Automatically prune NetworkGraph of stale channels hourly in BP

Author: TheBlueMatt

lightning-background-processor/src/lib.rs

@@ -34,6 +34,8 @@ use std::ops::Deref;
 ///   [`ChannelManager`] persistence should be done in the background.
 /// * Calling [`ChannelManager::timer_tick_occurred`] and [`PeerManager::timer_tick_occurred`]
 ///   at the appropriate intervals.
+/// * Calling [`NetworkGraph::remove_stale_channels`] (if a [`NetGraphMsgHandler`] 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.
@@ -68,6 +70,9 @@ const PING_TIMER: u64 = 30;
 #[cfg(test)]
 const PING_TIMER: u64 = 1;
 
+/// Prune the network graph of stale entries hourly.
+const NETWORK_PRUNE_TIMER: u64 = 60 * 60;
+
 /// Trait which handles persisting a [`ChannelManager`] to disk.
 ///
 /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
@@ -203,13 +208,16 @@ impl BackgroundProcessor {
 		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 = DecoratingEventHandler { event_handler, net_graph_msg_handler };
+			let event_handler = DecoratingEventHandler { event_handler, net_graph_msg_handler: net_graph_msg_handler.as_ref().map(|t| t.deref()) };
 
 			log_trace!(logger, "Calling ChannelManager's timer_tick_occurred on startup");
 			channel_manager.timer_tick_occurred();
 
 			let mut last_freshness_call = Instant::now();
 			let mut last_ping_call = Instant::now();
+			let mut last_prune_call = Instant::now();
+			let mut have_pruned = false;
+
 			loop {
 				peer_manager.process_events();
 				channel_manager.process_pending_events(&event_handler);
@@ -247,6 +255,19 @@ impl BackgroundProcessor {
 					peer_manager.timer_tick_occurred();
 					last_ping_call = Instant::now();
 				}
+
+				// 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.
+				if last_prune_call.elapsed().as_secs() > if have_pruned { NETWORK_PRUNE_TIMER } else { 60 } {
+					if let Some(ref handler) = net_graph_msg_handler {
+						log_trace!(logger, "Pruning network graph of stale entries");
+						handler.network_graph().remove_stale_channels();
+						last_prune_call = Instant::now();
+						have_pruned = true;
+					}
+				}
 			}
 		});
 		Self { stop_thread: stop_thread_clone, thread_handle: Some(handle) }

lightning/src/routing/network_graph.rs

@@ -249,6 +249,12 @@ where C::Target: chain::Access, L::Target: Logger
 		self.chain_access = chain_access;
 	}
 
+	/// Gets a reference to the underlying [`NetworkGraph`] which was provided in
+	/// [`NetGraphMsgHandler::new`].
+	pub fn network_graph(&self) -> &G {
+		&self.network_graph
+	}
+
 	/// Returns true when a full routing table sync should be performed with a peer.
 	fn should_request_full_sync(&self, _node_id: &PublicKey) -> bool {
 		//TODO: Determine whether to request a full sync based on the network map.
@@ -1074,6 +1080,8 @@ impl NetworkGraph {
 	/// updates every two weeks, the non-normative section of BOLT 7 currently suggests that
 	/// pruning occur for updates which are at least two weeks old, which we implement here.
 	///
+	/// Note that for users of the `lightning-background-processor` crate this method may be
+	/// automatically called regularly for you.
 	///
 	/// This method is only available with the `std` feature. See
 	/// [`NetworkGraph::remove_stale_channels_with_time`] for `no-std` use.