feat: add method to list channel monitor sizes

Author: rolznz

bindings/ldk_node.udl

@@ -174,6 +174,7 @@ interface Node {
 	sequence<PaymentDetails> list_payments();
 	sequence<PeerDetails> list_peers();
 	sequence<ChannelDetails> list_channels();
+	sequence<ChannelMonitorSizeInfo> list_channel_sizes();
 	NetworkGraph network_graph();
 	string sign_message([ByRef]sequence<u8> msg);
 	boolean verify_signature([ByRef]sequence<u8> msg, [ByRef]string sig, [ByRef]PublicKey pkey);
@@ -618,6 +619,11 @@ dictionary PeerDetails {
 	boolean is_connected;
 };
 
+dictionary ChannelMonitorSizeInfo {
+	ChannelId channel_id;
+	u64 size_bytes;
+};
+
 [Enum]
 interface LightningBalance {
 	ClaimableOnChannelClose (

src/lib.rs

@@ -161,8 +161,8 @@ use types::{
 	OnionMessenger, PaymentStore, PeerManager, Router, Scorer, Sweeper, Wallet,
 };
 pub use types::{
-	ChannelDetails, CustomTlvRecord, DynStore, PeerDetails, SyncAndAsyncKVStore, UserChannelId,
-	WordCount,
+	ChannelDetails, ChannelMonitorSizeInfo, CustomTlvRecord, DynStore, PeerDetails,
+	SyncAndAsyncKVStore, UserChannelId, WordCount,
 };
 pub use {
 	bip39, bitcoin, lightning, lightning_invoice, lightning_liquidity, lightning_types, tokio,
@@ -1051,6 +1051,31 @@ impl Node {
 		self.channel_manager.list_channels().into_iter().map(|c| c.into()).collect()
 	}
 
+	/// Alby: Retrieve a list of channel monitor sizes (how big each channel monitor is when serialized)
+	/// we use this to be able to notify users when their channel monitors are getting too large
+	/// (a risk that reading/writing to VSS could start taking too long)
+	pub fn list_channel_sizes(&self) -> Vec<ChannelMonitorSizeInfo> {
+		use lightning::util::ser::Writeable;
+		use std::ops::Deref;
+
+		let mut channel_sizes = Vec::new();
+
+		for channel_id in self.chain_monitor.list_monitors() {
+			if let Ok(monitor) = self.chain_monitor.get_monitor(channel_id) {
+				// Serialize the monitor to count bytes
+				let mut size_counter = Vec::new();
+				if monitor.deref().write(&mut size_counter).is_ok() {
+					channel_sizes.push(ChannelMonitorSizeInfo {
+						channel_id,
+						size_bytes: size_counter.len() as u64,
+					});
+				}
+			}
+		}
+
+		channel_sizes
+	}
+
 	/// Connect to a node on the peer-to-peer network.
 	///
 	/// If `persist` is set to `true`, we'll remember the peer and reconnect to it on restart.

src/types.rs

@@ -452,6 +452,17 @@ pub struct PeerDetails {
 	pub is_connected: bool,
 }
 
+/// Information about the size of a channel monitor.
+///
+/// This includes the channel ID and the serialized size in bytes.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ChannelMonitorSizeInfo {
+	/// The channel ID.
+	pub channel_id: ChannelId,
+	/// The size of the channel monitor in bytes when serialized.
+	pub size_bytes: u64,
+}
+
 /// Custom TLV entry. (Alby version)
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct TlvEntry {