From 88cf9b33c3982376b22d34ddaa4a958bf0d11bfd Mon Sep 17 00:00:00 2001 From: Jeffrey Czyz Date: Thu, 28 Oct 2021 23:23:45 -0500 Subject: [PATCH] Refactor channel failure penalty logic Move channel failure penalty logic into a ChannelFailure abstraction. This encapsulates the logic for accumulating penalties and decaying them over time. It also is responsible for the no-std behavior. This cleans up Scorer and will make it easier to serialize it. --- lightning/src/routing/scorer.rs | 104 ++++++++++++++++++-------------- 1 file changed, 58 insertions(+), 46 deletions(-) diff --git a/lightning/src/routing/scorer.rs b/lightning/src/routing/scorer.rs index 26fb05a72..9089a8932 100644 --- a/lightning/src/routing/scorer.rs +++ b/lightning/src/routing/scorer.rs @@ -52,7 +52,6 @@ use routing::network_graph::NodeId; use routing::router::RouteHop; use prelude::*; -#[cfg(not(feature = "no-std"))] use core::time::Duration; #[cfg(not(feature = "no-std"))] use std::time::Instant; @@ -67,10 +66,8 @@ use std::time::Instant; /// [module-level documentation]: crate::routing::scorer pub struct Scorer { params: ScoringParameters, - #[cfg(not(feature = "no-std"))] - channel_failures: HashMap, - #[cfg(feature = "no-std")] - channel_failures: HashMap, + // TODO: Remove entries of closed channels. + channel_failures: HashMap, } /// Parameters for configuring [`Scorer`]. @@ -78,18 +75,33 @@ 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 failure. + /// A penalty in msats to apply to a channel upon failing to relay a payment. /// - /// This may be reduced over time based on [`failure_penalty_half_life`]. + /// 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 needed before any accumulated channel failure penalties are cut in half. - #[cfg(not(feature = "no-std"))] + /// The time required to elapse before any accumulated [`failure_penalty_msat`] penalties are + /// cut in half. + /// + /// [`failure_penalty_msat`]: Self::failure_penalty_msat pub failure_penalty_half_life: Duration, } +/// Accounting for penalties against a channel for failing to relay any payments. +/// +/// Penalties decay over time, though accumulate as more failures occur. +struct ChannelFailure { + /// 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`. + #[cfg(not(feature = "no-std"))] + last_failed: Instant, +} + impl Scorer { /// Creates a new scorer using the given scoring parameters. pub fn new(params: ScoringParameters) -> Self { @@ -105,14 +117,41 @@ impl Scorer { Self::new(ScoringParameters { base_penalty_msat: penalty_msat, failure_penalty_msat: 0, - #[cfg(not(feature = "no-std"))] failure_penalty_half_life: Duration::from_secs(0), }) } +} - #[cfg(not(feature = "no-std"))] - fn decay_from(&self, penalty_msat: u64, last_failure: &Instant) -> u64 { - decay_from(penalty_msat, last_failure, self.params.failure_penalty_half_life) +impl ChannelFailure { + fn new(failure_penalty_msat: u64) -> Self { + Self { + undecayed_penalty_msat: failure_penalty_msat, + #[cfg(not(feature = "no-std"))] + last_failed: Instant::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; + #[cfg(not(feature = "no-std"))] + { + self.last_failed = Instant::now(); + } + } + + fn decayed_penalty_msat(&self, half_life: Duration) -> u64 { + let decays = self.elapsed().as_secs().checked_div(half_life.as_secs()); + match decays { + Some(decays) => self.undecayed_penalty_msat >> decays, + None => 0, + } + } + + fn elapsed(&self) -> Duration { + #[cfg(not(feature = "no-std"))] + return self.last_failed.elapsed(); + #[cfg(feature = "no-std")] + return Duration::from_secs(0); } } @@ -127,7 +166,6 @@ impl Default for ScoringParameters { Self { base_penalty_msat: 500, failure_penalty_msat: 1024 * 1000, - #[cfg(not(feature = "no-std"))] failure_penalty_half_life: Duration::from_secs(3600), } } @@ -137,45 +175,19 @@ impl routing::Score for Scorer { fn channel_penalty_msat( &self, short_channel_id: u64, _source: &NodeId, _target: &NodeId ) -> u64 { - #[cfg(not(feature = "no-std"))] - let failure_penalty_msat = match self.channel_failures.get(&short_channel_id) { - Some((penalty_msat, last_failure)) => self.decay_from(*penalty_msat, last_failure), - None => 0, - }; - #[cfg(feature = "no-std")] - let failure_penalty_msat = - self.channel_failures.get(&short_channel_id).copied().unwrap_or(0); + 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: &Vec, short_channel_id: u64) { let failure_penalty_msat = self.params.failure_penalty_msat; - #[cfg(not(feature = "no-std"))] - { - let half_life = self.params.failure_penalty_half_life; - self.channel_failures - .entry(short_channel_id) - .and_modify(|(penalty_msat, last_failure)| { - let decayed_penalty = decay_from(*penalty_msat, last_failure, half_life); - *penalty_msat = decayed_penalty + failure_penalty_msat; - *last_failure = Instant::now(); - }) - .or_insert_with(|| (failure_penalty_msat, Instant::now())); - } - #[cfg(feature = "no-std")] + let half_life = self.params.failure_penalty_half_life; self.channel_failures .entry(short_channel_id) - .and_modify(|penalty_msat| *penalty_msat += failure_penalty_msat) - .or_insert(failure_penalty_msat); - } -} - -#[cfg(not(feature = "no-std"))] -fn decay_from(penalty_msat: u64, last_failure: &Instant, half_life: Duration) -> u64 { - let decays = last_failure.elapsed().as_secs().checked_div(half_life.as_secs()); - match decays { - Some(decays) => penalty_msat >> decays, - None => 0, + .and_modify(|failure| failure.add_penalty(failure_penalty_msat, half_life)) + .or_insert_with(|| ChannelFailure::new(failure_penalty_msat)); } } -- 2.39.5