Avoid returning a reference to a u64.
[rust-lightning] / lightning-invoice / src / payment.rs
index 476d12a34751e885c43980453ede2db9288d0cd5..c7449acd2764085ac6ac250c9a07235b3a588019 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<S: Score> Router<S> for FakeRouter {
+//! # impl Router for FakeRouter {
 //! #     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: &[&RouteHop], short_channel_id: u64) {  unimplemented!() }
+//! #     fn notify_payment_path_successful(&self, path: &[&RouteHop]) {  unimplemented!() }
+//! #     fn notify_payment_probe_successful(&self, path: &[&RouteHop]) {  unimplemented!() }
+//! #     fn notify_payment_probe_failed(&self, path: &[&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 +140,13 @@ 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::scoring::{LockableScore, Score};
-use lightning::routing::router::{PaymentParameters, Route, RouteParameters};
+use lightning::routing::gossip::NodeId;
+use lightning::routing::router::{PaymentParameters, Route, RouteHop, RouteParameters};
+use lightning::util::errors::APIError;
 use lightning::util::events::{Event, EventHandler};
 use lightning::util::logger::Logger;
 use time_utils::Time;
@@ -165,7 +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;
@@ -175,23 +176,36 @@ 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, 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,
-       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
-       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.
-       payment_cache: Mutex<HashMap<PaymentHash, PaymentAttempts<T>>>,
+       payment_cache: Mutex<HashMap<PaymentHash, PaymentInfo<T>>>,
        retry: Retry,
 }
 
+/// Used by [`InvoicePayerUsingTime::payment_cache`] to track the payments that are either
+/// currently being made, or have outstanding paths that need retrying.
+struct PaymentInfo<T: Time> {
+       attempts: PaymentAttempts<T>,
+       paths: Vec<Vec<RouteHop>>,
+}
+
+impl<T: Time> PaymentInfo<T> {
+       fn new() -> Self {
+               PaymentInfo {
+                       attempts: PaymentAttempts::new(),
+                       paths: vec![],
+               }
+       }
+}
+
 /// Storing minimal payment attempts information required for determining if a outbound payment can
 /// be retried.
 #[derive(Clone, Copy)]
@@ -252,12 +266,20 @@ pub trait Payer {
 }
 
 /// A trait defining behavior for routing an [`Invoice`] payment.
-pub trait Router<S: Score> {
+pub trait Router {
        /// Finds a [`Route`] between `payer` and `payee` for a payment with the given values.
        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: &[&RouteHop], short_channel_id: u64);
+       /// Lets the router know that payment through a specific path was successful.
+       fn notify_payment_path_successful(&self, path: &[&RouteHop]);
+       /// Lets the router know that a payment probe was successful.
+       fn notify_payment_probe_successful(&self, path: &[&RouteHop]);
+       /// Lets the router know that a payment probe failed.
+       fn notify_payment_probe_failed(&self, path: &[&RouteHop], short_channel_id: u64);
 }
 
 /// Strategies available to retry payment path failures for an [`Invoice`].
@@ -299,11 +321,9 @@ pub enum PaymentError {
        Sending(PaymentSendFailure),
 }
 
-impl<P: Deref, R, 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,
-       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        /// Creates an invoice payer that retries failed payment paths.
@@ -311,12 +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()),
@@ -361,7 +380,7 @@ where
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
                match self.payment_cache.lock().unwrap().entry(payment_hash) {
                        hash_map::Entry::Occupied(_) => return Err(PaymentError::Invoice("payment pending")),
-                       hash_map::Entry::Vacant(entry) => entry.insert(PaymentAttempts::new()),
+                       hash_map::Entry::Vacant(entry) => entry.insert(PaymentInfo::new()),
                };
 
                let payment_secret = Some(invoice.payment_secret().clone());
@@ -397,7 +416,7 @@ where
                let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
                match self.payment_cache.lock().unwrap().entry(payment_hash) {
                        hash_map::Entry::Occupied(_) => return Err(PaymentError::Invoice("payment pending")),
-                       hash_map::Entry::Vacant(entry) => entry.insert(PaymentAttempts::new()),
+                       hash_map::Entry::Vacant(entry) => entry.insert(PaymentInfo::new()),
                };
 
                let route_params = RouteParameters {
@@ -425,28 +444,46 @@ where
 
                let payer = self.payer.node_id();
                let first_hops = self.payer.first_hops();
+               let inflight_htlcs = self.create_inflight_map();
                let route = self.router.find_route(
-                       &payer, params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &self.scorer.lock()
+                       &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
+                       inflight_htlcs
                ).map_err(|e| PaymentError::Routing(e))?;
 
                match send_payment(&route) {
-                       Ok(payment_id) => Ok(payment_id),
+                       Ok(payment_id) => {
+                               for path in route.paths {
+                                       self.process_path_inflight_htlcs(payment_hash, path);
+                               }
+                               Ok(payment_id)
+                       },
                        Err(e) => match e {
                                PaymentSendFailure::ParameterError(_) => Err(e),
                                PaymentSendFailure::PathParameterError(_) => Err(e),
                                PaymentSendFailure::AllFailedRetrySafe(_) => {
                                        let mut payment_cache = self.payment_cache.lock().unwrap();
-                                       let payment_attempts = payment_cache.get_mut(&payment_hash).unwrap();
-                                       payment_attempts.count += 1;
-                                       if self.retry.is_retryable_now(payment_attempts) {
+                                       let payment_info = payment_cache.get_mut(&payment_hash).unwrap();
+                                       payment_info.attempts.count += 1;
+                                       if self.retry.is_retryable_now(&payment_info.attempts) {
                                                core::mem::drop(payment_cache);
                                                Ok(self.pay_internal(params, payment_hash, send_payment)?)
                                        } else {
                                                Err(e)
                                        }
                                },
-                               PaymentSendFailure::PartialFailure { failed_paths_retry, payment_id, .. } => {
+                               PaymentSendFailure::PartialFailure { failed_paths_retry, payment_id, results } => {
+                                       // If a `PartialFailure` event returns a result that is an `Ok()`, it means that
+                                       // part of our payment is retried. When we receive `MonitorUpdateFailed`, it
+                                       // means that we are still waiting for our channel monitor update to be completed.
+                                       for (result, path) in results.iter().zip(route.paths.into_iter()) {
+                                               match result {
+                                                       Ok(_) | Err(APIError::MonitorUpdateFailed) => {
+                                                               self.process_path_inflight_htlcs(payment_hash, path);
+                                                       },
+                                                       _ => {},
+                                               }
+                                       }
+
                                        if let Some(retry_data) = failed_paths_retry {
                                                // Some paths were sent, even if we failed to send the full MPP value our
                                                // recipient may misbehave and claim the funds, at which point we have to
@@ -466,16 +503,36 @@ where
                }.map_err(|e| PaymentError::Sending(e))
        }
 
+       // Takes in a path to have its information stored in `payment_cache`. This is done for paths
+       // that are pending retry.
+       fn process_path_inflight_htlcs(&self, payment_hash: PaymentHash, path: Vec<RouteHop>) {
+               self.payment_cache.lock().unwrap().entry(payment_hash)
+                       .or_insert_with(|| PaymentInfo::new())
+                       .paths.push(path);
+       }
+
+       // Find the path we want to remove in `payment_cache`. If it doesn't exist, do nothing.
+       fn remove_path_inflight_htlcs(&self, payment_hash: PaymentHash, path: &Vec<RouteHop>) {
+               self.payment_cache.lock().unwrap().entry(payment_hash)
+                       .and_modify(|payment_info| {
+                               if let Some(idx) = payment_info.paths.iter().position(|p| p == path) {
+                                       payment_info.paths.swap_remove(idx);
+                               }
+                       });
+       }
+
        fn retry_payment(
                &self, payment_id: PaymentId, payment_hash: PaymentHash, params: &RouteParameters
        ) -> Result<(), ()> {
-               let attempts =
-                       *self.payment_cache.lock().unwrap().entry(payment_hash)
-                       .and_modify(|attempts| attempts.count += 1)
-                       .or_insert(PaymentAttempts {
-                               count: 1,
-                               first_attempted_at: T::now()
-                       });
+               let attempts = self.payment_cache.lock().unwrap().entry(payment_hash)
+                       .and_modify(|info| info.attempts.count += 1 )
+                       .or_insert_with(|| PaymentInfo {
+                               attempts: PaymentAttempts {
+                                       count: 1,
+                                       first_attempted_at: T::now(),
+                               },
+                               paths: vec![],
+                       }).attempts;
 
                if !self.retry.is_retryable_now(&attempts) {
                        log_trace!(self.logger, "Payment {} exceeded maximum attempts; not retrying ({})", log_bytes!(payment_hash.0), attempts);
@@ -491,17 +548,25 @@ where
 
                let payer = self.payer.node_id();
                let first_hops = self.payer.first_hops();
+               let inflight_htlcs = self.create_inflight_map();
+
                let route = self.router.find_route(
                        &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &self.scorer.lock()
+                       inflight_htlcs
                );
+
                if route.is_err() {
                        log_trace!(self.logger, "Failed to find a route for payment {}; not retrying ({:})", log_bytes!(payment_hash.0), attempts);
                        return Err(());
                }
 
-               match self.payer.retry_payment(&route.unwrap(), payment_id) {
-                       Ok(()) => Ok(()),
+               match self.payer.retry_payment(&route.as_ref().unwrap(), payment_id) {
+                       Ok(()) => {
+                               for path in route.unwrap().paths.into_iter() {
+                                       self.process_path_inflight_htlcs(payment_hash, path);
+                               }
+                               Ok(())
+                       },
                        Err(PaymentSendFailure::ParameterError(_)) |
                        Err(PaymentSendFailure::PathParameterError(_)) => {
                                log_trace!(self.logger, "Failed to retry for payment {} due to bogus route/payment data, not retrying.", log_bytes!(payment_hash.0));
@@ -510,7 +575,19 @@ where
                        Err(PaymentSendFailure::AllFailedRetrySafe(_)) => {
                                self.retry_payment(payment_id, payment_hash, params)
                        },
-                       Err(PaymentSendFailure::PartialFailure { failed_paths_retry, .. }) => {
+                       Err(PaymentSendFailure::PartialFailure { failed_paths_retry, results, .. }) => {
+                               // If a `PartialFailure` error contains a result that is an `Ok()`, it means that
+                               // part of our payment is retried. When we receive `MonitorUpdateFailed`, it
+                               // means that we are still waiting for our channel monitor update to complete.
+                               for (result, path) in results.iter().zip(route.unwrap().paths.into_iter()) {
+                                       match result {
+                                               Ok(_) | Err(APIError::MonitorUpdateFailed) => {
+                                                       self.process_path_inflight_htlcs(payment_hash, path);
+                                               },
+                                               _ => {},
+                                       }
+                               }
+
                                if let Some(retry) = failed_paths_retry {
                                        // Always return Ok for the same reason as noted in pay_internal.
                                        let _ = self.retry_payment(payment_id, payment_hash, &retry);
@@ -527,6 +604,47 @@ where
        pub fn remove_cached_payment(&self, payment_hash: &PaymentHash) {
                self.payment_cache.lock().unwrap().remove(payment_hash);
        }
+
+       /// Given a [`PaymentHash`], this function looks up inflight path attempts in the payment_cache.
+       /// Then, it uses the path information inside the cache to construct a HashMap mapping a channel's
+       /// short channel id and direction to the amount being sent through it.
+       ///
+       /// This function should be called whenever we need information about currently used up liquidity
+       /// across payments.
+       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
+               // HashMap.
+               for payment_info in self.payment_cache.lock().unwrap().values() {
+                       for path in &payment_info.paths {
+                               if path.is_empty() { break };
+                               // total_inflight_map needs to be direction-sensitive when keeping track of the HTLC value
+                               // that is held up. However, the `hops` array, which is a path returned by `find_route` in
+                               // the router excludes the payer node. In the following lines, the payer's information is
+                               // hardcoded with an inflight value of 0 so that we can correctly represent the first hop
+                               // in our sliding window of two.
+                               let our_node_id: PublicKey = self.payer.node_id();
+                               let reversed_hops_with_payer = path.iter().rev().skip(1)
+                                       .map(|hop| hop.pubkey)
+                                       .chain(core::iter::once(our_node_id));
+                               let mut cumulative_msat = 0;
+
+                               // Taking the reversed vector from above, we zip it with just the reversed hops list to
+                               // work "backwards" of the given path, since the last hop's `fee_msat` actually represents
+                               // the total amount sent.
+                               for (next_hop, prev_hop) in path.iter().rev().zip(reversed_hops_with_payer) {
+                                       cumulative_msat += next_hop.fee_msat;
+                                       total_inflight_map
+                                               .entry((next_hop.short_channel_id, NodeId::from_pubkey(&prev_hop) < NodeId::from_pubkey(&next_hop.pubkey)))
+                                               .and_modify(|used_liquidity_msat| *used_liquidity_msat += cumulative_msat)
+                                               .or_insert(cumulative_msat);
+                               }
+                       }
+               }
+
+               InFlightHtlcs(total_inflight_map)
+       }
 }
 
 fn expiry_time_from_unix_epoch(invoice: &Invoice) -> Duration {
@@ -540,26 +658,34 @@ fn has_expired(route_params: &RouteParameters) -> bool {
        } else { false }
 }
 
-impl<P: Deref, R, 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,
-       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        fn handle_event(&self, event: &Event) {
+               match event {
+                       Event::PaymentPathFailed { payment_hash, path, ..  }
+                       | Event::PaymentPathSuccessful { path, payment_hash: Some(payment_hash), .. }
+                       | Event::ProbeSuccessful { payment_hash, path, .. }
+                       | Event::ProbeFailed { payment_hash, path, .. } => {
+                               self.remove_path_inflight_htlcs(*payment_hash, path);
+                       },
+                       _ => {},
+               }
+
                match event {
                        Event::PaymentPathFailed {
-                               payment_id, payment_hash, rejected_by_dest, path, short_channel_id, retry, ..
+                               payment_id, payment_hash, payment_failed_permanently, path, short_channel_id, retry, ..
                        } => {
                                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() {
                                        log_trace!(self.logger, "Payment {} has no id; not retrying", log_bytes!(payment_hash.0));
-                               } else if *rejected_by_dest {
+                               } else if *payment_failed_permanently {
                                        log_trace!(self.logger, "Payment {} rejected by destination; not retrying", log_bytes!(payment_hash.0));
                                        self.payer.abandon_payment(payment_id.unwrap());
                                } else if retry.is_none() {
@@ -577,25 +703,25 @@ 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();
                                let attempts = payment_cache
                                        .remove(payment_hash)
-                                       .map_or(1, |attempts| attempts.count + 1);
+                                       .map_or(1, |payment_info| payment_info.attempts.count + 1);
                                log_trace!(self.logger, "Payment {} succeeded (attempts: {})", log_bytes!(payment_hash.0), attempts);
                        },
                        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);
                                }
                        },
                        _ => {},
@@ -606,28 +732,55 @@ 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)).map(|v| *v)
+       }
+}
+
+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::features::{ChannelFeatures, NodeFeatures, InitFeatures};
        use lightning::ln::functional_test_utils::*;
        use lightning::ln::msgs::{ChannelMessageHandler, ErrorAction, LightningError};
-       use lightning::routing::gossip::NodeId;
+       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;
+       use lightning::util::errors::APIError::{ChannelUnavailable, MonitorUpdateFailed};
 
        fn invoice(payment_preimage: PaymentPreimage) -> Invoice {
                let payment_hash = Sha256::hash(&payment_preimage.0);
@@ -706,11 +859,10 @@ 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);
@@ -735,11 +887,10 @@ 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);
@@ -748,7 +899,7 @@ mod tests {
                        payment_id,
                        payment_hash,
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: TestRouter::path_for_value(final_value_msat),
                        short_channel_id: None,
@@ -775,16 +926,15 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new()
-                       .fails_with_partial_failure(retry.clone(), OnAttempt(1))
-                       .fails_with_partial_failure(retry, OnAttempt(2))
+                       .fails_with_partial_failure(retry.clone(), OnAttempt(1), None)
+                       .fails_with_partial_failure(retry, OnAttempt(2), None)
                        .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());
        }
@@ -802,18 +952,17 @@ 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 {
                        payment_id,
                        payment_hash,
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: TestRouter::path_for_value(final_value_msat),
                        short_channel_id: None,
@@ -847,11 +996,10 @@ 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);
@@ -860,7 +1008,7 @@ mod tests {
                        payment_id,
                        payment_hash: PaymentHash(invoice.payment_hash().clone().into_inner()),
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: true,
                        path: TestRouter::path_for_value(final_value_msat),
                        short_channel_id: None,
@@ -874,7 +1022,7 @@ mod tests {
                        payment_id,
                        payment_hash: PaymentHash(invoice.payment_hash().clone().into_inner()),
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: TestRouter::path_for_value(final_value_msat / 2),
                        short_channel_id: None,
@@ -905,13 +1053,12 @@ 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);
@@ -920,7 +1067,7 @@ mod tests {
                        payment_id,
                        payment_hash: PaymentHash(invoice.payment_hash().clone().into_inner()),
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: true,
                        path: TestRouter::path_for_value(final_value_msat),
                        short_channel_id: None,
@@ -947,11 +1094,10 @@ 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);
@@ -960,7 +1106,7 @@ mod tests {
                        payment_id,
                        payment_hash: PaymentHash(invoice.payment_hash().clone().into_inner()),
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: vec![],
                        short_channel_id: None,
@@ -979,11 +1125,10 @@ 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);
@@ -1004,11 +1149,10 @@ 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);
@@ -1021,7 +1165,7 @@ mod tests {
                        payment_id,
                        payment_hash: PaymentHash(invoice.payment_hash().clone().into_inner()),
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: vec![],
                        short_channel_id: None,
@@ -1045,11 +1189,10 @@ 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);
@@ -1058,7 +1201,7 @@ mod tests {
                        payment_id,
                        payment_hash: PaymentHash(invoice.payment_hash().clone().into_inner()),
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: TestRouter::path_for_value(final_value_msat / 2),
                        short_channel_id: None,
@@ -1079,11 +1222,10 @@ 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);
@@ -1092,7 +1234,7 @@ mod tests {
                        payment_id,
                        payment_hash: PaymentHash(invoice.payment_hash().clone().into_inner()),
                        network_update: None,
-                       rejected_by_dest: true,
+                       payment_failed_permanently: true,
                        all_paths_failed: false,
                        path: vec![],
                        short_channel_id: None,
@@ -1115,11 +1257,10 @@ 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());
 
@@ -1141,7 +1282,7 @@ mod tests {
                        payment_id,
                        payment_hash,
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: vec![],
                        short_channel_id: None,
@@ -1155,10 +1296,9 @@ 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);
@@ -1178,11 +1318,10 @@ 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(_)) => {},
@@ -1202,11 +1341,10 @@ 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());
@@ -1225,11 +1363,10 @@ 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);
@@ -1256,11 +1393,10 @@ 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
@@ -1276,7 +1412,7 @@ mod tests {
                        payment_id,
                        payment_hash,
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path: vec![],
                        short_channel_id: None,
@@ -1309,20 +1445,20 @@ 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 {
                        payment_id,
                        payment_hash,
                        network_update: None,
-                       rejected_by_dest: false,
+                       payment_failed_permanently: false,
                        all_paths_failed: false,
                        path,
                        short_channel_id,
@@ -1344,14 +1480,13 @@ 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 {
@@ -1364,24 +1499,291 @@ mod tests {
                invoice_payer.handle_event(&event);
        }
 
-       struct TestRouter;
+       #[test]
+       fn generates_correct_inflight_map_data() {
+               let event_handled = core::cell::RefCell::new(false);
+               let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let payment_hash = Some(PaymentHash(invoice.payment_hash().clone().into_inner()));
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
+
+               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::new(TestScorer::new());
+               let logger = TestLogger::new();
+               let invoice_payer =
+                       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.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.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()
+               });
+
+               let inflight_map = invoice_payer.create_inflight_map();
+
+               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.0.get(&(3, false)).unwrap().clone(), 74);
+               assert_eq!(inflight_map.0.get(&(4, false)).unwrap().clone(), 64)
+       }
+
+       #[test]
+       fn considers_inflight_htlcs_between_invoice_payments_when_path_succeeds() {
+               // First, let's just send a payment through, but only make sure one of the path completes
+               let event_handled = core::cell::RefCell::new(false);
+               let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let payment_invoice = invoice(payment_preimage);
+               let payment_hash = Some(PaymentHash(payment_invoice.payment_hash().clone().into_inner()));
+               let final_value_msat = payment_invoice.amount_milli_satoshis().unwrap();
+
+               let payer = TestPayer::new()
+                       .expect_send(Amount::ForInvoice(final_value_msat))
+                       .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 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 } )
+                       .expect_usage(ChannelUsage { amount_msat: 94, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       // 1st invoice, 2nd path
+                       .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       .expect_usage(ChannelUsage { amount_msat: 74, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       // 2nd 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 } )
+                       .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 } );
+               let router = TestRouter::new(scorer);
+               let logger = TestLogger::new();
+               let invoice_payer =
+                       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();
+               invoice_payer.handle_event(&Event::PaymentPathSuccessful {
+                       payment_id, payment_hash, path: route.paths[0].clone()
+               });
+
+               // Let's pay a second invoice that will be using the same path. This should trigger the
+               // assertions that expect the last 4 ChannelUsage values above where TestScorer is initialized.
+               // Particularly, the 2nd path of the 1st payment, since it is not yet complete, should still
+               // have 64 msats inflight for paths considering the channel with scid of 1.
+               let payment_preimage_2 = PaymentPreimage([2; 32]);
+               let payment_invoice_2 = invoice(payment_preimage_2);
+               invoice_payer.pay_invoice(&payment_invoice_2).unwrap();
+       }
+
+       #[test]
+       fn considers_inflight_htlcs_between_retries() {
+               // First, let's just send a payment through, but only make sure one of the path completes
+               let event_handled = core::cell::RefCell::new(false);
+               let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let payment_invoice = invoice(payment_preimage);
+               let payment_hash = PaymentHash(payment_invoice.payment_hash().clone().into_inner());
+               let final_value_msat = payment_invoice.amount_milli_satoshis().unwrap();
+
+               let payer = TestPayer::new()
+                       .expect_send(Amount::ForInvoice(final_value_msat))
+                       .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 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 } )
+                       .expect_usage(ChannelUsage { amount_msat: 94, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       // 1st invoice, 2nd path
+                       .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       .expect_usage(ChannelUsage { amount_msat: 74, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       // Retry 1, 1st path
+                       .expect_usage(ChannelUsage { amount_msat: 32, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       .expect_usage(ChannelUsage { amount_msat: 52, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       .expect_usage(ChannelUsage { amount_msat: 62, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       // Retry 1, 2nd path
+                       .expect_usage(ChannelUsage { amount_msat: 32, inflight_htlc_msat: 64, effective_capacity: EffectiveCapacity::Unknown } )
+                       .expect_usage(ChannelUsage { amount_msat: 42, inflight_htlc_msat: 64 + 10, effective_capacity: EffectiveCapacity::Unknown } )
+                       // Retry 2, 1st path
+                       .expect_usage(ChannelUsage { amount_msat: 16, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       .expect_usage(ChannelUsage { amount_msat: 36, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
+                       .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 } );
+               let router = TestRouter::new(scorer);
+               let logger = TestLogger::new();
+               let invoice_payer =
+                       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());
+               invoice_payer.handle_event(&Event::PaymentPathFailed {
+                       payment_id,
+                       payment_hash,
+                       network_update: None,
+                       payment_failed_permanently: false,
+                       all_paths_failed: false,
+                       path: TestRouter::path_for_value(final_value_msat),
+                       short_channel_id: None,
+                       retry: Some(TestRouter::retry_for_invoice(&payment_invoice)),
+               });
+
+               // Fails again the 1st path of our retry
+               invoice_payer.handle_event(&Event::PaymentPathFailed {
+                       payment_id,
+                       payment_hash,
+                       network_update: None,
+                       payment_failed_permanently: false,
+                       all_paths_failed: false,
+                       path: TestRouter::path_for_value(final_value_msat / 2),
+                       short_channel_id: None,
+                       retry: Some(RouteParameters {
+                               final_value_msat: final_value_msat / 4,
+                               ..TestRouter::retry_for_invoice(&payment_invoice)
+                       }),
+               });
+       }
+
+       #[test]
+       fn accounts_for_some_inflight_htlcs_sent_during_partial_failure() {
+               let event_handled = core::cell::RefCell::new(false);
+               let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice_to_pay = invoice(payment_preimage);
+               let final_value_msat = invoice_to_pay.amount_milli_satoshis().unwrap();
+
+               let retry = TestRouter::retry_for_invoice(&invoice_to_pay);
+               let payer = TestPayer::new()
+                       .fails_with_partial_failure(
+                               retry.clone(), OnAttempt(1),
+                               Some(vec![
+                                       Err(ChannelUnavailable { err: "abc".to_string() }), Err(MonitorUpdateFailed)
+                               ]))
+                       .expect_send(Amount::ForInvoice(final_value_msat));
+
+               let router = TestRouter::new(TestScorer::new());
+               let logger = TestLogger::new();
+               let invoice_payer =
+                       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.0.len(), 2);
+       }
+
+       #[test]
+       fn accounts_for_all_inflight_htlcs_sent_during_partial_failure() {
+               let event_handled = core::cell::RefCell::new(false);
+               let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice_to_pay = invoice(payment_preimage);
+               let final_value_msat = invoice_to_pay.amount_milli_satoshis().unwrap();
+
+               let retry = TestRouter::retry_for_invoice(&invoice_to_pay);
+               let payer = TestPayer::new()
+                       .fails_with_partial_failure(
+                               retry.clone(), OnAttempt(1),
+                               Some(vec![
+                                       Ok(()), Err(MonitorUpdateFailed)
+                               ]))
+                       .expect_send(Amount::ForInvoice(final_value_msat));
+
+               let router = TestRouter::new(TestScorer::new());
+               let logger = TestLogger::new();
+               let invoice_payer =
+                       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.0.len(), 5);
+       }
+
+       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![
-                                       vec![RouteHop {
-                                               pubkey: PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap(),
-                                               channel_features: ChannelFeatures::empty(),
-                                               node_features: NodeFeatures::empty(),
-                                               short_channel_id: 0, fee_msat: final_value_msat / 2, cltv_expiry_delta: 144
-                                       }],
-                                       vec![RouteHop {
-                                               pubkey: PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap(),
-                                               channel_features: ChannelFeatures::empty(),
-                                               node_features: NodeFeatures::empty(),
-                                               short_channel_id: 1, fee_msat: final_value_msat / 2, cltv_expiry_delta: 144
-                                       }],
+                                       vec![
+                                               RouteHop {
+                                                       pubkey: PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap(),
+                                                       channel_features: ChannelFeatures::empty(),
+                                                       node_features: NodeFeatures::empty(),
+                                                       short_channel_id: 0,
+                                                       fee_msat: 10,
+                                                       cltv_expiry_delta: 0
+                                               },
+                                               RouteHop {
+                                                       pubkey: PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap(),
+                                                       channel_features: ChannelFeatures::empty(),
+                                                       node_features: NodeFeatures::empty(),
+                                                       short_channel_id: 1,
+                                                       fee_msat: 20,
+                                                       cltv_expiry_delta: 0
+                                               },
+                                               RouteHop {
+                                                       pubkey: PublicKey::from_slice(&hex::decode("027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007").unwrap()[..]).unwrap(),
+                                                       channel_features: ChannelFeatures::empty(),
+                                                       node_features: NodeFeatures::empty(),
+                                                       short_channel_id: 2,
+                                                       fee_msat: final_value_msat / 2,
+                                                       cltv_expiry_delta: 0
+                                               },
+                                       ],
+                                       vec![
+                                               RouteHop {
+                                                       pubkey: PublicKey::from_slice(&hex::decode("029e03a901b85534ff1e92c43c74431f7ce72046060fcf7a95c37e148f78c77255").unwrap()[..]).unwrap(),
+                                                       channel_features: ChannelFeatures::empty(),
+                                                       node_features: NodeFeatures::empty(),
+                                                       short_channel_id: 3,
+                                                       fee_msat: 10,
+                                                       cltv_expiry_delta: 144
+                                               },
+                                               RouteHop {
+                                                       pubkey: PublicKey::from_slice(&hex::decode("027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007").unwrap()[..]).unwrap(),
+                                                       channel_features: ChannelFeatures::empty(),
+                                                       node_features: NodeFeatures::empty(),
+                                                       short_channel_id: 4,
+                                                       fee_msat: final_value_msat / 2,
+                                                       cltv_expiry_delta: 144
+                                               }
+                                       ],
                                ],
                                payment_params: None,
                        }
@@ -1407,30 +1809,79 @@ mod tests {
                }
        }
 
-       impl<S: Score> Router<S> for TestRouter {
+       impl Router for TestRouter {
                fn find_route(
-                       &self, _payer: &PublicKey, route_params: &RouteParameters, _payment_hash: &PaymentHash,
-                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
+                       &self, payer: &PublicKey, route_params: &RouteParameters, _payment_hash: &PaymentHash,
+                       _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() {
+                                       aggregate_msat += hop.fee_msat;
+                                       let usage = ChannelUsage {
+                                               amount_msat: aggregate_msat,
+                                               inflight_htlc_msat: 0,
+                                               effective_capacity: EffectiveCapacity::Unknown,
+                                       };
+
+                                       // Since the path is reversed, the last element in our iteration is the first
+                                       // hop.
+                                       if idx == path.len() - 1 {
+                                               scorer.channel_penalty_msat(hop.short_channel_id, &NodeId::from_pubkey(payer), &NodeId::from_pubkey(&hop.pubkey), usage);
+                                       } else {
+                                               scorer.channel_penalty_msat(hop.short_channel_id, &NodeId::from_pubkey(&path[idx + 1].pubkey), &NodeId::from_pubkey(&hop.pubkey), usage);
+                                       }
+                               }
+                       }
+
                        Ok(Route {
                                payment_params: Some(route_params.payment_params.clone()), ..Self::route_for_value(route_params.final_value_msat)
                        })
                }
+
+               fn notify_payment_path_failed(&self, path: &[&RouteHop], short_channel_id: u64) {
+                       self.scorer.lock().payment_path_failed(path, short_channel_id);
+               }
+
+               fn notify_payment_path_successful(&self, path: &[&RouteHop]) {
+                       self.scorer.lock().payment_path_successful(path);
+               }
+
+               fn notify_payment_probe_successful(&self, path: &[&RouteHop]) {
+                       self.scorer.lock().probe_successful(path);
+               }
+
+               fn notify_payment_probe_failed(&self, path: &[&RouteHop], short_channel_id: u64) {
+                       self.scorer.lock().probe_failed(path, short_channel_id);
+               }
        }
 
        struct FailingRouter;
 
-       impl<S: Score> Router<S> for FailingRouter {
+       impl Router for FailingRouter {
                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: &[&RouteHop], _short_channel_id: u64) {}
+
+               fn notify_payment_path_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_failed(&self, _path: &[&RouteHop], _short_channel_id: u64) {}
        }
 
        struct TestScorer {
-               expectations: Option<VecDeque<TestResult>>,
+               event_expectations: Option<VecDeque<TestResult>>,
+               scorer_expectations: RefCell<Option<VecDeque<ChannelUsage>>>,
        }
 
        #[derive(Debug)]
@@ -1442,12 +1893,18 @@ mod tests {
        impl TestScorer {
                fn new() -> Self {
                        Self {
-                               expectations: None,
+                               event_expectations: None,
+                               scorer_expectations: RefCell::new(None),
                        }
                }
 
                fn expect(mut self, expectation: TestResult) -> Self {
-                       self.expectations.get_or_insert_with(|| VecDeque::new()).push_back(expectation);
+                       self.event_expectations.get_or_insert_with(|| VecDeque::new()).push_back(expectation);
+                       self
+               }
+
+               fn expect_usage(self, expectation: ChannelUsage) -> Self {
+                       self.scorer_expectations.borrow_mut().get_or_insert_with(|| VecDeque::new()).push_back(expectation);
                        self
                }
        }
@@ -1459,11 +1916,22 @@ mod tests {
 
        impl Score for TestScorer {
                fn channel_penalty_msat(
-                       &self, _short_channel_id: u64, _source: &NodeId, _target: &NodeId, _usage: ChannelUsage
-               ) -> u64 { 0 }
+                       &self, _short_channel_id: u64, _source: &NodeId, _target: &NodeId, usage: ChannelUsage
+               ) -> u64 {
+                       if let Some(scorer_expectations) = self.scorer_expectations.borrow_mut().as_mut() {
+                               match scorer_expectations.pop_front() {
+                                       Some(expectation) => {
+                                               assert_eq!(expectation.amount_msat, usage.amount_msat);
+                                               assert_eq!(expectation.inflight_htlc_msat, usage.inflight_htlc_msat);
+                                       },
+                                       None => {},
+                               }
+                       }
+                       0
+               }
 
                fn payment_path_failed(&mut self, actual_path: &[&RouteHop], actual_short_channel_id: u64) {
-                       if let Some(expectations) = &mut self.expectations {
+                       if let Some(expectations) = &mut self.event_expectations {
                                match expectations.pop_front() {
                                        Some(TestResult::PaymentFailure { path, short_channel_id }) => {
                                                assert_eq!(actual_path, &path.iter().collect::<Vec<_>>()[..]);
@@ -1472,13 +1940,13 @@ 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),
                                }
                        }
                }
 
                fn payment_path_successful(&mut self, actual_path: &[&RouteHop]) {
-                       if let Some(expectations) = &mut self.expectations {
+                       if let Some(expectations) = &mut self.event_expectations {
                                match expectations.pop_front() {
                                        Some(TestResult::PaymentFailure { path, .. }) => {
                                                panic!("Unexpected payment path failure: {:?}", path)
@@ -1486,13 +1954,13 @@ 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),
                                }
                        }
                }
 
                fn probe_failed(&mut self, actual_path: &[&RouteHop], _: u64) {
-                       if let Some(expectations) = &mut self.expectations {
+                       if let Some(expectations) = &mut self.event_expectations {
                                match expectations.pop_front() {
                                        Some(TestResult::PaymentFailure { path, .. }) => {
                                                panic!("Unexpected failed payment path: {:?}", path)
@@ -1500,12 +1968,12 @@ 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),
                                }
                        }
                }
                fn probe_successful(&mut self, actual_path: &[&RouteHop]) {
-                       if let Some(expectations) = &mut self.expectations {
+                       if let Some(expectations) = &mut self.event_expectations {
                                match expectations.pop_front() {
                                        Some(TestResult::PaymentFailure { path, .. }) => {
                                                panic!("Unexpected payment path failure: {:?}", path)
@@ -1513,7 +1981,7 @@ 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),
                                }
                        }
                }
@@ -1525,9 +1993,15 @@ mod tests {
                                return;
                        }
 
-                       if let Some(expectations) = &self.expectations {
-                               if !expectations.is_empty() {
-                                       panic!("Unsatisfied scorer expectations: {:?}", expectations);
+                       if let Some(event_expectations) = &self.event_expectations {
+                               if !event_expectations.is_empty() {
+                                       panic!("Unsatisfied event expectations: {:?}", event_expectations);
+                               }
+                       }
+
+                       if let Some(scorer_expectations) = self.scorer_expectations.borrow().as_ref() {
+                               if !scorer_expectations.is_empty() {
+                                       panic!("Unsatisfied scorer expectations: {:?}", scorer_expectations)
                                }
                        }
                }
@@ -1567,9 +2041,9 @@ mod tests {
                        self.fails_with(failure, OnAttempt(attempt))
                }
 
-               fn fails_with_partial_failure(self, retry: RouteParameters, attempt: OnAttempt) -> Self {
+               fn fails_with_partial_failure(self, retry: RouteParameters, attempt: OnAttempt, results: Option<Vec<Result<(), APIError>>>) -> Self {
                        self.fails_with(PaymentSendFailure::PartialFailure {
-                               results: vec![],
+                               results: results.unwrap_or(vec![]),
                                failed_paths_retry: Some(retry),
                                payment_id: PaymentId([1; 32]),
                        }, attempt)
@@ -1650,13 +2124,21 @@ mod tests {
        // *** Full Featured Functional Tests with a Real ChannelManager ***
        struct ManualRouter(RefCell<VecDeque<Result<Route, LightningError>>>);
 
-       impl<S: Score> Router<S> for ManualRouter {
+       impl Router for ManualRouter {
                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: &[&RouteHop], _short_channel_id: u64) {}
+
+               fn notify_payment_path_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_failed(&self, _path: &[&RouteHop], _short_channel_id: u64) {}
        }
        impl ManualRouter {
                fn expect_find_route(&self, result: Result<Route, LightningError>) {
@@ -1712,8 +2194,7 @@ 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(),
@@ -1758,8 +2239,7 @@ 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(),
@@ -1840,8 +2320,7 @@ 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(),
@@ -1913,8 +2392,8 @@ mod tests {
                // treated this as "HTLC complete" and dropped the retry counter, causing us to retry again
                // if the final HTLC failed.
                expected_events.borrow_mut().push_back(&|ev: &Event| {
-                       if let Event::PaymentPathFailed { rejected_by_dest, all_paths_failed, .. } = ev {
-                               assert!(!rejected_by_dest);
+                       if let Event::PaymentPathFailed { payment_failed_permanently, all_paths_failed, .. } = ev {
+                               assert!(!payment_failed_permanently);
                                assert!(all_paths_failed);
                        } else { panic!("Unexpected event"); }
                });
@@ -1931,8 +2410,8 @@ mod tests {
                commitment_signed_dance!(nodes[0], nodes[1], &bs_fail_update.commitment_signed, false, true);
 
                expected_events.borrow_mut().push_back(&|ev: &Event| {
-                       if let Event::PaymentPathFailed { rejected_by_dest, all_paths_failed, .. } = ev {
-                               assert!(!rejected_by_dest);
+                       if let Event::PaymentPathFailed { payment_failed_permanently, all_paths_failed, .. } = ev {
+                               assert!(!payment_failed_permanently);
                                assert!(all_paths_failed);
                        } else { panic!("Unexpected event"); }
                });