Merge pull request #1694 from jurvis/jurvis/2022-08-move-scorer-from-router
[rust-lightning] / lightning-invoice / src / payment.rs
index b9f4486339d199dbdc3d93f09cad652a64fe335c..21d7def4a51e9feadac7b4e6c7488b5714f98409 100644 (file)
 //! and payee using information provided by the payer and from the payee's [`Invoice`], when
 //! applicable.
 //!
-//! [`InvoicePayer`] is parameterized by a [`LockableScore`], which it uses for scoring failed and
-//! successful payment paths upon receiving [`Event::PaymentPathFailed`] and
-//! [`Event::PaymentPathSuccessful`] events, respectively.
+//! [`InvoicePayer`] uses its [`Router`] parameterization for optionally notifying scorers upon
+//! receiving the [`Event::PaymentPathFailed`] and [`Event::PaymentPathSuccessful`] events.
+//! It also does the same for payment probe failure and success events using [`Event::ProbeFailed`]
+//! and [`Event::ProbeSuccessful`].
 //!
 //! [`InvoicePayer`] is capable of retrying failed payments. It accomplishes this by implementing
 //! [`EventHandler`] which decorates a user-provided handler. It will intercept any
@@ -32,9 +33,7 @@
 //! # extern crate lightning_invoice;
 //! # extern crate secp256k1;
 //! #
-//! # #[cfg(feature = "no-std")]
-//! # extern crate core2;
-//! #
+//! # use lightning::io;
 //! # use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 //! # use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 //! # use lightning::ln::msgs::LightningError;
 //! # use lightning::util::logger::{Logger, Record};
 //! # use lightning::util::ser::{Writeable, Writer};
 //! # use lightning_invoice::Invoice;
-//! # use lightning_invoice::payment::{InvoicePayer, Payer, Retry, Router};
+//! # use lightning_invoice::payment::{InFlightHtlcs, InvoicePayer, Payer, Retry, Router};
 //! # use secp256k1::PublicKey;
 //! # use std::cell::RefCell;
 //! # use std::ops::Deref;
 //! #
-//! # #[cfg(not(feature = "std"))]
-//! # use core2::io;
-//! # #[cfg(feature = "std")]
-//! # use std::io;
-//! #
 //! # struct FakeEventProvider {}
 //! # impl EventsProvider for FakeEventProvider {
 //! #     fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {}
 //! #
 //! # struct FakeRouter {}
 //! # impl Router for FakeRouter {
-//! #     fn find_route<S: Score>(
+//! #     fn find_route(
 //! #         &self, payer: &PublicKey, params: &RouteParameters, payment_hash: &PaymentHash,
-//! #         first_hops: Option<&[&ChannelDetails]>, scorer: &S
+//! #         first_hops: Option<&[&ChannelDetails]>, _inflight_htlcs: InFlightHtlcs
 //! #     ) -> Result<Route, LightningError> { unimplemented!() }
+//! #
+//! #     fn notify_payment_path_failed(&self, path: Vec<&RouteHop>, short_channel_id: u64) {  unimplemented!() }
+//! #     fn notify_payment_path_successful(&self, path: Vec<&RouteHop>) {  unimplemented!() }
+//! #     fn notify_payment_probe_successful(&self, path: Vec<&RouteHop>) {  unimplemented!() }
+//! #     fn notify_payment_probe_failed(&self, path: Vec<&RouteHop>, short_channel_id: u64) { unimplemented!() }
 //! # }
 //! #
 //! # struct FakeScorer {}
 //! # let router = FakeRouter {};
 //! # let scorer = RefCell::new(FakeScorer {});
 //! # let logger = FakeLogger {};
-//! let invoice_payer = InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+//! let invoice_payer = InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 //!
 //! let invoice = "...";
 //! if let Ok(invoice) = invoice.parse::<Invoice>() {
@@ -141,11 +140,11 @@ use bitcoin_hashes::Hash;
 use bitcoin_hashes::sha256::Hash as Sha256;
 
 use crate::prelude::*;
+use lightning::io;
 use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 use lightning::ln::msgs::LightningError;
 use lightning::routing::gossip::NodeId;
-use lightning::routing::scoring::{ChannelUsage, LockableScore, Score};
 use lightning::routing::router::{PaymentParameters, Route, RouteHop, RouteParameters};
 use lightning::util::errors::APIError;
 use lightning::util::events::{Event, EventHandler};
@@ -167,7 +166,7 @@ use std::time::SystemTime;
 /// See [module-level documentation] for details.
 ///
 /// [module-level documentation]: crate::payment
-pub type InvoicePayer<P, R, S, L, E> = InvoicePayerUsingTime::<P, R, S, L, E, ConfiguredTime>;
+pub type InvoicePayer<P, R, L, E> = InvoicePayerUsingTime::<P, R, L, E, ConfiguredTime>;
 
 #[cfg(not(feature = "no-std"))]
 type ConfiguredTime = std::time::Instant;
@@ -177,15 +176,13 @@ use time_utils;
 type ConfiguredTime = time_utils::Eternity;
 
 /// (C-not exported) generally all users should use the [`InvoicePayer`] type alias.
-pub struct InvoicePayerUsingTime<P: Deref, R: Router, S: Deref, L: Deref, E: EventHandler, T: Time>
+pub struct InvoicePayerUsingTime<P: Deref, R: Router, L: Deref, E: EventHandler, T: Time>
 where
        P::Target: Payer,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        payer: P,
        router: R,
-       scorer: S,
        logger: L,
        event_handler: E,
        /// Caches the overall attempts at making a payment, which is updated prior to retrying.
@@ -209,49 +206,6 @@ impl<T: Time> PaymentInfo<T> {
        }
 }
 
-/// Used to store information about all the HTLCs that are inflight across all payment attempts
-struct AccountForInFlightHtlcs<'a, S: Score> {
-       scorer: &'a mut S,
-       /// Maps a channel's short channel id and its direction to the liquidity used up.
-       inflight_htlcs: HashMap<(u64, bool), u64>,
-}
-
-#[cfg(c_bindings)]
-impl<'a, S:Score> lightning::util::ser::Writeable for AccountForInFlightHtlcs<'a, S> {
-       fn write<W: lightning::util::ser::Writer>(&self, writer: &mut W) -> Result<(), std::io::Error> { self.scorer.write(writer) }
-}
-
-impl<'a, S: Score> Score for AccountForInFlightHtlcs<'a, S> {
-       fn channel_penalty_msat(&self, short_channel_id: u64, source: &NodeId, target: &NodeId, usage: ChannelUsage) -> u64 {
-               if let Some(used_liqudity) = self.inflight_htlcs.get(&(short_channel_id, source < target)) {
-                       let usage = ChannelUsage {
-                               inflight_htlc_msat: usage.inflight_htlc_msat + used_liqudity,
-                               ..usage
-                       };
-
-                       self.scorer.channel_penalty_msat(short_channel_id, source, target, usage)
-               } else {
-                       self.scorer.channel_penalty_msat(short_channel_id, source, target, usage)
-               }
-       }
-
-       fn payment_path_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
-               self.scorer.payment_path_failed(path, short_channel_id)
-       }
-
-       fn payment_path_successful(&mut self, path: &[&RouteHop]) {
-               self.scorer.payment_path_successful(path)
-       }
-
-       fn probe_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
-               self.scorer.probe_failed(path, short_channel_id)
-       }
-
-       fn probe_successful(&mut self, path: &[&RouteHop]) {
-               self.scorer.probe_successful(path)
-       }
-}
-
 /// Storing minimal payment attempts information required for determining if a outbound payment can
 /// be retried.
 #[derive(Clone, Copy)]
@@ -314,10 +268,18 @@ pub trait Payer {
 /// A trait defining behavior for routing an [`Invoice`] payment.
 pub trait Router {
        /// Finds a [`Route`] between `payer` and `payee` for a payment with the given values.
-       fn find_route<S: Score>(
+       fn find_route(
                &self, payer: &PublicKey, route_params: &RouteParameters, payment_hash: &PaymentHash,
-               first_hops: Option<&[&ChannelDetails]>, scorer: &S
+               first_hops: Option<&[&ChannelDetails]>, inflight_htlcs: InFlightHtlcs
        ) -> Result<Route, LightningError>;
+       /// Lets the router know that payment through a specific path has failed.
+       fn notify_payment_path_failed(&self, path: Vec<&RouteHop>, short_channel_id: u64);
+       /// Lets the router know that payment through a specific path was successful.
+       fn notify_payment_path_successful(&self, path: Vec<&RouteHop>);
+       /// Lets the router know that a payment probe was successful.
+       fn notify_payment_probe_successful(&self, path: Vec<&RouteHop>);
+       /// Lets the router know that a payment probe failed.
+       fn notify_payment_probe_failed(&self, path: Vec<&RouteHop>, short_channel_id: u64);
 }
 
 /// Strategies available to retry payment path failures for an [`Invoice`].
@@ -359,10 +321,9 @@ pub enum PaymentError {
        Sending(PaymentSendFailure),
 }
 
-impl<P: Deref, R: Router, S: Deref, L: Deref, E: EventHandler, T: Time> InvoicePayerUsingTime<P, R, S, L, E, T>
+impl<P: Deref, R: Router, L: Deref, E: EventHandler, T: Time> InvoicePayerUsingTime<P, R, L, E, T>
 where
        P::Target: Payer,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        /// Creates an invoice payer that retries failed payment paths.
@@ -370,12 +331,11 @@ where
        /// Will forward any [`Event::PaymentPathFailed`] events to the decorated `event_handler` once
        /// `retry` has been exceeded for a given [`Invoice`].
        pub fn new(
-               payer: P, router: R, scorer: S, logger: L, event_handler: E, retry: Retry
+               payer: P, router: R, logger: L, event_handler: E, retry: Retry
        ) -> Self {
                Self {
                        payer,
                        router,
-                       scorer,
                        logger,
                        event_handler,
                        payment_cache: Mutex::new(HashMap::new()),
@@ -487,7 +447,7 @@ where
                let inflight_htlcs = self.create_inflight_map();
                let route = self.router.find_route(
                        &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &AccountForInFlightHtlcs { scorer: &mut self.scorer.lock(), inflight_htlcs }
+                       inflight_htlcs
                ).map_err(|e| PaymentError::Routing(e))?;
 
                match send_payment(&route) {
@@ -592,7 +552,7 @@ where
 
                let route = self.router.find_route(
                        &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &AccountForInFlightHtlcs { scorer: &mut self.scorer.lock(), inflight_htlcs }
+                       inflight_htlcs
                );
 
                if route.is_err() {
@@ -651,7 +611,7 @@ where
        ///
        /// This function should be called whenever we need information about currently used up liquidity
        /// across payments.
-       fn create_inflight_map(&self) -> HashMap<(u64, bool), u64> {
+       fn create_inflight_map(&self) -> InFlightHtlcs {
                let mut total_inflight_map: HashMap<(u64, bool), u64> = HashMap::new();
                // Make an attempt at finding existing payment information from `payment_cache`. If it
                // does not exist, it probably is a fresh payment and we can just return an empty
@@ -683,7 +643,7 @@ where
                        }
                }
 
-               total_inflight_map
+               InFlightHtlcs(total_inflight_map)
        }
 }
 
@@ -698,10 +658,9 @@ fn has_expired(route_params: &RouteParameters) -> bool {
        } else { false }
 }
 
-impl<P: Deref, R: Router, S: Deref, L: Deref, E: EventHandler, T: Time> EventHandler for InvoicePayerUsingTime<P, R, S, L, E, T>
+impl<P: Deref, R: Router, L: Deref, E: EventHandler, T: Time> EventHandler for InvoicePayerUsingTime<P, R, L, E, T>
 where
        P::Target: Payer,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        fn handle_event(&self, event: &Event) {
@@ -721,7 +680,7 @@ where
                        } => {
                                if let Some(short_channel_id) = short_channel_id {
                                        let path = path.iter().collect::<Vec<_>>();
-                                       self.scorer.lock().payment_path_failed(&path, *short_channel_id);
+                                       self.router.notify_payment_path_failed(path, *short_channel_id)
                                }
 
                                if payment_id.is_none() {
@@ -744,7 +703,7 @@ where
                        },
                        Event::PaymentPathSuccessful { path, .. } => {
                                let path = path.iter().collect::<Vec<_>>();
-                               self.scorer.lock().payment_path_successful(&path);
+                               self.router.notify_payment_path_successful(path);
                        },
                        Event::PaymentSent { payment_hash, .. } => {
                                let mut payment_cache = self.payment_cache.lock().unwrap();
@@ -756,13 +715,13 @@ where
                        Event::ProbeSuccessful { payment_hash, path, .. } => {
                                log_trace!(self.logger, "Probe payment {} of {}msat was successful", log_bytes!(payment_hash.0), path.last().unwrap().fee_msat);
                                let path = path.iter().collect::<Vec<_>>();
-                               self.scorer.lock().probe_successful(&path);
+                               self.router.notify_payment_probe_successful(path);
                        },
                        Event::ProbeFailed { payment_hash, path, short_channel_id, .. } => {
                                if let Some(short_channel_id) = short_channel_id {
                                        log_trace!(self.logger, "Probe payment {} of {}msat failed at channel {}", log_bytes!(payment_hash.0), path.last().unwrap().fee_msat, *short_channel_id);
                                        let path = path.iter().collect::<Vec<_>>();
-                                       self.scorer.lock().probe_failed(&path, *short_channel_id);
+                                       self.router.notify_payment_probe_failed(path, *short_channel_id);
                                }
                        },
                        _ => {},
@@ -773,11 +732,36 @@ where
        }
 }
 
+/// A map with liquidity value (in msat) keyed by a short channel id and the direction the HTLC
+/// is traveling in. The direction boolean is determined by checking if the HTLC source's public
+/// key is less than its destination. See [`InFlightHtlcs::used_liquidity_msat`] for more
+/// details.
+pub struct InFlightHtlcs(HashMap<(u64, bool), u64>);
+
+impl InFlightHtlcs {
+       /// Returns liquidity in msat given the public key of the HTLC source, target, and short channel
+       /// id.
+       pub fn used_liquidity_msat(&self, source: &NodeId, target: &NodeId, channel_scid: u64) -> Option<&u64> {
+               self.0.get(&(channel_scid, source < target))
+       }
+}
+
+impl lightning::util::ser::Writeable for InFlightHtlcs {
+       fn write<W: lightning::util::ser::Writer>(&self, writer: &mut W) -> Result<(), io::Error> { self.0.write(writer) }
+}
+
+impl lightning::util::ser::Readable for InFlightHtlcs {
+       fn read<R: io::Read>(reader: &mut R) -> Result<Self, lightning::ln::msgs::DecodeError> {
+               let infight_map: HashMap<(u64, bool), u64> = lightning::util::ser::Readable::read(reader)?;
+               Ok(Self(infight_map))
+       }
+}
+
 #[cfg(test)]
 mod tests {
        use super::*;
        use crate::{InvoiceBuilder, Currency};
-       use utils::create_invoice_from_channelmanager_and_duration_since_epoch;
+       use utils::{ScorerAccountingForInFlightHtlcs, create_invoice_from_channelmanager_and_duration_since_epoch};
        use bitcoin_hashes::sha256::Hash as Sha256;
        use lightning::ln::PaymentPreimage;
        use lightning::ln::channelmanager;
@@ -786,13 +770,14 @@ mod tests {
        use lightning::ln::msgs::{ChannelMessageHandler, ErrorAction, LightningError};
        use lightning::routing::gossip::{EffectiveCapacity, NodeId};
        use lightning::routing::router::{PaymentParameters, Route, RouteHop};
-       use lightning::routing::scoring::ChannelUsage;
+       use lightning::routing::scoring::{ChannelUsage, LockableScore, Score};
        use lightning::util::test_utils::TestLogger;
        use lightning::util::errors::APIError;
        use lightning::util::events::{Event, EventsProvider, MessageSendEvent, MessageSendEventsProvider};
        use secp256k1::{SecretKey, PublicKey, Secp256k1};
        use std::cell::RefCell;
        use std::collections::VecDeque;
+       use std::ops::DerefMut;
        use std::time::{SystemTime, Duration};
        use time_utils::tests::SinceEpoch;
        use DEFAULT_EXPIRY_TIME;
@@ -875,11 +860,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -904,11 +888,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -949,11 +932,10 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                assert!(invoice_payer.pay_invoice(&invoice).is_ok());
        }
@@ -971,11 +953,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(PaymentId([1; 32]));
                let event = Event::PaymentPathFailed {
@@ -1016,11 +997,10 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1074,13 +1054,12 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
 
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
-               type InvoicePayerUsingSinceEpoch <P, R, S, L, E> = InvoicePayerUsingTime::<P, R, S, L, E, SinceEpoch>;
+               type InvoicePayerUsingSinceEpoch <P, R, L, E> = InvoicePayerUsingTime::<P, R, L, E, SinceEpoch>;
 
                let invoice_payer =
-                       InvoicePayerUsingSinceEpoch::new(&payer, router, &scorer, &logger, event_handler, Retry::Timeout(Duration::from_secs(120)));
+                       InvoicePayerUsingSinceEpoch::new(&payer, router, &logger, event_handler, Retry::Timeout(Duration::from_secs(120)));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1116,11 +1095,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1148,11 +1126,10 @@ mod tests {
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
                let payer = TestPayer::new();
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = expired_invoice(payment_preimage);
@@ -1173,11 +1150,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router,  &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1214,11 +1190,10 @@ mod tests {
                        .fails_on_attempt(2)
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1248,11 +1223,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1284,11 +1258,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
 
@@ -1324,10 +1297,9 @@ mod tests {
        fn fails_paying_invoice_with_routing_errors() {
                let payer = TestPayer::new();
                let router = FailingRouter {};
-               let scorer = RefCell::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, |_: &_| {}, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, |_: &_| {}, Retry::Attempts(0));
 
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = invoice(payment_preimage);
@@ -1347,11 +1319,10 @@ mod tests {
                let payer = TestPayer::new()
                        .fails_on_attempt(1)
                        .expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, |_: &_| {}, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, |_: &_| {}, Retry::Attempts(0));
 
                match invoice_payer.pay_invoice(&invoice) {
                        Err(PaymentError::Sending(_)) => {},
@@ -1371,11 +1342,10 @@ mod tests {
                let final_value_msat = 100;
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id =
                        Some(invoice_payer.pay_zero_value_invoice(&invoice, final_value_msat).unwrap());
@@ -1394,11 +1364,10 @@ mod tests {
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
                let payer = TestPayer::new();
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router,  &logger, event_handler, Retry::Attempts(0));
 
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = invoice(payment_preimage);
@@ -1425,11 +1394,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::Spontaneous(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_pubkey(
                                pubkey, payment_preimage, final_value_msat, final_cltv_expiry_delta
@@ -1478,13 +1446,13 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new().expect(TestResult::PaymentFailure {
+               let scorer = TestScorer::new().expect(TestResult::PaymentFailure {
                        path: path.clone(), short_channel_id: path[0].short_channel_id,
-               }));
+               });
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                let event = Event::PaymentPathFailed {
@@ -1513,14 +1481,13 @@ mod tests {
 
                // Expect that scorer is given short_channel_id upon handling the event.
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new()
+               let scorer = TestScorer::new()
                        .expect(TestResult::PaymentSuccess { path: route.paths[0].clone() })
-                       .expect(TestResult::PaymentSuccess { path: route.paths[1].clone() })
-               );
+                       .expect(TestResult::PaymentSuccess { path: route.paths[1].clone() });
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = invoice_payer.pay_invoice(&invoice).unwrap();
                let event = Event::PaymentPathSuccessful {
@@ -1546,23 +1513,22 @@ mod tests {
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
                let route = TestRouter::route_for_value(final_value_msat);
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id = invoice_payer.pay_invoice(&invoice).unwrap();
 
                let inflight_map = invoice_payer.create_inflight_map();
                // First path check
-               assert_eq!(inflight_map.get(&(0, false)).unwrap().clone(), 94);
-               assert_eq!(inflight_map.get(&(1, true)).unwrap().clone(), 84);
-               assert_eq!(inflight_map.get(&(2, false)).unwrap().clone(), 64);
+               assert_eq!(inflight_map.0.get(&(0, false)).unwrap().clone(), 94);
+               assert_eq!(inflight_map.0.get(&(1, true)).unwrap().clone(), 84);
+               assert_eq!(inflight_map.0.get(&(2, false)).unwrap().clone(), 64);
 
                // Second path check
-               assert_eq!(inflight_map.get(&(3, false)).unwrap().clone(), 74);
-               assert_eq!(inflight_map.get(&(4, false)).unwrap().clone(), 64);
+               assert_eq!(inflight_map.0.get(&(3, false)).unwrap().clone(), 74);
+               assert_eq!(inflight_map.0.get(&(4, false)).unwrap().clone(), 64);
 
                invoice_payer.handle_event(&Event::PaymentPathSuccessful {
                        payment_id, payment_hash, path: route.paths[0].clone()
@@ -1570,13 +1536,13 @@ mod tests {
 
                let inflight_map = invoice_payer.create_inflight_map();
 
-               assert_eq!(inflight_map.get(&(0, false)), None);
-               assert_eq!(inflight_map.get(&(1, true)), None);
-               assert_eq!(inflight_map.get(&(2, false)), None);
+               assert_eq!(inflight_map.0.get(&(0, false)), None);
+               assert_eq!(inflight_map.0.get(&(1, true)), None);
+               assert_eq!(inflight_map.0.get(&(2, false)), None);
 
                // Second path should still be inflight
-               assert_eq!(inflight_map.get(&(3, false)).unwrap().clone(), 74);
-               assert_eq!(inflight_map.get(&(4, false)).unwrap().clone(), 64)
+               assert_eq!(inflight_map.0.get(&(3, false)).unwrap().clone(), 74);
+               assert_eq!(inflight_map.0.get(&(4, false)).unwrap().clone(), 64)
        }
 
        #[test]
@@ -1595,8 +1561,7 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat));
                let final_value_msat = payment_invoice.amount_milli_satoshis().unwrap();
                let route = TestRouter::route_for_value(final_value_msat);
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new()
+               let scorer = TestScorer::new()
                        // 1st invoice, 1st path
                        .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        .expect_usage(ChannelUsage { amount_msat: 84, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
@@ -1610,11 +1575,11 @@ mod tests {
                        .expect_usage(ChannelUsage { amount_msat: 94, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        // 2nd invoice, 2nd path
                        .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 64, effective_capacity: EffectiveCapacity::Unknown } )
-                       .expect_usage(ChannelUsage { amount_msat: 74, inflight_htlc_msat: 74, effective_capacity: EffectiveCapacity::Unknown } )
-               );
+                       .expect_usage(ChannelUsage { amount_msat: 74, inflight_htlc_msat: 74, effective_capacity: EffectiveCapacity::Unknown } );
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                // Succeed 1st path, leave 2nd path inflight
                let payment_id = invoice_payer.pay_invoice(&payment_invoice).unwrap();
@@ -1647,8 +1612,7 @@ mod tests {
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 4));
                let final_value_msat = payment_invoice.amount_milli_satoshis().unwrap();
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new()
+               let scorer = TestScorer::new()
                        // 1st invoice, 1st path
                        .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        .expect_usage(ChannelUsage { amount_msat: 84, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
@@ -1669,11 +1633,11 @@ mod tests {
                        .expect_usage(ChannelUsage { amount_msat: 46, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        // Retry 2, 2nd path
                        .expect_usage(ChannelUsage { amount_msat: 16, inflight_htlc_msat: 64 + 32, effective_capacity: EffectiveCapacity::Unknown } )
-                       .expect_usage(ChannelUsage { amount_msat: 26, inflight_htlc_msat: 74 + 32 + 10, effective_capacity: EffectiveCapacity::Unknown } )
-               );
+                       .expect_usage(ChannelUsage { amount_msat: 26, inflight_htlc_msat: 74 + 32 + 10, effective_capacity: EffectiveCapacity::Unknown } );
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                // Fail 1st path, leave 2nd path inflight
                let payment_id = Some(invoice_payer.pay_invoice(&payment_invoice).unwrap());
@@ -1722,18 +1686,17 @@ mod tests {
                                ]))
                        .expect_send(Amount::ForInvoice(final_value_msat));
 
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                invoice_payer.pay_invoice(&invoice_to_pay).unwrap();
                let inflight_map = invoice_payer.create_inflight_map();
 
                // Only the second path, which failed with `MonitorUpdateFailed` should be added to our
                // inflight map because retries are disabled.
-               assert_eq!(inflight_map.len(), 2);
+               assert_eq!(inflight_map.0.len(), 2);
        }
 
        #[test]
@@ -1754,22 +1717,27 @@ mod tests {
                                ]))
                        .expect_send(Amount::ForInvoice(final_value_msat));
 
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                invoice_payer.pay_invoice(&invoice_to_pay).unwrap();
                let inflight_map = invoice_payer.create_inflight_map();
 
                // All paths successful, hence we check of the existence of all 5 hops.
-               assert_eq!(inflight_map.len(), 5);
+               assert_eq!(inflight_map.0.len(), 5);
        }
 
-       struct TestRouter;
+       struct TestRouter {
+               scorer: RefCell<TestScorer>,
+       }
 
        impl TestRouter {
+               fn new(scorer: TestScorer) -> Self {
+                       TestRouter { scorer: RefCell::new(scorer) }
+               }
+
                fn route_for_value(final_value_msat: u64) -> Route {
                        Route {
                                paths: vec![
@@ -1843,12 +1811,14 @@ mod tests {
        }
 
        impl Router for TestRouter {
-               fn find_route<S: Score>(
+               fn find_route(
                        &self, payer: &PublicKey, route_params: &RouteParameters, _payment_hash: &PaymentHash,
-                       _first_hops: Option<&[&ChannelDetails]>, scorer: &S
+                       _first_hops: Option<&[&ChannelDetails]>, inflight_htlcs: InFlightHtlcs
                ) -> Result<Route, LightningError> {
                        // Simulate calling the Scorer just as you would in find_route
                        let route = Self::route_for_value(route_params.final_value_msat);
+                       let mut locked_scorer = self.scorer.lock();
+                       let scorer = ScorerAccountingForInFlightHtlcs::new(locked_scorer.deref_mut(), inflight_htlcs);
                        for path in route.paths {
                                let mut aggregate_msat = 0u64;
                                for (idx, hop) in path.iter().rev().enumerate() {
@@ -1873,17 +1843,41 @@ mod tests {
                                payment_params: Some(route_params.payment_params.clone()), ..Self::route_for_value(route_params.final_value_msat)
                        })
                }
+
+               fn notify_payment_path_failed(&self, path: Vec<&RouteHop>, short_channel_id: u64) {
+                       self.scorer.lock().payment_path_failed(&path, short_channel_id);
+               }
+
+               fn notify_payment_path_successful(&self, path: Vec<&RouteHop>) {
+                       self.scorer.lock().payment_path_successful(&path);
+               }
+
+               fn notify_payment_probe_successful(&self, path: Vec<&RouteHop>) {
+                       self.scorer.lock().probe_successful(&path);
+               }
+
+               fn notify_payment_probe_failed(&self, path: Vec<&RouteHop>, short_channel_id: u64) {
+                       self.scorer.lock().probe_failed(&path, short_channel_id);
+               }
        }
 
        struct FailingRouter;
 
        impl Router for FailingRouter {
-               fn find_route<S: Score>(
+               fn find_route(
                        &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
-                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
+                       _first_hops: Option<&[&ChannelDetails]>, _inflight_htlcs: InFlightHtlcs
                ) -> Result<Route, LightningError> {
                        Err(LightningError { err: String::new(), action: ErrorAction::IgnoreError })
                }
+
+               fn notify_payment_path_failed(&self, _path: Vec<&RouteHop>, _short_channel_id: u64) {}
+
+               fn notify_payment_path_successful(&self, _path: Vec<&RouteHop>) {}
+
+               fn notify_payment_probe_successful(&self, _path: Vec<&RouteHop>) {}
+
+               fn notify_payment_probe_failed(&self, _path: Vec<&RouteHop>, _short_channel_id: u64) {}
        }
 
        struct TestScorer {
@@ -1947,7 +1941,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                panic!("Unexpected successful payment path: {:?}", path)
                                        },
-                                       None => panic!("Unexpected payment_path_failed call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_failed call: {:?}", actual_path),
                                }
                        }
                }
@@ -1961,7 +1955,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                assert_eq!(actual_path, &path.iter().collect::<Vec<_>>()[..]);
                                        },
-                                       None => panic!("Unexpected payment_path_successful call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_successful call: {:?}", actual_path),
                                }
                        }
                }
@@ -1975,7 +1969,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                panic!("Unexpected successful payment path: {:?}", path)
                                        },
-                                       None => panic!("Unexpected payment_path_failed call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_failed call: {:?}", actual_path),
                                }
                        }
                }
@@ -1988,7 +1982,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                panic!("Unexpected successful payment path: {:?}", path)
                                        },
-                                       None => panic!("Unexpected payment_path_successful call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_successful call: {:?}", actual_path),
                                }
                        }
                }
@@ -2132,12 +2126,20 @@ mod tests {
        struct ManualRouter(RefCell<VecDeque<Result<Route, LightningError>>>);
 
        impl Router for ManualRouter {
-               fn find_route<S: Score>(
+               fn find_route(
                        &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
-                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
+                       _first_hops: Option<&[&ChannelDetails]>, _inflight_htlcs: InFlightHtlcs
                ) -> Result<Route, LightningError> {
                        self.0.borrow_mut().pop_front().unwrap()
                }
+
+               fn notify_payment_path_failed(&self, _path: Vec<&RouteHop>, _short_channel_id: u64) {}
+
+               fn notify_payment_path_successful(&self, _path: Vec<&RouteHop>) {}
+
+               fn notify_payment_probe_successful(&self, _path: Vec<&RouteHop>) {}
+
+               fn notify_payment_probe_failed(&self, _path: Vec<&RouteHop>, _short_channel_id: u64) {}
        }
        impl ManualRouter {
                fn expect_find_route(&self, result: Result<Route, LightningError>) {
@@ -2193,8 +2195,7 @@ mod tests {
                router.expect_find_route(Ok(route.clone()));
 
                let event_handler = |_: &_| { panic!(); };
-               let scorer = RefCell::new(TestScorer::new());
-               let invoice_payer = InvoicePayer::new(nodes[0].node, router, &scorer, nodes[0].logger, event_handler, Retry::Attempts(1));
+               let invoice_payer = InvoicePayer::new(nodes[0].node, router, nodes[0].logger, event_handler, Retry::Attempts(1));
 
                assert!(invoice_payer.pay_invoice(&create_invoice_from_channelmanager_and_duration_since_epoch(
                        &nodes[1].node, nodes[1].keys_manager, Currency::Bitcoin, Some(100_010_000), "Invoice".to_string(),
@@ -2239,8 +2240,7 @@ mod tests {
                router.expect_find_route(Ok(route.clone()));
 
                let event_handler = |_: &_| { panic!(); };
-               let scorer = RefCell::new(TestScorer::new());
-               let invoice_payer = InvoicePayer::new(nodes[0].node, router, &scorer, nodes[0].logger, event_handler, Retry::Attempts(1));
+               let invoice_payer = InvoicePayer::new(nodes[0].node, router, nodes[0].logger, event_handler, Retry::Attempts(1));
 
                assert!(invoice_payer.pay_invoice(&create_invoice_from_channelmanager_and_duration_since_epoch(
                        &nodes[1].node, nodes[1].keys_manager, Currency::Bitcoin, Some(100_010_000), "Invoice".to_string(),
@@ -2321,8 +2321,7 @@ mod tests {
                        let event_checker = expected_events.borrow_mut().pop_front().unwrap();
                        event_checker(event);
                };
-               let scorer = RefCell::new(TestScorer::new());
-               let invoice_payer = InvoicePayer::new(nodes[0].node, router, &scorer, nodes[0].logger, event_handler, Retry::Attempts(1));
+               let invoice_payer = InvoicePayer::new(nodes[0].node, router, nodes[0].logger, event_handler, Retry::Attempts(1));
 
                assert!(invoice_payer.pay_invoice(&create_invoice_from_channelmanager_and_duration_since_epoch(
                        &nodes[1].node, nodes[1].keys_manager, Currency::Bitcoin, Some(100_010_000), "Invoice".to_string(),