_ Git - rapid-gossip-sync-server/blob - src/snapshot.rs

   1 use std::collections::HashMap;
   2 use std::fs;
   3 use std::os::unix::fs::symlink;
   4 use std::sync::Arc;
   5 use std::time::{Duration, SystemTime, UNIX_EPOCH};
   6
   7 use lightning::routing::gossip::NetworkGraph;
   8 use lightning::util::logger::Logger;
   9
  10 use crate::config;
  11 use crate::config::cache_path;
  12
  13 pub(crate) struct Snapshotter<L: Logger> {
  14         network_graph: Arc<NetworkGraph<Arc<L>>>,
  15 }
  16
  17 impl<L: Logger> Snapshotter<L> {
  18         pub fn new(network_graph: Arc<NetworkGraph<Arc<L>>>) -> Self {
  19                 Self { network_graph }
  20         }
  21
  22         pub(crate) async fn snapshot_gossip(&self) {
  23                 println!("Initiating snapshotting service");
  24
  25                 let snapshot_sync_day_factors = [1, 2, 3, 4, 5, 6, 7, 14, 21, u64::MAX];
  26                 let round_day_seconds = config::SNAPSHOT_CALCULATION_INTERVAL as u64;
  27
  28                 let pending_snapshot_directory = format!("{}/snapshots_pending", cache_path());
  29                 let pending_symlink_directory = format!("{}/symlinks_pending", cache_path());
  30                 let finalized_snapshot_directory = format!("{}/snapshots", cache_path());
  31                 let finalized_symlink_directory = format!("{}/symlinks", cache_path());
  32                 let relative_symlink_to_snapshot_path = "../snapshots";
  33
  34                 // this is gonna be a never-ending background job
  35                 loop {
  36                         // 1. get the current timestamp
  37                         let snapshot_generation_timestamp = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
  38                         let reference_timestamp = Self::round_down_to_nearest_multiple(snapshot_generation_timestamp, round_day_seconds);
  39                         println!("Capturing snapshots at {} for: {}", snapshot_generation_timestamp, reference_timestamp);
  40
  41                         // 2. sleep until the next round 24 hours
  42                         // 3. refresh all snapshots
  43
  44                         // the stored snapshots should adhere to the following format
  45                         // from one day ago
  46                         // from two days ago
  47                         // …
  48                         // from a week ago
  49                         // from two weeks ago
  50                         // from three weeks ago
  51                         // full
  52                         // That means that at any given moment, there should only ever be
  53                         // 6 (daily) + 3 (weekly) + 1 (total) = 10 cached snapshots
  54                         // The snapshots, unlike dynamic updates, should account for all intermediate
  55                         // channel updates
  56
  57                         // purge and recreate the pending directories
  58                         if fs::metadata(&pending_snapshot_directory).is_ok(){
  59                                 fs::remove_dir_all(&pending_snapshot_directory).expect("Failed to remove pending snapshot directory.");
  60                         }
  61                         if fs::metadata(&pending_symlink_directory).is_ok(){
  62                                 fs::remove_dir_all(&pending_symlink_directory).expect("Failed to remove pending symlink directory.");
  63                         }
  64                         fs::create_dir_all(&pending_snapshot_directory).expect("Failed to create pending snapshot directory");
  65                         fs::create_dir_all(&pending_symlink_directory).expect("Failed to create pending symlink directory");
  66
  67                         let mut snapshot_sync_timestamps: Vec<(u64, u64)> = Vec::new();
  68                         for factor in &snapshot_sync_day_factors {
  69                                 // basically timestamp - day_seconds * factor
  70                                 let timestamp = reference_timestamp.saturating_sub(round_day_seconds.saturating_mul(factor.clone()));
  71                                 snapshot_sync_timestamps.push((factor.clone(), timestamp));
  72                         };
  73
  74                         let mut snapshot_filenames_by_day_range: HashMap<u64, String> = HashMap::with_capacity(10);
  75
  76                         for (day_range, current_last_sync_timestamp) in &snapshot_sync_timestamps {
  77                                 let network_graph_clone = self.network_graph.clone();
  78                                 {
  79                                         println!("Calculating {}-day snapshot", day_range);
  80                                         // calculate the snapshot
  81                                         let snapshot = super::serialize_delta(network_graph_clone, current_last_sync_timestamp.clone() as u32).await;
  82
  83                                         // persist the snapshot and update the symlink
  84                                         let snapshot_filename = format!("snapshot__calculated-at:{}__range:{}-days__previous-sync:{}.lngossip", reference_timestamp, day_range, current_last_sync_timestamp);
  85                                         let snapshot_path = format!("{}/{}", pending_snapshot_directory, snapshot_filename);
  86                                         println!("Persisting {}-day snapshot: {} ({} messages, {} announcements, {} updates ({} full, {} incremental))", day_range, snapshot_filename, snapshot.message_count, snapshot.announcement_count, snapshot.update_count, snapshot.update_count_full, snapshot.update_count_incremental);
  87                                         fs::write(&snapshot_path, snapshot.data).unwrap();
  88                                         snapshot_filenames_by_day_range.insert(day_range.clone(), snapshot_filename);
  89                                 }
  90                         }
  91
  92                         {
  93                                 // create dummy symlink
  94                                 let dummy_filename = "empty_delta.lngossip";
  95                                 let dummy_snapshot = super::serialize_empty_blob(reference_timestamp);
  96                                 let dummy_snapshot_path = format!("{}/{}", pending_snapshot_directory, dummy_filename);
  97                                 fs::write(&dummy_snapshot_path, dummy_snapshot).unwrap();
  98
  99                                 let dummy_symlink_path = format!("{}/{}.bin", pending_symlink_directory, reference_timestamp);
 100                                 let relative_dummy_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, dummy_filename);
 101                                 println!("Symlinking dummy: {} -> {}", dummy_symlink_path, relative_dummy_snapshot_path);
 102                                 symlink(&relative_dummy_snapshot_path, &dummy_symlink_path).unwrap();
 103                         }
 104
 105                         for i in 0..10_001u64 {
 106                                 // let's create non-dummy-symlinks
 107
 108                                 // first, determine which snapshot range should be referenced
 109                                 let referenced_day_range = if i == 0 {
 110                                         // special-case 0 to always refer to a full/initial sync
 111                                         u64::MAX
 112                                 } else {
 113                                         // find min(x) in snapshot_sync_day_factors where x >= i
 114                                         snapshot_sync_day_factors.iter().find(|x| {
 115                                                 x >= &&i
 116                                         }).unwrap().clone()
 117                                 };
 118
 119                                 let snapshot_filename = snapshot_filenames_by_day_range.get(&referenced_day_range).unwrap();
 120                                 let relative_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, snapshot_filename);
 121
 122                                 let canonical_last_sync_timestamp = if i == 0 {
 123                                         // special-case 0 to always refer to a full/initial sync
 124                                         0
 125                                 } else {
 126                                         reference_timestamp.saturating_sub(round_day_seconds.saturating_mul(i))
 127                                 };
 128                                 let symlink_path = format!("{}/{}.bin", pending_symlink_directory, canonical_last_sync_timestamp);
 129
 130                                 println!("Symlinking: {} -> {} ({} -> {}", i, referenced_day_range, symlink_path, relative_snapshot_path);
 131                                 symlink(&relative_snapshot_path, &symlink_path).unwrap();
 132                         }
 133
 134                         let update_time_path = format!("{}/update_time.txt", pending_symlink_directory);
 135                         let update_time = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
 136                         fs::write(&update_time_path, format!("{}", update_time)).unwrap();
 137
 138                         if fs::metadata(&finalized_snapshot_directory).is_ok(){
 139                                 fs::remove_dir_all(&finalized_snapshot_directory).expect("Failed to remove finalized snapshot directory.");
 140                         }
 141                         if fs::metadata(&finalized_symlink_directory).is_ok(){
 142                                 fs::remove_dir_all(&finalized_symlink_directory).expect("Failed to remove pending symlink directory.");
 143                         }
 144                         fs::rename(&pending_snapshot_directory, &finalized_snapshot_directory).expect("Failed to finalize snapshot directory.");
 145                         fs::rename(&pending_symlink_directory, &finalized_symlink_directory).expect("Failed to finalize symlink directory.");
 146
 147                         // constructing the snapshots may have taken a while
 148                         let current_time = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
 149                         let remainder = current_time % round_day_seconds;
 150                         let time_until_next_day = round_day_seconds - remainder;
 151
 152                         println!("Sleeping until next snapshot capture: {}s", time_until_next_day);
 153                         // add in an extra five seconds to assure the rounding down works correctly
 154                         let sleep = tokio::time::sleep(Duration::from_secs(time_until_next_day + 5));
 155                         sleep.await;
 156                 }
 157         }
 158
 159         pub(super) fn round_down_to_nearest_multiple(number: u64, multiple: u64) -> u64 {
 160                 let round_multiple_delta = number % multiple;
 161                 number - round_multiple_delta
 162         }
 163 }