Generate v1 and v2 dummy snapshots

Previously, our dummy snapshots were unversioned. This commit ensures
that we generate no-op serializations for both currently supported
versions, and introduces unit tests to ascertain their validity.

src/lib.rs

@@ -160,8 +160,9 @@ pub(crate) async fn connect_to_db() -> Client {
 /// of our granularity constant. Note that for that purpose, this method could be very dangerous,
 /// because if consumed, the `timestamp` value calculated here will overwrite the timestamp that
 /// the client previously had, which could result in duplicated or omitted gossip down the line.
-fn serialize_empty_blob(current_timestamp: u64) -> Vec<u8> {
+fn serialize_empty_blob(current_timestamp: u64, serialization_version: u8) -> Vec<u8> {
 	let mut blob = GOSSIP_PREFIX.to_vec();
+	serialization_version.write(&mut blob).unwrap();
 
 	let network = config::network();
 	let chain_hash = ChainHash::using_genesis_block(network);
@@ -170,6 +171,10 @@ fn serialize_empty_blob(current_timestamp: u64) -> Vec<u8> {
 	let blob_timestamp = Snapshotter::<Arc<RGSSLogger>>::round_down_to_nearest_multiple(current_timestamp, SYMLINK_GRANULARITY_INTERVAL as u64) as u32;
 	blob_timestamp.write(&mut blob).unwrap();
 
+	if serialization_version >= 2 {
+		0u8.write(&mut blob).unwrap(); // default node feature count
+	}
+
 	0u32.write(&mut blob).unwrap(); // node count
 	0u32.write(&mut blob).unwrap(); // announcement count
 	0u32.write(&mut blob).unwrap(); // update count

src/snapshot.rs

@@ -138,9 +138,12 @@ impl<L: Deref + Clone> Snapshotter<L> where L::Target: Logger {
 		{
 			// create dummy symlink
 			let dummy_filename = "empty_delta.lngossip";
-			let dummy_snapshot = super::serialize_empty_blob(reference_timestamp);
-			let dummy_snapshot_path = format!("{}/{}", pending_snapshot_directory, dummy_filename);
-			fs::write(&dummy_snapshot_path, dummy_snapshot).unwrap();
+			let dummy_snapshot_v1 = super::serialize_empty_blob(reference_timestamp, 1);
+			let dummy_snapshot_v2 = super::serialize_empty_blob(reference_timestamp, 2);
+			let dummy_snapshot_path_v1 = format!("{}/{}", pending_snapshot_directory, dummy_filename);
+			let dummy_snapshot_path_v2 = format!("{}/v2/{}", pending_snapshot_directory, dummy_filename);
+			fs::write(&dummy_snapshot_path_v1, dummy_snapshot_v1).unwrap();
+			fs::write(&dummy_snapshot_path_v2, dummy_snapshot_v2).unwrap();
 
 			let dummy_symlink_path = format!("{}/{}.bin", pending_symlink_directory, reference_timestamp);
 			let relative_dummy_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, dummy_filename);

src/tests/mod.rs

@@ -16,7 +16,7 @@ use lightning::ln::msgs::{ChannelAnnouncement, ChannelUpdate, NodeAnnouncement,
 use lightning::routing::gossip::{NetworkGraph, NodeAlias, NodeId};
 use lightning::util::ser::Writeable;
 use lightning_rapid_gossip_sync::RapidGossipSync;
-use crate::{calculate_delta, config, serialize_delta};
+use crate::{calculate_delta, config, serialize_delta, serialize_empty_blob};
 use crate::persistence::GossipPersister;
 use crate::snapshot::Snapshotter;
 use crate::types::{GossipMessage, tests::TestLogger};
@@ -221,6 +221,19 @@ async fn test_persistence_runtime() {
 }
 
 
+#[test]
+fn test_no_op() {
+	let logger = Arc::new(TestLogger::with_id("test_no_op".to_string()));
+	for serialization_version in 1..3 {
+		let serialization = serialize_empty_blob(current_time() as u64, serialization_version);
+
+		let client_graph = NetworkGraph::new(Network::Bitcoin, logger.clone());
+		let client_graph_arc = Arc::new(client_graph);
+		let rgs = RapidGossipSync::new(client_graph_arc.clone(), logger.clone());
+		rgs.update_network_graph(&serialization).unwrap();
+	}
+}
+
 #[tokio::test]
 async fn test_trivial_setup() {
 	let _sanitizer = SchemaSanitizer::new();