_ Git - rust-lightning/blob - lightning/src/routing/scorer.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! Utilities for scoring payment channels.
  11 //!
  12 //! [`Scorer`] may be given to [`find_route`] to score payment channels during path finding when a
  13 //! custom [`routing::Score`] implementation is not needed.
  14 //!
  15 //! # Example
  16 //!
  17 //! ```
  18 //! # extern crate secp256k1;
  19 //! #
  20 //! # use lightning::routing::network_graph::NetworkGraph;
  21 //! # use lightning::routing::router::{RouteParameters, find_route};
  22 //! # use lightning::routing::scorer::{Scorer, ScoringParameters};
  23 //! # use lightning::util::logger::{Logger, Record};
  24 //! # use secp256k1::key::PublicKey;
  25 //! #
  26 //! # struct FakeLogger {};
  27 //! # impl Logger for FakeLogger {
  28 //! #     fn log(&self, record: &Record) { unimplemented!() }
  29 //! # }
  30 //! # fn find_scored_route(payer: PublicKey, params: RouteParameters, network_graph: NetworkGraph) {
  31 //! # let logger = FakeLogger {};
  32 //! #
  33 //! // Use the default channel penalties.
  34 //! let scorer = Scorer::default();
  35 //!
  36 //! // Or use custom channel penalties.
  37 //! let scorer = Scorer::new(ScoringParameters {
  38 //!     base_penalty_msat: 1000,
  39 //!     failure_penalty_msat: 2 * 1024 * 1000,
  40 //!     ..ScoringParameters::default()
  41 //! });
  42 //!
  43 //! let route = find_route(&payer, &params, &network_graph, None, &logger, &scorer);
  44 //! # }
  45 //! ```
  46 //!
  47 //! [`find_route`]: crate::routing::router::find_route
  48
  49 use routing;
  50
  51 use routing::network_graph::NodeId;
  52 use routing::router::RouteHop;
  53
  54 use prelude::*;
  55 use core::time::Duration;
  56 #[cfg(not(feature = "no-std"))]
  57 use std::time::Instant;
  58
  59 /// [`routing::Score`] implementation that provides reasonable default behavior.
  60 ///
  61 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
  62 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
  63 ///
  64 /// See [module-level documentation] for usage.
  65 ///
  66 /// [module-level documentation]: crate::routing::scorer
  67 pub struct Scorer {
  68         params: ScoringParameters,
  69         // TODO: Remove entries of closed channels.
  70         channel_failures: HashMap<u64, ChannelFailure>,
  71 }
  72
  73 /// Parameters for configuring [`Scorer`].
  74 pub struct ScoringParameters {
  75         /// A fixed penalty in msats to apply to each channel.
  76         pub base_penalty_msat: u64,
  77
  78         /// A penalty in msats to apply to a channel upon failing to relay a payment.
  79         ///
  80         /// This accumulates for each failure but may be reduced over time based on
  81         /// [`failure_penalty_half_life`].
  82         ///
  83         /// [`failure_penalty_half_life`]: Self::failure_penalty_half_life
  84         pub failure_penalty_msat: u64,
  85
  86         /// The time required to elapse before any accumulated [`failure_penalty_msat`] penalties are
  87         /// cut in half.
  88         ///
  89         /// [`failure_penalty_msat`]: Self::failure_penalty_msat
  90         pub failure_penalty_half_life: Duration,
  91 }
  92
  93 /// Accounting for penalties against a channel for failing to relay any payments.
  94 ///
  95 /// Penalties decay over time, though accumulate as more failures occur.
  96 struct ChannelFailure {
  97         /// Accumulated penalty in msats for the channel as of `last_failed`.
  98         undecayed_penalty_msat: u64,
  99
 100         /// Last time the channel failed. Used to decay `undecayed_penalty_msat`.
 101         #[cfg(not(feature = "no-std"))]
 102         last_failed: Instant,
 103 }
 104
 105 impl Scorer {
 106         /// Creates a new scorer using the given scoring parameters.
 107         pub fn new(params: ScoringParameters) -> Self {
 108                 Self {
 109                         params,
 110                         channel_failures: HashMap::new(),
 111                 }
 112         }
 113
 114         /// Creates a new scorer using `penalty_msat` as a fixed channel penalty.
 115         #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
 116         pub fn with_fixed_penalty(penalty_msat: u64) -> Self {
 117                 Self::new(ScoringParameters {
 118                         base_penalty_msat: penalty_msat,
 119                         failure_penalty_msat: 0,
 120                         failure_penalty_half_life: Duration::from_secs(0),
 121                 })
 122         }
 123 }
 124
 125 impl ChannelFailure {
 126         fn new(failure_penalty_msat: u64) -> Self {
 127                 Self {
 128                         undecayed_penalty_msat: failure_penalty_msat,
 129                         #[cfg(not(feature = "no-std"))]
 130                         last_failed: Instant::now(),
 131                 }
 132         }
 133
 134         fn add_penalty(&mut self, failure_penalty_msat: u64, half_life: Duration) {
 135                 self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) + failure_penalty_msat;
 136                 #[cfg(not(feature = "no-std"))]
 137                 {
 138                         self.last_failed = Instant::now();
 139                 }
 140         }
 141
 142         fn decayed_penalty_msat(&self, half_life: Duration) -> u64 {
 143                 let decays = self.elapsed().as_secs().checked_div(half_life.as_secs());
 144                 match decays {
 145                         Some(decays) => self.undecayed_penalty_msat >> decays,
 146                         None => 0,
 147                 }
 148         }
 149
 150         fn elapsed(&self) -> Duration {
 151                 #[cfg(not(feature = "no-std"))]
 152                 return self.last_failed.elapsed();
 153                 #[cfg(feature = "no-std")]
 154                 return Duration::from_secs(0);
 155         }
 156 }
 157
 158 impl Default for Scorer {
 159         fn default() -> Self {
 160                 Scorer::new(ScoringParameters::default())
 161         }
 162 }
 163
 164 impl Default for ScoringParameters {
 165         fn default() -> Self {
 166                 Self {
 167                         base_penalty_msat: 500,
 168                         failure_penalty_msat: 1024 * 1000,
 169                         failure_penalty_half_life: Duration::from_secs(3600),
 170                 }
 171         }
 172 }
 173
 174 impl routing::Score for Scorer {
 175         fn channel_penalty_msat(
 176                 &self, short_channel_id: u64, _source: &NodeId, _target: &NodeId
 177         ) -> u64 {
 178                 let failure_penalty_msat = self.channel_failures
 179                         .get(&short_channel_id)
 180                         .map_or(0, |value| value.decayed_penalty_msat(self.params.failure_penalty_half_life));
 181
 182                 self.params.base_penalty_msat + failure_penalty_msat
 183         }
 184
 185         fn payment_path_failed(&mut self, _path: &Vec<RouteHop>, short_channel_id: u64) {
 186                 let failure_penalty_msat = self.params.failure_penalty_msat;
 187                 let half_life = self.params.failure_penalty_half_life;
 188                 self.channel_failures
 189                         .entry(short_channel_id)
 190                         .and_modify(|failure| failure.add_penalty(failure_penalty_msat, half_life))
 191                         .or_insert_with(|| ChannelFailure::new(failure_penalty_msat));
 192         }
 193 }