+ pub(crate) async fn generate_snapshots(&self, granularity_interval: u64, snapshot_interval: u64, snapshot_scopes: &[u64], cache_path: &str, max_symlink_count: Option<u64>) {
+ let pending_snapshot_directory = format!("{}/snapshots_pending", cache_path);
+ let pending_symlink_directory = format!("{}/symlinks_pending", cache_path);
+ let finalized_snapshot_directory = format!("{}/snapshots", cache_path);
+ let finalized_symlink_directory = format!("{}/symlinks", cache_path);
+ let relative_symlink_to_snapshot_path = "../snapshots";
+
+ // 1. get the current timestamp
+ let snapshot_generation_timestamp = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
+ let reference_timestamp = Self::round_down_to_nearest_multiple(snapshot_generation_timestamp, snapshot_interval as u64);
+ log_info!(self.logger, "Capturing snapshots at {} for: {}", snapshot_generation_timestamp, reference_timestamp);
+
+ // 2. sleep until the next round interval
+ // 3. refresh all snapshots
+
+ // the stored snapshots should adhere to the following format
+ // from one day ago
+ // from two days ago
+ // …
+ // from a week ago
+ // from two weeks ago
+ // from three weeks ago
+ // full
+ // That means that at any given moment, there should only ever be
+ // 6 (daily) + 3 (weekly) + 1 (total) = 10 cached snapshots
+ // The snapshots, unlike dynamic updates, should account for all intermediate
+ // channel updates
+
+ // purge and recreate the pending directories
+ if fs::metadata(&pending_snapshot_directory).is_ok() {
+ fs::remove_dir_all(&pending_snapshot_directory).expect("Failed to remove pending snapshot directory.");
+ }
+ if fs::metadata(&pending_symlink_directory).is_ok() {
+ fs::remove_dir_all(&pending_symlink_directory).expect("Failed to remove pending symlink directory.");
+ }
+ fs::create_dir_all(&pending_snapshot_directory).expect("Failed to create pending snapshot directory");
+ fs::create_dir_all(&pending_symlink_directory).expect("Failed to create pending symlink directory");
+
+ let mut snapshot_sync_timestamps: Vec<(u64, u64)> = Vec::new();
+ for current_scope in snapshot_scopes {
+ let timestamp = reference_timestamp.saturating_sub(current_scope.clone());
+ snapshot_sync_timestamps.push((current_scope.clone(), timestamp));
+ };
+
+ let mut snapshot_filenames_by_scope: HashMap<u64, String> = HashMap::with_capacity(10);
+
+ for (current_scope, current_last_sync_timestamp) in &snapshot_sync_timestamps {
+ let network_graph_clone = self.network_graph.clone();
+ {
+ log_info!(self.logger, "Calculating {}-second snapshot", current_scope);
+ // calculate the snapshot
+ let snapshot = super::serialize_delta(network_graph_clone, current_last_sync_timestamp.clone() as u32, self.logger.clone()).await;
+
+ // persist the snapshot and update the symlink
+ let snapshot_filename = format!("snapshot__calculated-at:{}__range:{}-scope__previous-sync:{}.lngossip", reference_timestamp, current_scope, current_last_sync_timestamp);
+ let snapshot_path = format!("{}/{}", pending_snapshot_directory, snapshot_filename);
+ log_info!(self.logger, "Persisting {}-second snapshot: {} ({} messages, {} announcements, {} updates ({} full, {} incremental))", current_scope, snapshot_filename, snapshot.message_count, snapshot.announcement_count, snapshot.update_count, snapshot.update_count_full, snapshot.update_count_incremental);
+ fs::write(&snapshot_path, snapshot.data).unwrap();
+ snapshot_filenames_by_scope.insert(current_scope.clone(), snapshot_filename);
+ }
+ }
+
+ {
+ // 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_symlink_path = format!("{}/{}.bin", pending_symlink_directory, reference_timestamp);
+ let relative_dummy_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, dummy_filename);
+ log_info!(self.logger, "Symlinking dummy: {} -> {}", dummy_symlink_path, relative_dummy_snapshot_path);
+ symlink(&relative_dummy_snapshot_path, &dummy_symlink_path).unwrap();
+ }
+
+ // Number of intervals since Jan 1, 2022, a few months before RGS server was released.
+ let mut symlink_count = (reference_timestamp - 1640995200) / granularity_interval;
+ if let Some(max_symlink_count) = max_symlink_count {
+ // this is primarily useful for testing
+ symlink_count = std::cmp::min(symlink_count, max_symlink_count);
+ };
+
+ for i in 0..symlink_count {
+ // let's create non-dummy-symlinks
+
+ // first, determine which snapshot range should be referenced
+ let referenced_scope = if i == 0 {
+ // special-case 0 to always refer to a full/initial sync
+ u64::MAX
+ } else {
+ /*
+ We have snapshots for 6-day- and 7-day-intervals, but the next interval is
+ 14 days. So if somebody requests an update with a timestamp that is 10 days old,
+ there is no longer a snapshot for that specific interval.
+
+ The correct snapshot will be the next highest interval, i. e. for 14 days.
+
+ The `snapshot_sync_day_factors` array is sorted ascendingly, so find() will
+ return on the first iteration that is at least equal to the requested interval.
+
+ Note, however, that the last value in the array is u64::max, which means that
+ multiplying it with snapshot_interval will overflow. To avoid that, we use
+ saturating_mul.
+ */
+
+ // find min(x) in snapshot_scopes where i * granularity <= x (the current scope)
+ snapshot_scopes.iter().find(|current_scope| {
+ i * granularity_interval <= **current_scope
+ }).unwrap().clone()
+ };
+ log_info!(self.logger, "i: {}, referenced scope: {}", i, referenced_scope);
+
+ let snapshot_filename = snapshot_filenames_by_scope.get(&referenced_scope).unwrap();
+ let relative_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, snapshot_filename);
+
+ let canonical_last_sync_timestamp = if i == 0 {
+ // special-case 0 to always refer to a full/initial sync
+ 0
+ } else {
+ reference_timestamp.saturating_sub(granularity_interval.saturating_mul(i))
+ };
+ let symlink_path = format!("{}/{}.bin", pending_symlink_directory, canonical_last_sync_timestamp);
+
+ log_info!(self.logger, "Symlinking: {} -> {} ({} -> {}", i, referenced_scope, symlink_path, relative_snapshot_path);
+ symlink(&relative_snapshot_path, &symlink_path).unwrap();
+ }
+
+ let update_time_path = format!("{}/update_time.txt", pending_symlink_directory);
+ let update_time = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
+ fs::write(&update_time_path, format!("{}", update_time)).unwrap();
+
+ if fs::metadata(&finalized_snapshot_directory).is_ok() {
+ fs::remove_dir_all(&finalized_snapshot_directory).expect("Failed to remove finalized snapshot directory.");
+ }
+ if fs::metadata(&finalized_symlink_directory).is_ok() {
+ fs::remove_dir_all(&finalized_symlink_directory).expect("Failed to remove pending symlink directory.");
+ }
+ fs::rename(&pending_snapshot_directory, &finalized_snapshot_directory).expect("Failed to finalize snapshot directory.");
+ fs::rename(&pending_symlink_directory, &finalized_symlink_directory).expect("Failed to finalize symlink directory.");
+ }
+