1 // This file is Copyright its original authors, visible in version control
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
10 //! Utilities for scoring payment channels.
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.
18 //! # extern crate secp256k1;
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;
26 //! # struct FakeLogger {};
27 //! # impl Logger for FakeLogger {
28 //! # fn log(&self, record: &Record) { unimplemented!() }
30 //! # fn find_scored_route(payer: PublicKey, params: RouteParameters, network_graph: NetworkGraph) {
31 //! # let logger = FakeLogger {};
33 //! // Use the default channel penalties.
34 //! let scorer = Scorer::default();
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()
43 //! let route = find_route(&payer, ¶ms, &network_graph, None, &logger, &scorer);
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.
53 //! [`find_route`]: crate::routing::router::find_route
57 use ln::msgs::DecodeError;
58 use routing::network_graph::NodeId;
59 use routing::router::RouteHop;
60 use util::ser::{Readable, Writeable, Writer};
64 use core::time::Duration;
67 /// [`routing::Score`] implementation that provides reasonable default behavior.
69 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
70 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
72 /// See [module-level documentation] for usage.
74 /// [module-level documentation]: crate::routing::scorer
75 pub type Scorer = ScorerUsingTime::<DefaultTime>;
77 /// Time used by [`Scorer`].
78 #[cfg(not(feature = "no-std"))]
79 pub type DefaultTime = std::time::Instant;
81 /// Time used by [`Scorer`].
82 #[cfg(feature = "no-std")]
83 pub type DefaultTime = Eternity;
85 /// [`routing::Score`] implementation parameterized by [`Time`].
87 /// See [`Scorer`] for details.
91 /// Mixing [`Time`] types between serialization and deserialization results in undefined behavior.
92 pub struct ScorerUsingTime<T: Time> {
93 params: ScoringParameters,
94 // TODO: Remove entries of closed channels.
95 channel_failures: HashMap<u64, ChannelFailure<T>>,
98 /// Parameters for configuring [`Scorer`].
99 pub struct ScoringParameters {
100 /// A fixed penalty in msats to apply to each channel.
101 pub base_penalty_msat: u64,
103 /// A penalty in msats to apply to a channel upon failing to relay a payment.
105 /// This accumulates for each failure but may be reduced over time based on
106 /// [`failure_penalty_half_life`].
108 /// [`failure_penalty_half_life`]: Self::failure_penalty_half_life
109 pub failure_penalty_msat: u64,
111 /// The time required to elapse before any accumulated [`failure_penalty_msat`] penalties are
116 /// When time is an [`Eternity`], as is default when enabling feature `no-std`, it will never
117 /// elapse. Therefore, this penalty will never decay.
119 /// [`failure_penalty_msat`]: Self::failure_penalty_msat
120 pub failure_penalty_half_life: Duration,
123 impl_writeable_tlv_based!(ScoringParameters, {
124 (0, base_penalty_msat, required),
125 (2, failure_penalty_msat, required),
126 (4, failure_penalty_half_life, required),
129 /// Accounting for penalties against a channel for failing to relay any payments.
131 /// Penalties decay over time, though accumulate as more failures occur.
132 struct ChannelFailure<T: Time> {
133 /// Accumulated penalty in msats for the channel as of `last_failed`.
134 undecayed_penalty_msat: u64,
136 /// Last time the channel failed. Used to decay `undecayed_penalty_msat`.
140 /// A measurement of time.
141 pub trait Time: Sub<Duration, Output = Self> where Self: Sized {
142 /// Returns an instance corresponding to the current moment.
145 /// Returns the amount of time elapsed since `self` was created.
146 fn elapsed(&self) -> Duration;
148 /// Returns the amount of time passed since the beginning of [`Time`].
150 /// Used during (de-)serialization.
151 fn duration_since_epoch() -> Duration;
154 impl<T: Time> ScorerUsingTime<T> {
155 /// Creates a new scorer using the given scoring parameters.
156 pub fn new(params: ScoringParameters) -> Self {
159 channel_failures: HashMap::new(),
163 /// Creates a new scorer using `penalty_msat` as a fixed channel penalty.
164 #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
165 pub fn with_fixed_penalty(penalty_msat: u64) -> Self {
166 Self::new(ScoringParameters {
167 base_penalty_msat: penalty_msat,
168 failure_penalty_msat: 0,
169 failure_penalty_half_life: Duration::from_secs(0),
174 impl<T: Time> ChannelFailure<T> {
175 fn new(failure_penalty_msat: u64) -> Self {
177 undecayed_penalty_msat: failure_penalty_msat,
178 last_failed: T::now(),
182 fn add_penalty(&mut self, failure_penalty_msat: u64, half_life: Duration) {
183 self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) + failure_penalty_msat;
184 self.last_failed = T::now();
187 fn decayed_penalty_msat(&self, half_life: Duration) -> u64 {
188 let decays = self.last_failed.elapsed().as_secs().checked_div(half_life.as_secs());
190 Some(decays) => self.undecayed_penalty_msat >> decays,
196 impl<T: Time> Default for ScorerUsingTime<T> {
197 fn default() -> Self {
198 Self::new(ScoringParameters::default())
202 impl Default for ScoringParameters {
203 fn default() -> Self {
205 base_penalty_msat: 500,
206 failure_penalty_msat: 1024 * 1000,
207 failure_penalty_half_life: Duration::from_secs(3600),
212 impl<T: Time> routing::Score for ScorerUsingTime<T> {
213 fn channel_penalty_msat(
214 &self, short_channel_id: u64, _source: &NodeId, _target: &NodeId
216 let failure_penalty_msat = self.channel_failures
217 .get(&short_channel_id)
218 .map_or(0, |value| value.decayed_penalty_msat(self.params.failure_penalty_half_life));
220 self.params.base_penalty_msat + failure_penalty_msat
223 fn payment_path_failed(&mut self, _path: &[&RouteHop], short_channel_id: u64) {
224 let failure_penalty_msat = self.params.failure_penalty_msat;
225 let half_life = self.params.failure_penalty_half_life;
226 self.channel_failures
227 .entry(short_channel_id)
228 .and_modify(|failure| failure.add_penalty(failure_penalty_msat, half_life))
229 .or_insert_with(|| ChannelFailure::new(failure_penalty_msat));
233 #[cfg(not(feature = "no-std"))]
234 impl Time for std::time::Instant {
236 std::time::Instant::now()
239 fn duration_since_epoch() -> Duration {
240 use std::time::SystemTime;
241 SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap()
244 fn elapsed(&self) -> Duration {
245 std::time::Instant::elapsed(self)
249 /// A state in which time has no meaning.
250 #[derive(Debug, PartialEq, Eq)]
253 impl Time for Eternity {
258 fn duration_since_epoch() -> Duration {
259 Duration::from_secs(0)
262 fn elapsed(&self) -> Duration {
263 Duration::from_secs(0)
267 impl Sub<Duration> for Eternity {
270 fn sub(self, _other: Duration) -> Self {
275 impl<T: Time> Writeable for ScorerUsingTime<T> {
277 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
278 self.params.write(w)?;
279 self.channel_failures.write(w)?;
280 write_tlv_fields!(w, {});
285 impl<T: Time> Readable for ScorerUsingTime<T> {
287 fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
289 params: Readable::read(r)?,
290 channel_failures: Readable::read(r)?,
292 read_tlv_fields!(r, {});
297 impl<T: Time> Writeable for ChannelFailure<T> {
299 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
300 let duration_since_epoch = T::duration_since_epoch() - self.last_failed.elapsed();
301 write_tlv_fields!(w, {
302 (0, self.undecayed_penalty_msat, required),
303 (2, duration_since_epoch, required),
309 impl<T: Time> Readable for ChannelFailure<T> {
311 fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
312 let mut undecayed_penalty_msat = 0;
313 let mut duration_since_epoch = Duration::from_secs(0);
314 read_tlv_fields!(r, {
315 (0, undecayed_penalty_msat, required),
316 (2, duration_since_epoch, required),
319 undecayed_penalty_msat,
320 last_failed: T::now() - (T::duration_since_epoch() - duration_since_epoch),
327 use super::{Eternity, ScoringParameters, ScorerUsingTime, Time};
330 use routing::network_graph::NodeId;
331 use util::ser::{Readable, Writeable};
333 use bitcoin::secp256k1::PublicKey;
334 use core::cell::Cell;
336 use core::time::Duration;
339 /// Time that can be advanced manually in tests.
340 #[derive(Debug, PartialEq, Eq)]
341 struct SinceEpoch(Duration);
345 static ELAPSED: Cell<Duration> = core::cell::Cell::new(Duration::from_secs(0));
348 fn advance(duration: Duration) {
349 Self::ELAPSED.with(|elapsed| elapsed.set(elapsed.get() + duration))
353 impl Time for SinceEpoch {
355 Self(Self::duration_since_epoch())
358 fn duration_since_epoch() -> Duration {
359 Self::ELAPSED.with(|elapsed| elapsed.get())
362 fn elapsed(&self) -> Duration {
363 Self::duration_since_epoch() - self.0
367 impl Sub<Duration> for SinceEpoch {
370 fn sub(self, other: Duration) -> Self {
376 fn time_passes_when_advanced() {
377 let now = SinceEpoch::now();
378 assert_eq!(now.elapsed(), Duration::from_secs(0));
380 SinceEpoch::advance(Duration::from_secs(1));
381 SinceEpoch::advance(Duration::from_secs(1));
383 let elapsed = now.elapsed();
384 let later = SinceEpoch::now();
386 assert_eq!(elapsed, Duration::from_secs(2));
387 assert_eq!(later - elapsed, now);
391 fn time_never_passes_in_an_eternity() {
392 let now = Eternity::now();
393 let elapsed = now.elapsed();
394 let later = Eternity::now();
396 assert_eq!(now.elapsed(), Duration::from_secs(0));
397 assert_eq!(later - elapsed, now);
400 /// A scorer for testing with time that can be manually advanced.
401 type Scorer = ScorerUsingTime::<SinceEpoch>;
403 fn source_node_id() -> NodeId {
404 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap())
407 fn target_node_id() -> NodeId {
408 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap())
412 fn penalizes_without_channel_failures() {
413 let scorer = Scorer::new(ScoringParameters {
414 base_penalty_msat: 1_000,
415 failure_penalty_msat: 512,
416 failure_penalty_half_life: Duration::from_secs(1),
418 let source = source_node_id();
419 let target = target_node_id();
420 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
422 SinceEpoch::advance(Duration::from_secs(1));
423 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
427 fn accumulates_channel_failure_penalties() {
428 let mut scorer = Scorer::new(ScoringParameters {
429 base_penalty_msat: 1_000,
430 failure_penalty_msat: 64,
431 failure_penalty_half_life: Duration::from_secs(10),
433 let source = source_node_id();
434 let target = target_node_id();
435 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
437 scorer.payment_path_failed(&[], 42);
438 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_064);
440 scorer.payment_path_failed(&[], 42);
441 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_128);
443 scorer.payment_path_failed(&[], 42);
444 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_192);
448 fn decays_channel_failure_penalties_over_time() {
449 let mut scorer = Scorer::new(ScoringParameters {
450 base_penalty_msat: 1_000,
451 failure_penalty_msat: 512,
452 failure_penalty_half_life: Duration::from_secs(10),
454 let source = source_node_id();
455 let target = target_node_id();
456 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
458 scorer.payment_path_failed(&[], 42);
459 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
461 SinceEpoch::advance(Duration::from_secs(9));
462 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
464 SinceEpoch::advance(Duration::from_secs(1));
465 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_256);
467 SinceEpoch::advance(Duration::from_secs(10 * 8));
468 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_001);
470 SinceEpoch::advance(Duration::from_secs(10));
471 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
473 SinceEpoch::advance(Duration::from_secs(10));
474 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
478 fn accumulates_channel_failure_penalties_after_decay() {
479 let mut scorer = Scorer::new(ScoringParameters {
480 base_penalty_msat: 1_000,
481 failure_penalty_msat: 512,
482 failure_penalty_half_life: Duration::from_secs(10),
484 let source = source_node_id();
485 let target = target_node_id();
486 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_000);
488 scorer.payment_path_failed(&[], 42);
489 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
491 SinceEpoch::advance(Duration::from_secs(10));
492 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_256);
494 scorer.payment_path_failed(&[], 42);
495 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_768);
497 SinceEpoch::advance(Duration::from_secs(10));
498 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_384);
502 fn restores_persisted_channel_failure_penalties() {
503 let mut scorer = Scorer::new(ScoringParameters {
504 base_penalty_msat: 1_000,
505 failure_penalty_msat: 512,
506 failure_penalty_half_life: Duration::from_secs(10),
508 let source = source_node_id();
509 let target = target_node_id();
511 scorer.payment_path_failed(&[], 42);
512 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
514 SinceEpoch::advance(Duration::from_secs(10));
515 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_256);
517 scorer.payment_path_failed(&[], 43);
518 assert_eq!(scorer.channel_penalty_msat(43, &source, &target), 1_512);
520 let mut serialized_scorer = Vec::new();
521 scorer.write(&mut serialized_scorer).unwrap();
523 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
524 assert_eq!(deserialized_scorer.channel_penalty_msat(42, &source, &target), 1_256);
525 assert_eq!(deserialized_scorer.channel_penalty_msat(43, &source, &target), 1_512);
529 fn decays_persisted_channel_failure_penalties() {
530 let mut scorer = Scorer::new(ScoringParameters {
531 base_penalty_msat: 1_000,
532 failure_penalty_msat: 512,
533 failure_penalty_half_life: Duration::from_secs(10),
535 let source = source_node_id();
536 let target = target_node_id();
538 scorer.payment_path_failed(&[], 42);
539 assert_eq!(scorer.channel_penalty_msat(42, &source, &target), 1_512);
541 let mut serialized_scorer = Vec::new();
542 scorer.write(&mut serialized_scorer).unwrap();
544 SinceEpoch::advance(Duration::from_secs(10));
546 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
547 assert_eq!(deserialized_scorer.channel_penalty_msat(42, &source, &target), 1_256);
549 SinceEpoch::advance(Duration::from_secs(10));
550 assert_eq!(deserialized_scorer.channel_penalty_msat(42, &source, &target), 1_128);