoch::advance(Duration::from_secs(1));
+		SinceEpoch::advance(Duration::from_secs(1));
+
+		let elapsed = now.elapsed();
+		let later = SinceEpoch::now();
+
+		assert_eq!(elapsed, Duration::from_secs(2));
+		assert_eq!(later - elapsed, now);
+	}
+
+	#[test]
+	fn time_never_passes_in_an_eternity() {
+		let now = Eternity::now();
+		let elapsed = now.elapsed();
+		let later = Eternity::now();
+
+		assert_eq!(now.elapsed(), Duration::from_secs(0));
+		assert_eq!(later - elapsed, now);
+	}
+
+	/// A scorer for testing with time that can be manually advanced.
+	type Scorer = ScorerUsingTime::<SinceEpoch>;
+
+	fn source_node_id() -> NodeId {
+		NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap())
+	}
+
+	fn target_node_id() -> NodeId {
+		NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap())
+	}
+
+	#[test]
+	fn penalizes_without_channel_failures() {
+		let scorer = Scorer::new(ScoringParameters {
+			base_penalty_msat: 1_000,
+			failure_penalty_msat: 512,
+			failure_penalty_half_life: Duration::from_secs(1),
+		});
+		let source = source_node_id();
+		let target = target_node_id();
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
+
+		SinceEpoch::advance(Duration::from_secs(1));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
+	}
+
+	#[test]
+	fn accumulates_channel_failure_penalties() {
+		let mut scorer = Scorer::new(ScoringParameters {
+			base_penalty_msat: 1_000,
+			failure_penalty_msat: 64,
+			failure_penalty_half_life: Duration::from_secs(10),
+		});
+		let source = source_node_id();
+		let target = target_node_id();
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_064);
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_128);
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_192);
+	}
+
+	#[test]
+	fn decays_channel_failure_penalties_over_time() {
+		let mut scorer = Scorer::new(ScoringParameters {
+			base_penalty_msat: 1_000,
+			failure_penalty_msat: 512,
+			failure_penalty_half_life: Duration::from_secs(10),
+		});
+		let source = source_node_id();
+		let target = target_node_id();
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
+
+		SinceEpoch::advance(Duration::from_secs(9));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
+
+		SinceEpoch::advance(Duration::from_secs(1));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_256);
+
+		SinceEpoch::advance(Duration::from_secs(10 * 8));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_001);
+
+		SinceEpoch::advance(Duration::from_secs(10));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
+
+		SinceEpoch::advance(Duration::from_secs(10));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
+	}
+
+	#[test]
+	fn accumulates_channel_failure_penalties_after_decay() {
+		let mut scorer = Scorer::new(ScoringParameters {
+			base_penalty_msat: 1_000,
+			failure_penalty_msat: 512,
+			failure_penalty_half_life: Duration::from_secs(10),
+		});
+		let source = source_node_id();
+		let target = target_node_id();
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
+
+		SinceEpoch::advance(Duration::from_secs(10));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_256);
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_768);
+
+		SinceEpoch::advance(Duration::from_secs(10));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_384);
+	}
+
+	#[test]
+	fn restores_persisted_channel_failure_penalties() {
+		let mut scorer = Scorer::new(ScoringParameters {
+			base_penalty_msat: 1_000,
+			failure_penalty_msat: 512,
+			failure_penalty_half_life: Duration::from_secs(10),
+		});
+		let source = source_node_id();
+		let target = target_node_id();
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
+
+		SinceEpoch::advance(Duration::from_secs(10));
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_256);
+
+		scorer.payment_path_failed(&[], 43);
+		assert_eq!(scorer.channel_penalty_msat(43, &source, &target), 1_512);
+
+		let mut serialized_scorer = Vec::new();
+		scorer.write(&mut serialized_scorer).unwrap();
+
+		let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
+		assert_eq!(deserialized_scorer.channel_penalty_msat(42, &source, &target), 1_256);
+		assert_eq!(deserialized_scorer.channel_penalty_msat(43, &source, &target), 1_512);
+	}
+
+	#[test]
+	fn decays_persisted_channel_failure_penalties() {
+		let mut scorer = Scorer::new(ScoringParameters {
+			base_penalty_msat: 1_000,
+			failure_penalty_msat: 512,
+			failure_penalty_half_life: Duration::from_secs(10),
+		});
+		let source = source_node_id();
+		let target = target_node_id();
+
+		scorer.payment_path_failed(&[], 42);
+		assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
+
+		let mut serialized_scorer = Vec::new();
+		scorer.write(&mut serialized_scorer).unwrap();
+
+		SinceEpoch::advance(Duration::from_secs(10));
+
+		let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
+		assert_eq!(deserialized_scorer.channel_penalty_msat(42, &source, &target), 1_256);
+
+		SinceEpoch::advance(Duration::from_secs(10));
+		assert_eq!(deserialized_scorer.channel_penalty_msat(42, &source, &target), 1_128);
 	}
 }