use std::collections::VecDeque; use std::convert::TryInto; use std::sync::{Arc, Mutex}; use std::time::{Duration, Instant}; use futures::future::join_all; use futures::{pin_mut, 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_rpc::ring::Ring; use garage_util::data::*; use garage_util::error::Error; 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 { data: Arc>, aux: Arc>, todo: Mutex, } type RootCk = Vec<(MerklePartition, Hash)>; #[derive(Debug, Clone, Copy, Serialize, Deserialize)] pub struct PartitionRange { begin: MerklePartition, // if end is None, go all the way to partition 0xFFFF included end: Option, } #[derive(Serialize, Deserialize)] pub(crate) enum SyncRPC { RootCkHash(PartitionRange, Hash), RootCkList(PartitionRange, RootCk), CkNoDifference, GetNode(MerkleNodeKey), Node(MerkleNodeKey, MerkleNode), } struct SyncTodo { todo: Vec, } #[derive(Debug, Clone)] struct TodoPartition { range: PartitionRange, // Are we a node that stores this partition or not? retain: bool, } impl TableSyncer where F: TableSchema + 'static, R: TableReplication + 'static, { pub(crate) fn launch(data: Arc>, aux: Arc>) -> Arc { let todo = SyncTodo { todo: vec![] }; let syncer = Arc::new(Self { data: data.clone(), aux: aux.clone(), todo: Mutex::new(todo), }); let (busy_tx, busy_rx) = mpsc::unbounded_channel(); let s1 = syncer.clone(); aux.system.background.spawn_worker( format!("table sync watcher for {}", data.name), move |must_exit: watch::Receiver| s1.watcher_task(must_exit, busy_rx), ); let s2 = syncer.clone(); aux.system.background.spawn_worker( format!("table syncer for {}", data.name), move |must_exit: watch::Receiver| s2.syncer_task(must_exit, busy_tx), ); let s3 = syncer.clone(); tokio::spawn(async move { tokio::time::delay_for(Duration::from_secs(20)).await; s3.add_full_sync(); }); syncer } async fn watcher_task( self: Arc, mut must_exit: watch::Receiver, mut busy_rx: mpsc::UnboundedReceiver, ) -> Result<(), Error> { let mut ring_recv: watch::Receiver> = self.aux.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 new_ring_r.is_some() { debug!("({}) Ring changed, adding full sync to syncer todo list", self.data.name); self.add_full_sync(); } } 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 >= 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(); } } } } Ok(()) } pub fn add_full_sync(&self) { self.todo .lock() .unwrap() .add_full_sync(&self.data, &self.aux); } async fn syncer_task( self: Arc, mut must_exit: watch::Receiver, busy_tx: mpsc::UnboundedSender, ) -> Result<(), Error> { while !*must_exit.borrow() { let task = self.todo.lock().unwrap().pop_task(); if let Some(partition) = 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.data.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> { if partition.retain { let my_id = self.aux.system.id; let nodes = self .aux .replication .write_nodes( &hash_of_merkle_partition(partition.range.begin), &self.aux.system, ) .into_iter() .filter(|node| *node != my_id) .collect::>(); 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::>(); 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.aux.replication.max_write_errors() { return Err(Error::Message(format!( "Sync failed with too many nodes (should have been: {:?}).", nodes ))); } } else { self.offload_partition( &hash_of_merkle_partition(partition.range.begin), &hash_of_merkle_partition_opt(partition.range.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, begin: &Hash, end: &Hash, must_exit: &mut watch::Receiver, ) -> 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 .aux .replication .write_nodes(&begin, &self.aux.system) .into_iter() .collect::>(); if nodes.contains(&self.aux.system.id) { warn!("Interrupting offload as partitions seem to have changed"); break; } if nodes.len() < self.aux.replication.write_quorum(&self.aux.system) { return Err(Error::Message(format!("Not offloading as we don't have a quorum of nodes to write to."))); } counter += 1; debug!( "Offloading {} items from {:?}..{:?} ({})", items.len(), begin, end, counter ); self.offload_items(&items, &nodes[..]).await?; } else { break; } } Ok(()) } async fn offload_items( self: &Arc, items: &Vec<(Vec, Arc)>, nodes: &[UUID], ) -> Result<(), Error> { let values = items.iter().map(|(_k, v)| v.clone()).collect::>(); let update_msg = Arc::new(TableRPC::::Update(values)); for res in join_all(nodes.iter().map(|to| { self.aux .rpc_client .call_arc(*to, update_msg.clone(), TABLE_SYNC_RPC_TIMEOUT) })) .await { res?; } // 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...)", 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, range: PartitionRange) -> Result { let begin = u16::from_be_bytes(range.begin); let range_iter = match range.end { Some(end) => { let end = u16::from_be_bytes(end); begin..=(end - 1) } None => begin..=0xFFFF, }; let mut ret = vec![]; for i in range_iter { let key = MerkleNodeKey { partition: u16::to_be_bytes(i), prefix: vec![], }; match self.data.merkle_updater.read_node(&key)? { MerkleNode::Empty => (), x => { ret.push((key.partition, hash_of(&x)?)); } } } Ok(ret) } async fn do_sync_with( self: Arc, partition: TodoPartition, who: UUID, must_exit: watch::Receiver, ) -> Result<(), Error> { let root_ck = self.get_root_ck(partition.range)?; let root_ck_hash = hash_of(&root_ck)?; // If their root checksum has level > than us, use that as a reference let root_resp = self .aux .rpc_client .call( who, TableRPC::::SyncRPC(SyncRPC::RootCkHash(partition.range, root_ck_hash)), TABLE_SYNC_RPC_TIMEOUT, ) .await?; let mut todo = match root_resp { TableRPC::::SyncRPC(SyncRPC::CkNoDifference) => { debug!( "({}) Sync {:?} with {:?}: no difference", self.data.name, partition, who ); return Ok(()); } TableRPC::::SyncRPC(SyncRPC::RootCkList(_, their_root_ck)) => { let join = join_ordered(&root_ck[..], &their_root_ck[..]); let mut todo = VecDeque::new(); for (p, v1, v2) in join.iter() { let diff = match (v1, v2) { (Some(_), None) | (None, Some(_)) => true, (Some(a), Some(b)) => a != b, _ => false, }; if diff { todo.push_back(MerkleNodeKey { partition: **p, prefix: vec![], }); } } debug!( "({}) Sync {:?} with {:?}: todo.len() = {}", self.data.name, partition, who, todo.len() ); todo } 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.data.merkle_updater.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)", 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)", 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 .aux .rpc_client .call( who, TableRPC::::SyncRPC(SyncRPC::GetNode(key.clone())), TABLE_SYNC_RPC_TIMEOUT, ) .await? { TableRPC::::SyncRPC(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>) -> 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::>(); let rpc_resp = self .aux .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) ))) } } // ======= SYNCHRONIZATION PROCEDURE -- RECEIVER SIDE ====== pub(crate) async fn handle_rpc(self: &Arc, message: &SyncRPC) -> Result { match message { SyncRPC::RootCkHash(range, h) => { let root_ck = self.get_root_ck(*range)?; let hash = hash_of(&root_ck)?; if hash == *h { Ok(SyncRPC::CkNoDifference) } else { Ok(SyncRPC::RootCkList(*range, root_ck)) } } SyncRPC::GetNode(k) => { let node = self.data.merkle_updater.read_node(&k)?; Ok(SyncRPC::Node(k.clone(), node)) } _ => Err(Error::Message(format!("Unexpected sync RPC"))), } } } impl SyncTodo { fn add_full_sync( &mut self, data: &TableData, aux: &TableAux, ) { let my_id = aux.system.id; self.todo.clear(); let ring = aux.system.ring.borrow().clone(); let split_points = aux.replication.split_points(&ring); for i in 0..split_points.len() { let begin: MerklePartition = { let b = split_points[i]; assert_eq!(b.as_slice()[2..], [0u8; 30][..]); b.as_slice()[..2].try_into().unwrap() }; let end: Option = if i + 1 < split_points.len() { let e = split_points[i + 1]; assert_eq!(e.as_slice()[2..], [0u8; 30][..]); Some(e.as_slice()[..2].try_into().unwrap()) } else { None }; let begin_hash = hash_of_merkle_partition(begin); let end_hash = hash_of_merkle_partition_opt(end); let nodes = aux.replication.replication_nodes(&begin_hash, &ring); let retain = nodes.contains(&my_id); if !retain { // Check if we have some data to send, otherwise skip if data.store.range(begin_hash..end_hash).next().is_none() { continue; } } self.todo.push(TodoPartition { range: PartitionRange { begin, end }, retain, }); } } 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) } } } fn hash_of(x: &T) -> Result { 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((&x[i].0, None, Some(&y[j].1))); j += 1; } else { unreachable!(); } } ret }