use rand::Rng; use std::collections::{BTreeMap, VecDeque}; use std::sync::Arc; use std::time::{Duration, Instant}; use futures::future::BoxFuture; use futures::{pin_mut, select}; use futures_util::future::*; use futures_util::stream::*; use serde::{Deserialize, Serialize}; use serde_bytes::ByteBuf; use tokio::sync::Mutex; use tokio::sync::{mpsc, watch}; use crate::data::*; use crate::error::Error; use crate::membership::Ring; use crate::table::*; const MAX_DEPTH: usize = 16; const SCAN_INTERVAL: Duration = Duration::from_secs(1800); const CHECKSUM_CACHE_TIMEOUT: Duration = Duration::from_secs(1800); const TABLE_SYNC_RPC_TIMEOUT: Duration = Duration::from_secs(30); pub struct TableSyncer { table: Arc>, todo: Mutex, cache: Vec>>, } #[derive(Serialize, Deserialize)] pub enum SyncRPC { GetRootChecksumRange(Hash, Hash), RootChecksumRange(SyncRange), Checksums(Vec, bool), Difference(Vec, Vec>), } pub struct SyncTodo { todo: Vec, } #[derive(Debug, Clone)] struct TodoPartition { begin: Hash, end: Hash, retain: bool, } // A SyncRange defines a query on the dataset stored by a node, in the following way: // - all items whose key are >= `begin` // - stopping at the first item whose key hash has at least `level` leading zero bytes (excluded) // - except if the first item of the range has such many leading zero bytes // - and stopping at `end` (excluded) if such an item is not found // The checksum itself does not store all of the items in the database, only the hashes of the "sub-ranges" // i.e. of ranges of level `level-1` that cover the same range // (ranges of level 0 do not exist and their hash is simply the hash of the first item >= begin) // See RangeChecksum for the struct that stores this information. #[derive(Hash, PartialEq, Eq, Debug, Clone, Serialize, Deserialize)] pub struct SyncRange { begin: Vec, end: Vec, level: usize, } impl std::cmp::PartialOrd for SyncRange { fn partial_cmp(&self, other: &Self) -> Option { Some(self.cmp(other)) } } impl std::cmp::Ord for SyncRange { fn cmp(&self, other: &Self) -> std::cmp::Ordering { self.begin .cmp(&other.begin) .then(self.level.cmp(&other.level)) .then(self.end.cmp(&other.end)) } } #[derive(Debug, Clone, Serialize, Deserialize)] pub struct RangeChecksum { bounds: SyncRange, children: Vec<(SyncRange, Hash)>, found_limit: Option>, #[serde(skip, default = "std::time::Instant::now")] time: Instant, } #[derive(Debug, Clone)] pub struct RangeChecksumCache { hash: Option, // None if no children found_limit: Option>, time: Instant, } impl TableSyncer where F: TableSchema + 'static, R: TableReplication + 'static, { pub async fn launch(table: Arc>) -> Arc { let todo = SyncTodo { todo: Vec::new() }; let syncer = Arc::new(TableSyncer { table: table.clone(), todo: Mutex::new(todo), cache: (0..MAX_DEPTH) .map(|_| Mutex::new(BTreeMap::new())) .collect::>(), }); let (busy_tx, busy_rx) = mpsc::unbounded_channel(); let s1 = syncer.clone(); table .system .background .spawn_worker( format!("table sync watcher for {}", table.name), move |must_exit: watch::Receiver| s1.watcher_task(must_exit, busy_rx), ) .await; let s2 = syncer.clone(); table .system .background .spawn_worker( format!("table syncer for {}", table.name), move |must_exit: watch::Receiver| s2.syncer_task(must_exit, busy_tx), ) .await; syncer } async fn watcher_task( self: Arc, mut must_exit: watch::Receiver, mut busy_rx: mpsc::UnboundedReceiver, ) -> Result<(), Error> { let mut prev_ring: Arc = self.table.system.ring.borrow().clone(); let mut ring_recv: watch::Receiver> = self.table.system.ring.clone(); let mut nothing_to_do_since = Some(Instant::now()); while !*must_exit.borrow() { let s_ring_recv = ring_recv.recv().fuse(); let s_busy = busy_rx.recv().fuse(); let s_must_exit = must_exit.recv().fuse(); let s_timeout = tokio::time::delay_for(Duration::from_secs(1)).fuse(); pin_mut!(s_ring_recv, s_busy, s_must_exit, s_timeout); select! { new_ring_r = s_ring_recv => { if let Some(new_ring) = new_ring_r { debug!("({}) Adding ring difference to syncer todo list", self.table.name); self.todo.lock().await.add_ring_difference(&self.table, &prev_ring, &new_ring); prev_ring = new_ring; } } busy_opt = s_busy => { if let Some(busy) = busy_opt { if busy { nothing_to_do_since = None; } else { if nothing_to_do_since.is_none() { nothing_to_do_since = Some(Instant::now()); } } } } must_exit_v = s_must_exit => { if must_exit_v.unwrap_or(false) { break; } } _ = s_timeout => { if nothing_to_do_since.map(|t| Instant::now() - t >= SCAN_INTERVAL).unwrap_or(false) { nothing_to_do_since = None; debug!("({}) Adding full scan to syncer todo list", self.table.name); self.add_full_scan().await; } } } } Ok(()) } pub async fn add_full_scan(&self) { self.todo.lock().await.add_full_scan(&self.table); } async fn syncer_task( self: Arc, mut must_exit: watch::Receiver, busy_tx: mpsc::UnboundedSender, ) -> Result<(), Error> { while !*must_exit.borrow() { if let Some(partition) = self.todo.lock().await.pop_task() { busy_tx.send(true)?; let res = self .clone() .sync_partition(&partition, &mut must_exit) .await; if let Err(e) = res { warn!( "({}) Error while syncing {:?}: {}", self.table.name, partition, e ); } } else { busy_tx.send(false)?; tokio::time::delay_for(Duration::from_secs(1)).await; } } Ok(()) } async fn sync_partition( self: Arc, partition: &TodoPartition, must_exit: &mut watch::Receiver, ) -> Result<(), Error> { let my_id = self.table.system.id.clone(); let nodes = self .table .replication .write_nodes(&partition.begin, &self.table.system) .into_iter() .filter(|node| *node != my_id) .collect::>(); debug!( "({}) Preparing to sync {:?} with {:?}...", self.table.name, partition, nodes ); let root_cks = self .root_checksum(&partition.begin, &partition.end, must_exit) .await?; let mut sync_futures = nodes .iter() .map(|node| { self.clone().do_sync_with( partition.clone(), root_cks.clone(), node.clone(), partition.retain, must_exit.clone(), ) }) .collect::>(); let mut n_errors = 0; while let Some(r) = sync_futures.next().await { if let Err(e) = r { n_errors += 1; warn!("({}) Sync error: {}", self.table.name, e); } } if n_errors > self.table.replication.max_write_errors() { return Err(Error::Message(format!( "Sync failed with too many nodes (should have been: {:?}).", nodes ))); } if !partition.retain { self.table .delete_range(&partition.begin, &partition.end) .await?; } Ok(()) } async fn root_checksum( self: &Arc, begin: &Hash, end: &Hash, must_exit: &mut watch::Receiver, ) -> Result { for i in 1..MAX_DEPTH { let rc = self .range_checksum( &SyncRange { begin: begin.to_vec(), end: end.to_vec(), level: i, }, must_exit, ) .await?; if rc.found_limit.is_none() { return Ok(rc); } } Err(Error::Message(format!( "Unable to compute root checksum (this should never happen)" ))) } async fn range_checksum( self: &Arc, range: &SyncRange, must_exit: &mut watch::Receiver, ) -> Result { assert!(range.level != 0); if range.level == 1 { let mut children = vec![]; for item in self .table .store .range(range.begin.clone()..range.end.clone()) { let (key, value) = item?; let key_hash = hash(&key[..]); if children.len() > 0 && key_hash.as_slice()[0..range.level] .iter() .all(|x| *x == 0u8) { return Ok(RangeChecksum { bounds: range.clone(), children, found_limit: Some(key.to_vec()), time: Instant::now(), }); } let item_range = SyncRange { begin: key.to_vec(), end: vec![], level: 0, }; children.push((item_range, hash(&value[..]))); } Ok(RangeChecksum { bounds: range.clone(), children, found_limit: None, time: Instant::now(), }) } else { let mut children = vec![]; let mut sub_range = SyncRange { begin: range.begin.clone(), end: range.end.clone(), level: range.level - 1, }; let mut time = Instant::now(); while !*must_exit.borrow() { let sub_ck = self .range_checksum_cached_hash(&sub_range, must_exit) .await?; if let Some(hash) = &sub_ck.hash { children.push((sub_range.clone(), hash.clone())); if sub_ck.time < time { time = sub_ck.time; } } if sub_ck.found_limit.is_none() || sub_ck.hash.is_none() { return Ok(RangeChecksum { bounds: range.clone(), children, found_limit: None, time, }); } let found_limit = sub_ck.found_limit.unwrap(); let actual_limit_hash = hash(&found_limit[..]); if actual_limit_hash.as_slice()[0..range.level] .iter() .all(|x| *x == 0u8) { return Ok(RangeChecksum { bounds: range.clone(), children, found_limit: Some(found_limit.clone()), time, }); } sub_range.begin = found_limit; } Err(Error::Message(format!("Exiting."))) } } fn range_checksum_cached_hash<'a>( self: &'a Arc, range: &'a SyncRange, must_exit: &'a mut watch::Receiver, ) -> BoxFuture<'a, Result> { async move { let mut cache = self.cache[range.level].lock().await; if let Some(v) = cache.get(&range) { if Instant::now() - v.time < CHECKSUM_CACHE_TIMEOUT { return Ok(v.clone()); } } cache.remove(&range); drop(cache); let v = self.range_checksum(&range, must_exit).await?; trace!( "({}) New checksum calculated for {}-{}/{}, {} children", self.table.name, hex::encode(&range.begin) .chars() .take(16) .collect::(), hex::encode(&range.end).chars().take(16).collect::(), range.level, v.children.len() ); let hash = if v.children.len() > 0 { Some(hash(&rmp_to_vec_all_named(&v)?[..])) } else { None }; let cache_entry = RangeChecksumCache { hash, found_limit: v.found_limit, time: v.time, }; let mut cache = self.cache[range.level].lock().await; cache.insert(range.clone(), cache_entry.clone()); Ok(cache_entry) } .boxed() } async fn do_sync_with( self: Arc, partition: TodoPartition, root_ck: RangeChecksum, who: UUID, retain: bool, mut must_exit: watch::Receiver, ) -> Result<(), Error> { let mut todo = VecDeque::new(); // If their root checksum has level > than us, use that as a reference let root_cks_resp = self .table .rpc_client .call( &who, &TableRPC::::SyncRPC(SyncRPC::GetRootChecksumRange( partition.begin.clone(), partition.end.clone(), )), TABLE_SYNC_RPC_TIMEOUT, ) .await?; if let TableRPC::::SyncRPC(SyncRPC::RootChecksumRange(range)) = root_cks_resp { if range.level > root_ck.bounds.level { let their_root_range_ck = self.range_checksum(&range, &mut must_exit).await?; todo.push_back(their_root_range_ck); } else { todo.push_back(root_ck); } } else { return Err(Error::BadRequest(format!( "Invalid respone to GetRootChecksumRange RPC: {}", debug_serialize(root_cks_resp) ))); } while !todo.is_empty() && !*must_exit.borrow() { let total_children = todo.iter().map(|x| x.children.len()).fold(0, |x, y| x + y); trace!( "({}) Sync with {:?}: {} ({}) remaining", self.table.name, who, todo.len(), total_children ); let step_size = std::cmp::min(16, todo.len()); let step = todo.drain(..step_size).collect::>(); let rpc_resp = self .table .rpc_client .call( &who, &TableRPC::::SyncRPC(SyncRPC::Checksums(step, retain)), TABLE_SYNC_RPC_TIMEOUT, ) .await?; if let TableRPC::::SyncRPC(SyncRPC::Difference(mut diff_ranges, diff_items)) = rpc_resp { if diff_ranges.len() > 0 || diff_items.len() > 0 { info!( "({}) Sync with {:?}: difference {} ranges, {} items", self.table.name, who, diff_ranges.len(), diff_items.len() ); } let mut items_to_send = vec![]; for differing in diff_ranges.drain(..) { if differing.level == 0 { items_to_send.push(differing.begin); } else { let checksum = self.range_checksum(&differing, &mut must_exit).await?; todo.push_back(checksum); } } if retain && diff_items.len() > 0 { self.table.handle_update(diff_items).await?; } if items_to_send.len() > 0 { self.send_items(who.clone(), items_to_send).await?; } } else { return Err(Error::BadRequest(format!( "Unexpected response to sync RPC checksums: {}", debug_serialize(&rpc_resp) ))); } } Ok(()) } async fn send_items(&self, who: UUID, item_list: Vec>) -> Result<(), Error> { info!( "({}) Sending {} items to {:?}", self.table.name, item_list.len(), who ); let mut values = vec![]; for item in item_list.iter() { if let Some(v) = self.table.store.get(&item[..])? { values.push(Arc::new(ByteBuf::from(v.as_ref()))); } } let rpc_resp = self .table .rpc_client .call(&who, &TableRPC::::Update(values), TABLE_SYNC_RPC_TIMEOUT) .await?; if let TableRPC::::Ok = rpc_resp { Ok(()) } else { Err(Error::Message(format!( "Unexpected response to RPC Update: {}", debug_serialize(&rpc_resp) ))) } } pub async fn handle_rpc( self: &Arc, message: &SyncRPC, mut must_exit: watch::Receiver, ) -> Result { match message { SyncRPC::GetRootChecksumRange(begin, end) => { let root_cks = self.root_checksum(&begin, &end, &mut must_exit).await?; Ok(SyncRPC::RootChecksumRange(root_cks.bounds)) } SyncRPC::Checksums(checksums, retain) => { self.handle_checksums_rpc(&checksums[..], *retain, &mut must_exit) .await } _ => Err(Error::Message(format!("Unexpected sync RPC"))), } } async fn handle_checksums_rpc( self: &Arc, checksums: &[RangeChecksum], retain: bool, must_exit: &mut watch::Receiver, ) -> Result { let mut ret_ranges = vec![]; let mut ret_items = vec![]; for their_ckr in checksums.iter() { let our_ckr = self.range_checksum(&their_ckr.bounds, must_exit).await?; for (their_range, their_hash) in their_ckr.children.iter() { let differs = match our_ckr .children .binary_search_by(|(our_range, _)| our_range.cmp(&their_range)) { Err(_) => { if their_range.level >= 1 { let cached_hash = self .range_checksum_cached_hash(&their_range, must_exit) .await?; cached_hash.hash.map(|h| h != *their_hash).unwrap_or(true) } else { true } } Ok(i) => our_ckr.children[i].1 != *their_hash, }; if differs { ret_ranges.push(their_range.clone()); if retain && their_range.level == 0 { if let Some(item_bytes) = self.table.store.get(their_range.begin.as_slice())? { ret_items.push(Arc::new(ByteBuf::from(item_bytes.to_vec()))); } } } } for (our_range, _hash) in our_ckr.children.iter() { if let Some(their_found_limit) = &their_ckr.found_limit { if our_range.begin.as_slice() > their_found_limit.as_slice() { break; } } let not_present = our_ckr .children .binary_search_by(|(their_range, _)| their_range.cmp(&our_range)) .is_err(); if not_present { if our_range.level > 0 { ret_ranges.push(our_range.clone()); } if retain && our_range.level == 0 { if let Some(item_bytes) = self.table.store.get(our_range.begin.as_slice())? { ret_items.push(Arc::new(ByteBuf::from(item_bytes.to_vec()))); } } } } } let n_checksums = checksums .iter() .map(|x| x.children.len()) .fold(0, |x, y| x + y); if ret_ranges.len() > 0 || ret_items.len() > 0 { trace!( "({}) Checksum comparison RPC: {} different + {} items for {} received", self.table.name, ret_ranges.len(), ret_items.len(), n_checksums ); } Ok(SyncRPC::Difference(ret_ranges, ret_items)) } pub async fn invalidate(self: Arc, item_key: Vec) -> Result<(), Error> { for i in 1..MAX_DEPTH { let needle = SyncRange { begin: item_key.to_vec(), end: vec![], level: i, }; let mut cache = self.cache[i].lock().await; if let Some(cache_entry) = cache.range(..=needle).rev().next() { if cache_entry.0.begin <= item_key && cache_entry.0.end > item_key { let index = cache_entry.0.clone(); drop(cache_entry); cache.remove(&index); } } } Ok(()) } } impl SyncTodo { fn add_full_scan(&mut self, table: &Table) { let my_id = table.system.id.clone(); self.todo.clear(); let ring = table.system.ring.borrow().clone(); let split_points = table.replication.split_points(&ring); for i in 0..split_points.len() - 1 { let begin = split_points[i].clone(); let end = split_points[i + 1].clone(); let nodes = table.replication.replication_nodes(&begin, &ring); let retain = nodes.contains(&my_id); if !retain { // Check if we have some data to send, otherwise skip if table .store .range(begin.clone()..end.clone()) .next() .is_none() { continue; } } self.todo.push(TodoPartition { begin, end, retain }); } } fn add_ring_difference( &mut self, table: &Table, old_ring: &Ring, new_ring: &Ring, ) { let my_id = table.system.id.clone(); // If it is us who are entering or leaving the system, // initiate a full sync instead of incremental sync if old_ring.config.members.contains_key(&my_id) != new_ring.config.members.contains_key(&my_id) { self.add_full_scan(table); return; } let mut all_points = None .into_iter() .chain(table.replication.split_points(old_ring).drain(..)) .chain(table.replication.split_points(new_ring).drain(..)) .chain(self.todo.iter().map(|x| x.begin.clone())) .chain(self.todo.iter().map(|x| x.end.clone())) .collect::>(); all_points.sort(); all_points.dedup(); let mut old_todo = std::mem::replace(&mut self.todo, vec![]); old_todo.sort_by(|x, y| x.begin.cmp(&y.begin)); let mut new_todo = vec![]; for i in 0..all_points.len() - 1 { let begin = all_points[i].clone(); let end = all_points[i + 1].clone(); let was_ours = table .replication .replication_nodes(&begin, &old_ring) .contains(&my_id); let is_ours = table .replication .replication_nodes(&begin, &new_ring) .contains(&my_id); let was_todo = match old_todo.binary_search_by(|x| x.begin.cmp(&begin)) { Ok(_) => true, Err(j) => { (j > 0 && old_todo[j - 1].begin < end && begin < old_todo[j - 1].end) || (j < old_todo.len() && old_todo[j].begin < end && begin < old_todo[j].end) } }; if was_todo || (is_ours && !was_ours) || (was_ours && !is_ours) { new_todo.push(TodoPartition { begin, end, retain: is_ours, }); } } self.todo = new_todo; } fn pop_task(&mut self) -> Option { if self.todo.is_empty() { return None; } let i = rand::thread_rng().gen_range::(0, self.todo.len()); if i == self.todo.len() - 1 { self.todo.pop() } else { let replacement = self.todo.pop().unwrap(); let ret = std::mem::replace(&mut self.todo[i], replacement); Some(ret) } } }