use std::collections::VecDeque; use std::sync::{Arc, Mutex}; use std::time::{Duration, Instant}; use futures::select; use futures_util::future::*; use futures_util::stream::*; use rand::Rng; use serde::{Deserialize, Serialize}; use serde_bytes::ByteBuf; use tokio::sync::{mpsc, watch}; use garage_util::data::*; use garage_util::error::Error; use garage_rpc::membership::System; use garage_rpc::ring::*; use garage_rpc::rpc_client::*; use garage_rpc::rpc_server::*; use crate::data::*; use crate::merkle::*; use crate::replication::*; use crate::*; const TABLE_SYNC_RPC_TIMEOUT: Duration = Duration::from_secs(30); // Do anti-entropy every 10 minutes const ANTI_ENTROPY_INTERVAL: Duration = Duration::from_secs(10 * 60); pub struct TableSyncer<F: TableSchema, R: TableReplication> { system: Arc<System>, data: Arc<TableData<F, R>>, merkle: Arc<MerkleUpdater<F, R>>, todo: Mutex<SyncTodo>, rpc_client: Arc<RpcClient<SyncRPC>>, } #[derive(Serialize, Deserialize)] pub(crate) enum SyncRPC { RootCkHash(Partition, Hash), RootCkDifferent(bool), GetNode(MerkleNodeKey), Node(MerkleNodeKey, MerkleNode), Items(Vec<Arc<ByteBuf>>), Ok, } impl RpcMessage for SyncRPC {} struct SyncTodo { todo: Vec<TodoPartition>, } #[derive(Debug, Clone)] struct TodoPartition { partition: Partition, begin: Hash, end: Hash, // Are we a node that stores this partition or not? retain: bool, } impl<F, R> TableSyncer<F, R> where F: TableSchema + 'static, R: TableReplication + 'static, { pub(crate) fn launch( system: Arc<System>, data: Arc<TableData<F, R>>, merkle: Arc<MerkleUpdater<F, R>>, rpc_server: &mut RpcServer, ) -> Arc<Self> { let rpc_path = format!("table_{}/sync", data.name); let rpc_client = system.rpc_client::<SyncRPC>(&rpc_path); let todo = SyncTodo { todo: vec![] }; let syncer = Arc::new(Self { system: system.clone(), data: data.clone(), merkle, todo: Mutex::new(todo), rpc_client, }); syncer.register_handler(rpc_server, rpc_path); let (busy_tx, busy_rx) = mpsc::unbounded_channel(); let s1 = syncer.clone(); system.background.spawn_worker( format!("table sync watcher for {}", data.name), move |must_exit: watch::Receiver<bool>| s1.watcher_task(must_exit, busy_rx), ); let s2 = syncer.clone(); system.background.spawn_worker( format!("table syncer for {}", data.name), move |must_exit: watch::Receiver<bool>| s2.syncer_task(must_exit, busy_tx), ); let s3 = syncer.clone(); tokio::spawn(async move { tokio::time::sleep(Duration::from_secs(20)).await; s3.add_full_sync(); }); syncer } fn register_handler(self: &Arc<Self>, rpc_server: &mut RpcServer, path: String) { let self2 = self.clone(); rpc_server.add_handler::<SyncRPC, _, _>(path, move |msg, _addr| { let self2 = self2.clone(); async move { self2.handle_rpc(&msg).await } }); let self2 = self.clone(); self.rpc_client .set_local_handler(self.system.id, move |msg| { let self2 = self2.clone(); async move { self2.handle_rpc(&msg).await } }); } async fn watcher_task( self: Arc<Self>, mut must_exit: watch::Receiver<bool>, mut busy_rx: mpsc::UnboundedReceiver<bool>, ) { let mut prev_ring: Arc<Ring> = self.system.ring.borrow().clone(); let mut ring_recv: watch::Receiver<Arc<Ring>> = self.system.ring.clone(); let mut nothing_to_do_since = Some(Instant::now()); while !*must_exit.borrow() { select! { _ = ring_recv.changed().fuse() => { let new_ring = ring_recv.borrow(); if !Arc::ptr_eq(&new_ring, &prev_ring) { debug!("({}) Ring changed, adding full sync to syncer todo list", self.data.name); self.add_full_sync(); prev_ring = new_ring.clone(); } } busy_opt = busy_rx.recv().fuse() => { 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.changed().fuse() => (), _ = tokio::time::sleep(Duration::from_secs(1)).fuse() => { if nothing_to_do_since.map(|t| Instant::now() - t >= ANTI_ENTROPY_INTERVAL).unwrap_or(false) { nothing_to_do_since = None; debug!("({}) Interval passed, adding full sync to syncer todo list", self.data.name); self.add_full_sync(); } } } } } pub fn add_full_sync(&self) { self.todo .lock() .unwrap() .add_full_sync(&self.data, &self.system); } async fn syncer_task( self: Arc<Self>, mut must_exit: watch::Receiver<bool>, busy_tx: mpsc::UnboundedSender<bool>, ) { while !*must_exit.borrow() { let task = self.todo.lock().unwrap().pop_task(); if let Some(partition) = task { busy_tx.send(true).unwrap(); let res = self .clone() .sync_partition(&partition, &mut must_exit) .await; if let Err(e) = res { warn!( "({}) Error while syncing {:?}: {}", self.data.name, partition, e ); } } else { busy_tx.send(false).unwrap(); tokio::time::sleep(Duration::from_secs(1)).await; } } } async fn sync_partition( self: Arc<Self>, partition: &TodoPartition, must_exit: &mut watch::Receiver<bool>, ) -> Result<(), Error> { if partition.retain { let my_id = self.system.id; let nodes = self .data .replication .write_nodes(&partition.begin) .into_iter() .filter(|node| *node != my_id) .collect::<Vec<_>>(); debug!( "({}) Syncing {:?} with {:?}...", self.data.name, partition, nodes ); let mut sync_futures = nodes .iter() .map(|node| { self.clone() .do_sync_with(partition.clone(), *node, must_exit.clone()) }) .collect::<FuturesUnordered<_>>(); 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.data.name, e); } } if n_errors > self.data.replication.max_write_errors() { return Err(Error::Message(format!( "Sync failed with too many nodes (should have been: {:?}).", nodes ))); } } else { self.offload_partition(&partition.begin, &partition.end, must_exit) .await?; } Ok(()) } // Offload partition: this partition is not something we are storing, // so send it out to all other nodes that store it and delete items locally. // We don't bother checking if the remote nodes already have the items, // we just batch-send everything. Offloading isn't supposed to happen very often. // If any of the nodes that are supposed to store the items is unable to // save them, we interrupt the process. async fn offload_partition( self: &Arc<Self>, begin: &Hash, end: &Hash, must_exit: &mut watch::Receiver<bool>, ) -> Result<(), Error> { let mut counter: usize = 0; while !*must_exit.borrow() { let mut items = Vec::new(); for item in self.data.store.range(begin.to_vec()..end.to_vec()) { let (key, value) = item?; items.push((key.to_vec(), Arc::new(ByteBuf::from(value.as_ref())))); if items.len() >= 1024 { break; } } if items.len() > 0 { let nodes = self .data .replication .write_nodes(&begin) .into_iter() .collect::<Vec<_>>(); if nodes.contains(&self.system.id) { warn!( "({}) Interrupting offload as partitions seem to have changed", self.data.name ); break; } if nodes.len() < self.data.replication.write_quorum() { return Err(Error::Message(format!( "Not offloading as we don't have a quorum of nodes to write to." ))); } counter += 1; info!( "({}) Offloading {} items from {:?}..{:?} ({})", self.data.name, items.len(), begin, end, counter ); self.offload_items(&items, &nodes[..]).await?; } else { break; } } Ok(()) } async fn offload_items( self: &Arc<Self>, items: &Vec<(Vec<u8>, Arc<ByteBuf>)>, nodes: &[UUID], ) -> Result<(), Error> { let values = items.iter().map(|(_k, v)| v.clone()).collect::<Vec<_>>(); self.rpc_client .try_call_many( &nodes[..], SyncRPC::Items(values), RequestStrategy::with_quorum(nodes.len()).with_timeout(TABLE_SYNC_RPC_TIMEOUT), ) .await?; // All remote nodes have written those items, now we can delete them locally let mut not_removed = 0; for (k, v) in items.iter() { if !self.data.delete_if_equal(&k[..], &v[..])? { not_removed += 1; } } if not_removed > 0 { debug!("({}) {} items not removed during offload because they changed in between (trying again...)", self.data.name, not_removed); } Ok(()) } // ======= SYNCHRONIZATION PROCEDURE -- DRIVER SIDE ====== // The driver side is only concerned with sending out the item it has // and the other side might not have. Receiving items that differ from one // side to the other will happen when the other side syncs with us, // which they also do regularly. fn get_root_ck(&self, partition: Partition) -> Result<(MerkleNodeKey, MerkleNode), Error> { let key = MerkleNodeKey { partition, prefix: vec![], }; let node = self.merkle.read_node(&key)?; Ok((key, node)) } async fn do_sync_with( self: Arc<Self>, partition: TodoPartition, who: UUID, must_exit: watch::Receiver<bool>, ) -> Result<(), Error> { let (root_ck_key, root_ck) = self.get_root_ck(partition.partition)?; if root_ck.is_empty() { debug!( "({}) Sync {:?} with {:?}: partition is empty.", self.data.name, partition, who ); return Ok(()); } let root_ck_hash = hash_of::<MerkleNode>(&root_ck)?; // Check if they have the same root checksum // If so, do nothing. let root_resp = self .rpc_client .call( who, SyncRPC::RootCkHash(partition.partition, root_ck_hash), TABLE_SYNC_RPC_TIMEOUT, ) .await?; let mut todo = match root_resp { SyncRPC::RootCkDifferent(false) => { debug!( "({}) Sync {:?} with {:?}: no difference", self.data.name, partition, who ); return Ok(()); } SyncRPC::RootCkDifferent(true) => VecDeque::from(vec![root_ck_key]), x => { return Err(Error::Message(format!( "Invalid respone to RootCkHash RPC: {}", debug_serialize(x) ))); } }; let mut todo_items = vec![]; while !todo.is_empty() && !*must_exit.borrow() { let key = todo.pop_front().unwrap(); let node = self.merkle.read_node(&key)?; match node { MerkleNode::Empty => { // They have items we don't have. // We don't request those items from them, they will send them. // We only bother with pushing items that differ } MerkleNode::Leaf(ik, ivhash) => { // Just send that item directly if let Some(val) = self.data.store.get(&ik[..])? { if blake2sum(&val[..]) != ivhash { warn!("({}) Hashes differ between stored value and Merkle tree, key: {:?} (if your server is very busy, don't worry, this happens when the Merkle tree can't be updated fast enough)", self.data.name, ik); } todo_items.push(val.to_vec()); } else { warn!("({}) Item from Merkle tree not found in store: {:?} (if your server is very busy, don't worry, this happens when the Merkle tree can't be updated fast enough)", self.data.name, ik); } } MerkleNode::Intermediate(l) => { // Get Merkle node for this tree position at remote node // and compare it with local node let remote_node = match self .rpc_client .call(who, SyncRPC::GetNode(key.clone()), TABLE_SYNC_RPC_TIMEOUT) .await? { SyncRPC::Node(_, node) => node, x => { return Err(Error::Message(format!( "Invalid respone to GetNode RPC: {}", debug_serialize(x) ))); } }; let int_l2 = match remote_node { // If they have an intermediate node at this tree position, // we can compare them to find differences MerkleNode::Intermediate(l2) => l2, // Otherwise, treat it as if they have nothing for this subtree, // which will have the consequence of sending them everything _ => vec![], }; let join = join_ordered(&l[..], &int_l2[..]); for (p, v1, v2) in join.into_iter() { let diff = match (v1, v2) { (Some(_), None) | (None, Some(_)) => true, (Some(a), Some(b)) => a != b, _ => false, }; if diff { todo.push_back(key.add_byte(*p)); } } } } if todo_items.len() >= 256 { self.send_items(who, std::mem::replace(&mut todo_items, vec![])) .await?; } } if !todo_items.is_empty() { self.send_items(who, todo_items).await?; } Ok(()) } async fn send_items(&self, who: UUID, item_value_list: Vec<Vec<u8>>) -> Result<(), Error> { info!( "({}) Sending {} items to {:?}", self.data.name, item_value_list.len(), who ); let values = item_value_list .into_iter() .map(|x| Arc::new(ByteBuf::from(x))) .collect::<Vec<_>>(); let rpc_resp = self .rpc_client .call(who, SyncRPC::Items(values), TABLE_SYNC_RPC_TIMEOUT) .await?; if let SyncRPC::Ok = rpc_resp { Ok(()) } else { Err(Error::Message(format!( "Unexpected response to RPC Update: {}", debug_serialize(&rpc_resp) ))) } } // ======= SYNCHRONIZATION PROCEDURE -- RECEIVER SIDE ====== async fn handle_rpc(self: &Arc<Self>, message: &SyncRPC) -> Result<SyncRPC, Error> { match message { SyncRPC::RootCkHash(range, h) => { let (_root_ck_key, root_ck) = self.get_root_ck(*range)?; let hash = hash_of::<MerkleNode>(&root_ck)?; Ok(SyncRPC::RootCkDifferent(hash != *h)) } SyncRPC::GetNode(k) => { let node = self.merkle.read_node(&k)?; Ok(SyncRPC::Node(k.clone(), node)) } SyncRPC::Items(items) => { self.data.update_many(items)?; Ok(SyncRPC::Ok) } _ => Err(Error::Message(format!("Unexpected sync RPC"))), } } } impl SyncTodo { fn add_full_sync<F: TableSchema, R: TableReplication>( &mut self, data: &TableData<F, R>, system: &System, ) { let my_id = system.id; self.todo.clear(); let partitions = data.replication.partitions(); for i in 0..partitions.len() { let begin = partitions[i].1; let end = if i + 1 < partitions.len() { partitions[i + 1].1 } else { [0xFFu8; 32].into() }; let nodes = data.replication.write_nodes(&begin); let retain = nodes.contains(&my_id); if !retain { // Check if we have some data to send, otherwise skip if data.store.range(begin..end).next().is_none() { continue; } } self.todo.push(TodoPartition { partition: partitions[i].0, begin, end, retain, }); } } fn pop_task(&mut self) -> Option<TodoPartition> { 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) } } } fn hash_of<T: Serialize>(x: &T) -> Result<Hash, Error> { Ok(blake2sum(&rmp_to_vec_all_named(x)?[..])) } fn join_ordered<'a, K: Ord + Eq, V1, V2>( x: &'a [(K, V1)], y: &'a [(K, V2)], ) -> Vec<(&'a K, Option<&'a V1>, Option<&'a V2>)> { let mut ret = vec![]; let mut i = 0; let mut j = 0; while i < x.len() || j < y.len() { if i < x.len() && j < y.len() && x[i].0 == y[j].0 { ret.push((&x[i].0, Some(&x[i].1), Some(&y[j].1))); i += 1; j += 1; } else if i < x.len() && (j == y.len() || x[i].0 < y[j].0) { ret.push((&x[i].0, Some(&x[i].1), None)); i += 1; } else if j < y.len() && (i == x.len() || x[i].0 > y[j].0) { ret.push((&y[j].0, None, Some(&y[j].1))); j += 1; } else { unreachable!(); } } ret }