_ Git - rust-lightning/blob - lightning/src/routing/scoring.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 [`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::scoring::{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 //! # Note
  48 //!
  49 //! If persisting [`Scorer`], it must be restored using the same [`Time`] parameterization. Using a
  50 //! different type results in undefined behavior. Specifically, persisting when built with feature
  51 //! `no-std` and restoring without it, or vice versa, uses different types and thus is undefined.
  52 //!
  53 //! [`find_route`]: crate::routing::router::find_route
  54
  55 use ln::msgs::DecodeError;
  56 use routing::network_graph::NodeId;
  57 use routing::router::RouteHop;
  58 use util::ser::{Readable, Writeable, Writer};
  59
  60 use prelude::*;
  61 use core::cell::{RefCell, RefMut};
  62 use core::ops::{DerefMut, Sub};
  63 use core::time::Duration;
  64 use io::{self, Read}; use sync::{Mutex, MutexGuard};
  65
  66 /// We define Score ever-so-slightly differently based on whether we are being built for C bindings
  67 /// or not. For users, `LockableScore` must somehow be writeable to disk. For Rust users, this is
  68 /// no problem - you move a `Score` that implements `Writeable` into a `Mutex`, lock it, and now
  69 /// you have the original, concrete, `Score` type, which presumably implements `Writeable`.
  70 ///
  71 /// For C users, once you've moved the `Score` into a `LockableScore` all you have after locking it
  72 /// is an opaque trait object with an opaque pointer with no type info. Users could take the unsafe
  73 /// approach of blindly casting that opaque pointer to a concrete type and calling `Writeable` from
  74 /// there, but other languages downstream of the C bindings (e.g. Java) can't even do that.
  75 /// Instead, we really want `Score` and `LockableScore` to implement `Writeable` directly, which we
  76 /// do here by defining `Score` differently for `cfg(c_bindings)`.
  77 macro_rules! define_score { ($($supertrait: path)*) => {
  78 /// An interface used to score payment channels for path finding.
  79 ///
  80 ///     Scoring is in terms of fees willing to be paid in order to avoid routing through a channel.
  81 pub trait Score $(: $supertrait)* {
  82         /// Returns the fee in msats willing to be paid to avoid routing `send_amt_msat` through the
  83         /// given channel in the direction from `source` to `target`.
  84         ///
  85         /// The channel's capacity (less any other MPP parts which are also being considered for use in
  86         /// the same payment) is given by `channel_capacity_msat`. It may be guessed from various
  87         /// sources or assumed from no data at all.
  88         ///
  89         /// For hints provided in the invoice, we assume the channel has sufficient capacity to accept
  90         /// the invoice's full amount, and provide a `channel_capacity_msat` of `None`. In all other
  91         /// cases it is set to `Some`, even if we're guessing at the channel value.
  92         ///
  93         /// Your code should be overflow-safe through a `channel_capacity_msat` of 21 million BTC.
  94         fn channel_penalty_msat(&self, short_channel_id: u64, send_amt_msat: u64, channel_capacity_msat: Option<u64>, source: &NodeId, target: &NodeId) -> u64;
  95
  96         /// Handles updating channel penalties after failing to route through a channel.
  97         fn payment_path_failed(&mut self, path: &[&RouteHop], short_channel_id: u64);
  98 }
  99
 100 impl<S: Score, T: DerefMut<Target=S> $(+ $supertrait)*> Score for T {
 101         fn channel_penalty_msat(&self, short_channel_id: u64, send_amt_msat: u64, channel_capacity_msat: Option<u64>, source: &NodeId, target: &NodeId) -> u64 {
 102                 self.deref().channel_penalty_msat(short_channel_id, send_amt_msat, channel_capacity_msat, source, target)
 103         }
 104
 105         fn payment_path_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
 106                 self.deref_mut().payment_path_failed(path, short_channel_id)
 107         }
 108 }
 109 } }
 110
 111 #[cfg(c_bindings)]
 112 define_score!(Writeable);
 113 #[cfg(not(c_bindings))]
 114 define_score!();
 115
 116 /// A scorer that is accessed under a lock.
 117 ///
 118 /// Needed so that calls to [`Score::channel_penalty_msat`] in [`find_route`] can be made while
 119 /// having shared ownership of a scorer but without requiring internal locking in [`Score`]
 120 /// implementations. Internal locking would be detrimental to route finding performance and could
 121 /// result in [`Score::channel_penalty_msat`] returning a different value for the same channel.
 122 ///
 123 /// [`find_route`]: crate::routing::router::find_route
 124 pub trait LockableScore<'a> {
 125         /// The locked [`Score`] type.
 126         type Locked: 'a + Score;
 127
 128         /// Returns the locked scorer.
 129         fn lock(&'a self) -> Self::Locked;
 130 }
 131
 132 /// (C-not exported)
 133 impl<'a, T: 'a + Score> LockableScore<'a> for Mutex<T> {
 134         type Locked = MutexGuard<'a, T>;
 135
 136         fn lock(&'a self) -> MutexGuard<'a, T> {
 137                 Mutex::lock(self).unwrap()
 138         }
 139 }
 140
 141 impl<'a, T: 'a + Score> LockableScore<'a> for RefCell<T> {
 142         type Locked = RefMut<'a, T>;
 143
 144         fn lock(&'a self) -> RefMut<'a, T> {
 145                 self.borrow_mut()
 146         }
 147 }
 148
 149 #[cfg(c_bindings)]
 150 /// A concrete implementation of [`LockableScore`] which supports multi-threading.
 151 pub struct MultiThreadedLockableScore<S: Score> {
 152         score: Mutex<S>,
 153 }
 154 #[cfg(c_bindings)]
 155 /// (C-not exported)
 156 impl<'a, T: Score + 'a> LockableScore<'a> for MultiThreadedLockableScore<T> {
 157         type Locked = MutexGuard<'a, T>;
 158
 159         fn lock(&'a self) -> MutexGuard<'a, T> {
 160                 Mutex::lock(&self.score).unwrap()
 161         }
 162 }
 163
 164 #[cfg(c_bindings)]
 165 /// (C-not exported)
 166 impl<'a, T: Writeable> Writeable for RefMut<'a, T> {
 167         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 168                 T::write(&**self, writer)
 169         }
 170 }
 171
 172 #[cfg(c_bindings)]
 173 /// (C-not exported)
 174 impl<'a, S: Writeable> Writeable for MutexGuard<'a, S> {
 175         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 176                 S::write(&**self, writer)
 177         }
 178 }
 179
 180 /// [`Score`] implementation that provides reasonable default behavior.
 181 ///
 182 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
 183 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
 184 ///
 185 /// See [module-level documentation] for usage.
 186 ///
 187 /// [module-level documentation]: crate::routing::scoring
 188 pub type Scorer = ScorerUsingTime::<DefaultTime>;
 189
 190 /// Time used by [`Scorer`].
 191 #[cfg(not(feature = "no-std"))]
 192 pub type DefaultTime = std::time::Instant;
 193
 194 /// Time used by [`Scorer`].
 195 #[cfg(feature = "no-std")]
 196 pub type DefaultTime = Eternity;
 197
 198 /// [`Score`] implementation parameterized by [`Time`].
 199 ///
 200 /// See [`Scorer`] for details.
 201 ///
 202 /// # Note
 203 ///
 204 /// Mixing [`Time`] types between serialization and deserialization results in undefined behavior.
 205 pub struct ScorerUsingTime<T: Time> {
 206         params: ScoringParameters,
 207         // TODO: Remove entries of closed channels.
 208         channel_failures: HashMap<u64, ChannelFailure<T>>,
 209 }
 210
 211 /// Parameters for configuring [`Scorer`].
 212 pub struct ScoringParameters {
 213         /// A fixed penalty in msats to apply to each channel.
 214         ///
 215         /// Default value: 500 msat
 216         pub base_penalty_msat: u64,
 217
 218         /// A penalty in msats to apply to a channel upon failing to relay a payment.
 219         ///
 220         /// This accumulates for each failure but may be reduced over time based on
 221         /// [`failure_penalty_half_life`].
 222         ///
 223         /// Default value: 1,024,000 msat
 224         ///
 225         /// [`failure_penalty_half_life`]: Self::failure_penalty_half_life
 226         pub failure_penalty_msat: u64,
 227
 228         /// When the amount being sent over a channel is this many 1024ths of the total channel
 229         /// capacity, we begin applying [`overuse_penalty_msat_per_1024th`].
 230         ///
 231         /// Default value: 128 1024ths (i.e. begin penalizing when an HTLC uses 1/8th of a channel)
 232         ///
 233         /// [`overuse_penalty_msat_per_1024th`]: Self::overuse_penalty_msat_per_1024th
 234         pub overuse_penalty_start_1024th: u16,
 235
 236         /// A penalty applied, per whole 1024ths of the channel capacity which the amount being sent
 237         /// over the channel exceeds [`overuse_penalty_start_1024th`] by.
 238         ///
 239         /// Default value: 20 msat (i.e. 2560 msat penalty to use 1/4th of a channel, 7680 msat penalty
 240         ///                to use half a channel, and 12,560 msat penalty to use 3/4ths of a channel)
 241         ///
 242         /// [`overuse_penalty_start_1024th`]: Self::overuse_penalty_start_1024th
 243         pub overuse_penalty_msat_per_1024th: u64,
 244
 245         /// The time required to elapse before any accumulated [`failure_penalty_msat`] penalties are
 246         /// cut in half.
 247         ///
 248         /// # Note
 249         ///
 250         /// When time is an [`Eternity`], as is default when enabling feature `no-std`, it will never
 251         /// elapse. Therefore, this penalty will never decay.
 252         ///
 253         /// [`failure_penalty_msat`]: Self::failure_penalty_msat
 254         pub failure_penalty_half_life: Duration,
 255 }
 256
 257 impl_writeable_tlv_based!(ScoringParameters, {
 258         (0, base_penalty_msat, required),
 259         (1, overuse_penalty_start_1024th, (default_value, 128)),
 260         (2, failure_penalty_msat, required),
 261         (3, overuse_penalty_msat_per_1024th, (default_value, 20)),
 262         (4, failure_penalty_half_life, required),
 263 });
 264
 265 /// Accounting for penalties against a channel for failing to relay any payments.
 266 ///
 267 /// Penalties decay over time, though accumulate as more failures occur.
 268 struct ChannelFailure<T: Time> {
 269         /// Accumulated penalty in msats for the channel as of `last_failed`.
 270         undecayed_penalty_msat: u64,
 271
 272         /// Last time the channel failed. Used to decay `undecayed_penalty_msat`.
 273         last_failed: T,
 274 }
 275
 276 /// A measurement of time.
 277 pub trait Time: Sub<Duration, Output = Self> where Self: Sized {
 278         /// Returns an instance corresponding to the current moment.
 279         fn now() -> Self;
 280
 281         /// Returns the amount of time elapsed since `self` was created.
 282         fn elapsed(&self) -> Duration;
 283
 284         /// Returns the amount of time passed since the beginning of [`Time`].
 285         ///
 286         /// Used during (de-)serialization.
 287         fn duration_since_epoch() -> Duration;
 288 }
 289
 290 impl<T: Time> ScorerUsingTime<T> {
 291         /// Creates a new scorer using the given scoring parameters.
 292         pub fn new(params: ScoringParameters) -> Self {
 293                 Self {
 294                         params,
 295                         channel_failures: HashMap::new(),
 296                 }
 297         }
 298
 299         /// Creates a new scorer using `penalty_msat` as a fixed channel penalty.
 300         #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
 301         pub fn with_fixed_penalty(penalty_msat: u64) -> Self {
 302                 Self::new(ScoringParameters {
 303                         base_penalty_msat: penalty_msat,
 304                         failure_penalty_msat: 0,
 305                         failure_penalty_half_life: Duration::from_secs(0),
 306                         overuse_penalty_start_1024th: 1024,
 307                         overuse_penalty_msat_per_1024th: 0,
 308                 })
 309         }
 310 }
 311
 312 impl<T: Time> ChannelFailure<T> {
 313         fn new(failure_penalty_msat: u64) -> Self {
 314                 Self {
 315                         undecayed_penalty_msat: failure_penalty_msat,
 316                         last_failed: T::now(),
 317                 }
 318         }
 319
 320         fn add_penalty(&mut self, failure_penalty_msat: u64, half_life: Duration) {
 321                 self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) + failure_penalty_msat;
 322                 self.last_failed = T::now();
 323         }
 324
 325         fn decayed_penalty_msat(&self, half_life: Duration) -> u64 {
 326                 let decays = self.last_failed.elapsed().as_secs().checked_div(half_life.as_secs());
 327                 match decays {
 328                         Some(decays) => self.undecayed_penalty_msat >> decays,
 329                         None => 0,
 330                 }
 331         }
 332 }
 333
 334 impl<T: Time> Default for ScorerUsingTime<T> {
 335         fn default() -> Self {
 336                 Self::new(ScoringParameters::default())
 337         }
 338 }
 339
 340 impl Default for ScoringParameters {
 341         fn default() -> Self {
 342                 Self {
 343                         base_penalty_msat: 500,
 344                         failure_penalty_msat: 1024 * 1000,
 345                         failure_penalty_half_life: Duration::from_secs(3600),
 346                         overuse_penalty_start_1024th: 1024 / 8,
 347                         overuse_penalty_msat_per_1024th: 20,
 348                 }
 349         }
 350 }
 351
 352 impl<T: Time> Score for ScorerUsingTime<T> {
 353         fn channel_penalty_msat(
 354                 &self, short_channel_id: u64, send_amt_msat: u64, chan_capacity_opt: Option<u64>, _source: &NodeId, _target: &NodeId
 355         ) -> u64 {
 356                 let failure_penalty_msat = self.channel_failures
 357                         .get(&short_channel_id)
 358                         .map_or(0, |value| value.decayed_penalty_msat(self.params.failure_penalty_half_life));
 359
 360                 let mut penalty_msat = self.params.base_penalty_msat + failure_penalty_msat;
 361
 362                 if let Some(chan_capacity_msat) = chan_capacity_opt {
 363                         let send_1024ths = send_amt_msat.checked_mul(1024).unwrap_or(u64::max_value()) / chan_capacity_msat;
 364
 365                         if send_1024ths > self.params.overuse_penalty_start_1024th as u64 {
 366                                 penalty_msat = penalty_msat.checked_add(
 367                                                 (send_1024ths - self.params.overuse_penalty_start_1024th as u64)
 368                                                 .checked_mul(self.params.overuse_penalty_msat_per_1024th).unwrap_or(u64::max_value()))
 369                                         .unwrap_or(u64::max_value());
 370                         }
 371                 }
 372
 373                 penalty_msat
 374         }
 375
 376         fn payment_path_failed(&mut self, _path: &[&RouteHop], short_channel_id: u64) {
 377                 let failure_penalty_msat = self.params.failure_penalty_msat;
 378                 let half_life = self.params.failure_penalty_half_life;
 379                 self.channel_failures
 380                         .entry(short_channel_id)
 381                         .and_modify(|failure| failure.add_penalty(failure_penalty_msat, half_life))
 382                         .or_insert_with(|| ChannelFailure::new(failure_penalty_msat));
 383         }
 384 }
 385
 386 #[cfg(not(feature = "no-std"))]
 387 impl Time for std::time::Instant {
 388         fn now() -> Self {
 389                 std::time::Instant::now()
 390         }
 391
 392         fn duration_since_epoch() -> Duration {
 393                 use std::time::SystemTime;
 394                 SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap()
 395         }
 396
 397         fn elapsed(&self) -> Duration {
 398                 std::time::Instant::elapsed(self)
 399         }
 400 }
 401
 402 /// A state in which time has no meaning.
 403 #[derive(Debug, PartialEq, Eq)]
 404 pub struct Eternity;
 405
 406 impl Time for Eternity {
 407         fn now() -> Self {
 408                 Self
 409         }
 410
 411         fn duration_since_epoch() -> Duration {
 412                 Duration::from_secs(0)
 413         }
 414
 415         fn elapsed(&self) -> Duration {
 416                 Duration::from_secs(0)
 417         }
 418 }
 419
 420 impl Sub<Duration> for Eternity {
 421         type Output = Self;
 422
 423         fn sub(self, _other: Duration) -> Self {
 424                 self
 425         }
 426 }
 427
 428 impl<T: Time> Writeable for ScorerUsingTime<T> {
 429         #[inline]
 430         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 431                 self.params.write(w)?;
 432                 self.channel_failures.write(w)?;
 433                 write_tlv_fields!(w, {});
 434                 Ok(())
 435         }
 436 }
 437
 438 impl<T: Time> Readable for ScorerUsingTime<T> {
 439         #[inline]
 440         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 441                 let res = Ok(Self {
 442                         params: Readable::read(r)?,
 443                         channel_failures: Readable::read(r)?,
 444                 });
 445                 read_tlv_fields!(r, {});
 446                 res
 447         }
 448 }
 449
 450 impl<T: Time> Writeable for ChannelFailure<T> {
 451         #[inline]
 452         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 453                 let duration_since_epoch = T::duration_since_epoch() - self.last_failed.elapsed();
 454                 write_tlv_fields!(w, {
 455                         (0, self.undecayed_penalty_msat, required),
 456                         (2, duration_since_epoch, required),
 457                 });
 458                 Ok(())
 459         }
 460 }
 461
 462 impl<T: Time> Readable for ChannelFailure<T> {
 463         #[inline]
 464         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 465                 let mut undecayed_penalty_msat = 0;
 466                 let mut duration_since_epoch = Duration::from_secs(0);
 467                 read_tlv_fields!(r, {
 468                         (0, undecayed_penalty_msat, required),
 469                         (2, duration_since_epoch, required),
 470                 });
 471                 Ok(Self {
 472                         undecayed_penalty_msat,
 473                         last_failed: T::now() - (T::duration_since_epoch() - duration_since_epoch),
 474                 })
 475         }
 476 }
 477
 478 #[cfg(test)]
 479 mod tests {
 480         use super::{Eternity, ScoringParameters, ScorerUsingTime, Time};
 481
 482         use routing::scoring::Score;
 483         use routing::network_graph::NodeId;
 484         use util::ser::{Readable, Writeable};
 485
 486         use bitcoin::secp256k1::PublicKey;
 487         use core::cell::Cell;
 488         use core::ops::Sub;
 489         use core::time::Duration;
 490         use io;
 491
 492         /// Time that can be advanced manually in tests.
 493         #[derive(Debug, PartialEq, Eq)]
 494         struct SinceEpoch(Duration);
 495
 496         impl SinceEpoch {
 497                 thread_local! {
 498                         static ELAPSED: Cell<Duration> = core::cell::Cell::new(Duration::from_secs(0));
 499                 }
 500
 501                 fn advance(duration: Duration) {
 502                         Self::ELAPSED.with(|elapsed| elapsed.set(elapsed.get() + duration))
 503                 }
 504         }
 505
 506         impl Time for SinceEpoch {
 507                 fn now() -> Self {
 508                         Self(Self::duration_since_epoch())
 509                 }
 510
 511                 fn duration_since_epoch() -> Duration {
 512                         Self::ELAPSED.with(|elapsed| elapsed.get())
 513                 }
 514
 515                 fn elapsed(&self) -> Duration {
 516                         Self::duration_since_epoch() - self.0
 517                 }
 518         }
 519
 520         impl Sub<Duration> for SinceEpoch {
 521                 type Output = Self;
 522
 523                 fn sub(self, other: Duration) -> Self {
 524                         Self(self.0 - other)
 525                 }
 526         }
 527
 528         #[test]
 529         fn time_passes_when_advanced() {
 530                 let now = SinceEpoch::now();
 531                 assert_eq!(now.elapsed(), Duration::from_secs(0));
 532
 533                 SinceEpoch::advance(Duration::from_secs(1));
 534                 SinceEpoch::advance(Duration::from_secs(1));
 535
 536                 let elapsed = now.elapsed();
 537                 let later = SinceEpoch::now();
 538
 539                 assert_eq!(elapsed, Duration::from_secs(2));
 540                 assert_eq!(later - elapsed, now);
 541         }
 542
 543         #[test]
 544         fn time_never_passes_in_an_eternity() {
 545                 let now = Eternity::now();
 546                 let elapsed = now.elapsed();
 547                 let later = Eternity::now();
 548
 549                 assert_eq!(now.elapsed(), Duration::from_secs(0));
 550                 assert_eq!(later - elapsed, now);
 551         }
 552
 553         /// A scorer for testing with time that can be manually advanced.
 554         type Scorer = ScorerUsingTime::<SinceEpoch>;
 555
 556         fn source_node_id() -> NodeId {
 557                 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap())
 558         }
 559
 560         fn target_node_id() -> NodeId {
 561                 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap())
 562         }
 563
 564         #[test]
 565         fn penalizes_without_channel_failures() {
 566                 let scorer = Scorer::new(ScoringParameters {
 567                         base_penalty_msat: 1_000,
 568                         failure_penalty_msat: 512,
 569                         failure_penalty_half_life: Duration::from_secs(1),
 570                         overuse_penalty_start_1024th: 1024,
 571                         overuse_penalty_msat_per_1024th: 0,
 572                 });
 573                 let source = source_node_id();
 574                 let target = target_node_id();
 575                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 576
 577                 SinceEpoch::advance(Duration::from_secs(1));
 578                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 579         }
 580
 581         #[test]
 582         fn accumulates_channel_failure_penalties() {
 583                 let mut scorer = Scorer::new(ScoringParameters {
 584                         base_penalty_msat: 1_000,
 585                         failure_penalty_msat: 64,
 586                         failure_penalty_half_life: Duration::from_secs(10),
 587                         overuse_penalty_start_1024th: 1024,
 588                         overuse_penalty_msat_per_1024th: 0,
 589                 });
 590                 let source = source_node_id();
 591                 let target = target_node_id();
 592                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 593
 594                 scorer.payment_path_failed(&[], 42);
 595                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_064);
 596
 597                 scorer.payment_path_failed(&[], 42);
 598                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_128);
 599
 600                 scorer.payment_path_failed(&[], 42);
 601                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_192);
 602         }
 603
 604         #[test]
 605         fn decays_channel_failure_penalties_over_time() {
 606                 let mut scorer = Scorer::new(ScoringParameters {
 607                         base_penalty_msat: 1_000,
 608                         failure_penalty_msat: 512,
 609                         failure_penalty_half_life: Duration::from_secs(10),
 610                         overuse_penalty_start_1024th: 1024,
 611                         overuse_penalty_msat_per_1024th: 0,
 612                 });
 613                 let source = source_node_id();
 614                 let target = target_node_id();
 615                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 616
 617                 scorer.payment_path_failed(&[], 42);
 618                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 619
 620                 SinceEpoch::advance(Duration::from_secs(9));
 621                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 622
 623                 SinceEpoch::advance(Duration::from_secs(1));
 624                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 625
 626                 SinceEpoch::advance(Duration::from_secs(10 * 8));
 627                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_001);
 628
 629                 SinceEpoch::advance(Duration::from_secs(10));
 630                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 631
 632                 SinceEpoch::advance(Duration::from_secs(10));
 633                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 634         }
 635
 636         #[test]
 637         fn accumulates_channel_failure_penalties_after_decay() {
 638                 let mut scorer = Scorer::new(ScoringParameters {
 639                         base_penalty_msat: 1_000,
 640                         failure_penalty_msat: 512,
 641                         failure_penalty_half_life: Duration::from_secs(10),
 642                         overuse_penalty_start_1024th: 1024,
 643                         overuse_penalty_msat_per_1024th: 0,
 644                 });
 645                 let source = source_node_id();
 646                 let target = target_node_id();
 647                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 648
 649                 scorer.payment_path_failed(&[], 42);
 650                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 651
 652                 SinceEpoch::advance(Duration::from_secs(10));
 653                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 654
 655                 scorer.payment_path_failed(&[], 42);
 656                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_768);
 657
 658                 SinceEpoch::advance(Duration::from_secs(10));
 659                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_384);
 660         }
 661
 662         #[test]
 663         fn restores_persisted_channel_failure_penalties() {
 664                 let mut scorer = Scorer::new(ScoringParameters {
 665                         base_penalty_msat: 1_000,
 666                         failure_penalty_msat: 512,
 667                         failure_penalty_half_life: Duration::from_secs(10),
 668                         overuse_penalty_start_1024th: 1024,
 669                         overuse_penalty_msat_per_1024th: 0,
 670                 });
 671                 let source = source_node_id();
 672                 let target = target_node_id();
 673
 674                 scorer.payment_path_failed(&[], 42);
 675                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 676
 677                 SinceEpoch::advance(Duration::from_secs(10));
 678                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 679
 680                 scorer.payment_path_failed(&[], 43);
 681                 assert_eq!(scorer.channel_penalty_msat(43, 1, Some(1), &source, &target), 1_512);
 682
 683                 let mut serialized_scorer = Vec::new();
 684                 scorer.write(&mut serialized_scorer).unwrap();
 685
 686                 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
 687                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 688                 assert_eq!(deserialized_scorer.channel_penalty_msat(43, 1, Some(1), &source, &target), 1_512);
 689         }
 690
 691         #[test]
 692         fn decays_persisted_channel_failure_penalties() {
 693                 let mut scorer = Scorer::new(ScoringParameters {
 694                         base_penalty_msat: 1_000,
 695                         failure_penalty_msat: 512,
 696                         failure_penalty_half_life: Duration::from_secs(10),
 697                         overuse_penalty_start_1024th: 1024,
 698                         overuse_penalty_msat_per_1024th: 0,
 699                 });
 700                 let source = source_node_id();
 701                 let target = target_node_id();
 702
 703                 scorer.payment_path_failed(&[], 42);
 704                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 705
 706                 let mut serialized_scorer = Vec::new();
 707                 scorer.write(&mut serialized_scorer).unwrap();
 708
 709                 SinceEpoch::advance(Duration::from_secs(10));
 710
 711                 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
 712                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 713
 714                 SinceEpoch::advance(Duration::from_secs(10));
 715                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_128);
 716         }
 717
 718         #[test]
 719         fn charges_per_1024th_penalty() {
 720                 let scorer = Scorer::new(ScoringParameters {
 721                         base_penalty_msat: 0,
 722                         failure_penalty_msat: 0,
 723                         failure_penalty_half_life: Duration::from_secs(0),
 724                         overuse_penalty_start_1024th: 256,
 725                         overuse_penalty_msat_per_1024th: 100,
 726                 });
 727                 let source = source_node_id();
 728                 let target = target_node_id();
 729
 730                 assert_eq!(scorer.channel_penalty_msat(42, 1_000, None, &source, &target), 0);
 731                 assert_eq!(scorer.channel_penalty_msat(42, 1_000, Some(1_024_000), &source, &target), 0);
 732                 assert_eq!(scorer.channel_penalty_msat(42, 256_999, Some(1_024_000), &source, &target), 0);
 733                 assert_eq!(scorer.channel_penalty_msat(42, 257_000, Some(1_024_000), &source, &target), 100);
 734                 assert_eq!(scorer.channel_penalty_msat(42, 258_000, Some(1_024_000), &source, &target), 200);
 735                 assert_eq!(scorer.channel_penalty_msat(42, 512_000, Some(1_024_000), &source, &target), 256 * 100);
 736         }
 737 }