From e31773bd74197082c327fdeb878f28664ee65e21 Mon Sep 17 00:00:00 2001
From: Jeffrey Czyz <jkczyz@gmail.com>
Date: Tue, 2 Nov 2021 16:06:05 -0500
Subject: [PATCH] Persist channel scores

---
 src/disk.rs | 23 +++++++++++++++++++++++
 src/main.rs | 25 +++++++++++++++++++++----
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/src/disk.rs b/src/disk.rs
index b641ebb..7be070c 100644
--- a/src/disk.rs
+++ b/src/disk.rs
@@ -3,6 +3,7 @@ use bitcoin::secp256k1::key::PublicKey;
 use bitcoin::BlockHash;
 use chrono::Utc;
 use lightning::routing::network_graph::NetworkGraph;
+use lightning::routing::scorer::Scorer;
 use lightning::util::logger::{Logger, Record};
 use lightning::util::ser::{Readable, Writeable, Writer};
 use std::collections::HashMap;
@@ -92,3 +93,25 @@ pub(crate) fn read_network(path: &Path, genesis_hash: BlockHash) -> NetworkGraph
 	}
 	NetworkGraph::new(genesis_hash)
 }
+
+pub(crate) fn persist_scorer(path: &Path, scorer: &Scorer) -> std::io::Result<()> {
+	let mut tmp_path = path.to_path_buf().into_os_string();
+	tmp_path.push(".tmp");
+	let file = fs::OpenOptions::new().write(true).create(true).open(&tmp_path)?;
+	let write_res = scorer.write(&mut BufWriter::new(file));
+	if let Err(e) = write_res.and_then(|_| fs::rename(&tmp_path, path)) {
+		let _ = fs::remove_file(&tmp_path);
+		Err(e)
+	} else {
+		Ok(())
+	}
+}
+
+pub(crate) fn read_scorer(path: &Path) -> Scorer {
+	if let Ok(file) = File::open(path) {
+		if let Ok(scorer) = Scorer::read(&mut BufReader::new(file)) {
+			return scorer;
+		}
+	}
+	Scorer::default()
+}
diff --git a/src/main.rs b/src/main.rs
index b85fb4b..421069b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -596,9 +596,26 @@ async fn start_ldk() {
 		));
 	};
 
-	// Step 16: Create InvoicePayer
+	// Step 16: Initialize routing Scorer
+	let scorer_path = format!("{}/scorer", ldk_data_dir.clone());
+	let scorer = Arc::new(Mutex::new(disk::read_scorer(Path::new(&scorer_path))));
+	let scorer_persist = Arc::clone(&scorer);
+	tokio::spawn(async move {
+		let mut interval = tokio::time::interval(Duration::from_secs(600));
+		loop {
+			interval.tick().await;
+			if disk::persist_scorer(Path::new(&scorer_path), &scorer_persist.lock().unwrap())
+				.is_err()
+			{
+				// Persistence errors here are non-fatal as channels will be re-scored as payments
+				// fail, but they may indicate a disk error which could be fatal elsewhere.
+				eprintln!("Warning: Failed to persist scorer, check your disk and permissions");
+			}
+		}
+	});
+
+	// Step 17: Create InvoicePayer
 	let router = DefaultRouter::new(network_graph.clone(), logger.clone());
-	let scorer = Arc::new(Mutex::new(Scorer::default()));
 	let invoice_payer = Arc::new(InvoicePayer::new(
 		channel_manager.clone(),
 		router,
@@ -608,12 +625,12 @@ async fn start_ldk() {
 		payment::RetryAttempts(5),
 	));
 
-	// Step 17: Persist ChannelManager
+	// Step 18: Persist ChannelManager
 	let data_dir = ldk_data_dir.clone();
 	let persist_channel_manager_callback =
 		move |node: &ChannelManager| FilesystemPersister::persist_manager(data_dir.clone(), &*node);
 
-	// Step 18: Background Processing
+	// Step 19: Background Processing
 	let background_processor = BackgroundProcessor::start(
 		persist_channel_manager_callback,
 		invoice_payer.clone(),
-- 
2.30.2