lightning_background_processor/

lib.rs

//! Utilities that take care of tasks that (1) need to happen periodically to keep Rust-Lightning
//! running properly, and (2) either can or should be run in the background.
#![cfg_attr(feature = "std", doc = "See docs for [`BackgroundProcessor`] for more details.")]
#![deny(rustdoc::broken_intra_doc_links)]
#![deny(rustdoc::private_intra_doc_links)]
#![deny(missing_docs)]
#![cfg_attr(not(feature = "futures"), deny(unsafe_code))]
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
#![cfg_attr(all(not(feature = "std"), not(test)), no_std)]

#[cfg(any(test, feature = "std"))]
extern crate core;

#[cfg(not(feature = "std"))]
extern crate alloc;

#[macro_use]
extern crate lightning;
extern crate lightning_rapid_gossip_sync;

use lightning::chain;
use lightning::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
use lightning::chain::chainmonitor::{ChainMonitor, Persist};
#[cfg(feature = "std")]
use lightning::events::EventHandler;
#[cfg(feature = "std")]
use lightning::events::EventsProvider;
#[cfg(feature = "futures")]
use lightning::events::ReplayEvent;
use lightning::events::{Event, PathFailure};

use lightning::ln::channelmanager::AChannelManager;
use lightning::ln::msgs::OnionMessageHandler;
use lightning::ln::peer_handler::APeerManager;
use lightning::onion_message::messenger::AOnionMessenger;
use lightning::routing::gossip::{NetworkGraph, P2PGossipSync};
use lightning::routing::scoring::{ScoreUpdate, WriteableScore};
use lightning::routing::utxo::UtxoLookup;
use lightning::util::logger::Logger;
use lightning::util::persist::Persister;
#[cfg(feature = "std")]
use lightning::util::wakers::Sleeper;
use lightning_rapid_gossip_sync::RapidGossipSync;

use core::ops::Deref;
use core::time::Duration;

#[cfg(feature = "std")]
use core::sync::atomic::{AtomicBool, Ordering};
#[cfg(feature = "std")]
use std::sync::Arc;
#[cfg(feature = "std")]
use std::thread::{self, JoinHandle};
#[cfg(feature = "std")]
use std::time::Instant;

#[cfg(not(feature = "std"))]
use alloc::boxed::Box;

/// `BackgroundProcessor` takes care of tasks that (1) need to happen periodically to keep
/// Rust-Lightning running properly, and (2) either can or should be run in the background. Its
/// responsibilities are:
/// * Processing [`Event`]s with a user-provided [`EventHandler`].
/// * Monitoring whether the [`ChannelManager`] needs to be re-persisted to disk, and if so,
///   writing it to disk/backups by invoking the callback given to it at startup.
///   [`ChannelManager`] persistence should be done in the background.
/// * Calling [`ChannelManager::timer_tick_occurred`], [`ChainMonitor::rebroadcast_pending_claims`]
///   and [`PeerManager::timer_tick_occurred`] at the appropriate intervals.
/// * Calling [`NetworkGraph::remove_stale_channels_and_tracking`] (if a [`GossipSync`] with a
///   [`NetworkGraph`] is provided to [`BackgroundProcessor::start`]).
///
/// It will also call [`PeerManager::process_events`] periodically though this shouldn't be relied
/// upon as doing so may result in high latency.
///
/// # Note
///
/// If [`ChannelManager`] persistence fails and the persisted manager becomes out-of-date, then
/// there is a risk of channels force-closing on startup when the manager realizes it's outdated.
/// However, as long as [`ChannelMonitor`] backups are sound, no funds besides those used for
/// unilateral chain closure fees are at risk.
///
/// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
/// [`ChannelManager::timer_tick_occurred`]: lightning::ln::channelmanager::ChannelManager::timer_tick_occurred
/// [`ChannelMonitor`]: lightning::chain::channelmonitor::ChannelMonitor
/// [`Event`]: lightning::events::Event
/// [`PeerManager::timer_tick_occurred`]: lightning::ln::peer_handler::PeerManager::timer_tick_occurred
/// [`PeerManager::process_events`]: lightning::ln::peer_handler::PeerManager::process_events
#[cfg(feature = "std")]
#[must_use = "BackgroundProcessor will immediately stop on drop. It should be stored until shutdown."]
pub struct BackgroundProcessor {
	stop_thread: Arc<AtomicBool>,
	thread_handle: Option<JoinHandle<Result<(), std::io::Error>>>,
}

#[cfg(not(test))]
const FRESHNESS_TIMER: u64 = 60;
#[cfg(test)]
const FRESHNESS_TIMER: u64 = 1;

#[cfg(all(not(test), not(debug_assertions)))]
const PING_TIMER: u64 = 10;
/// Signature operations take a lot longer without compiler optimisations.
/// Increasing the ping timer allows for this but slower devices will be disconnected if the
/// timeout is reached.
#[cfg(all(not(test), debug_assertions))]
const PING_TIMER: u64 = 30;
#[cfg(test)]
const PING_TIMER: u64 = 1;

#[cfg(not(test))]
const ONION_MESSAGE_HANDLER_TIMER: u64 = 10;
#[cfg(test)]
const ONION_MESSAGE_HANDLER_TIMER: u64 = 1;

/// Prune the network graph of stale entries hourly.
const NETWORK_PRUNE_TIMER: u64 = 60 * 60;

#[cfg(not(test))]
const SCORER_PERSIST_TIMER: u64 = 60 * 5;
#[cfg(test)]
const SCORER_PERSIST_TIMER: u64 = 1;

#[cfg(not(test))]
const FIRST_NETWORK_PRUNE_TIMER: u64 = 60;
#[cfg(test)]
const FIRST_NETWORK_PRUNE_TIMER: u64 = 1;

#[cfg(not(test))]
const REBROADCAST_TIMER: u64 = 30;
#[cfg(test)]
const REBROADCAST_TIMER: u64 = 1;

#[cfg(feature = "futures")]
/// core::cmp::min is not currently const, so we define a trivial (and equivalent) replacement
const fn min_u64(a: u64, b: u64) -> u64 {
	if a < b {
		a
	} else {
		b
	}
}
#[cfg(feature = "futures")]
const FASTEST_TIMER: u64 = min_u64(
	min_u64(FRESHNESS_TIMER, PING_TIMER),
	min_u64(SCORER_PERSIST_TIMER, min_u64(FIRST_NETWORK_PRUNE_TIMER, REBROADCAST_TIMER)),
);

/// Either [`P2PGossipSync`] or [`RapidGossipSync`].
pub enum GossipSync<
	P: Deref<Target = P2PGossipSync<G, U, L>>,
	R: Deref<Target = RapidGossipSync<G, L>>,
	G: Deref<Target = NetworkGraph<L>>,
	U: Deref,
	L: Deref,
> where
	U::Target: UtxoLookup,
	L::Target: Logger,
{
	/// Gossip sync via the lightning peer-to-peer network as defined by BOLT 7.
	P2P(P),
	/// Rapid gossip sync from a trusted server.
	Rapid(R),
	/// No gossip sync.
	None,
}

impl<
		P: Deref<Target = P2PGossipSync<G, U, L>>,
		R: Deref<Target = RapidGossipSync<G, L>>,
		G: Deref<Target = NetworkGraph<L>>,
		U: Deref,
		L: Deref,
	> GossipSync<P, R, G, U, L>
where
	U::Target: UtxoLookup,
	L::Target: Logger,
{
	fn network_graph(&self) -> Option<&G> {
		match self {
			GossipSync::P2P(gossip_sync) => Some(gossip_sync.network_graph()),
			GossipSync::Rapid(gossip_sync) => Some(gossip_sync.network_graph()),
			GossipSync::None => None,
		}
	}

	fn prunable_network_graph(&self) -> Option<&G> {
		match self {
			GossipSync::P2P(gossip_sync) => Some(gossip_sync.network_graph()),
			GossipSync::Rapid(gossip_sync) => {
				if gossip_sync.is_initial_sync_complete() {
					Some(gossip_sync.network_graph())
				} else {
					None
				}
			},
			GossipSync::None => None,
		}
	}
}

/// This is not exported to bindings users as the bindings concretize everything and have constructors for us
impl<
		P: Deref<Target = P2PGossipSync<G, U, L>>,
		G: Deref<Target = NetworkGraph<L>>,
		U: Deref,
		L: Deref,
	> GossipSync<P, &RapidGossipSync<G, L>, G, U, L>
where
	U::Target: UtxoLookup,
	L::Target: Logger,
{
	/// Initializes a new [`GossipSync::P2P`] variant.
	pub fn p2p(gossip_sync: P) -> Self {
		GossipSync::P2P(gossip_sync)
	}
}

/// This is not exported to bindings users as the bindings concretize everything and have constructors for us
impl<
		'a,
		R: Deref<Target = RapidGossipSync<G, L>>,
		G: Deref<Target = NetworkGraph<L>>,
		L: Deref,
	>
	GossipSync<
		&P2PGossipSync<G, &'a (dyn UtxoLookup + Send + Sync), L>,
		R,
		G,
		&'a (dyn UtxoLookup + Send + Sync),
		L,
	> where
	L::Target: Logger,
{
	/// Initializes a new [`GossipSync::Rapid`] variant.
	pub fn rapid(gossip_sync: R) -> Self {
		GossipSync::Rapid(gossip_sync)
	}
}

/// This is not exported to bindings users as the bindings concretize everything and have constructors for us
impl<'a, L: Deref>
	GossipSync<
		&P2PGossipSync<&'a NetworkGraph<L>, &'a (dyn UtxoLookup + Send + Sync), L>,
		&RapidGossipSync<&'a NetworkGraph<L>, L>,
		&'a NetworkGraph<L>,
		&'a (dyn UtxoLookup + Send + Sync),
		L,
	> where
	L::Target: Logger,
{
	/// Initializes a new [`GossipSync::None`] variant.
	pub fn none() -> Self {
		GossipSync::None
	}
}

fn handle_network_graph_update<L: Deref>(network_graph: &NetworkGraph<L>, event: &Event)
where
	L::Target: Logger,
{
	if let Event::PaymentPathFailed {
		failure: PathFailure::OnPath { network_update: Some(ref upd) },
		..
	} = event
	{
		network_graph.handle_network_update(upd);
	}
}

/// Updates scorer based on event and returns whether an update occurred so we can decide whether
/// to persist.
fn update_scorer<'a, S: 'static + Deref<Target = SC> + Send + Sync, SC: 'a + WriteableScore<'a>>(
	scorer: &'a S, event: &Event, duration_since_epoch: Duration,
) -> bool {
	match event {
		Event::PaymentPathFailed { ref path, short_channel_id: Some(scid), .. } => {
			let mut score = scorer.write_lock();
			score.payment_path_failed(path, *scid, duration_since_epoch);
		},
		Event::PaymentPathFailed { ref path, payment_failed_permanently: true, .. } => {
			// Reached if the destination explicitly failed it back. We treat this as a successful probe
			// because the payment made it all the way to the destination with sufficient liquidity.
			let mut score = scorer.write_lock();
			score.probe_successful(path, duration_since_epoch);
		},
		Event::PaymentPathSuccessful { path, .. } => {
			let mut score = scorer.write_lock();
			score.payment_path_successful(path, duration_since_epoch);
		},
		Event::ProbeSuccessful { path, .. } => {
			let mut score = scorer.write_lock();
			score.probe_successful(path, duration_since_epoch);
		},
		Event::ProbeFailed { path, short_channel_id: Some(scid), .. } => {
			let mut score = scorer.write_lock();
			score.probe_failed(path, *scid, duration_since_epoch);
		},
		_ => return false,
	}
	true
}

macro_rules! define_run_body {
	(
		$persister: ident, $chain_monitor: ident, $process_chain_monitor_events: expr,
		$channel_manager: ident, $process_channel_manager_events: expr,
		$onion_messenger: ident, $process_onion_message_handler_events: expr,
		$peer_manager: ident, $gossip_sync: ident,
		$logger: ident, $scorer: ident, $loop_exit_check: expr, $await: expr, $get_timer: expr,
		$timer_elapsed: expr, $check_slow_await: expr, $time_fetch: expr,
	) => { {
		log_trace!($logger, "Calling ChannelManager's timer_tick_occurred on startup");
		$channel_manager.get_cm().timer_tick_occurred();
		log_trace!($logger, "Rebroadcasting monitor's pending claims on startup");
		$chain_monitor.rebroadcast_pending_claims();

		let mut last_freshness_call = $get_timer(FRESHNESS_TIMER);
		let mut last_onion_message_handler_call = $get_timer(ONION_MESSAGE_HANDLER_TIMER);
		let mut last_ping_call = $get_timer(PING_TIMER);
		let mut last_prune_call = $get_timer(FIRST_NETWORK_PRUNE_TIMER);
		let mut last_scorer_persist_call = $get_timer(SCORER_PERSIST_TIMER);
		let mut last_rebroadcast_call = $get_timer(REBROADCAST_TIMER);
		let mut have_pruned = false;
		let mut have_decayed_scorer = false;

		loop {
			$process_channel_manager_events;
			$process_chain_monitor_events;
			$process_onion_message_handler_events;

			// Note that the PeerManager::process_events may block on ChannelManager's locks,
			// hence it comes last here. When the ChannelManager finishes whatever it's doing,
			// we want to ensure we get into `persist_manager` as quickly as we can, especially
			// without running the normal event processing above and handing events to users.
			//
			// Specifically, on an *extremely* slow machine, we may see ChannelManager start
			// processing a message effectively at any point during this loop. In order to
			// minimize the time between such processing completing and persisting the updated
			// ChannelManager, we want to minimize methods blocking on a ChannelManager
			// generally, and as a fallback place such blocking only immediately before
			// persistence.
			$peer_manager.as_ref().process_events();

			// Exit the loop if the background processor was requested to stop.
			if $loop_exit_check {
				log_trace!($logger, "Terminating background processor.");
				break;
			}

			// We wait up to 100ms, but track how long it takes to detect being put to sleep,
			// see `await_start`'s use below.
			let mut await_start = None;
			if $check_slow_await { await_start = Some($get_timer(1)); }
			$await;
			let await_slow = if $check_slow_await { $timer_elapsed(&mut await_start.unwrap(), 1) } else { false };

			// Exit the loop if the background processor was requested to stop.
			if $loop_exit_check {
				log_trace!($logger, "Terminating background processor.");
				break;
			}

			if $channel_manager.get_cm().get_and_clear_needs_persistence() {
				log_trace!($logger, "Persisting ChannelManager...");
				$persister.persist_manager(&$channel_manager)?;
				log_trace!($logger, "Done persisting ChannelManager.");
			}
			if $timer_elapsed(&mut last_freshness_call, FRESHNESS_TIMER) {
				log_trace!($logger, "Calling ChannelManager's timer_tick_occurred");
				$channel_manager.get_cm().timer_tick_occurred();
				last_freshness_call = $get_timer(FRESHNESS_TIMER);
			}
			if $timer_elapsed(&mut last_onion_message_handler_call, ONION_MESSAGE_HANDLER_TIMER) {
				if let Some(om) = &$onion_messenger {
					log_trace!($logger, "Calling OnionMessageHandler's timer_tick_occurred");
					om.get_om().timer_tick_occurred();
				}
				last_onion_message_handler_call = $get_timer(ONION_MESSAGE_HANDLER_TIMER);
			}
			if await_slow {
				// On various platforms, we may be starved of CPU cycles for several reasons.
				// E.g. on iOS, if we've been in the background, we will be entirely paused.
				// Similarly, if we're on a desktop platform and the device has been asleep, we
				// may not get any cycles.
				// We detect this by checking if our max-100ms-sleep, above, ran longer than a
				// full second, at which point we assume sockets may have been killed (they
				// appear to be at least on some platforms, even if it has only been a second).
				// Note that we have to take care to not get here just because user event
				// processing was slow at the top of the loop. For example, the sample client
				// may call Bitcoin Core RPCs during event handling, which very often takes
				// more than a handful of seconds to complete, and shouldn't disconnect all our
				// peers.
				log_trace!($logger, "100ms sleep took more than a second, disconnecting peers.");
				$peer_manager.as_ref().disconnect_all_peers();
				last_ping_call = $get_timer(PING_TIMER);
			} else if $timer_elapsed(&mut last_ping_call, PING_TIMER) {
				log_trace!($logger, "Calling PeerManager's timer_tick_occurred");
				$peer_manager.as_ref().timer_tick_occurred();
				last_ping_call = $get_timer(PING_TIMER);
			}

			// Note that we want to run a graph prune once not long after startup before
			// falling back to our usual hourly prunes. This avoids short-lived clients never
			// pruning their network graph. We run once 60 seconds after startup before
			// continuing our normal cadence. For RGS, since 60 seconds is likely too long,
			// we prune after an initial sync completes.
			let prune_timer = if have_pruned { NETWORK_PRUNE_TIMER } else { FIRST_NETWORK_PRUNE_TIMER };
			let prune_timer_elapsed = $timer_elapsed(&mut last_prune_call, prune_timer);
			let should_prune = match $gossip_sync {
				GossipSync::Rapid(_) => !have_pruned || prune_timer_elapsed,
				_ => prune_timer_elapsed,
			};
			if should_prune {
				// The network graph must not be pruned while rapid sync completion is pending
				if let Some(network_graph) = $gossip_sync.prunable_network_graph() {
					if let Some(duration_since_epoch) = $time_fetch() {
						log_trace!($logger, "Pruning and persisting network graph.");
						network_graph.remove_stale_channels_and_tracking_with_time(duration_since_epoch.as_secs());
					} else {
						log_warn!($logger, "Not pruning network graph, consider enabling `std` or doing so manually with remove_stale_channels_and_tracking_with_time.");
						log_trace!($logger, "Persisting network graph.");
					}

					if let Err(e) = $persister.persist_graph(network_graph) {
						log_error!($logger, "Error: Failed to persist network graph, check your disk and permissions {}", e)
					}

					have_pruned = true;
				}
				let prune_timer = if have_pruned { NETWORK_PRUNE_TIMER } else { FIRST_NETWORK_PRUNE_TIMER };
				last_prune_call = $get_timer(prune_timer);
			}

			if !have_decayed_scorer {
				if let Some(ref scorer) = $scorer {
					if let Some(duration_since_epoch) = $time_fetch() {
						log_trace!($logger, "Calling time_passed on scorer at startup");
						scorer.write_lock().time_passed(duration_since_epoch);
					}
				}
				have_decayed_scorer = true;
			}

			if $timer_elapsed(&mut last_scorer_persist_call, SCORER_PERSIST_TIMER) {
				if let Some(ref scorer) = $scorer {
					if let Some(duration_since_epoch) = $time_fetch() {
						log_trace!($logger, "Calling time_passed and persisting scorer");
						scorer.write_lock().time_passed(duration_since_epoch);
					} else {
						log_trace!($logger, "Persisting scorer");
					}
					if let Err(e) = $persister.persist_scorer(&scorer) {
						log_error!($logger, "Error: Failed to persist scorer, check your disk and permissions {}", e)
					}
				}
				last_scorer_persist_call = $get_timer(SCORER_PERSIST_TIMER);
			}

			if $timer_elapsed(&mut last_rebroadcast_call, REBROADCAST_TIMER) {
				log_trace!($logger, "Rebroadcasting monitor's pending claims");
				$chain_monitor.rebroadcast_pending_claims();
				last_rebroadcast_call = $get_timer(REBROADCAST_TIMER);
			}
		}

		// After we exit, ensure we persist the ChannelManager one final time - this avoids
		// some races where users quit while channel updates were in-flight, with
		// ChannelMonitor update(s) persisted without a corresponding ChannelManager update.
		$persister.persist_manager(&$channel_manager)?;

		// Persist Scorer on exit
		if let Some(ref scorer) = $scorer {
			$persister.persist_scorer(&scorer)?;
		}

		// Persist NetworkGraph on exit
		if let Some(network_graph) = $gossip_sync.network_graph() {
			$persister.persist_graph(network_graph)?;
		}

		Ok(())
	} }
}

#[cfg(feature = "futures")]
pub(crate) mod futures_util {
	use core::future::Future;
	use core::marker::Unpin;
	use core::pin::Pin;
	use core::task::{Poll, RawWaker, RawWakerVTable, Waker};
	pub(crate) struct Selector<
		A: Future<Output = ()> + Unpin,
		B: Future<Output = ()> + Unpin,
		C: Future<Output = ()> + Unpin,
		D: Future<Output = bool> + Unpin,
	> {
		pub a: A,
		pub b: B,
		pub c: C,
		pub d: D,
	}

	pub(crate) enum SelectorOutput {
		A,
		B,
		C,
		D(bool),
	}

	impl<
			A: Future<Output = ()> + Unpin,
			B: Future<Output = ()> + Unpin,
			C: Future<Output = ()> + Unpin,
			D: Future<Output = bool> + Unpin,
		> Future for Selector<A, B, C, D>
	{
		type Output = SelectorOutput;
		fn poll(
			mut self: Pin<&mut Self>, ctx: &mut core::task::Context<'_>,
		) -> Poll<SelectorOutput> {
			match Pin::new(&mut self.a).poll(ctx) {
				Poll::Ready(()) => {
					return Poll::Ready(SelectorOutput::A);
				},
				Poll::Pending => {},
			}
			match Pin::new(&mut self.b).poll(ctx) {
				Poll::Ready(()) => {
					return Poll::Ready(SelectorOutput::B);
				},
				Poll::Pending => {},
			}
			match Pin::new(&mut self.c).poll(ctx) {
				Poll::Ready(()) => {
					return Poll::Ready(SelectorOutput::C);
				},
				Poll::Pending => {},
			}
			match Pin::new(&mut self.d).poll(ctx) {
				Poll::Ready(res) => {
					return Poll::Ready(SelectorOutput::D(res));
				},
				Poll::Pending => {},
			}
			Poll::Pending
		}
	}

	/// A selector that takes a future wrapped in an option that will be polled if it is `Some` and
	/// will always be pending otherwise.
	pub(crate) struct OptionalSelector<F: Future<Output = ()> + Unpin> {
		pub optional_future: Option<F>,
	}

	impl<F: Future<Output = ()> + Unpin> Future for OptionalSelector<F> {
		type Output = ();
		fn poll(mut self: Pin<&mut Self>, ctx: &mut core::task::Context<'_>) -> Poll<Self::Output> {
			match self.optional_future.as_mut() {
				Some(f) => match Pin::new(f).poll(ctx) {
					Poll::Ready(()) => {
						self.optional_future.take();
						Poll::Ready(())
					},
					Poll::Pending => Poll::Pending,
				},
				None => Poll::Pending,
			}
		}
	}

	// If we want to poll a future without an async context to figure out if it has completed or
	// not without awaiting, we need a Waker, which needs a vtable...we fill it with dummy values
	// but sadly there's a good bit of boilerplate here.
	fn dummy_waker_clone(_: *const ()) -> RawWaker {
		RawWaker::new(core::ptr::null(), &DUMMY_WAKER_VTABLE)
	}
	fn dummy_waker_action(_: *const ()) {}

	const DUMMY_WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(
		dummy_waker_clone,
		dummy_waker_action,
		dummy_waker_action,
		dummy_waker_action,
	);
	pub(crate) fn dummy_waker() -> Waker {
		unsafe { Waker::from_raw(RawWaker::new(core::ptr::null(), &DUMMY_WAKER_VTABLE)) }
	}
}
#[cfg(feature = "futures")]
use core::task;
#[cfg(feature = "futures")]
use futures_util::{dummy_waker, OptionalSelector, Selector, SelectorOutput};

/// Processes background events in a future.
///
/// `sleeper` should return a future which completes in the given amount of time and returns a
/// boolean indicating whether the background processing should exit. Once `sleeper` returns a
/// future which outputs `true`, the loop will exit and this function's future will complete.
/// The `sleeper` future is free to return early after it has triggered the exit condition.
///
/// See [`BackgroundProcessor::start`] for information on which actions this handles.
///
/// Requires the `futures` feature. Note that while this method is available without the `std`
/// feature, doing so will skip calling [`NetworkGraph::remove_stale_channels_and_tracking`],
/// you should call [`NetworkGraph::remove_stale_channels_and_tracking_with_time`] regularly
/// manually instead.
///
/// The `mobile_interruptable_platform` flag should be set if we're currently running on a
/// mobile device, where we may need to check for interruption of the application regularly. If you
/// are unsure, you should set the flag, as the performance impact of it is minimal unless there
/// are hundreds or thousands of simultaneous process calls running.
///
/// The `fetch_time` parameter should return the current wall clock time, if one is available. If
/// no time is available, some features may be disabled, however the node will still operate fine.
///
/// For example, in order to process background events in a [Tokio](https://tokio.rs/) task, you
/// could setup `process_events_async` like this:
/// ```
/// # use lightning::io;
/// # use lightning::events::ReplayEvent;
/// # use std::sync::{Arc, RwLock};
/// # use std::sync::atomic::{AtomicBool, Ordering};
/// # use std::time::SystemTime;
/// # use lightning_background_processor::{process_events_async, GossipSync};
/// # struct Logger {}
/// # impl lightning::util::logger::Logger for Logger {
/// #     fn log(&self, _record: lightning::util::logger::Record) {}
/// # }
/// # struct Store {}
/// # impl lightning::util::persist::KVStore for Store {
/// #     fn read(&self, primary_namespace: &str, secondary_namespace: &str, key: &str) -> io::Result<Vec<u8>> { Ok(Vec::new()) }
/// #     fn write(&self, primary_namespace: &str, secondary_namespace: &str, key: &str, buf: &[u8]) -> io::Result<()> { Ok(()) }
/// #     fn remove(&self, primary_namespace: &str, secondary_namespace: &str, key: &str, lazy: bool) -> io::Result<()> { Ok(()) }
/// #     fn list(&self, primary_namespace: &str, secondary_namespace: &str) -> io::Result<Vec<String>> { Ok(Vec::new()) }
/// # }
/// # struct EventHandler {}
/// # impl EventHandler {
/// #     async fn handle_event(&self, _: lightning::events::Event) -> Result<(), ReplayEvent> { Ok(()) }
/// # }
/// # #[derive(Eq, PartialEq, Clone, Hash)]
/// # struct SocketDescriptor {}
/// # impl lightning::ln::peer_handler::SocketDescriptor for SocketDescriptor {
/// #     fn send_data(&mut self, _data: &[u8], _resume_read: bool) -> usize { 0 }
/// #     fn disconnect_socket(&mut self) {}
/// # }
/// # type ChainMonitor<B, F, FE> = lightning::chain::chainmonitor::ChainMonitor<lightning::sign::InMemorySigner, Arc<F>, Arc<B>, Arc<FE>, Arc<Logger>, Arc<Store>>;
/// # type NetworkGraph = lightning::routing::gossip::NetworkGraph<Arc<Logger>>;
/// # type P2PGossipSync<UL> = lightning::routing::gossip::P2PGossipSync<Arc<NetworkGraph>, Arc<UL>, Arc<Logger>>;
/// # type ChannelManager<B, F, FE> = lightning::ln::channelmanager::SimpleArcChannelManager<ChainMonitor<B, F, FE>, B, FE, Logger>;
/// # type OnionMessenger<B, F, FE> = lightning::onion_message::messenger::OnionMessenger<Arc<lightning::sign::KeysManager>, Arc<lightning::sign::KeysManager>, Arc<Logger>, Arc<ChannelManager<B, F, FE>>, Arc<lightning::onion_message::messenger::DefaultMessageRouter<Arc<NetworkGraph>, Arc<Logger>, Arc<lightning::sign::KeysManager>>>, Arc<ChannelManager<B, F, FE>>, lightning::ln::peer_handler::IgnoringMessageHandler, lightning::ln::peer_handler::IgnoringMessageHandler, lightning::ln::peer_handler::IgnoringMessageHandler>;
/// # type Scorer = RwLock<lightning::routing::scoring::ProbabilisticScorer<Arc<NetworkGraph>, Arc<Logger>>>;
/// # type PeerManager<B, F, FE, UL> = lightning::ln::peer_handler::SimpleArcPeerManager<SocketDescriptor, ChainMonitor<B, F, FE>, B, FE, Arc<UL>, Logger>;
/// #
/// # struct Node<
/// #     B: lightning::chain::chaininterface::BroadcasterInterface + Send + Sync + 'static,
/// #     F: lightning::chain::Filter + Send + Sync + 'static,
/// #     FE: lightning::chain::chaininterface::FeeEstimator + Send + Sync + 'static,
/// #     UL: lightning::routing::utxo::UtxoLookup + Send + Sync + 'static,
/// # > {
/// #     peer_manager: Arc<PeerManager<B, F, FE, UL>>,
/// #     event_handler: Arc<EventHandler>,
/// #     channel_manager: Arc<ChannelManager<B, F, FE>>,
/// #     onion_messenger: Arc<OnionMessenger<B, F, FE>>,
/// #     chain_monitor: Arc<ChainMonitor<B, F, FE>>,
/// #     gossip_sync: Arc<P2PGossipSync<UL>>,
/// #     persister: Arc<Store>,
/// #     logger: Arc<Logger>,
/// #     scorer: Arc<Scorer>,
/// # }
/// #
/// # async fn setup_background_processing<
/// #     B: lightning::chain::chaininterface::BroadcasterInterface + Send + Sync + 'static,
/// #     F: lightning::chain::Filter + Send + Sync + 'static,
/// #     FE: lightning::chain::chaininterface::FeeEstimator + Send + Sync + 'static,
/// #     UL: lightning::routing::utxo::UtxoLookup + Send + Sync + 'static,
/// # >(node: Node<B, F, FE, UL>) {
///	let background_persister = Arc::clone(&node.persister);
///	let background_event_handler = Arc::clone(&node.event_handler);
///	let background_chain_mon = Arc::clone(&node.chain_monitor);
///	let background_chan_man = Arc::clone(&node.channel_manager);
///	let background_gossip_sync = GossipSync::p2p(Arc::clone(&node.gossip_sync));
///	let background_peer_man = Arc::clone(&node.peer_manager);
///	let background_onion_messenger = Arc::clone(&node.onion_messenger);
///	let background_logger = Arc::clone(&node.logger);
///	let background_scorer = Arc::clone(&node.scorer);
///
///	// Setup the sleeper.
///	let (stop_sender, stop_receiver) = tokio::sync::watch::channel(());
///
///	let sleeper = move |d| {
///		let mut receiver = stop_receiver.clone();
///		Box::pin(async move {
///			tokio::select!{
///				_ = tokio::time::sleep(d) => false,
///				_ = receiver.changed() => true,
///			}
///		})
///	};
///
///	let mobile_interruptable_platform = false;
///
///	let handle = tokio::spawn(async move {
///		process_events_async(
///			background_persister,
///			|e| background_event_handler.handle_event(e),
///			background_chain_mon,
///			background_chan_man,
///			Some(background_onion_messenger),
///			background_gossip_sync,
///			background_peer_man,
///			background_logger,
///			Some(background_scorer),
///			sleeper,
///			mobile_interruptable_platform,
///			|| Some(SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap())
///		)
///		.await
///		.expect("Failed to process events");
///	});
///
///	// Stop the background processing.
///	stop_sender.send(()).unwrap();
///	handle.await.unwrap();
///	# }
///```
#[cfg(feature = "futures")]
pub async fn process_events_async<
	'a,
	UL: 'static + Deref + Send + Sync,
	CF: 'static + Deref + Send + Sync,
	T: 'static + Deref + Send + Sync,
	F: 'static + Deref + Send + Sync,
	G: 'static + Deref<Target = NetworkGraph<L>> + Send + Sync,
	L: 'static + Deref + Send + Sync,
	P: 'static + Deref + Send + Sync,
	EventHandlerFuture: core::future::Future<Output = Result<(), ReplayEvent>>,
	EventHandler: Fn(Event) -> EventHandlerFuture,
	PS: 'static + Deref + Send,
	M: 'static
		+ Deref<Target = ChainMonitor<<CM::Target as AChannelManager>::Signer, CF, T, F, L, P>>
		+ Send
		+ Sync,
	CM: 'static + Deref + Send + Sync,
	OM: 'static + Deref + Send + Sync,
	PGS: 'static + Deref<Target = P2PGossipSync<G, UL, L>> + Send + Sync,
	RGS: 'static + Deref<Target = RapidGossipSync<G, L>> + Send,
	PM: 'static + Deref + Send + Sync,
	S: 'static + Deref<Target = SC> + Send + Sync,
	SC: for<'b> WriteableScore<'b>,
	SleepFuture: core::future::Future<Output = bool> + core::marker::Unpin,
	Sleeper: Fn(Duration) -> SleepFuture,
	FetchTime: Fn() -> Option<Duration>,
>(
	persister: PS, event_handler: EventHandler, chain_monitor: M, channel_manager: CM,
	onion_messenger: Option<OM>, gossip_sync: GossipSync<PGS, RGS, G, UL, L>, peer_manager: PM,
	logger: L, scorer: Option<S>, sleeper: Sleeper, mobile_interruptable_platform: bool,
	fetch_time: FetchTime,
) -> Result<(), lightning::io::Error>
where
	UL::Target: 'static + UtxoLookup,
	CF::Target: 'static + chain::Filter,
	T::Target: 'static + BroadcasterInterface,
	F::Target: 'static + FeeEstimator,
	L::Target: 'static + Logger,
	P::Target: 'static + Persist<<CM::Target as AChannelManager>::Signer>,
	PS::Target: 'static + Persister<'a, CM, L, S>,
	CM::Target: AChannelManager + Send + Sync,
	OM::Target: AOnionMessenger + Send + Sync,
	PM::Target: APeerManager + Send + Sync,
{
	let mut should_break = false;
	let async_event_handler = |event| {
		let network_graph = gossip_sync.network_graph();
		let event_handler = &event_handler;
		let scorer = &scorer;
		let logger = &logger;
		let persister = &persister;
		let fetch_time = &fetch_time;
		// We should be able to drop the Box once our MSRV is 1.68
		Box::pin(async move {
			if let Some(network_graph) = network_graph {
				handle_network_graph_update(network_graph, &event)
			}
			if let Some(ref scorer) = scorer {
				if let Some(duration_since_epoch) = fetch_time() {
					if update_scorer(scorer, &event, duration_since_epoch) {
						log_trace!(logger, "Persisting scorer after update");
						if let Err(e) = persister.persist_scorer(&*scorer) {
							log_error!(logger, "Error: Failed to persist scorer, check your disk and permissions {}", e);
							// We opt not to abort early on persistence failure here as persisting
							// the scorer is non-critical and we still hope that it will have
							// resolved itself when it is potentially critical in event handling
							// below.
						}
					}
				}
			}
			event_handler(event).await
		})
	};
	define_run_body!(
		persister,
		chain_monitor,
		chain_monitor.process_pending_events_async(async_event_handler).await,
		channel_manager,
		channel_manager.get_cm().process_pending_events_async(async_event_handler).await,
		onion_messenger,
		if let Some(om) = &onion_messenger {
			om.get_om().process_pending_events_async(async_event_handler).await
		},
		peer_manager,
		gossip_sync,
		logger,
		scorer,
		should_break,
		{
			let om_fut = if let Some(om) = onion_messenger.as_ref() {
				let fut = om.get_om().get_update_future();
				OptionalSelector { optional_future: Some(fut) }
			} else {
				OptionalSelector { optional_future: None }
			};
			let fut = Selector {
				a: channel_manager.get_cm().get_event_or_persistence_needed_future(),
				b: chain_monitor.get_update_future(),
				c: om_fut,
				d: sleeper(if mobile_interruptable_platform {
					Duration::from_millis(100)
				} else {
					Duration::from_secs(FASTEST_TIMER)
				}),
			};
			match fut.await {
				SelectorOutput::A | SelectorOutput::B | SelectorOutput::C => {},
				SelectorOutput::D(exit) => {
					should_break = exit;
				},
			}
		},
		|t| sleeper(Duration::from_secs(t)),
		|fut: &mut SleepFuture, _| {
			let mut waker = dummy_waker();
			let mut ctx = task::Context::from_waker(&mut waker);
			match core::pin::Pin::new(fut).poll(&mut ctx) {
				task::Poll::Ready(exit) => {
					should_break = exit;
					true
				},
				task::Poll::Pending => false,
			}
		},
		mobile_interruptable_platform,
		fetch_time,
	)
}

#[cfg(feature = "std")]
impl BackgroundProcessor {
	/// Start a background thread that takes care of responsibilities enumerated in the [top-level
	/// documentation].
	///
	/// The thread runs indefinitely unless the object is dropped, [`stop`] is called, or
	/// [`Persister::persist_manager`] returns an error. In case of an error, the error is retrieved by calling
	/// either [`join`] or [`stop`].
	///
	/// # Data Persistence
	///
	/// [`Persister::persist_manager`] is responsible for writing out the [`ChannelManager`] to disk, and/or
	/// uploading to one or more backup services. See [`ChannelManager::write`] for writing out a
	/// [`ChannelManager`]. See the `lightning-persister` crate for LDK's
	/// provided implementation.
	///
	/// [`Persister::persist_graph`] is responsible for writing out the [`NetworkGraph`] to disk, if
	/// [`GossipSync`] is supplied. See [`NetworkGraph::write`] for writing out a [`NetworkGraph`].
	/// See the `lightning-persister` crate for LDK's provided implementation.
	///
	/// Typically, users should either implement [`Persister::persist_manager`] to never return an
	/// error or call [`join`] and handle any error that may arise. For the latter case,
	/// `BackgroundProcessor` must be restarted by calling `start` again after handling the error.
	///
	/// # Event Handling
	///
	/// `event_handler` is responsible for handling events that users should be notified of (e.g.,
	/// payment failed). [`BackgroundProcessor`] may decorate the given [`EventHandler`] with common
	/// functionality implemented by other handlers.
	/// * [`P2PGossipSync`] if given will update the [`NetworkGraph`] based on payment failures.
	///
	/// # Rapid Gossip Sync
	///
	/// If rapid gossip sync is meant to run at startup, pass [`RapidGossipSync`] via `gossip_sync`
	/// to indicate that the [`BackgroundProcessor`] should not prune the [`NetworkGraph`] instance
	/// until the [`RapidGossipSync`] instance completes its first sync.
	///
	/// [top-level documentation]: BackgroundProcessor
	/// [`join`]: Self::join
	/// [`stop`]: Self::stop
	/// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
	/// [`ChannelManager::write`]: lightning::ln::channelmanager::ChannelManager#impl-Writeable
	/// [`Persister::persist_manager`]: lightning::util::persist::Persister::persist_manager
	/// [`Persister::persist_graph`]: lightning::util::persist::Persister::persist_graph
	/// [`NetworkGraph`]: lightning::routing::gossip::NetworkGraph
	/// [`NetworkGraph::write`]: lightning::routing::gossip::NetworkGraph#impl-Writeable
	pub fn start<
		'a,
		UL: 'static + Deref + Send + Sync,
		CF: 'static + Deref + Send + Sync,
		T: 'static + Deref + Send + Sync,
		F: 'static + Deref + Send + Sync,
		G: 'static + Deref<Target = NetworkGraph<L>> + Send + Sync,
		L: 'static + Deref + Send + Sync,
		P: 'static + Deref + Send + Sync,
		EH: 'static + EventHandler + Send,
		PS: 'static + Deref + Send,
		M: 'static
			+ Deref<Target = ChainMonitor<<CM::Target as AChannelManager>::Signer, CF, T, F, L, P>>
			+ Send
			+ Sync,
		CM: 'static + Deref + Send + Sync,
		OM: 'static + Deref + Send + Sync,
		PGS: 'static + Deref<Target = P2PGossipSync<G, UL, L>> + Send + Sync,
		RGS: 'static + Deref<Target = RapidGossipSync<G, L>> + Send,
		PM: 'static + Deref + Send + Sync,
		S: 'static + Deref<Target = SC> + Send + Sync,
		SC: for<'b> WriteableScore<'b>,
	>(
		persister: PS, event_handler: EH, chain_monitor: M, channel_manager: CM,
		onion_messenger: Option<OM>, gossip_sync: GossipSync<PGS, RGS, G, UL, L>, peer_manager: PM,
		logger: L, scorer: Option<S>,
	) -> Self
	where
		UL::Target: 'static + UtxoLookup,
		CF::Target: 'static + chain::Filter,
		T::Target: 'static + BroadcasterInterface,
		F::Target: 'static + FeeEstimator,
		L::Target: 'static + Logger,
		P::Target: 'static + Persist<<CM::Target as AChannelManager>::Signer>,
		PS::Target: 'static + Persister<'a, CM, L, S>,
		CM::Target: AChannelManager + Send + Sync,
		OM::Target: AOnionMessenger + Send + Sync,
		PM::Target: APeerManager + Send + Sync,
	{
		let stop_thread = Arc::new(AtomicBool::new(false));
		let stop_thread_clone = stop_thread.clone();
		let handle = thread::spawn(move || -> Result<(), std::io::Error> {
			let event_handler = |event| {
				let network_graph = gossip_sync.network_graph();
				if let Some(network_graph) = network_graph {
					handle_network_graph_update(network_graph, &event)
				}
				if let Some(ref scorer) = scorer {
					use std::time::SystemTime;
					let duration_since_epoch = SystemTime::now()
						.duration_since(SystemTime::UNIX_EPOCH)
						.expect("Time should be sometime after 1970");
					if update_scorer(scorer, &event, duration_since_epoch) {
						log_trace!(logger, "Persisting scorer after update");
						if let Err(e) = persister.persist_scorer(&scorer) {
							log_error!(logger, "Error: Failed to persist scorer, check your disk and permissions {}", e)
						}
					}
				}
				event_handler.handle_event(event)
			};
			define_run_body!(
				persister,
				chain_monitor,
				chain_monitor.process_pending_events(&event_handler),
				channel_manager,
				channel_manager.get_cm().process_pending_events(&event_handler),
				onion_messenger,
				if let Some(om) = &onion_messenger {
					om.get_om().process_pending_events(&event_handler)
				},
				peer_manager,
				gossip_sync,
				logger,
				scorer,
				stop_thread.load(Ordering::Acquire),
				{
					let sleeper = if let Some(om) = onion_messenger.as_ref() {
						Sleeper::from_three_futures(
							&channel_manager.get_cm().get_event_or_persistence_needed_future(),
							&chain_monitor.get_update_future(),
							&om.get_om().get_update_future(),
						)
					} else {
						Sleeper::from_two_futures(
							&channel_manager.get_cm().get_event_or_persistence_needed_future(),
							&chain_monitor.get_update_future(),
						)
					};
					sleeper.wait_timeout(Duration::from_millis(100));
				},
				|_| Instant::now(),
				|time: &Instant, dur| time.elapsed().as_secs() > dur,
				false,
				|| {
					use std::time::SystemTime;
					Some(
						SystemTime::now()
							.duration_since(SystemTime::UNIX_EPOCH)
							.expect("Time should be sometime after 1970"),
					)
				},
			)
		});
		Self { stop_thread: stop_thread_clone, thread_handle: Some(handle) }
	}

	/// Join `BackgroundProcessor`'s thread, returning any error that occurred while persisting
	/// [`ChannelManager`].
	///
	/// # Panics
	///
	/// This function panics if the background thread has panicked such as while persisting or
	/// handling events.
	///
	/// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
	pub fn join(mut self) -> Result<(), std::io::Error> {
		assert!(self.thread_handle.is_some());
		self.join_thread()
	}

	/// Stop `BackgroundProcessor`'s thread, returning any error that occurred while persisting
	/// [`ChannelManager`].
	///
	/// # Panics
	///
	/// This function panics if the background thread has panicked such as while persisting or
	/// handling events.
	///
	/// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
	pub fn stop(mut self) -> Result<(), std::io::Error> {
		assert!(self.thread_handle.is_some());
		self.stop_and_join_thread()
	}

	fn stop_and_join_thread(&mut self) -> Result<(), std::io::Error> {
		self.stop_thread.store(true, Ordering::Release);
		self.join_thread()
	}

	fn join_thread(&mut self) -> Result<(), std::io::Error> {
		match self.thread_handle.take() {
			Some(handle) => handle.join().unwrap(),
			None => Ok(()),
		}
	}
}

#[cfg(feature = "std")]
impl Drop for BackgroundProcessor {
	fn drop(&mut self) {
		self.stop_and_join_thread().unwrap();
	}
}

#[cfg(all(feature = "std", test))]
mod tests {
	use super::{BackgroundProcessor, GossipSync, FRESHNESS_TIMER};
	use bitcoin::constants::{genesis_block, ChainHash};
	use bitcoin::hashes::Hash;
	use bitcoin::locktime::absolute::LockTime;
	use bitcoin::network::Network;
	use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
	use bitcoin::transaction::Version;
	use bitcoin::transaction::{Transaction, TxOut};
	use bitcoin::{Amount, ScriptBuf, Txid};
	use core::sync::atomic::{AtomicBool, Ordering};
	use lightning::chain::channelmonitor::ANTI_REORG_DELAY;
	use lightning::chain::transaction::OutPoint;
	use lightning::chain::{chainmonitor, BestBlock, Confirm, Filter};
	use lightning::events::{
		Event, MessageSendEvent, MessageSendEventsProvider, PathFailure, ReplayEvent,
	};
	use lightning::ln::channelmanager;
	use lightning::ln::channelmanager::{
		ChainParameters, PaymentId, BREAKDOWN_TIMEOUT, MIN_CLTV_EXPIRY_DELTA,
	};
	use lightning::ln::functional_test_utils::*;
	use lightning::ln::msgs::{ChannelMessageHandler, Init};
	use lightning::ln::peer_handler::{
		IgnoringMessageHandler, MessageHandler, PeerManager, SocketDescriptor,
	};
	use lightning::ln::types::ChannelId;
	use lightning::onion_message::messenger::{DefaultMessageRouter, OnionMessenger};
	use lightning::routing::gossip::{NetworkGraph, P2PGossipSync};
	use lightning::routing::router::{CandidateRouteHop, DefaultRouter, Path, RouteHop};
	use lightning::routing::scoring::{ChannelUsage, LockableScore, ScoreLookUp, ScoreUpdate};
	use lightning::sign::{ChangeDestinationSource, InMemorySigner, KeysManager};
	use lightning::types::features::{ChannelFeatures, NodeFeatures};
	use lightning::types::payment::PaymentHash;
	use lightning::util::config::UserConfig;
	use lightning::util::persist::{
		KVStore, CHANNEL_MANAGER_PERSISTENCE_KEY, CHANNEL_MANAGER_PERSISTENCE_PRIMARY_NAMESPACE,
		CHANNEL_MANAGER_PERSISTENCE_SECONDARY_NAMESPACE, NETWORK_GRAPH_PERSISTENCE_KEY,
		NETWORK_GRAPH_PERSISTENCE_PRIMARY_NAMESPACE, NETWORK_GRAPH_PERSISTENCE_SECONDARY_NAMESPACE,
		SCORER_PERSISTENCE_KEY, SCORER_PERSISTENCE_PRIMARY_NAMESPACE,
		SCORER_PERSISTENCE_SECONDARY_NAMESPACE,
	};
	use lightning::util::ser::Writeable;
	use lightning::util::sweep::{OutputSpendStatus, OutputSweeper};
	use lightning::util::test_utils;
	use lightning::{get_event, get_event_msg};
	use lightning_persister::fs_store::FilesystemStore;
	use lightning_rapid_gossip_sync::RapidGossipSync;
	use std::collections::VecDeque;
	use std::path::PathBuf;
	use std::sync::mpsc::SyncSender;
	use std::sync::Arc;
	use std::time::Duration;
	use std::{env, fs};

	const EVENT_DEADLINE: u64 = 5 * FRESHNESS_TIMER;

	#[derive(Clone, Hash, PartialEq, Eq)]
	struct TestDescriptor {}
	impl SocketDescriptor for TestDescriptor {
		fn send_data(&mut self, _data: &[u8], _resume_read: bool) -> usize {
			0
		}

		fn disconnect_socket(&mut self) {}
	}

	#[cfg(c_bindings)]
	type LockingWrapper<T> = lightning::routing::scoring::MultiThreadedLockableScore<T>;
	#[cfg(not(c_bindings))]
	type LockingWrapper<T> = std::sync::Mutex<T>;

	type ChannelManager = channelmanager::ChannelManager<
		Arc<ChainMonitor>,
		Arc<test_utils::TestBroadcaster>,
		Arc<KeysManager>,
		Arc<KeysManager>,
		Arc<KeysManager>,
		Arc<test_utils::TestFeeEstimator>,
		Arc<
			DefaultRouter<
				Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
				Arc<test_utils::TestLogger>,
				Arc<KeysManager>,
				Arc<LockingWrapper<TestScorer>>,
				(),
				TestScorer,
			>,
		>,
		Arc<
			DefaultMessageRouter<
				Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
				Arc<test_utils::TestLogger>,
				Arc<KeysManager>,
			>,
		>,
		Arc<test_utils::TestLogger>,
	>;

	type ChainMonitor = chainmonitor::ChainMonitor<
		InMemorySigner,
		Arc<test_utils::TestChainSource>,
		Arc<test_utils::TestBroadcaster>,
		Arc<test_utils::TestFeeEstimator>,
		Arc<test_utils::TestLogger>,
		Arc<FilesystemStore>,
	>;

	type PGS = Arc<
		P2PGossipSync<
			Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
			Arc<test_utils::TestChainSource>,
			Arc<test_utils::TestLogger>,
		>,
	>;
	type RGS = Arc<
		RapidGossipSync<
			Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
			Arc<test_utils::TestLogger>,
		>,
	>;

	type OM = OnionMessenger<
		Arc<KeysManager>,
		Arc<KeysManager>,
		Arc<test_utils::TestLogger>,
		Arc<ChannelManager>,
		Arc<
			DefaultMessageRouter<
				Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
				Arc<test_utils::TestLogger>,
				Arc<KeysManager>,
			>,
		>,
		IgnoringMessageHandler,
		Arc<ChannelManager>,
		IgnoringMessageHandler,
		IgnoringMessageHandler,
	>;

	struct Node {
		node: Arc<ChannelManager>,
		messenger: Arc<OM>,
		p2p_gossip_sync: PGS,
		rapid_gossip_sync: RGS,
		peer_manager: Arc<
			PeerManager<
				TestDescriptor,
				Arc<test_utils::TestChannelMessageHandler>,
				Arc<test_utils::TestRoutingMessageHandler>,
				Arc<OM>,
				Arc<test_utils::TestLogger>,
				IgnoringMessageHandler,
				Arc<KeysManager>,
			>,
		>,
		chain_monitor: Arc<ChainMonitor>,
		kv_store: Arc<FilesystemStore>,
		tx_broadcaster: Arc<test_utils::TestBroadcaster>,
		network_graph: Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
		logger: Arc<test_utils::TestLogger>,
		best_block: BestBlock,
		scorer: Arc<LockingWrapper<TestScorer>>,
		sweeper: Arc<
			OutputSweeper<
				Arc<test_utils::TestBroadcaster>,
				Arc<TestWallet>,
				Arc<test_utils::TestFeeEstimator>,
				Arc<dyn Filter + Sync + Send>,
				Arc<FilesystemStore>,
				Arc<test_utils::TestLogger>,
				Arc<KeysManager>,
			>,
		>,
	}

	impl Node {
		fn p2p_gossip_sync(
			&self,
		) -> GossipSync<
			PGS,
			RGS,
			Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
			Arc<test_utils::TestChainSource>,
			Arc<test_utils::TestLogger>,
		> {
			GossipSync::P2P(self.p2p_gossip_sync.clone())
		}

		fn rapid_gossip_sync(
			&self,
		) -> GossipSync<
			PGS,
			RGS,
			Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
			Arc<test_utils::TestChainSource>,
			Arc<test_utils::TestLogger>,
		> {
			GossipSync::Rapid(self.rapid_gossip_sync.clone())
		}

		fn no_gossip_sync(
			&self,
		) -> GossipSync<
			PGS,
			RGS,
			Arc<NetworkGraph<Arc<test_utils::TestLogger>>>,
			Arc<test_utils::TestChainSource>,
			Arc<test_utils::TestLogger>,
		> {
			GossipSync::None
		}
	}

	impl Drop for Node {
		fn drop(&mut self) {
			let data_dir = self.kv_store.get_data_dir();
			match fs::remove_dir_all(data_dir.clone()) {
				Err(e) => {
					println!("Failed to remove test store directory {}: {}", data_dir.display(), e)
				},
				_ => {},
			}
		}
	}

	struct Persister {
		graph_error: Option<(std::io::ErrorKind, &'static str)>,
		graph_persistence_notifier: Option<SyncSender<()>>,
		manager_error: Option<(std::io::ErrorKind, &'static str)>,
		scorer_error: Option<(std::io::ErrorKind, &'static str)>,
		kv_store: FilesystemStore,
	}

	impl Persister {
		fn new(data_dir: PathBuf) -> Self {
			let kv_store = FilesystemStore::new(data_dir);
			Self {
				graph_error: None,
				graph_persistence_notifier: None,
				manager_error: None,
				scorer_error: None,
				kv_store,
			}
		}

		fn with_graph_error(self, error: std::io::ErrorKind, message: &'static str) -> Self {
			Self { graph_error: Some((error, message)), ..self }
		}

		fn with_graph_persistence_notifier(self, sender: SyncSender<()>) -> Self {
			Self { graph_persistence_notifier: Some(sender), ..self }
		}

		fn with_manager_error(self, error: std::io::ErrorKind, message: &'static str) -> Self {
			Self { manager_error: Some((error, message)), ..self }
		}

		fn with_scorer_error(self, error: std::io::ErrorKind, message: &'static str) -> Self {
			Self { scorer_error: Some((error, message)), ..self }
		}
	}

	impl KVStore for Persister {
		fn read(
			&self, primary_namespace: &str, secondary_namespace: &str, key: &str,
		) -> lightning::io::Result<Vec<u8>> {
			self.kv_store.read(primary_namespace, secondary_namespace, key)
		}

		fn write(
			&self, primary_namespace: &str, secondary_namespace: &str, key: &str, buf: &[u8],
		) -> lightning::io::Result<()> {
			if primary_namespace == CHANNEL_MANAGER_PERSISTENCE_PRIMARY_NAMESPACE
				&& secondary_namespace == CHANNEL_MANAGER_PERSISTENCE_SECONDARY_NAMESPACE
				&& key == CHANNEL_MANAGER_PERSISTENCE_KEY
			{
				if let Some((error, message)) = self.manager_error {
					return Err(std::io::Error::new(error, message).into());
				}
			}

			if primary_namespace == NETWORK_GRAPH_PERSISTENCE_PRIMARY_NAMESPACE
				&& secondary_namespace == NETWORK_GRAPH_PERSISTENCE_SECONDARY_NAMESPACE
				&& key == NETWORK_GRAPH_PERSISTENCE_KEY
			{
				if let Some(sender) = &self.graph_persistence_notifier {
					match sender.send(()) {
						Ok(()) => {},
						Err(std::sync::mpsc::SendError(())) => {
							println!("Persister failed to notify as receiver went away.")
						},
					}
				};

				if let Some((error, message)) = self.graph_error {
					return Err(std::io::Error::new(error, message).into());
				}
			}

			if primary_namespace == SCORER_PERSISTENCE_PRIMARY_NAMESPACE
				&& secondary_namespace == SCORER_PERSISTENCE_SECONDARY_NAMESPACE
				&& key == SCORER_PERSISTENCE_KEY
			{
				if let Some((error, message)) = self.scorer_error {
					return Err(std::io::Error::new(error, message).into());
				}
			}

			self.kv_store.write(primary_namespace, secondary_namespace, key, buf)
		}

		fn remove(
			&self, primary_namespace: &str, secondary_namespace: &str, key: &str, lazy: bool,
		) -> lightning::io::Result<()> {
			self.kv_store.remove(primary_namespace, secondary_namespace, key, lazy)
		}

		fn list(
			&self, primary_namespace: &str, secondary_namespace: &str,
		) -> lightning::io::Result<Vec<String>> {
			self.kv_store.list(primary_namespace, secondary_namespace)
		}
	}

	struct TestScorer {
		event_expectations: Option<VecDeque<TestResult>>,
	}

	#[derive(Debug)]
	enum TestResult {
		PaymentFailure { path: Path, short_channel_id: u64 },
		PaymentSuccess { path: Path },
		ProbeFailure { path: Path },
		ProbeSuccess { path: Path },
	}

	impl TestScorer {
		fn new() -> Self {
			Self { event_expectations: None }
		}

		fn expect(&mut self, expectation: TestResult) {
			self.event_expectations.get_or_insert_with(VecDeque::new).push_back(expectation);
		}
	}

	impl lightning::util::ser::Writeable for TestScorer {
		fn write<W: lightning::util::ser::Writer>(
			&self, _: &mut W,
		) -> Result<(), lightning::io::Error> {
			Ok(())
		}
	}

	impl ScoreLookUp for TestScorer {
		type ScoreParams = ();
		fn channel_penalty_msat(
			&self, _candidate: &CandidateRouteHop, _usage: ChannelUsage,
			_score_params: &Self::ScoreParams,
		) -> u64 {
			unimplemented!();
		}
	}

	impl ScoreUpdate for TestScorer {
		fn payment_path_failed(
			&mut self, actual_path: &Path, actual_short_channel_id: u64, _: Duration,
		) {
			if let Some(expectations) = &mut self.event_expectations {
				match expectations.pop_front().unwrap() {
					TestResult::PaymentFailure { path, short_channel_id } => {
						assert_eq!(actual_path, &path);
						assert_eq!(actual_short_channel_id, short_channel_id);
					},
					TestResult::PaymentSuccess { path } => {
						panic!("Unexpected successful payment path: {:?}", path)
					},
					TestResult::ProbeFailure { path } => {
						panic!("Unexpected probe failure: {:?}", path)
					},
					TestResult::ProbeSuccess { path } => {
						panic!("Unexpected probe success: {:?}", path)
					},
				}
			}
		}

		fn payment_path_successful(&mut self, actual_path: &Path, _: Duration) {
			if let Some(expectations) = &mut self.event_expectations {
				match expectations.pop_front().unwrap() {
					TestResult::PaymentFailure { path, .. } => {
						panic!("Unexpected payment path failure: {:?}", path)
					},
					TestResult::PaymentSuccess { path } => {
						assert_eq!(actual_path, &path);
					},
					TestResult::ProbeFailure { path } => {
						panic!("Unexpected probe failure: {:?}", path)
					},
					TestResult::ProbeSuccess { path } => {
						panic!("Unexpected probe success: {:?}", path)
					},
				}
			}
		}

		fn probe_failed(&mut self, actual_path: &Path, _: u64, _: Duration) {
			if let Some(expectations) = &mut self.event_expectations {
				match expectations.pop_front().unwrap() {
					TestResult::PaymentFailure { path, .. } => {
						panic!("Unexpected payment path failure: {:?}", path)
					},
					TestResult::PaymentSuccess { path } => {
						panic!("Unexpected payment path success: {:?}", path)
					},
					TestResult::ProbeFailure { path } => {
						assert_eq!(actual_path, &path);
					},
					TestResult::ProbeSuccess { path } => {
						panic!("Unexpected probe success: {:?}", path)
					},
				}
			}
		}
		fn probe_successful(&mut self, actual_path: &Path, _: Duration) {
			if let Some(expectations) = &mut self.event_expectations {
				match expectations.pop_front().unwrap() {
					TestResult::PaymentFailure { path, .. } => {
						panic!("Unexpected payment path failure: {:?}", path)
					},
					TestResult::PaymentSuccess { path } => {
						panic!("Unexpected payment path success: {:?}", path)
					},
					TestResult::ProbeFailure { path } => {
						panic!("Unexpected probe failure: {:?}", path)
					},
					TestResult::ProbeSuccess { path } => {
						assert_eq!(actual_path, &path);
					},
				}
			}
		}
		fn time_passed(&mut self, _: Duration) {}
	}

	#[cfg(c_bindings)]
	impl lightning::routing::scoring::Score for TestScorer {}

	impl Drop for TestScorer {
		fn drop(&mut self) {
			if std::thread::panicking() {
				return;
			}

			if let Some(event_expectations) = &self.event_expectations {
				if !event_expectations.is_empty() {
					panic!("Unsatisfied event expectations: {:?}", event_expectations);
				}
			}
		}
	}

	struct TestWallet {}

	impl ChangeDestinationSource for TestWallet {
		fn get_change_destination_script(&self) -> Result<ScriptBuf, ()> {
			Ok(ScriptBuf::new())
		}
	}

	fn get_full_filepath(filepath: String, filename: String) -> String {
		let mut path = PathBuf::from(filepath);
		path.push(filename);
		path.to_str().unwrap().to_string()
	}

	fn create_nodes(num_nodes: usize, persist_dir: &str) -> (String, Vec<Node>) {
		let persist_temp_path = env::temp_dir().join(persist_dir);
		let persist_dir = persist_temp_path.to_string_lossy().to_string();
		let network = Network::Bitcoin;
		let mut nodes = Vec::new();
		for i in 0..num_nodes {
			let tx_broadcaster = Arc::new(test_utils::TestBroadcaster::new(network));
			let fee_estimator = Arc::new(test_utils::TestFeeEstimator::new(253));
			let logger = Arc::new(test_utils::TestLogger::with_id(format!("node {}", i)));
			let genesis_block = genesis_block(network);
			let network_graph = Arc::new(NetworkGraph::new(network, logger.clone()));
			let scorer = Arc::new(LockingWrapper::new(TestScorer::new()));
			let now = Duration::from_secs(genesis_block.header.time as u64);
			let seed = [i as u8; 32];
			let keys_manager = Arc::new(KeysManager::new(&seed, now.as_secs(), now.subsec_nanos()));
			let router = Arc::new(DefaultRouter::new(
				network_graph.clone(),
				logger.clone(),
				Arc::clone(&keys_manager),
				scorer.clone(),
				Default::default(),
			));
			let msg_router = Arc::new(DefaultMessageRouter::new(
				network_graph.clone(),
				Arc::clone(&keys_manager),
			));
			let chain_source = Arc::new(test_utils::TestChainSource::new(Network::Bitcoin));
			let kv_store =
				Arc::new(FilesystemStore::new(format!("{}_persister_{}", &persist_dir, i).into()));
			let now = Duration::from_secs(genesis_block.header.time as u64);
			let keys_manager = Arc::new(KeysManager::new(&seed, now.as_secs(), now.subsec_nanos()));
			let chain_monitor = Arc::new(chainmonitor::ChainMonitor::new(
				Some(chain_source.clone()),
				tx_broadcaster.clone(),
				logger.clone(),
				fee_estimator.clone(),
				kv_store.clone(),
			));
			let best_block = BestBlock::from_network(network);
			let params = ChainParameters { network, best_block };
			let manager = Arc::new(ChannelManager::new(
				fee_estimator.clone(),
				chain_monitor.clone(),
				tx_broadcaster.clone(),
				router.clone(),
				msg_router.clone(),
				logger.clone(),
				keys_manager.clone(),
				keys_manager.clone(),
				keys_manager.clone(),
				UserConfig::default(),
				params,
				genesis_block.header.time,
			));
			let messenger = Arc::new(OnionMessenger::new(
				keys_manager.clone(),
				keys_manager.clone(),
				logger.clone(),
				manager.clone(),
				msg_router.clone(),
				IgnoringMessageHandler {},
				manager.clone(),
				IgnoringMessageHandler {},
				IgnoringMessageHandler {},
			));
			let wallet = Arc::new(TestWallet {});
			let sweeper = Arc::new(OutputSweeper::new(
				best_block,
				Arc::clone(&tx_broadcaster),
				Arc::clone(&fee_estimator),
				None::<Arc<dyn Filter + Sync + Send>>,
				Arc::clone(&keys_manager),
				wallet,
				Arc::clone(&kv_store),
				Arc::clone(&logger),
			));
			let p2p_gossip_sync = Arc::new(P2PGossipSync::new(
				network_graph.clone(),
				Some(chain_source.clone()),
				logger.clone(),
			));
			let rapid_gossip_sync =
				Arc::new(RapidGossipSync::new(network_graph.clone(), logger.clone()));
			let msg_handler = MessageHandler {
				chan_handler: Arc::new(test_utils::TestChannelMessageHandler::new(
					ChainHash::using_genesis_block(Network::Testnet),
				)),
				route_handler: Arc::new(test_utils::TestRoutingMessageHandler::new()),
				onion_message_handler: messenger.clone(),
				custom_message_handler: IgnoringMessageHandler {},
			};
			let peer_manager = Arc::new(PeerManager::new(
				msg_handler,
				0,
				&seed,
				logger.clone(),
				keys_manager.clone(),
			));
			let node = Node {
				node: manager,
				p2p_gossip_sync,
				rapid_gossip_sync,
				peer_manager,
				chain_monitor,
				kv_store,
				tx_broadcaster,
				network_graph,
				logger,
				best_block,
				scorer,
				sweeper,
				messenger,
			};
			nodes.push(node);
		}

		for i in 0..num_nodes {
			for j in (i + 1)..num_nodes {
				let init_i = Init {
					features: nodes[j].node.init_features(),
					networks: None,
					remote_network_address: None,
				};
				nodes[i]
					.node
					.peer_connected(nodes[j].node.get_our_node_id(), &init_i, true)
					.unwrap();
				let init_j = Init {
					features: nodes[i].node.init_features(),
					networks: None,
					remote_network_address: None,
				};
				nodes[j]
					.node
					.peer_connected(nodes[i].node.get_our_node_id(), &init_j, false)
					.unwrap();
			}
		}

		(persist_dir, nodes)
	}

	macro_rules! open_channel {
		($node_a: expr, $node_b: expr, $channel_value: expr) => {{
			begin_open_channel!($node_a, $node_b, $channel_value);
			let events = $node_a.node.get_and_clear_pending_events();
			assert_eq!(events.len(), 1);
			let (temporary_channel_id, tx) =
				handle_funding_generation_ready!(events[0], $channel_value);
			$node_a
				.node
				.funding_transaction_generated(
					temporary_channel_id,
					$node_b.node.get_our_node_id(),
					tx.clone(),
				)
				.unwrap();
			let msg_a = get_event_msg!(
				$node_a,
				MessageSendEvent::SendFundingCreated,
				$node_b.node.get_our_node_id()
			);
			$node_b.node.handle_funding_created($node_a.node.get_our_node_id(), &msg_a);
			get_event!($node_b, Event::ChannelPending);
			let msg_b = get_event_msg!(
				$node_b,
				MessageSendEvent::SendFundingSigned,
				$node_a.node.get_our_node_id()
			);
			$node_a.node.handle_funding_signed($node_b.node.get_our_node_id(), &msg_b);
			get_event!($node_a, Event::ChannelPending);
			tx
		}};
	}

	macro_rules! begin_open_channel {
		($node_a: expr, $node_b: expr, $channel_value: expr) => {{
			$node_a
				.node
				.create_channel($node_b.node.get_our_node_id(), $channel_value, 100, 42, None, None)
				.unwrap();
			let msg_a = get_event_msg!(
				$node_a,
				MessageSendEvent::SendOpenChannel,
				$node_b.node.get_our_node_id()
			);
			$node_b.node.handle_open_channel($node_a.node.get_our_node_id(), &msg_a);
			let msg_b = get_event_msg!(
				$node_b,
				MessageSendEvent::SendAcceptChannel,
				$node_a.node.get_our_node_id()
			);
			$node_a.node.handle_accept_channel($node_b.node.get_our_node_id(), &msg_b);
		}};
	}

	macro_rules! handle_funding_generation_ready {
		($event: expr, $channel_value: expr) => {{
			match $event {
				Event::FundingGenerationReady {
					temporary_channel_id,
					channel_value_satoshis,
					ref output_script,
					user_channel_id,
					..
				} => {
					assert_eq!(channel_value_satoshis, $channel_value);
					assert_eq!(user_channel_id, 42);

					let tx = Transaction {
						version: Version::ONE,
						lock_time: LockTime::ZERO,
						input: Vec::new(),
						output: vec![TxOut {
							value: Amount::from_sat(channel_value_satoshis),
							script_pubkey: output_script.clone(),
						}],
					};
					(temporary_channel_id, tx)
				},
				_ => panic!("Unexpected event"),
			}
		}};
	}

	fn confirm_transaction_depth(node: &mut Node, tx: &Transaction, depth: u32) {
		for i in 1..=depth {
			let prev_blockhash = node.best_block.block_hash;
			let height = node.best_block.height + 1;
			let header = create_dummy_header(prev_blockhash, height);
			let txdata = vec![(0, tx)];
			node.best_block = BestBlock::new(header.block_hash(), height);
			match i {
				1 => {
					node.node.transactions_confirmed(&header, &txdata, height);
					node.chain_monitor.transactions_confirmed(&header, &txdata, height);
					node.sweeper.transactions_confirmed(&header, &txdata, height);
				},
				x if x == depth => {
					// We need the TestBroadcaster to know about the new height so that it doesn't think
					// we're violating the time lock requirements of transactions broadcasted at that
					// point.
					let block = (genesis_block(Network::Bitcoin), height);
					node.tx_broadcaster.blocks.lock().unwrap().push(block);
					node.node.best_block_updated(&header, height);
					node.chain_monitor.best_block_updated(&header, height);
					node.sweeper.best_block_updated(&header, height);
				},
				_ => {},
			}
		}
	}

	fn advance_chain(node: &mut Node, num_blocks: u32) {
		for i in 1..=num_blocks {
			let prev_blockhash = node.best_block.block_hash;
			let height = node.best_block.height + 1;
			let header = create_dummy_header(prev_blockhash, height);
			node.best_block = BestBlock::new(header.block_hash(), height);
			if i == num_blocks {
				// We need the TestBroadcaster to know about the new height so that it doesn't think
				// we're violating the time lock requirements of transactions broadcasted at that
				// point.
				let block = (genesis_block(Network::Bitcoin), height);
				node.tx_broadcaster.blocks.lock().unwrap().push(block);
				node.node.best_block_updated(&header, height);
				node.chain_monitor.best_block_updated(&header, height);
				node.sweeper.best_block_updated(&header, height);
			}
		}
	}

	fn confirm_transaction(node: &mut Node, tx: &Transaction) {
		confirm_transaction_depth(node, tx, ANTI_REORG_DELAY);
	}

	#[test]
	fn test_background_processor() {
		// Test that when a new channel is created, the ChannelManager needs to be re-persisted with
		// updates. Also test that when new updates are available, the manager signals that it needs
		// re-persistence and is successfully re-persisted.
		let (persist_dir, nodes) = create_nodes(2, "test_background_processor");

		// Go through the channel creation process so that each node has something to persist. Since
		// open_channel consumes events, it must complete before starting BackgroundProcessor to
		// avoid a race with processing events.
		let tx = open_channel!(nodes[0], nodes[1], 100000);

		// Initiate the background processors to watch each node.
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir));
		let event_handler = |_: _| Ok(());
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].p2p_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		macro_rules! check_persisted_data {
			($node: expr, $filepath: expr) => {
				let mut expected_bytes = Vec::new();
				loop {
					expected_bytes.clear();
					match $node.write(&mut expected_bytes) {
						Ok(()) => match std::fs::read($filepath) {
							Ok(bytes) => {
								if bytes == expected_bytes {
									break;
								} else {
									continue;
								}
							},
							Err(_) => continue,
						},
						Err(e) => panic!("Unexpected error: {}", e),
					}
				}
			};
		}

		// Check that the initial channel manager data is persisted as expected.
		let filepath =
			get_full_filepath(format!("{}_persister_0", &persist_dir), "manager".to_string());
		check_persisted_data!(nodes[0].node, filepath.clone());

		loop {
			if !nodes[0].node.get_event_or_persist_condvar_value() {
				break;
			}
		}

		// Force-close the channel.
		let error_message = "Channel force-closed";
		nodes[0]
			.node
			.force_close_broadcasting_latest_txn(
				&ChannelId::v1_from_funding_outpoint(OutPoint {
					txid: tx.compute_txid(),
					index: 0,
				}),
				&nodes[1].node.get_our_node_id(),
				error_message.to_string(),
			)
			.unwrap();

		// Check that the force-close updates are persisted.
		check_persisted_data!(nodes[0].node, filepath.clone());
		loop {
			if !nodes[0].node.get_event_or_persist_condvar_value() {
				break;
			}
		}

		// Check network graph is persisted
		let filepath =
			get_full_filepath(format!("{}_persister_0", &persist_dir), "network_graph".to_string());
		check_persisted_data!(nodes[0].network_graph, filepath.clone());

		// Check scorer is persisted
		let filepath =
			get_full_filepath(format!("{}_persister_0", &persist_dir), "scorer".to_string());
		check_persisted_data!(nodes[0].scorer, filepath.clone());

		if !std::thread::panicking() {
			bg_processor.stop().unwrap();
		}
	}

	#[test]
	fn test_timer_tick_called() {
		// Test that:
		// - `ChannelManager::timer_tick_occurred` is called every `FRESHNESS_TIMER`,
		// - `ChainMonitor::rebroadcast_pending_claims` is called every `REBROADCAST_TIMER`,
		// - `PeerManager::timer_tick_occurred` is called every `PING_TIMER`, and
		// - `OnionMessageHandler::timer_tick_occurred` is called every `ONION_MESSAGE_HANDLER_TIMER`.
		let (_, nodes) = create_nodes(1, "test_timer_tick_called");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir));
		let event_handler = |_: _| Ok(());
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);
		loop {
			let log_entries = nodes[0].logger.lines.lock().unwrap();
			let desired_log_1 = "Calling ChannelManager's timer_tick_occurred".to_string();
			let desired_log_2 = "Calling PeerManager's timer_tick_occurred".to_string();
			let desired_log_3 = "Rebroadcasting monitor's pending claims".to_string();
			let desired_log_4 = "Calling OnionMessageHandler's timer_tick_occurred".to_string();
			if log_entries.get(&("lightning_background_processor", desired_log_1)).is_some()
				&& log_entries.get(&("lightning_background_processor", desired_log_2)).is_some()
				&& log_entries.get(&("lightning_background_processor", desired_log_3)).is_some()
				&& log_entries.get(&("lightning_background_processor", desired_log_4)).is_some()
			{
				break;
			}
		}

		if !std::thread::panicking() {
			bg_processor.stop().unwrap();
		}
	}

	#[test]
	fn test_channel_manager_persist_error() {
		// Test that if we encounter an error during manager persistence, the thread panics.
		let (_, nodes) = create_nodes(2, "test_persist_error");
		open_channel!(nodes[0], nodes[1], 100000);

		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(
			Persister::new(data_dir).with_manager_error(std::io::ErrorKind::Other, "test"),
		);
		let event_handler = |_: _| Ok(());
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);
		match bg_processor.join() {
			Ok(_) => panic!("Expected error persisting manager"),
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::Other);
				assert_eq!(e.get_ref().unwrap().to_string(), "test");
			},
		}
	}

	#[tokio::test]
	#[cfg(feature = "futures")]
	async fn test_channel_manager_persist_error_async() {
		// Test that if we encounter an error during manager persistence, the thread panics.
		let (_, nodes) = create_nodes(2, "test_persist_error_sync");
		open_channel!(nodes[0], nodes[1], 100000);

		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(
			Persister::new(data_dir).with_manager_error(std::io::ErrorKind::Other, "test"),
		);

		let bp_future = super::process_events_async(
			persister,
			|_: _| async { Ok(()) },
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].rapid_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
			move |dur: Duration| {
				Box::pin(async move {
					tokio::time::sleep(dur).await;
					false // Never exit
				})
			},
			false,
			|| Some(Duration::ZERO),
		);
		match bp_future.await {
			Ok(_) => panic!("Expected error persisting manager"),
			Err(e) => {
				assert_eq!(e.kind(), lightning::io::ErrorKind::Other);
				assert_eq!(e.get_ref().unwrap().to_string(), "test");
			},
		}
	}

	#[test]
	fn test_network_graph_persist_error() {
		// Test that if we encounter an error during network graph persistence, an error gets returned.
		let (_, nodes) = create_nodes(2, "test_persist_network_graph_error");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister =
			Arc::new(Persister::new(data_dir).with_graph_error(std::io::ErrorKind::Other, "test"));
		let event_handler = |_: _| Ok(());
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].p2p_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		match bg_processor.stop() {
			Ok(_) => panic!("Expected error persisting network graph"),
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::Other);
				assert_eq!(e.get_ref().unwrap().to_string(), "test");
			},
		}
	}

	#[test]
	fn test_scorer_persist_error() {
		// Test that if we encounter an error during scorer persistence, an error gets returned.
		let (_, nodes) = create_nodes(2, "test_persist_scorer_error");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister =
			Arc::new(Persister::new(data_dir).with_scorer_error(std::io::ErrorKind::Other, "test"));
		let event_handler = |_: _| Ok(());
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		match bg_processor.stop() {
			Ok(_) => panic!("Expected error persisting scorer"),
			Err(e) => {
				assert_eq!(e.kind(), std::io::ErrorKind::Other);
				assert_eq!(e.get_ref().unwrap().to_string(), "test");
			},
		}
	}

	#[test]
	fn test_background_event_handling() {
		let (_, mut nodes) = create_nodes(2, "test_background_event_handling");
		let node_0_id = nodes[0].node.get_our_node_id();
		let node_1_id = nodes[1].node.get_our_node_id();

		let channel_value = 100000;
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir.clone()));

		// Set up a background event handler for FundingGenerationReady events.
		let (funding_generation_send, funding_generation_recv) = std::sync::mpsc::sync_channel(1);
		let (channel_pending_send, channel_pending_recv) = std::sync::mpsc::sync_channel(1);
		let event_handler = move |event: Event| {
			match event {
				Event::FundingGenerationReady { .. } => funding_generation_send
					.send(handle_funding_generation_ready!(event, channel_value))
					.unwrap(),
				Event::ChannelPending { .. } => channel_pending_send.send(()).unwrap(),
				Event::ChannelReady { .. } => {},
				_ => panic!("Unexpected event: {:?}", event),
			}
			Ok(())
		};

		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		// Open a channel and check that the FundingGenerationReady event was handled.
		begin_open_channel!(nodes[0], nodes[1], channel_value);
		let (temporary_channel_id, funding_tx) = funding_generation_recv
			.recv_timeout(Duration::from_secs(EVENT_DEADLINE))
			.expect("FundingGenerationReady not handled within deadline");
		nodes[0]
			.node
			.funding_transaction_generated(temporary_channel_id, node_1_id, funding_tx.clone())
			.unwrap();
		let msg_0 = get_event_msg!(nodes[0], MessageSendEvent::SendFundingCreated, node_1_id);
		nodes[1].node.handle_funding_created(node_0_id, &msg_0);
		get_event!(nodes[1], Event::ChannelPending);
		let msg_1 = get_event_msg!(nodes[1], MessageSendEvent::SendFundingSigned, node_0_id);
		nodes[0].node.handle_funding_signed(node_1_id, &msg_1);
		let _ = channel_pending_recv
			.recv_timeout(Duration::from_secs(EVENT_DEADLINE))
			.expect("ChannelPending not handled within deadline");

		// Confirm the funding transaction.
		confirm_transaction(&mut nodes[0], &funding_tx);
		let as_funding = get_event_msg!(nodes[0], MessageSendEvent::SendChannelReady, node_1_id);
		confirm_transaction(&mut nodes[1], &funding_tx);
		let bs_funding = get_event_msg!(nodes[1], MessageSendEvent::SendChannelReady, node_0_id);
		nodes[0].node.handle_channel_ready(node_1_id, &bs_funding);
		let _as_channel_update =
			get_event_msg!(nodes[0], MessageSendEvent::SendChannelUpdate, node_1_id);
		nodes[1].node.handle_channel_ready(node_0_id, &as_funding);
		let _bs_channel_update =
			get_event_msg!(nodes[1], MessageSendEvent::SendChannelUpdate, node_0_id);
		let broadcast_funding =
			nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().pop().unwrap();
		assert_eq!(broadcast_funding.compute_txid(), funding_tx.compute_txid());
		assert!(nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().is_empty());

		if !std::thread::panicking() {
			bg_processor.stop().unwrap();
		}

		// Set up a background event handler for SpendableOutputs events.
		let (sender, receiver) = std::sync::mpsc::sync_channel(1);
		let event_handler = move |event: Event| {
			match event {
				Event::SpendableOutputs { .. } => sender.send(event).unwrap(),
				Event::ChannelReady { .. } => {},
				Event::ChannelClosed { .. } => {},
				_ => panic!("Unexpected event: {:?}", event),
			}
			Ok(())
		};
		let persister = Arc::new(Persister::new(data_dir));
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		// Force close the channel and check that the SpendableOutputs event was handled.
		let error_message = "Channel force-closed";
		nodes[0]
			.node
			.force_close_broadcasting_latest_txn(
				&nodes[0].node.list_channels()[0].channel_id,
				&node_1_id,
				error_message.to_string(),
			)
			.unwrap();
		let commitment_tx = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().pop().unwrap();
		confirm_transaction_depth(&mut nodes[0], &commitment_tx, BREAKDOWN_TIMEOUT as u32);

		let event = receiver
			.recv_timeout(Duration::from_secs(EVENT_DEADLINE))
			.expect("Events not handled within deadline");
		match event {
			Event::SpendableOutputs { outputs, channel_id } => {
				nodes[0]
					.sweeper
					.track_spendable_outputs(outputs, channel_id, false, Some(153))
					.unwrap();
			},
			_ => panic!("Unexpected event: {:?}", event),
		}

		// Check we don't generate an initial sweeping tx until we reach the required height.
		assert_eq!(nodes[0].sweeper.tracked_spendable_outputs().len(), 1);
		let tracked_output = nodes[0].sweeper.tracked_spendable_outputs().first().unwrap().clone();
		if let Some(sweep_tx_0) = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().pop() {
			assert!(!tracked_output.is_spent_in(&sweep_tx_0));
			match tracked_output.status {
				OutputSpendStatus::PendingInitialBroadcast { delayed_until_height } => {
					assert_eq!(delayed_until_height, Some(153));
				},
				_ => panic!("Unexpected status"),
			}
		}

		advance_chain(&mut nodes[0], 3);

		// Check we generate an initial sweeping tx.
		assert_eq!(nodes[0].sweeper.tracked_spendable_outputs().len(), 1);
		let tracked_output = nodes[0].sweeper.tracked_spendable_outputs().first().unwrap().clone();
		let sweep_tx_0 = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().pop().unwrap();
		match tracked_output.status {
			OutputSpendStatus::PendingFirstConfirmation { latest_spending_tx, .. } => {
				assert_eq!(sweep_tx_0.compute_txid(), latest_spending_tx.compute_txid());
			},
			_ => panic!("Unexpected status"),
		}

		// Check we regenerate and rebroadcast the sweeping tx each block.
		advance_chain(&mut nodes[0], 1);
		assert_eq!(nodes[0].sweeper.tracked_spendable_outputs().len(), 1);
		let tracked_output = nodes[0].sweeper.tracked_spendable_outputs().first().unwrap().clone();
		let sweep_tx_1 = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().pop().unwrap();
		match tracked_output.status {
			OutputSpendStatus::PendingFirstConfirmation { latest_spending_tx, .. } => {
				assert_eq!(sweep_tx_1.compute_txid(), latest_spending_tx.compute_txid());
			},
			_ => panic!("Unexpected status"),
		}
		assert_ne!(sweep_tx_0, sweep_tx_1);

		advance_chain(&mut nodes[0], 1);
		assert_eq!(nodes[0].sweeper.tracked_spendable_outputs().len(), 1);
		let tracked_output = nodes[0].sweeper.tracked_spendable_outputs().first().unwrap().clone();
		let sweep_tx_2 = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().pop().unwrap();
		match tracked_output.status {
			OutputSpendStatus::PendingFirstConfirmation { latest_spending_tx, .. } => {
				assert_eq!(sweep_tx_2.compute_txid(), latest_spending_tx.compute_txid());
			},
			_ => panic!("Unexpected status"),
		}
		assert_ne!(sweep_tx_0, sweep_tx_2);
		assert_ne!(sweep_tx_1, sweep_tx_2);

		// Check we still track the spendable outputs up to ANTI_REORG_DELAY confirmations.
		confirm_transaction_depth(&mut nodes[0], &sweep_tx_2, 5);
		assert_eq!(nodes[0].sweeper.tracked_spendable_outputs().len(), 1);
		let tracked_output = nodes[0].sweeper.tracked_spendable_outputs().first().unwrap().clone();
		match tracked_output.status {
			OutputSpendStatus::PendingThresholdConfirmations { latest_spending_tx, .. } => {
				assert_eq!(sweep_tx_2.compute_txid(), latest_spending_tx.compute_txid());
			},
			_ => panic!("Unexpected status"),
		}

		// Check we still see the transaction as confirmed if we unconfirm any untracked
		// transaction. (We previously had a bug that would mark tracked transactions as
		// unconfirmed if any transaction at an unknown block height would be unconfirmed.)
		let unconf_txid = Txid::from_slice(&[0; 32]).unwrap();
		nodes[0].sweeper.transaction_unconfirmed(&unconf_txid);

		assert_eq!(nodes[0].sweeper.tracked_spendable_outputs().len(), 1);
		let tracked_output = nodes[0].sweeper.tracked_spendable_outputs().first().unwrap().clone();
		match tracked_output.status {
			OutputSpendStatus::PendingThresholdConfirmations { latest_spending_tx, .. } => {
				assert_eq!(sweep_tx_2.compute_txid(), latest_spending_tx.compute_txid());
			},
			_ => panic!("Unexpected status"),
		}

		// Check we stop tracking the spendable outputs when one of the txs reaches
		// ANTI_REORG_DELAY confirmations.
		confirm_transaction_depth(&mut nodes[0], &sweep_tx_0, ANTI_REORG_DELAY);
		assert_eq!(nodes[0].sweeper.tracked_spendable_outputs().len(), 0);

		if !std::thread::panicking() {
			bg_processor.stop().unwrap();
		}
	}

	#[test]
	fn test_event_handling_failures_are_replayed() {
		let (_, nodes) = create_nodes(2, "test_event_handling_failures_are_replayed");
		let channel_value = 100000;
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir.clone()));

		let (first_event_send, first_event_recv) = std::sync::mpsc::sync_channel(1);
		let (second_event_send, second_event_recv) = std::sync::mpsc::sync_channel(1);
		let should_fail_event_handling = Arc::new(AtomicBool::new(true));
		let event_handler = move |event: Event| {
			if let Ok(true) = should_fail_event_handling.compare_exchange(
				true,
				false,
				Ordering::Acquire,
				Ordering::Relaxed,
			) {
				first_event_send.send(event).unwrap();
				return Err(ReplayEvent());
			}

			second_event_send.send(event).unwrap();
			Ok(())
		};

		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		begin_open_channel!(nodes[0], nodes[1], channel_value);
		assert_eq!(
			first_event_recv.recv_timeout(Duration::from_secs(EVENT_DEADLINE)).unwrap(),
			second_event_recv.recv_timeout(Duration::from_secs(EVENT_DEADLINE)).unwrap()
		);

		if !std::thread::panicking() {
			bg_processor.stop().unwrap();
		}
	}

	#[test]
	fn test_scorer_persistence() {
		let (_, nodes) = create_nodes(2, "test_scorer_persistence");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir));
		let event_handler = |_: _| Ok(());
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		loop {
			let log_entries = nodes[0].logger.lines.lock().unwrap();
			let expected_log = "Calling time_passed and persisting scorer".to_string();
			if log_entries.get(&("lightning_background_processor", expected_log)).is_some() {
				break;
			}
		}

		if !std::thread::panicking() {
			bg_processor.stop().unwrap();
		}
	}

	macro_rules! do_test_not_pruning_network_graph_until_graph_sync_completion {
		($nodes: expr, $receive: expr, $sleep: expr) => {
			let features = ChannelFeatures::empty();
			$nodes[0]
				.network_graph
				.add_channel_from_partial_announcement(
					42,
					53,
					features,
					$nodes[0].node.get_our_node_id(),
					$nodes[1].node.get_our_node_id(),
				)
				.expect("Failed to update channel from partial announcement");
			let original_graph_description = $nodes[0].network_graph.to_string();
			assert!(original_graph_description.contains("42: features: 0000, node_one:"));
			assert_eq!($nodes[0].network_graph.read_only().channels().len(), 1);

			loop {
				$sleep;
				let log_entries = $nodes[0].logger.lines.lock().unwrap();
				let loop_counter = "Calling ChannelManager's timer_tick_occurred".to_string();
				if *log_entries.get(&("lightning_background_processor", loop_counter)).unwrap_or(&0)
					> 1
				{
					// Wait until the loop has gone around at least twice.
					break;
				}
			}

			let initialization_input = vec![
				76, 68, 75, 1, 111, 226, 140, 10, 182, 241, 179, 114, 193, 166, 162, 70, 174, 99,
				247, 79, 147, 30, 131, 101, 225, 90, 8, 156, 104, 214, 25, 0, 0, 0, 0, 0, 97, 227,
				98, 218, 0, 0, 0, 4, 2, 22, 7, 207, 206, 25, 164, 197, 231, 230, 231, 56, 102, 61,
				250, 251, 187, 172, 38, 46, 79, 247, 108, 44, 155, 48, 219, 238, 252, 53, 192, 6,
				67, 2, 36, 125, 157, 176, 223, 175, 234, 116, 94, 248, 201, 225, 97, 235, 50, 47,
				115, 172, 63, 136, 88, 216, 115, 11, 111, 217, 114, 84, 116, 124, 231, 107, 2, 158,
				1, 242, 121, 152, 106, 204, 131, 186, 35, 93, 70, 216, 10, 237, 224, 183, 89, 95,
				65, 3, 83, 185, 58, 138, 181, 64, 187, 103, 127, 68, 50, 2, 201, 19, 17, 138, 136,
				149, 185, 226, 156, 137, 175, 110, 32, 237, 0, 217, 90, 31, 100, 228, 149, 46, 219,
				175, 168, 77, 4, 143, 38, 128, 76, 97, 0, 0, 0, 2, 0, 0, 255, 8, 153, 192, 0, 2,
				27, 0, 0, 0, 1, 0, 0, 255, 2, 68, 226, 0, 6, 11, 0, 1, 2, 3, 0, 0, 0, 2, 0, 40, 0,
				0, 0, 0, 0, 0, 3, 232, 0, 0, 3, 232, 0, 0, 0, 1, 0, 0, 0, 0, 58, 85, 116, 216, 255,
				8, 153, 192, 0, 2, 27, 0, 0, 25, 0, 0, 0, 1, 0, 0, 0, 125, 255, 2, 68, 226, 0, 6,
				11, 0, 1, 5, 0, 0, 0, 0, 29, 129, 25, 192,
			];
			$nodes[0]
				.rapid_gossip_sync
				.update_network_graph_no_std(&initialization_input[..], Some(1642291930))
				.unwrap();

			// this should have added two channels and pruned the previous one.
			assert_eq!($nodes[0].network_graph.read_only().channels().len(), 2);

			$receive.expect("Network graph not pruned within deadline");

			// all channels should now be pruned
			assert_eq!($nodes[0].network_graph.read_only().channels().len(), 0);
		};
	}

	#[test]
	fn test_not_pruning_network_graph_until_graph_sync_completion() {
		let (sender, receiver) = std::sync::mpsc::sync_channel(1);

		let (_, nodes) =
			create_nodes(2, "test_not_pruning_network_graph_until_graph_sync_completion");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir).with_graph_persistence_notifier(sender));

		let event_handler = |_: _| Ok(());
		let background_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].rapid_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		do_test_not_pruning_network_graph_until_graph_sync_completion!(
			nodes,
			receiver.recv_timeout(Duration::from_secs(super::FIRST_NETWORK_PRUNE_TIMER * 5)),
			std::thread::sleep(Duration::from_millis(1))
		);

		background_processor.stop().unwrap();
	}

	#[tokio::test]
	#[cfg(feature = "futures")]
	async fn test_not_pruning_network_graph_until_graph_sync_completion_async() {
		let (sender, receiver) = std::sync::mpsc::sync_channel(1);

		let (_, nodes) =
			create_nodes(2, "test_not_pruning_network_graph_until_graph_sync_completion_async");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir).with_graph_persistence_notifier(sender));

		let (exit_sender, exit_receiver) = tokio::sync::watch::channel(());
		let bp_future = super::process_events_async(
			persister,
			|_: _| async { Ok(()) },
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].rapid_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
			move |dur: Duration| {
				let mut exit_receiver = exit_receiver.clone();
				Box::pin(async move {
					tokio::select! {
						_ = tokio::time::sleep(dur) => false,
						_ = exit_receiver.changed() => true,
					}
				})
			},
			false,
			|| Some(Duration::from_secs(1696300000)),
		);

		let t1 = tokio::spawn(bp_future);
		let t2 = tokio::spawn(async move {
			do_test_not_pruning_network_graph_until_graph_sync_completion!(
				nodes,
				{
					let mut i = 0;
					loop {
						tokio::time::sleep(Duration::from_secs(super::FIRST_NETWORK_PRUNE_TIMER))
							.await;
						if let Ok(()) = receiver.try_recv() {
							break Ok::<(), ()>(());
						}
						assert!(i < 5);
						i += 1;
					}
				},
				tokio::time::sleep(Duration::from_millis(1)).await
			);
			exit_sender.send(()).unwrap();
		});
		let (r1, r2) = tokio::join!(t1, t2);
		r1.unwrap().unwrap();
		r2.unwrap()
	}

	macro_rules! do_test_payment_path_scoring {
		($nodes: expr, $receive: expr) => {
			// Ensure that we update the scorer when relevant events are processed. In this case, we ensure
			// that we update the scorer upon a payment path succeeding (note that the channel must be
			// public or else we won't score it).
			// A background event handler for FundingGenerationReady events must be hooked up to a
			// running background processor.
			let scored_scid = 4242;
			let secp_ctx = Secp256k1::new();
			let node_1_privkey = SecretKey::from_slice(&[42; 32]).unwrap();
			let node_1_id = PublicKey::from_secret_key(&secp_ctx, &node_1_privkey);

			let path = Path { hops: vec![RouteHop {
				pubkey: node_1_id,
				node_features: NodeFeatures::empty(),
				short_channel_id: scored_scid,
				channel_features: ChannelFeatures::empty(),
				fee_msat: 0,
				cltv_expiry_delta: MIN_CLTV_EXPIRY_DELTA as u32,
				maybe_announced_channel: true,
			}], blinded_tail: None };

			$nodes[0].scorer.write_lock().expect(TestResult::PaymentFailure { path: path.clone(), short_channel_id: scored_scid });
			$nodes[0].node.push_pending_event(Event::PaymentPathFailed {
				payment_id: None,
				payment_hash: PaymentHash([42; 32]),
				payment_failed_permanently: false,
				failure: PathFailure::OnPath { network_update: None },
				path: path.clone(),
				short_channel_id: Some(scored_scid),
			});
			let event = $receive.expect("PaymentPathFailed not handled within deadline");
			match event {
				Event::PaymentPathFailed { .. } => {},
				_ => panic!("Unexpected event"),
			}

			// Ensure we'll score payments that were explicitly failed back by the destination as
			// ProbeSuccess.
			$nodes[0].scorer.write_lock().expect(TestResult::ProbeSuccess { path: path.clone() });
			$nodes[0].node.push_pending_event(Event::PaymentPathFailed {
				payment_id: None,
				payment_hash: PaymentHash([42; 32]),
				payment_failed_permanently: true,
				failure: PathFailure::OnPath { network_update: None },
				path: path.clone(),
				short_channel_id: None,
			});
			let event = $receive.expect("PaymentPathFailed not handled within deadline");
			match event {
				Event::PaymentPathFailed { .. } => {},
				_ => panic!("Unexpected event"),
			}

			$nodes[0].scorer.write_lock().expect(TestResult::PaymentSuccess { path: path.clone() });
			$nodes[0].node.push_pending_event(Event::PaymentPathSuccessful {
				payment_id: PaymentId([42; 32]),
				payment_hash: None,
				path: path.clone(),
			});
			let event = $receive.expect("PaymentPathSuccessful not handled within deadline");
			match event {
				Event::PaymentPathSuccessful { .. } => {},
				_ => panic!("Unexpected event"),
			}

			$nodes[0].scorer.write_lock().expect(TestResult::ProbeSuccess { path: path.clone() });
			$nodes[0].node.push_pending_event(Event::ProbeSuccessful {
				payment_id: PaymentId([42; 32]),
				payment_hash: PaymentHash([42; 32]),
				path: path.clone(),
			});
			let event = $receive.expect("ProbeSuccessful not handled within deadline");
			match event {
				Event::ProbeSuccessful  { .. } => {},
				_ => panic!("Unexpected event"),
			}

			$nodes[0].scorer.write_lock().expect(TestResult::ProbeFailure { path: path.clone() });
			$nodes[0].node.push_pending_event(Event::ProbeFailed {
				payment_id: PaymentId([42; 32]),
				payment_hash: PaymentHash([42; 32]),
				path,
				short_channel_id: Some(scored_scid),
			});
			let event = $receive.expect("ProbeFailure not handled within deadline");
			match event {
				Event::ProbeFailed { .. } => {},
				_ => panic!("Unexpected event"),
			}
		}
	}

	#[test]
	fn test_payment_path_scoring() {
		let (sender, receiver) = std::sync::mpsc::sync_channel(1);
		let event_handler = move |event: Event| {
			match event {
				Event::PaymentPathFailed { .. } => sender.send(event).unwrap(),
				Event::PaymentPathSuccessful { .. } => sender.send(event).unwrap(),
				Event::ProbeSuccessful { .. } => sender.send(event).unwrap(),
				Event::ProbeFailed { .. } => sender.send(event).unwrap(),
				_ => panic!("Unexpected event: {:?}", event),
			}
			Ok(())
		};

		let (_, nodes) = create_nodes(1, "test_payment_path_scoring");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir));
		let bg_processor = BackgroundProcessor::start(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
		);

		do_test_payment_path_scoring!(
			nodes,
			receiver.recv_timeout(Duration::from_secs(EVENT_DEADLINE))
		);

		if !std::thread::panicking() {
			bg_processor.stop().unwrap();
		}

		let log_entries = nodes[0].logger.lines.lock().unwrap();
		let expected_log = "Persisting scorer after update".to_string();
		assert_eq!(*log_entries.get(&("lightning_background_processor", expected_log)).unwrap(), 5);
	}

	#[tokio::test]
	#[cfg(feature = "futures")]
	async fn test_payment_path_scoring_async() {
		let (sender, mut receiver) = tokio::sync::mpsc::channel(1);
		let event_handler = move |event: Event| {
			let sender_ref = sender.clone();
			async move {
				match event {
					Event::PaymentPathFailed { .. } => sender_ref.send(event).await.unwrap(),
					Event::PaymentPathSuccessful { .. } => sender_ref.send(event).await.unwrap(),
					Event::ProbeSuccessful { .. } => sender_ref.send(event).await.unwrap(),
					Event::ProbeFailed { .. } => sender_ref.send(event).await.unwrap(),
					_ => panic!("Unexpected event: {:?}", event),
				}
				Ok(())
			}
		};

		let (_, nodes) = create_nodes(1, "test_payment_path_scoring_async");
		let data_dir = nodes[0].kv_store.get_data_dir();
		let persister = Arc::new(Persister::new(data_dir));

		let (exit_sender, exit_receiver) = tokio::sync::watch::channel(());

		let bp_future = super::process_events_async(
			persister,
			event_handler,
			nodes[0].chain_monitor.clone(),
			nodes[0].node.clone(),
			Some(nodes[0].messenger.clone()),
			nodes[0].no_gossip_sync(),
			nodes[0].peer_manager.clone(),
			nodes[0].logger.clone(),
			Some(nodes[0].scorer.clone()),
			move |dur: Duration| {
				let mut exit_receiver = exit_receiver.clone();
				Box::pin(async move {
					tokio::select! {
						_ = tokio::time::sleep(dur) => false,
						_ = exit_receiver.changed() => true,
					}
				})
			},
			false,
			|| Some(Duration::ZERO),
		);
		let t1 = tokio::spawn(bp_future);
		let t2 = tokio::spawn(async move {
			do_test_payment_path_scoring!(nodes, receiver.recv().await);
			exit_sender.send(()).unwrap();

			let log_entries = nodes[0].logger.lines.lock().unwrap();
			let expected_log = "Persisting scorer after update".to_string();
			assert_eq!(
				*log_entries.get(&("lightning_background_processor", expected_log)).unwrap(),
				5
			);
		});

		let (r1, r2) = tokio::join!(t1, t2);
		r1.unwrap().unwrap();
		r2.unwrap()
	}
}