Swap around generic argument ordering in InvoicePayer for bindings
[rust-lightning] / lightning-invoice / src / payment.rs
index b3b84e351b72f7a19d497810d2fb1a5e85b36a85..4e249a85c3f09d238a59cd09c1e55e6b920eea66 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`] is capable of retrying failed payments. It accomplishes this by implementing
 //! [`EventHandler`] which decorates a user-provided handler. It will intercept any
 //! [`Event::PaymentPathFailed`] events and retry the failed paths for a fixed number of total
 //! # use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 //! # use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 //! # use lightning::ln::msgs::LightningError;
-//! # use lightning::routing;
+//! # use lightning::routing::scoring::Score;
 //! # use lightning::routing::network_graph::NodeId;
 //! # use lightning::routing::router::{Route, RouteHop, RouteParameters};
 //! # use lightning::util::events::{Event, EventHandler, EventsProvider};
 //! # use lightning::util::logger::{Logger, Record};
+//! # use lightning::util::ser::{Writeable, Writer};
 //! # use lightning_invoice::Invoice;
 //! # use lightning_invoice::payment::{InvoicePayer, Payer, RetryAttempts, Router};
 //! # use secp256k1::key::PublicKey;
 //! #     fn retry_payment(
 //! #         &self, route: &Route, payment_id: PaymentId
 //! #     ) -> Result<(), PaymentSendFailure> { unimplemented!() }
+//! #     fn abandon_payment(&self, payment_id: PaymentId) { unimplemented!() }
 //! # }
 //! #
-//! # struct FakeRouter {};
-//! # impl<S: routing::Score> Router<S> for FakeRouter {
+//! # struct FakeRouter {}
+//! # impl<S: Score> Router<S> for FakeRouter {
 //! #     fn find_route(
-//! #         &self, payer: &PublicKey, params: &RouteParameters,
+//! #         &self, payer: &PublicKey, params: &RouteParameters, payment_hash: &PaymentHash,
 //! #         first_hops: Option<&[&ChannelDetails]>, scorer: &S
 //! #     ) -> Result<Route, LightningError> { unimplemented!() }
 //! # }
 //! #
-//! # struct FakeScorer {};
-//! # impl routing::Score for FakeScorer {
+//! # struct FakeScorer {}
+//! # impl Writeable for FakeScorer {
+//! #     fn write<W: Writer>(&self, w: &mut W) -> Result<(), std::io::Error> { unimplemented!(); }
+//! # }
+//! # impl Score for FakeScorer {
 //! #     fn channel_penalty_msat(
-//! #         &self, _short_channel_id: u64, _source: &NodeId, _target: &NodeId
+//! #         &self, _short_channel_id: u64, _send_amt: u64, _chan_amt: Option<u64>, _source: &NodeId, _target: &NodeId
 //! #     ) -> u64 { 0 }
 //! #     fn payment_path_failed(&mut self, _path: &[&RouteHop], _short_channel_id: u64) {}
+//! #     fn payment_path_successful(&mut self, _path: &[&RouteHop]) {}
 //! # }
 //! #
-//! # struct FakeLogger {};
+//! # struct FakeLogger {}
 //! # impl Logger for FakeLogger {
 //! #     fn log(&self, record: &Record) { unimplemented!() }
 //! # }
 //! let invoice_payer = InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 //!
 //! let invoice = "...";
-//! let invoice = invoice.parse::<Invoice>().unwrap();
-//! invoice_payer.pay_invoice(&invoice).unwrap();
+//! if let Ok(invoice) = invoice.parse::<Invoice>() {
+//!     invoice_payer.pay_invoice(&invoice).unwrap();
 //!
 //! # let event_provider = FakeEventProvider {};
-//! loop {
-//!     event_provider.process_pending_events(&invoice_payer);
+//!     loop {
+//!         event_provider.process_pending_events(&invoice_payer);
+//!     }
 //! }
 //! # }
 //! ```
@@ -122,8 +133,7 @@ use bitcoin_hashes::sha256::Hash as Sha256;
 use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 use lightning::ln::msgs::LightningError;
-use lightning::routing;
-use lightning::routing::{LockableScore, Score};
+use lightning::routing::scoring::{LockableScore, Score};
 use lightning::routing::router::{Payee, Route, RouteParameters};
 use lightning::util::events::{Event, EventHandler};
 use lightning::util::logger::Logger;
@@ -136,13 +146,16 @@ use std::sync::Mutex;
 use std::time::{Duration, SystemTime};
 
 /// A utility for paying [`Invoice`]s and sending spontaneous payments.
-pub struct InvoicePayer<P: Deref, R, S: Deref, L: Deref, E>
+///
+/// See [module-level documentation] for details.
+///
+/// [module-level documentation]: crate::payment
+pub struct InvoicePayer<P: Deref, R, S: Deref, L: Deref, E: EventHandler>
 where
        P::Target: Payer,
-       R: for <'a> Router<<<S as Deref>::Target as routing::LockableScore<'a>>::Locked>,
-       S::Target: for <'a> routing::LockableScore<'a>,
+       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
+       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
-       E: EventHandler,
 {
        payer: P,
        router: R,
@@ -174,14 +187,17 @@ pub trait Payer {
 
        /// Retries a failed payment path for the [`PaymentId`] using the given [`Route`].
        fn retry_payment(&self, route: &Route, payment_id: PaymentId) -> Result<(), PaymentSendFailure>;
+
+       /// Signals that no further retries for the given payment will occur.
+       fn abandon_payment(&self, payment_id: PaymentId);
 }
 
 /// A trait defining behavior for routing an [`Invoice`] payment.
-pub trait Router<S: routing::Score> {
+pub trait Router<S: Score> {
        /// Finds a [`Route`] between `payer` and `payee` for a payment with the given values.
        fn find_route(
-               &self, payer: &PublicKey, params: &RouteParameters, first_hops: Option<&[&ChannelDetails]>,
-               scorer: &S
+               &self, payer: &PublicKey, params: &RouteParameters, payment_hash: &PaymentHash,
+               first_hops: Option<&[&ChannelDetails]>, scorer: &S
        ) -> Result<Route, LightningError>;
 }
 
@@ -204,13 +220,12 @@ pub enum PaymentError {
        Sending(PaymentSendFailure),
 }
 
-impl<P: Deref, R, S: Deref, L: Deref, E> InvoicePayer<P, R, S, L, E>
+impl<P: Deref, R, S: Deref, L: Deref, E: EventHandler> InvoicePayer<P, R, S, L, E>
 where
        P::Target: Payer,
-       R: for <'a> Router<<<S as Deref>::Target as routing::LockableScore<'a>>::Locked>,
-       S::Target: for <'a> routing::LockableScore<'a>,
+       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
+       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
-       E: EventHandler,
 {
        /// Creates an invoice payer that retries failed payment paths.
        ///
@@ -329,10 +344,8 @@ where
                let payer = self.payer.node_id();
                let first_hops = self.payer.first_hops();
                let route = self.router.find_route(
-                       &payer,
-                       params,
-                       Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &self.scorer.lock(),
+                       &payer, params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
+                       &self.scorer.lock()
                ).map_err(|e| PaymentError::Routing(e))?;
 
                match send_payment(&route) {
@@ -392,7 +405,10 @@ where
 
                let payer = self.payer.node_id();
                let first_hops = self.payer.first_hops();
-               let route = self.router.find_route(&payer, &params, Some(&first_hops.iter().collect::<Vec<_>>()), &self.scorer.lock());
+               let route = self.router.find_route(
+                       &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
+                       &self.scorer.lock()
+               );
                if route.is_err() {
                        log_trace!(self.logger, "Failed to find a route for payment {}; not retrying (attempts: {})", log_bytes!(payment_hash.0), attempts);
                        return Err(());
@@ -437,37 +453,44 @@ fn has_expired(params: &RouteParameters) -> bool {
        } else { false }
 }
 
-impl<P: Deref, R, S: Deref, L: Deref, E> EventHandler for InvoicePayer<P, R, S, L, E>
+impl<P: Deref, R, S: Deref, L: Deref, E: EventHandler> EventHandler for InvoicePayer<P, R, S, L, E>
 where
        P::Target: Payer,
-       R: for <'a> Router<<<S as Deref>::Target as routing::LockableScore<'a>>::Locked>,
-       S::Target: for <'a> routing::LockableScore<'a>,
+       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
+       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
-       E: EventHandler,
 {
        fn handle_event(&self, event: &Event) {
                match event {
                        Event::PaymentPathFailed {
-                               all_paths_failed, payment_id, payment_hash, rejected_by_dest, path,
-                               short_channel_id, retry, ..
+                               payment_id, payment_hash, rejected_by_dest, 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);
                                }
 
-                               if *rejected_by_dest {
-                                       log_trace!(self.logger, "Payment {} rejected by destination; not retrying", log_bytes!(payment_hash.0));
-                               } else if payment_id.is_none() {
+                               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 {
+                                       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() {
                                        log_trace!(self.logger, "Payment {} missing retry params; not retrying", log_bytes!(payment_hash.0));
+                                       self.payer.abandon_payment(payment_id.unwrap());
                                } else if self.retry_payment(payment_id.unwrap(), *payment_hash, retry.as_ref().unwrap()).is_ok() {
                                        // We retried at least somewhat, don't provide the PaymentPathFailed event to the user.
                                        return;
+                               } else {
+                                       self.payer.abandon_payment(payment_id.unwrap());
                                }
-
-                               if *all_paths_failed { self.payment_cache.lock().unwrap().remove(payment_hash); }
+                       },
+                       Event::PaymentFailed { payment_hash, .. } => {
+                               self.remove_cached_payment(&payment_hash);
+                       },
+                       Event::PaymentPathSuccessful { path, .. } => {
+                               let path = path.iter().collect::<Vec<_>>();
+                               self.scorer.lock().payment_path_successful(&path);
                        },
                        Event::PaymentSent { payment_hash, .. } => {
                                let mut payment_cache = self.payment_cache.lock().unwrap();
@@ -493,12 +516,12 @@ mod tests {
        use lightning::ln::PaymentPreimage;
        use lightning::ln::features::{ChannelFeatures, NodeFeatures, InitFeatures};
        use lightning::ln::functional_test_utils::*;
-       use lightning::ln::msgs::{ErrorAction, LightningError};
+       use lightning::ln::msgs::{ChannelMessageHandler, ErrorAction, LightningError};
        use lightning::routing::network_graph::NodeId;
        use lightning::routing::router::{Payee, Route, RouteHop};
        use lightning::util::test_utils::TestLogger;
        use lightning::util::errors::APIError;
-       use lightning::util::events::{Event, MessageSendEventsProvider};
+       use lightning::util::events::{Event, EventsProvider, MessageSendEvent, MessageSendEventsProvider};
        use secp256k1::{SecretKey, PublicKey, Secp256k1};
        use std::cell::RefCell;
        use std::collections::VecDeque;
@@ -566,8 +589,9 @@ mod tests {
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = invoice(payment_preimage);
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
-               let payer = TestPayer::new();
+               let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
                let router = TestRouter {};
                let scorer = RefCell::new(TestScorer::new());
                let logger = TestLogger::new();
@@ -595,8 +619,8 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new()
-                       .expect_value_msat(final_value_msat)
-                       .expect_value_msat(final_value_msat / 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 logger = TestLogger::new();
@@ -627,6 +651,30 @@ mod tests {
                assert_eq!(*payer.attempts.borrow(), 2);
        }
 
+       #[test]
+       fn pays_invoice_on_partial_failure() {
+               let event_handler = |_: &_| { panic!() };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let retry = TestRouter::retry_for_invoice(&invoice);
+               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))
+                       .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 logger = TestLogger::new();
+               let invoice_payer =
+                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
+
+               assert!(invoice_payer.pay_invoice(&invoice).is_ok());
+       }
+
        #[test]
        fn retries_payment_path_for_unknown_payment() {
                let event_handled = core::cell::RefCell::new(false);
@@ -637,7 +685,9 @@ mod tests {
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
-               let payer = TestPayer::new();
+               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 logger = TestLogger::new();
@@ -680,9 +730,9 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new()
-                       .expect_value_msat(final_value_msat)
-                       .expect_value_msat(final_value_msat / 2)
-                       .expect_value_msat(final_value_msat / 2);
+                       .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 logger = TestLogger::new();
@@ -732,15 +782,17 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
 
@@ -783,15 +835,17 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
 
@@ -825,7 +879,8 @@ mod tests {
 
                let payer = TestPayer::new()
                        .fails_on_attempt(2)
-                       .expect_value_msat(final_value_msat);
+                       .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 logger = TestLogger::new();
@@ -855,15 +910,17 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
 
@@ -887,15 +944,19 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
+
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(0));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
 
                // Cannot repay an invoice pending payment.
@@ -946,15 +1007,19 @@ mod tests {
 
        #[test]
        fn fails_paying_invoice_with_sending_errors() {
-               let payer = TestPayer::new().fails_on_attempt(1);
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
+
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, |_: &_| {}, RetryAttempts(0));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                match invoice_payer.pay_invoice(&invoice) {
                        Err(PaymentError::Sending(_)) => {},
                        Err(_) => panic!("unexpected error"),
@@ -972,7 +1037,7 @@ mod tests {
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
                let final_value_msat = 100;
 
-               let payer = TestPayer::new().expect_value_msat(final_value_msat);
+               let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
                let router = TestRouter {};
                let scorer = RefCell::new(TestScorer::new());
                let logger = TestLogger::new();
@@ -1026,7 +1091,7 @@ mod tests {
 
                let payer = TestPayer::new()
                        .expect_send(Amount::Spontaneous(final_value_msat))
-                       .expect_send(Amount::ForInvoiceOrRetry(final_value_msat));
+                       .expect_send(Amount::OnRetry(final_value_msat));
                let router = TestRouter {};
                let scorer = RefCell::new(TestScorer::new());
                let logger = TestLogger::new();
@@ -1077,9 +1142,13 @@ mod tests {
                let short_channel_id = Some(path[0].short_channel_id);
 
                // Expect that scorer is given short_channel_id upon handling the event.
-               let payer = TestPayer::new();
+               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_channel_failure(short_channel_id.unwrap()));
+               let scorer = RefCell::new(TestScorer::new().expect(PaymentPath::Failure {
+                       path: path.clone(), short_channel_id: path[0].short_channel_id,
+               }));
                let logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
@@ -1098,6 +1167,39 @@ mod tests {
                invoice_payer.handle_event(&event);
        }
 
+       #[test]
+       fn scores_successful_channels() {
+               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 route = TestRouter::route_for_value(final_value_msat);
+
+               // 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()
+                       .expect(PaymentPath::Success { path: route.paths[0].clone() })
+                       .expect(PaymentPath::Success { path: route.paths[1].clone() })
+               );
+               let logger = TestLogger::new();
+               let invoice_payer =
+                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
+
+               let payment_id = invoice_payer.pay_invoice(&invoice).unwrap();
+               let event = Event::PaymentPathSuccessful {
+                       payment_id, payment_hash, path: route.paths[0].clone()
+               };
+               invoice_payer.handle_event(&event);
+               let event = Event::PaymentPathSuccessful {
+                       payment_id, payment_hash, path: route.paths[1].clone()
+               };
+               invoice_payer.handle_event(&event);
+       }
+
        struct TestRouter;
 
        impl TestRouter {
@@ -1141,13 +1243,10 @@ mod tests {
                }
        }
 
-       impl<S: routing::Score> Router<S> for TestRouter {
+       impl<S: Score> Router<S> for TestRouter {
                fn find_route(
-                       &self,
-                       _payer: &PublicKey,
-                       params: &RouteParameters,
-                       _first_hops: Option<&[&ChannelDetails]>,
-                       _scorer: &S,
+                       &self, _payer: &PublicKey, params: &RouteParameters, _payment_hash: &PaymentHash,
+                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
                ) -> Result<Route, LightningError> {
                        Ok(Route {
                                payee: Some(params.payee.clone()), ..Self::route_for_value(params.final_value_msat)
@@ -1157,43 +1256,74 @@ mod tests {
 
        struct FailingRouter;
 
-       impl<S: routing::Score> Router<S> for FailingRouter {
+       impl<S: Score> Router<S> for FailingRouter {
                fn find_route(
-                       &self,
-                       _payer: &PublicKey,
-                       _params: &RouteParameters,
-                       _first_hops: Option<&[&ChannelDetails]>,
-                       _scorer: &S,
+                       &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
+                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
                ) -> Result<Route, LightningError> {
                        Err(LightningError { err: String::new(), action: ErrorAction::IgnoreError })
                }
        }
 
        struct TestScorer {
-               expectations: VecDeque<u64>,
+               expectations: Option<VecDeque<PaymentPath>>,
+       }
+
+       #[derive(Debug)]
+       enum PaymentPath {
+               Failure { path: Vec<RouteHop>, short_channel_id: u64 },
+               Success { path: Vec<RouteHop> },
        }
 
        impl TestScorer {
                fn new() -> Self {
                        Self {
-                               expectations: VecDeque::new(),
+                               expectations: None,
                        }
                }
 
-               fn expect_channel_failure(mut self, short_channel_id: u64) -> Self {
-                       self.expectations.push_back(short_channel_id);
+               fn expect(mut self, expectation: PaymentPath) -> Self {
+                       self.expectations.get_or_insert_with(|| VecDeque::new()).push_back(expectation);
                        self
                }
        }
 
-       impl routing::Score for TestScorer {
+       #[cfg(c_bindings)]
+       impl lightning::util::ser::Writeable for TestScorer {
+               fn write<W: lightning::util::ser::Writer>(&self, _: &mut W) -> Result<(), std::io::Error> { unreachable!(); }
+       }
+
+       impl Score for TestScorer {
                fn channel_penalty_msat(
-                       &self, _short_channel_id: u64, _source: &NodeId, _target: &NodeId
+                       &self, _short_channel_id: u64, _send_amt: u64, _chan_amt: Option<u64>, _source: &NodeId, _target: &NodeId
                ) -> u64 { 0 }
 
-               fn payment_path_failed(&mut self, _path: &[&RouteHop], short_channel_id: u64) {
-                       if let Some(expected_short_channel_id) = self.expectations.pop_front() {
-                               assert_eq!(short_channel_id, expected_short_channel_id);
+               fn payment_path_failed(&mut self, actual_path: &[&RouteHop], actual_short_channel_id: u64) {
+                       if let Some(expectations) = &mut self.expectations {
+                               match expectations.pop_front() {
+                                       Some(PaymentPath::Failure { path, short_channel_id }) => {
+                                               assert_eq!(actual_path, &path.iter().collect::<Vec<_>>()[..]);
+                                               assert_eq!(actual_short_channel_id, short_channel_id);
+                                       },
+                                       Some(PaymentPath::Success { path }) => {
+                                               panic!("Unexpected successful payment path: {:?}", path)
+                                       },
+                                       None => panic!("Unexpected payment_path_failed call: {:?}", actual_path),
+                               }
+                       }
+               }
+
+               fn payment_path_successful(&mut self, actual_path: &[&RouteHop]) {
+                       if let Some(expectations) = &mut self.expectations {
+                               match expectations.pop_front() {
+                                       Some(PaymentPath::Failure { path, .. }) => {
+                                               panic!("Unexpected payment path failure: {:?}", path)
+                                       },
+                                       Some(PaymentPath::Success { path }) => {
+                                               assert_eq!(actual_path, &path.iter().collect::<Vec<_>>()[..]);
+                                       },
+                                       None => panic!("Unexpected payment_path_successful call: {:?}", actual_path),
+                               }
                        }
                }
        }
@@ -1204,8 +1334,10 @@ mod tests {
                                return;
                        }
 
-                       if !self.expectations.is_empty() {
-                               panic!("Unsatisfied channel failure expectations: {:?}", self.expectations);
+                       if let Some(expectations) = &self.expectations {
+                               if !expectations.is_empty() {
+                                       panic!("Unsatisfied scorer expectations: {:?}", expectations);
+                               }
                        }
                }
        }
@@ -1213,49 +1345,57 @@ mod tests {
        struct TestPayer {
                expectations: core::cell::RefCell<VecDeque<Amount>>,
                attempts: core::cell::RefCell<usize>,
-               failing_on_attempt: Option<usize>,
+               failing_on_attempt: core::cell::RefCell<HashMap<usize, PaymentSendFailure>>,
        }
 
        #[derive(Clone, Debug, PartialEq, Eq)]
        enum Amount {
-               ForInvoiceOrRetry(u64),
+               ForInvoice(u64),
                Spontaneous(u64),
+               OnRetry(u64),
        }
 
+       struct OnAttempt(usize);
+
        impl TestPayer {
                fn new() -> Self {
                        Self {
                                expectations: core::cell::RefCell::new(VecDeque::new()),
                                attempts: core::cell::RefCell::new(0),
-                               failing_on_attempt: None,
+                               failing_on_attempt: core::cell::RefCell::new(HashMap::new()),
                        }
                }
 
-               fn expect_value_msat(self, value_msat: u64) -> Self {
-                       self.expectations.borrow_mut().push_back(Amount::ForInvoiceOrRetry(value_msat));
-                       self
-               }
-
                fn expect_send(self, value_msat: Amount) -> Self {
                        self.expectations.borrow_mut().push_back(value_msat);
                        self
                }
 
                fn fails_on_attempt(self, attempt: usize) -> Self {
-                       Self {
-                               expectations: core::cell::RefCell::new(self.expectations.borrow().clone()),
-                               attempts: core::cell::RefCell::new(0),
-                               failing_on_attempt: Some(attempt),
-                       }
+                       let failure = PaymentSendFailure::ParameterError(APIError::MonitorUpdateFailed);
+                       self.fails_with(failure, OnAttempt(attempt))
+               }
+
+               fn fails_with_partial_failure(self, retry: RouteParameters, attempt: OnAttempt) -> Self {
+                       self.fails_with(PaymentSendFailure::PartialFailure {
+                               results: vec![],
+                               failed_paths_retry: Some(retry),
+                               payment_id: PaymentId([1; 32]),
+                       }, attempt)
                }
 
-               fn check_attempts(&self) -> bool {
+               fn fails_with(self, failure: PaymentSendFailure, attempt: OnAttempt) -> Self {
+                       self.failing_on_attempt.borrow_mut().insert(attempt.0, failure);
+                       self
+               }
+
+               fn check_attempts(&self) -> Result<PaymentId, PaymentSendFailure> {
                        let mut attempts = self.attempts.borrow_mut();
                        *attempts += 1;
-                       match self.failing_on_attempt {
-                               None => true,
-                               Some(attempt) if attempt != *attempts => true,
-                               Some(_) => false,
+
+                       match self.failing_on_attempt.borrow_mut().remove(&*attempts) {
+                               Some(failure) => Err(failure),
+                               None => Ok(PaymentId([1; 32])),
                        }
                }
 
@@ -1263,6 +1403,8 @@ mod tests {
                        let expected_value_msats = self.expectations.borrow_mut().pop_front();
                        if let Some(expected_value_msats) = expected_value_msats {
                                assert_eq!(actual_value_msats, expected_value_msats);
+                       } else {
+                               panic!("Unexpected amount: {:?}", actual_value_msats);
                        }
                }
        }
@@ -1290,50 +1432,38 @@ mod tests {
                }
 
                fn send_payment(
-                       &self,
-                       route: &Route,
-                       _payment_hash: PaymentHash,
+                       &self, route: &Route, _payment_hash: PaymentHash,
                        _payment_secret: &Option<PaymentSecret>
                ) -> Result<PaymentId, PaymentSendFailure> {
-                       if self.check_attempts() {
-                               self.check_value_msats(Amount::ForInvoiceOrRetry(route.get_total_amount()));
-                               Ok(PaymentId([1; 32]))
-                       } else {
-                               Err(PaymentSendFailure::ParameterError(APIError::MonitorUpdateFailed))
-                       }
+                       self.check_value_msats(Amount::ForInvoice(route.get_total_amount()));
+                       self.check_attempts()
                }
 
                fn send_spontaneous_payment(
-                       &self,
-                       route: &Route,
-                       _payment_preimage: PaymentPreimage,
+                       &self, route: &Route, _payment_preimage: PaymentPreimage,
                ) -> Result<PaymentId, PaymentSendFailure> {
-                       if self.check_attempts() {
-                               self.check_value_msats(Amount::Spontaneous(route.get_total_amount()));
-                               Ok(PaymentId([1; 32]))
-                       } else {
-                               Err(PaymentSendFailure::ParameterError(APIError::MonitorUpdateFailed))
-                       }
+                       self.check_value_msats(Amount::Spontaneous(route.get_total_amount()));
+                       self.check_attempts()
                }
 
                fn retry_payment(
                        &self, route: &Route, _payment_id: PaymentId
                ) -> Result<(), PaymentSendFailure> {
-                       if self.check_attempts() {
-                               self.check_value_msats(Amount::ForInvoiceOrRetry(route.get_total_amount()));
-                               Ok(())
-                       } else {
-                               Err(PaymentSendFailure::ParameterError(APIError::MonitorUpdateFailed))
-                       }
+                       self.check_value_msats(Amount::OnRetry(route.get_total_amount()));
+                       self.check_attempts().map(|_| ())
                }
+
+               fn abandon_payment(&self, _payment_id: PaymentId) { }
        }
 
        // *** Full Featured Functional Tests with a Real ChannelManager ***
        struct ManualRouter(RefCell<VecDeque<Result<Route, LightningError>>>);
 
-       impl<S: routing::Score> Router<S> for ManualRouter {
-               fn find_route(&self, _payer: &PublicKey, _params: &RouteParameters, _first_hops: Option<&[&ChannelDetails]>, _scorer: &S)
-               -> Result<Route, LightningError> {
+       impl<S: Score> Router<S> for ManualRouter {
+               fn find_route(
+                       &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
+                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
+               ) -> Result<Route, LightningError> {
                        self.0.borrow_mut().pop_front().unwrap()
                }
        }
@@ -1446,4 +1576,177 @@ mod tests {
                assert_eq!(htlc_msgs.len(), 2);
                check_added_monitors!(nodes[0], 2);
        }
+
+       #[test]
+       fn no_extra_retries_on_back_to_back_fail() {
+               // In a previous release, we had a race where we may exceed the payment retry count if we
+               // get two failures in a row with the second having `all_paths_failed` set.
+               // Generally, when we give up trying to retry a payment, we don't know for sure what the
+               // current state of the ChannelManager event queue is. Specifically, we cannot be sure that
+               // there are not multiple additional `PaymentPathFailed` or even `PaymentSent` events
+               // pending which we will see later. Thus, when we previously removed the retry tracking map
+               // entry after a `all_paths_failed` `PaymentPathFailed` event, we may have dropped the
+               // retry entry even though more events for the same payment were still pending. This led to
+               // us retrying a payment again even though we'd already given up on it.
+               //
+               // We now have a separate event - `PaymentFailed` which indicates no HTLCs remain and which
+               // is used to remove the payment retry counter entries instead. This tests for the specific
+               // excess-retry case while also testing `PaymentFailed` generation.
+
+               let chanmon_cfgs = create_chanmon_cfgs(3);
+               let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
+               let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
+               let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
+
+               let chan_1_scid = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 10_000_000, 0, InitFeatures::known(), InitFeatures::known()).0.contents.short_channel_id;
+               let chan_2_scid = create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 10_000_000, 0, InitFeatures::known(), InitFeatures::known()).0.contents.short_channel_id;
+
+               let mut route = Route {
+                       paths: vec![
+                               vec![RouteHop {
+                                       pubkey: nodes[1].node.get_our_node_id(),
+                                       node_features: NodeFeatures::known(),
+                                       short_channel_id: chan_1_scid,
+                                       channel_features: ChannelFeatures::known(),
+                                       fee_msat: 0,
+                                       cltv_expiry_delta: 100,
+                               }, RouteHop {
+                                       pubkey: nodes[2].node.get_our_node_id(),
+                                       node_features: NodeFeatures::known(),
+                                       short_channel_id: chan_2_scid,
+                                       channel_features: ChannelFeatures::known(),
+                                       fee_msat: 100_000_000,
+                                       cltv_expiry_delta: 100,
+                               }],
+                               vec![RouteHop {
+                                       pubkey: nodes[1].node.get_our_node_id(),
+                                       node_features: NodeFeatures::known(),
+                                       short_channel_id: chan_1_scid,
+                                       channel_features: ChannelFeatures::known(),
+                                       fee_msat: 0,
+                                       cltv_expiry_delta: 100,
+                               }, RouteHop {
+                                       pubkey: nodes[2].node.get_our_node_id(),
+                                       node_features: NodeFeatures::known(),
+                                       short_channel_id: chan_2_scid,
+                                       channel_features: ChannelFeatures::known(),
+                                       fee_msat: 100_000_000,
+                                       cltv_expiry_delta: 100,
+                               }]
+                       ],
+                       payee: Some(Payee::from_node_id(nodes[2].node.get_our_node_id())),
+               };
+               let router = ManualRouter(RefCell::new(VecDeque::new()));
+               router.expect_find_route(Ok(route.clone()));
+               // On retry, we'll only be asked for one path
+               route.paths.remove(1);
+               router.expect_find_route(Ok(route.clone()));
+
+               let expected_events: RefCell<VecDeque<&dyn Fn(&Event)>> = RefCell::new(VecDeque::new());
+               let event_handler = |event: &Event| {
+                       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, RetryAttempts(1));
+
+               assert!(invoice_payer.pay_invoice(&create_invoice_from_channelmanager(
+                       &nodes[1].node, nodes[1].keys_manager, Currency::Bitcoin, Some(100_010_000), "Invoice".to_string()).unwrap())
+                       .is_ok());
+               let htlc_updates = SendEvent::from_node(&nodes[0]);
+               check_added_monitors!(nodes[0], 1);
+               assert_eq!(htlc_updates.msgs.len(), 1);
+
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &htlc_updates.msgs[0]);
+               nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &htlc_updates.commitment_msg);
+               check_added_monitors!(nodes[1], 1);
+               let (bs_first_raa, bs_first_cs) = get_revoke_commit_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+
+               nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_first_raa);
+               check_added_monitors!(nodes[0], 1);
+               let second_htlc_updates = SendEvent::from_node(&nodes[0]);
+
+               nodes[0].node.handle_commitment_signed(&nodes[1].node.get_our_node_id(), &bs_first_cs);
+               check_added_monitors!(nodes[0], 1);
+               let as_first_raa = get_event_msg!(nodes[0], MessageSendEvent::SendRevokeAndACK, nodes[1].node.get_our_node_id());
+
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &second_htlc_updates.msgs[0]);
+               nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &second_htlc_updates.commitment_msg);
+               check_added_monitors!(nodes[1], 1);
+               let bs_second_raa = get_event_msg!(nodes[1], MessageSendEvent::SendRevokeAndACK, nodes[0].node.get_our_node_id());
+
+               nodes[1].node.handle_revoke_and_ack(&nodes[0].node.get_our_node_id(), &as_first_raa);
+               check_added_monitors!(nodes[1], 1);
+               let bs_fail_update = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+
+               nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_second_raa);
+               check_added_monitors!(nodes[0], 1);
+
+               nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &bs_fail_update.update_fail_htlcs[0]);
+               nodes[0].node.handle_commitment_signed(&nodes[1].node.get_our_node_id(), &bs_fail_update.commitment_signed);
+               check_added_monitors!(nodes[0], 1);
+               let (as_second_raa, as_third_cs) = get_revoke_commit_msgs!(nodes[0], nodes[1].node.get_our_node_id());
+
+               nodes[1].node.handle_revoke_and_ack(&nodes[0].node.get_our_node_id(), &as_second_raa);
+               check_added_monitors!(nodes[1], 1);
+               let bs_second_fail_update = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+
+               nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &as_third_cs);
+               check_added_monitors!(nodes[1], 1);
+               let bs_third_raa = get_event_msg!(nodes[1], MessageSendEvent::SendRevokeAndACK, nodes[0].node.get_our_node_id());
+
+               nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &bs_second_fail_update.update_fail_htlcs[0]);
+               nodes[0].node.handle_commitment_signed(&nodes[1].node.get_our_node_id(), &bs_second_fail_update.commitment_signed);
+               check_added_monitors!(nodes[0], 1);
+
+               nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_third_raa);
+               check_added_monitors!(nodes[0], 1);
+               let (as_third_raa, as_fourth_cs) = get_revoke_commit_msgs!(nodes[0], nodes[1].node.get_our_node_id());
+
+               nodes[1].node.handle_revoke_and_ack(&nodes[0].node.get_our_node_id(), &as_third_raa);
+               check_added_monitors!(nodes[1], 1);
+               nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &as_fourth_cs);
+               check_added_monitors!(nodes[1], 1);
+               let bs_fourth_raa = get_event_msg!(nodes[1], MessageSendEvent::SendRevokeAndACK, nodes[0].node.get_our_node_id());
+
+               nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_fourth_raa);
+               check_added_monitors!(nodes[0], 1);
+
+               // At this point A has sent two HTLCs which both failed due to lack of fee. It now has two
+               // pending `PaymentPathFailed` events, one with `all_paths_failed` unset, and the second
+               // with it set. The first event will use up the only retry we are allowed, with the second
+               // `PaymentPathFailed` being passed up to the user (us, in this case). Previously, we'd
+               // 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);
+                               assert!(all_paths_failed);
+                       } else { panic!("Unexpected event"); }
+               });
+               nodes[0].node.process_pending_events(&invoice_payer);
+               assert!(expected_events.borrow().is_empty());
+
+               let retry_htlc_updates = SendEvent::from_node(&nodes[0]);
+               check_added_monitors!(nodes[0], 1);
+
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &retry_htlc_updates.msgs[0]);
+               commitment_signed_dance!(nodes[1], nodes[0], &retry_htlc_updates.commitment_msg, false, true);
+               let bs_fail_update = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+               nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &bs_fail_update.update_fail_htlcs[0]);
+               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);
+                               assert!(all_paths_failed);
+                       } else { panic!("Unexpected event"); }
+               });
+               expected_events.borrow_mut().push_back(&|ev: &Event| {
+                       if let Event::PaymentFailed { .. } = ev {
+                       } else { panic!("Unexpected event"); }
+               });
+               nodes[0].node.process_pending_events(&invoice_payer);
+               assert!(expected_events.borrow().is_empty());
+       }
 }