Implement transient network graph option

bindings/ldk_node.udl

@@ -14,6 +14,7 @@ dictionary Config {
 	LogLevel log_level;
 	AnchorChannelsConfig? anchor_channels_config;
 	SendingParameters? sending_parameters;
+	boolean transient_network_graph;
 };
 
 dictionary AnchorChannelsConfig {

src/builder.rs

@@ -12,7 +12,7 @@ use crate::connection::ConnectionManager;
 use crate::event::EventQueue;
 use crate::fee_estimator::OnchainFeeEstimator;
 use crate::gossip::GossipSource;
-use crate::io::sqlite_store::SqliteStore;
+use crate::io::sqlite_store::{SqliteStore, SqliteStoreConfig};
 use crate::io::utils::{read_node_metrics, write_node_metrics};
 use crate::io::vss_store::VssStore;
 use crate::io::{
@@ -383,11 +383,14 @@ impl NodeBuilder {
 		let storage_dir_path = self.config.storage_dir_path.clone();
 		fs::create_dir_all(storage_dir_path.clone())
 			.map_err(|_| BuildError::StoragePathAccessFailed)?;
+		let sql_store_config =
+			SqliteStoreConfig { transient_graph: self.config.transient_network_graph };
 		let kv_store = Arc::new(
-			SqliteStore::new(
+			SqliteStore::with_config(
 				storage_dir_path.into(),
 				Some(io::sqlite_store::SQLITE_DB_FILE_NAME.to_string()),
 				Some(io::sqlite_store::KV_TABLE_NAME.to_string()),
+				sql_store_config,
 			)
 			.map_err(|_| BuildError::KVStoreSetupFailed)?,
 		);
@@ -554,11 +557,14 @@ impl NodeBuilder {
 
 		// Alby: use a secondary KV store for non-essential data (not needed by VSS)
 		let storage_dir_path = config.storage_dir_path.clone();
+		let sql_store_config =
+			SqliteStoreConfig { transient_graph: self.config.transient_network_graph };
 		let secondary_kv_store = Arc::new(
-			SqliteStore::new(
+			SqliteStore::with_config(
 				storage_dir_path.into(),
 				Some(io::sqlite_store::SQLITE_DB_FILE_NAME.to_string()),
 				Some(io::sqlite_store::KV_TABLE_NAME.to_string()),
+				sql_store_config,
 			)
 			.map_err(|_| BuildError::KVStoreSetupFailed)?,
 		) as Arc<DynStore>;

src/config.rs

@@ -166,6 +166,11 @@ pub struct Config {
 	/// **Note:** If unset, default parameters will be used, and you will be able to override the
 	/// parameters on a per-payment basis in the corresponding method calls.
 	pub sending_parameters: Option<SendingParameters>,
+	/// Alby: Transient network graph.
+	///
+	/// If set to `true`, the graph is not persisted in the database and is only kept in memory.
+	/// It will be rebuilt on each restart.
+	pub transient_network_graph: bool,
 }
 
 impl Default for Config {
@@ -181,6 +186,7 @@ impl Default for Config {
 			anchor_channels_config: Some(AnchorChannelsConfig::default()),
 			sending_parameters: None,
 			node_alias: None,
+			transient_network_graph: false,
 		}
 	}
 }

src/io/sqlite_store/mod.rs

@@ -9,7 +9,10 @@
 use crate::io::utils::check_namespace_key_validity;
 
 use lightning::io;
-use lightning::util::persist::KVStore;
+use lightning::util::persist::{
+	KVStore, NETWORK_GRAPH_PERSISTENCE_KEY, NETWORK_GRAPH_PERSISTENCE_PRIMARY_NAMESPACE,
+	NETWORK_GRAPH_PERSISTENCE_SECONDARY_NAMESPACE,
+};
 use lightning::util::string::PrintableString;
 
 use rusqlite::{named_params, Connection};
@@ -41,6 +44,19 @@ pub struct SqliteStore {
 	connection: Arc<Mutex<Connection>>,
 	data_dir: PathBuf,
 	kv_table_name: String,
+	config: SqliteStoreConfig,
+}
+
+/// Alby: extended SqliteStore configuration.
+pub struct SqliteStoreConfig {
+	/// Do not persist network graph.
+	pub(crate) transient_graph: bool,
+}
+
+impl Default for SqliteStoreConfig {
+	fn default() -> Self {
+		Self { transient_graph: false }
+	}
 }
 
 impl SqliteStore {
@@ -120,7 +136,28 @@ impl SqliteStore {
 		})?;
 
 		let connection = Arc::new(Mutex::new(connection));
-		Ok(Self { connection, data_dir, kv_table_name })
+		Ok(Self { connection, data_dir, kv_table_name, config: SqliteStoreConfig::default() })
+	}
+
+	/// Alby: constructs a new [`SqliteStore`] with an extended configuration.
+	pub fn with_config(
+		data_dir: PathBuf, db_file_name: Option<String>, kv_table_name: Option<String>,
+		config: SqliteStoreConfig,
+	) -> io::Result<Self> {
+		let mut ret = SqliteStore::new(data_dir, db_file_name, kv_table_name)?;
+
+		if config.transient_graph {
+			// Drop existing network graph if it has been persisted before.
+			ret.remove(
+				NETWORK_GRAPH_PERSISTENCE_PRIMARY_NAMESPACE,
+				NETWORK_GRAPH_PERSISTENCE_SECONDARY_NAMESPACE,
+				NETWORK_GRAPH_PERSISTENCE_KEY,
+				false,
+			)?;
+		}
+
+		ret.config = config;
+		Ok(ret)
 	}
 
 	/// Returns the data directory.
@@ -135,6 +172,15 @@ impl KVStore for SqliteStore {
 	) -> io::Result<Vec<u8>> {
 		check_namespace_key_validity(primary_namespace, secondary_namespace, Some(key), "read")?;
 
+		if self.config.transient_graph
+			&& primary_namespace == NETWORK_GRAPH_PERSISTENCE_PRIMARY_NAMESPACE
+			&& secondary_namespace == NETWORK_GRAPH_PERSISTENCE_SECONDARY_NAMESPACE
+			&& key == NETWORK_GRAPH_PERSISTENCE_KEY
+		{
+			// Alby: returning "not found" here will cause the network graph to be rebuilt from scratch.
+			return Err(io::Error::new(io::ErrorKind::NotFound, "network graph is not persisted"));
+		}
+
 		let locked_conn = self.connection.lock().unwrap();
 		let sql =
 			format!("SELECT value FROM {} WHERE primary_namespace=:primary_namespace AND secondary_namespace=:secondary_namespace AND key=:key;",
@@ -183,6 +229,15 @@ impl KVStore for SqliteStore {
 	) -> io::Result<()> {
 		check_namespace_key_validity(primary_namespace, secondary_namespace, Some(key), "write")?;
 
+		if self.config.transient_graph
+			&& primary_namespace == NETWORK_GRAPH_PERSISTENCE_PRIMARY_NAMESPACE
+			&& secondary_namespace == NETWORK_GRAPH_PERSISTENCE_SECONDARY_NAMESPACE
+			&& key == NETWORK_GRAPH_PERSISTENCE_KEY
+		{
+			// Alby: transient network graph is not persisted.
+			return Ok(());
+		}
+
 		let locked_conn = self.connection.lock().unwrap();
 
 		let sql = format!(