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

   1 use std::collections::HashMap;
   2 use std::fs;
   3 use std::ops::Deref;
   4 use std::os::unix::fs::symlink;
   5 use std::sync::Arc;
   6 use std::time::{Duration, SystemTime, UNIX_EPOCH};
   7
   8 use lightning::routing::gossip::NetworkGraph;
   9 use lightning::util::logger::Logger;
  10
  11 use crate::config;
  12 use crate::config::cache_path;
  13
  14 pub(crate) struct Snapshotter<L: Deref> where L::Target: Logger {
  15         network_graph: Arc<NetworkGraph<L>>,
  16 }
  17
  18 impl<L: Deref> Snapshotter<L> where L::Target: Logger {
  19         pub fn new(network_graph: Arc<NetworkGraph<L>>) -> Self {
  20                 Self { network_graph }
  21         }
  22
  23         pub(crate) async fn snapshot_gossip(&self) {
  24                 println!("Initiating snapshotting service");
  25
  26                 let snapshot_sync_day_factors = [1, 2, 3, 4, 5, 6, 7, 14, 21, u64::MAX];
  27                 let round_day_seconds = config::SNAPSHOT_CALCULATION_INTERVAL as u64;
  28
  29                 let pending_snapshot_directory = format!("{}/snapshots_pending", cache_path());
  30                 let pending_symlink_directory = format!("{}/symlinks_pending", cache_path());
  31                 let finalized_snapshot_directory = format!("{}/snapshots", cache_path());
  32                 let finalized_symlink_directory = format!("{}/symlinks", cache_path());
  33                 let relative_symlink_to_snapshot_path = "../snapshots";
  34
  35                 // this is gonna be a never-ending background job
  36                 loop {
  37                         // 1. get the current timestamp
  38                         let snapshot_generation_timestamp = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
  39                         let reference_timestamp = Self::round_down_to_nearest_multiple(snapshot_generation_timestamp, round_day_seconds);
  40                         println!("Capturing snapshots at {} for: {}", snapshot_generation_timestamp, reference_timestamp);
  41
  42                         // 2. sleep until the next round 24 hours
  43                         // 3. refresh all snapshots
  44
  45                         // the stored snapshots should adhere to the following format
  46                         // from one day ago
  47                         // from two days ago
  48                         // …
  49                         // from a week ago
  50                         // from two weeks ago
  51                         // from three weeks ago
  52                         // full
  53                         // That means that at any given moment, there should only ever be
  54                         // 6 (daily) + 3 (weekly) + 1 (total) = 10 cached snapshots
  55                         // The snapshots, unlike dynamic updates, should account for all intermediate
  56                         // channel updates
  57
  58                         // purge and recreate the pending directories
  59                         if fs::metadata(&pending_snapshot_directory).is_ok(){
  60                                 fs::remove_dir_all(&pending_snapshot_directory).expect("Failed to remove pending snapshot directory.");
  61                         }
  62                         if fs::metadata(&pending_symlink_directory).is_ok(){
  63                                 fs::remove_dir_all(&pending_symlink_directory).expect("Failed to remove pending symlink directory.");
  64                         }
  65                         fs::create_dir_all(&pending_snapshot_directory).expect("Failed to create pending snapshot directory");
  66                         fs::create_dir_all(&pending_symlink_directory).expect("Failed to create pending symlink directory");
  67
  68                         let mut snapshot_sync_timestamps: Vec<(u64, u64)> = Vec::new();
  69                         for factor in &snapshot_sync_day_factors {
  70                                 // basically timestamp - day_seconds * factor
  71                                 let timestamp = reference_timestamp.saturating_sub(round_day_seconds.saturating_mul(factor.clone()));
  72                                 snapshot_sync_timestamps.push((factor.clone(), timestamp));
  73                         };
  74
  75                         let mut snapshot_filenames_by_day_range: HashMap<u64, String> = HashMap::with_capacity(10);
  76
  77                         for (day_range, current_last_sync_timestamp) in &snapshot_sync_timestamps {
  78                                 let network_graph_clone = self.network_graph.clone();
  79                                 {
  80                                         println!("Calculating {}-day snapshot", day_range);
  81                                         // calculate the snapshot
  82                                         let snapshot = super::serialize_delta(network_graph_clone, current_last_sync_timestamp.clone() as u32).await;
  83
  84                                         // persist the snapshot and update the symlink
  85                                         let snapshot_filename = format!("snapshot__calculated-at:{}__range:{}-days__previous-sync:{}.lngossip", reference_timestamp, day_range, current_last_sync_timestamp);
  86                                         let snapshot_path = format!("{}/{}", pending_snapshot_directory, snapshot_filename);
  87                                         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);
  88                                         fs::write(&snapshot_path, snapshot.data).unwrap();
  89                                         snapshot_filenames_by_day_range.insert(day_range.clone(), snapshot_filename);
  90                                 }
  91                         }
  92
  93                         {
  94                                 // create dummy symlink
  95                                 let dummy_filename = "empty_delta.lngossip";
  96                                 let dummy_snapshot = super::serialize_empty_blob(reference_timestamp);
  97                                 let dummy_snapshot_path = format!("{}/{}", pending_snapshot_directory, dummy_filename);
  98                                 fs::write(&dummy_snapshot_path, dummy_snapshot).unwrap();
  99
 100                                 let dummy_symlink_path = format!("{}/{}.bin", pending_symlink_directory, reference_timestamp);
 101                                 let relative_dummy_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, dummy_filename);
 102                                 println!("Symlinking dummy: {} -> {}", dummy_symlink_path, relative_dummy_snapshot_path);
 103                                 symlink(&relative_dummy_snapshot_path, &dummy_symlink_path).unwrap();
 104                         }
 105
 106                         for i in 0..10_001u64 {
 107                                 // let's create non-dummy-symlinks
 108
 109                                 // first, determine which snapshot range should be referenced
 110                                 let referenced_day_range = if i == 0 {
 111                                         // special-case 0 to always refer to a full/initial sync
 112                                         u64::MAX
 113                                 } else {
 114                                         // find min(x) in snapshot_sync_day_factors where x >= i
 115                                         snapshot_sync_day_factors.iter().find(|x| {
 116                                                 x >= &&i
 117                                         }).unwrap().clone()
 118                                 };
 119
 120                                 let snapshot_filename = snapshot_filenames_by_day_range.get(&referenced_day_range).unwrap();
 121                                 let relative_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, snapshot_filename);
 122
 123                                 let canonical_last_sync_timestamp = if i == 0 {
 124                                         // special-case 0 to always refer to a full/initial sync
 125                                         0
 126                                 } else {
 127                                         reference_timestamp.saturating_sub(round_day_seconds.saturating_mul(i))
 128                                 };
 129                                 let symlink_path = format!("{}/{}.bin", pending_symlink_directory, canonical_last_sync_timestamp);
 130
 131                                 println!("Symlinking: {} -> {} ({} -> {}", i, referenced_day_range, symlink_path, relative_snapshot_path);
 132                                 symlink(&relative_snapshot_path, &symlink_path).unwrap();
 133                         }
 134
 135                         let update_time_path = format!("{}/update_time.txt", pending_symlink_directory);
 136                         let update_time = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
 137                         fs::write(&update_time_path, format!("{}", update_time)).unwrap();
 138
 139                         if fs::metadata(&finalized_snapshot_directory).is_ok(){
 140                                 fs::remove_dir_all(&finalized_snapshot_directory).expect("Failed to remove finalized snapshot directory.");
 141                         }
 142                         if fs::metadata(&finalized_symlink_directory).is_ok(){
 143                                 fs::remove_dir_all(&finalized_symlink_directory).expect("Failed to remove pending symlink directory.");
 144                         }
 145                         fs::rename(&pending_snapshot_directory, &finalized_snapshot_directory).expect("Failed to finalize snapshot directory.");
 146                         fs::rename(&pending_symlink_directory, &finalized_symlink_directory).expect("Failed to finalize symlink directory.");
 147
 148                         // constructing the snapshots may have taken a while
 149                         let current_time = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
 150                         let remainder = current_time % round_day_seconds;
 151                         let time_until_next_day = round_day_seconds - remainder;
 152
 153                         println!("Sleeping until next snapshot capture: {}s", time_until_next_day);
 154                         // add in an extra five seconds to assure the rounding down works correctly
 155                         let sleep = tokio::time::sleep(Duration::from_secs(time_until_next_day + 5));
 156                         sleep.await;
 157                 }
 158         }
 159
 160         pub(super) fn round_down_to_nearest_multiple(number: u64, multiple: u64) -> u64 {
 161                 let round_multiple_delta = number % multiple;
 162                 number - round_multiple_delta
 163         }
 164 }