_ 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 #[cfg(not(feature = "no-std"))]
  56 use core::time::Duration;
  57 #[cfg(not(feature = "no-std"))]
  58 use std::time::Instant;
  59
  60 /// [`routing::Score`] implementation that provides reasonable default behavior.
  61 ///
  62 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
  63 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
  64 ///
  65 /// See [module-level documentation] for usage.
  66 ///
  67 /// [module-level documentation]: crate::routing::scorer
  68 pub struct Scorer {
  69         params: ScoringParameters,
  70         #[cfg(not(feature = "no-std"))]
  71         channel_failures: HashMap<u64, (u64, Instant)>,
  72         #[cfg(feature = "no-std")]
  73         channel_failures: HashMap<u64, u64>,
  74 }
  75
  76 /// Parameters for configuring [`Scorer`].
  77 pub struct ScoringParameters {
  78         /// A fixed penalty in msats to apply to each channel.
  79         pub base_penalty_msat: u64,
  80
  81         /// A penalty in msats to apply to a channel upon failure.
  82         ///
  83         /// This may be reduced over time based on [`failure_penalty_half_life`].
  84         ///
  85         /// [`failure_penalty_half_life`]: Self::failure_penalty_half_life
  86         pub failure_penalty_msat: u64,
  87
  88         /// The time needed before any accumulated channel failure penalties are cut in half.
  89         #[cfg(not(feature = "no-std"))]
  90         pub failure_penalty_half_life: Duration,
  91 }
  92
  93 impl Scorer {
  94         /// Creates a new scorer using the given scoring parameters.
  95         pub fn new(params: ScoringParameters) -> Self {
  96                 Self {
  97                         params,
  98                         channel_failures: HashMap::new(),
  99                 }
 100         }
 101
 102         /// Creates a new scorer using `penalty_msat` as a fixed channel penalty.
 103         #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
 104         pub fn with_fixed_penalty(penalty_msat: u64) -> Self {
 105                 Self::new(ScoringParameters {
 106                         base_penalty_msat: penalty_msat,
 107                         failure_penalty_msat: 0,
 108                         #[cfg(not(feature = "no-std"))]
 109                         failure_penalty_half_life: Duration::from_secs(0),
 110                 })
 111         }
 112
 113         #[cfg(not(feature = "no-std"))]
 114         fn decay_from(&self, penalty_msat: u64, last_failure: &Instant) -> u64 {
 115                 decay_from(penalty_msat, last_failure, self.params.failure_penalty_half_life)
 116         }
 117 }
 118
 119 impl Default for Scorer {
 120         fn default() -> Self {
 121                 Scorer::new(ScoringParameters::default())
 122         }
 123 }
 124
 125 impl Default for ScoringParameters {
 126         fn default() -> Self {
 127                 Self {
 128                         base_penalty_msat: 500,
 129                         failure_penalty_msat: 1024 * 1000,
 130                         #[cfg(not(feature = "no-std"))]
 131                         failure_penalty_half_life: Duration::from_secs(3600),
 132                 }
 133         }
 134 }
 135
 136 impl routing::Score for Scorer {
 137         fn channel_penalty_msat(
 138                 &self, short_channel_id: u64, _source: &NodeId, _target: &NodeId
 139         ) -> u64 {
 140                 #[cfg(not(feature = "no-std"))]
 141                 let failure_penalty_msat = match self.channel_failures.get(&short_channel_id) {
 142                         Some((penalty_msat, last_failure)) => self.decay_from(*penalty_msat, last_failure),
 143                         None => 0,
 144                 };
 145                 #[cfg(feature = "no-std")]
 146                 let failure_penalty_msat =
 147                         self.channel_failures.get(&short_channel_id).copied().unwrap_or(0);
 148
 149                 self.params.base_penalty_msat + failure_penalty_msat
 150         }
 151
 152         fn payment_path_failed(&mut self, _path: &Vec<RouteHop>, short_channel_id: u64) {
 153                 let failure_penalty_msat = self.params.failure_penalty_msat;
 154                 #[cfg(not(feature = "no-std"))]
 155                 {
 156                         let half_life = self.params.failure_penalty_half_life;
 157                         self.channel_failures
 158                                 .entry(short_channel_id)
 159                                 .and_modify(|(penalty_msat, last_failure)| {
 160                                         let decayed_penalty = decay_from(*penalty_msat, last_failure, half_life);
 161                                         *penalty_msat = decayed_penalty + failure_penalty_msat;
 162                                         *last_failure = Instant::now();
 163                                 })
 164                                 .or_insert_with(|| (failure_penalty_msat, Instant::now()));
 165                 }
 166                 #[cfg(feature = "no-std")]
 167                 self.channel_failures
 168                         .entry(short_channel_id)
 169                         .and_modify(|penalty_msat| *penalty_msat += failure_penalty_msat)
 170                         .or_insert(failure_penalty_msat);
 171         }
 172 }
 173
 174 #[cfg(not(feature = "no-std"))]
 175 fn decay_from(penalty_msat: u64, last_failure: &Instant, half_life: Duration) -> u64 {
 176         let decays = last_failure.elapsed().as_secs().checked_div(half_life.as_secs());
 177         match decays {
 178                 Some(decays) => penalty_msat >> decays,
 179                 None => 0,
 180         }
 181 }