table sync: adapt to new layout history

src/rpc/layout/history.rs

@@ -47,11 +47,19 @@ impl LayoutHistory {
 
 	// ------------------ who stores what now? ---------------
 
-	pub fn max_ack(&self) -> u64 {
+	pub fn all_ack(&self) -> u64 {
 		self.calculate_global_min(&self.update_trackers.ack_map)
 	}
 
-	pub fn all_storage_nodes(&self) -> HashSet<Uuid> {
+	pub fn min_stored(&self) -> u64 {
+		self.versions.first().as_ref().unwrap().version
+	}
+
+	pub fn sync_versions(&self) -> (u64, u64, u64) {
+		(self.current().version, self.all_ack(), self.min_stored())
+	}
+
+	pub fn all_nongateway_nodes(&self) -> HashSet<Uuid> {
 		// TODO: cache this
 		self.versions
 			.iter()
@@ -71,11 +79,10 @@ impl LayoutHistory {
 		version.nodes_of(position, version.replication_factor)
 	}
 
-	pub fn write_sets_of(&self, position: &Hash) -> Vec<Vec<Uuid>> {
+	pub fn write_sets_of<'a>(&'a self, position: &'a Hash) -> impl Iterator<Item = Vec<Uuid>> + 'a {
 		self.versions
 			.iter()
-			.map(|x| x.nodes_of(position, x.replication_factor))
-			.collect::<Vec<_>>()
+			.map(move |x| x.nodes_of(position, x.replication_factor))
 	}
 
 	// ------------------ update tracking ---------------
@@ -129,7 +136,9 @@ impl LayoutHistory {
 	}
 
 	pub(crate) fn calculate_global_min(&self, tracker: &UpdateTracker) -> u64 {
-		let storage_nodes = self.all_storage_nodes();
+		// TODO: for TableFullReplication, counting gateway nodes might be
+		// necessary? Think about this more.
+		let storage_nodes = self.all_nongateway_nodes();
 		storage_nodes
 			.iter()
 			.map(|x| tracker.0.get(x).copied().unwrap_or(0))

src/rpc/layout/manager.rs

@@ -92,6 +92,7 @@ impl LayoutManager {
 			persist_cluster_layout,
 			layout,
 			change_notify,
+			table_sync_version: Mutex::new(HashMap::new()),
 			system_endpoint,
 			rpc_helper,
 		}))

src/rpc/layout/version.rs

@@ -98,15 +98,13 @@ impl LayoutVersion {
 	}
 
 	/// Get the list of partitions and the first hash of a partition key that would fall in it
-	pub fn partitions(&self) -> Vec<(Partition, Hash)> {
-		(0..(1 << PARTITION_BITS))
-			.map(|i| {
-				let top = (i as u16) << (16 - PARTITION_BITS);
-				let mut location = [0u8; 32];
-				location[..2].copy_from_slice(&u16::to_be_bytes(top)[..]);
-				(i as u16, Hash::from(location))
-			})
-			.collect::<Vec<_>>()
+	pub fn partitions(&self) -> impl Iterator<Item = (Partition, Hash)> + '_ {
+		(0..(1 << PARTITION_BITS)).map(|i| {
+			let top = (i as u16) << (16 - PARTITION_BITS);
+			let mut location = [0u8; 32];
+			location[..2].copy_from_slice(&u16::to_be_bytes(top)[..]);
+			(i as u16, Hash::from(location))
+		})
 	}
 
 	/// Return the n servers in which data for this hash should be replicated

src/rpc/system.rs

@@ -442,7 +442,7 @@ impl System {
 			.filter(|(x, _, _)| nodes.get(x).map(|n| n.is_up).unwrap_or(false))
 			.count();
 
-		let partitions = layout.current().partitions();
+		let partitions = layout.current().partitions().collect::<Vec<_>>();
 		let partitions_n_up = partitions
 			.iter()
 			.map(|(_, h)| {

src/table/replication/fullcopy.rs

@@ -1,3 +1,4 @@
+use std::iter::FromIterator;
 use std::sync::Arc;
 
 use garage_rpc::layout::*;
@@ -6,10 +7,17 @@ use garage_util::data::*;
 
 use crate::replication::*;
 
+// TODO: find a way to track layout changes for this as well
+// The hard thing is that this data is stored also on gateway nodes,
+// whereas sharded data is stored only on non-Gateway nodes (storage nodes)
+// Also we want to be more tolerant to failures of gateways so we don't
+// want to do too much holding back of data when progress of gateway
+// nodes is not reported in the layout history's ack/sync/sync_ack maps.
+
 /// Full replication schema: all nodes store everything
-/// Writes are disseminated in an epidemic manner in the network
 /// Advantage: do all reads locally, extremely fast
 /// Inconvenient: only suitable to reasonably small tables
+/// Inconvenient: if some writes fail, nodes will read outdated data
 #[derive(Clone)]
 pub struct TableFullReplication {
 	/// The membership manager of this node
@@ -44,7 +52,18 @@ impl TableReplication for TableFullReplication {
 	fn partition_of(&self, _hash: &Hash) -> Partition {
 		0u16
 	}
-	fn partitions(&self) -> Vec<(Partition, Hash)> {
-		vec![(0u16, [0u8; 32].into())]
+
+	fn sync_partitions(&self) -> SyncPartitions {
+		let layout = self.system.cluster_layout();
+		let layout_version = layout.current().version;
+		SyncPartitions {
+			layout_version,
+			partitions: vec![SyncPartition {
+				partition: 0u16,
+				first_hash: [0u8; 32].into(),
+				last_hash: [0xff; 32].into(),
+				storage_nodes: Vec::from_iter(layout.current().node_ids().to_vec()),
+			}],
+		}
 	}
 }

src/table/replication/parameters.rs

@@ -20,6 +20,21 @@ pub trait TableReplication: Send + Sync + 'static {
 	// Accessing partitions, for Merkle tree & sync
 	/// Get partition for data with given hash
 	fn partition_of(&self, hash: &Hash) -> Partition;
-	/// List of existing partitions
-	fn partitions(&self) -> Vec<(Partition, Hash)>;
+
+	/// List of partitions and nodes to sync with in current layout
+	fn sync_partitions(&self) -> SyncPartitions;
+}
+
+#[derive(Debug)]
+pub struct SyncPartitions {
+	pub layout_version: u64,
+	pub partitions: Vec<SyncPartition>,
+}
+
+#[derive(Debug)]
+pub struct SyncPartition {
+	pub partition: Partition,
+	pub first_hash: Hash,
+	pub last_hash: Hash,
+	pub storage_nodes: Vec<Uuid>,
 }

src/table/replication/sharded.rs

@@ -51,7 +51,42 @@ impl TableReplication for TableShardedReplication {
 	fn partition_of(&self, hash: &Hash) -> Partition {
 		self.system.cluster_layout().current().partition_of(hash)
 	}
-	fn partitions(&self) -> Vec<(Partition, Hash)> {
-		self.system.cluster_layout().current().partitions()
+
+	fn sync_partitions(&self) -> SyncPartitions {
+		let layout = self.system.cluster_layout();
+		let layout_version = layout.all_ack();
+
+		let mut partitions = layout
+			.current()
+			.partitions()
+			.map(|(partition, first_hash)| {
+				let mut storage_nodes = layout
+					.write_sets_of(&first_hash)
+					.map(|x| x.into_iter())
+					.flatten()
+					.collect::<Vec<_>>();
+				storage_nodes.sort();
+				storage_nodes.dedup();
+				SyncPartition {
+					partition,
+					first_hash,
+					last_hash: [0u8; 32].into(), // filled in just after
+					storage_nodes,
+				}
+			})
+			.collect::<Vec<_>>();
+
+		for i in 0..partitions.len() {
+			partitions[i].last_hash = if i + 1 < partitions.len() {
+				partitions[i + 1].first_hash
+			} else {
+				[0xFFu8; 32].into()
+			};
+		}
+
+		SyncPartitions {
+			layout_version,
+			partitions,
+		}
 	}
 }

src/table/sync.rs

@@ -6,7 +6,7 @@ use arc_swap::ArcSwapOption;
 use async_trait::async_trait;
 use futures_util::stream::*;
 use opentelemetry::KeyValue;
-use rand::Rng;
+use rand::prelude::*;
 use serde::{Deserialize, Serialize};
 use serde_bytes::ByteBuf;
 use tokio::select;
@@ -52,16 +52,6 @@ impl Rpc for SyncRpc {
 	type Response = Result<SyncRpc, Error>;
 }
 
-#[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: TableSchema, R: TableReplication> TableSyncer<F, R> {
 	pub(crate) fn new(
 		system: Arc<System>,
@@ -92,9 +82,9 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 		bg.spawn_worker(SyncWorker {
 			syncer: self.clone(),
 			layout_notify: self.system.layout_notify(),
-			layout_version: self.system.cluster_layout().current().version,
+			layout_versions: self.system.cluster_layout().sync_versions(),
 			add_full_sync_rx,
-			todo: vec![],
+			todo: None,
 			next_full_sync: Instant::now() + Duration::from_secs(20),
 		});
 	}
@@ -112,31 +102,26 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 
 	async fn sync_partition(
 		self: &Arc<Self>,
-		partition: &TodoPartition,
+		partition: &SyncPartition,
 		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<_>>();
+		let my_id = self.system.id;
+		let retain = partition.storage_nodes.contains(&my_id);
 
+		if retain {
 			debug!(
 				"({}) Syncing {:?} with {:?}...",
 				F::TABLE_NAME,
 				partition,
-				nodes
+				partition.storage_nodes
 			);
-			let mut sync_futures = nodes
+			let mut sync_futures = partition
+				.storage_nodes
 				.iter()
+				.filter(|node| **node != my_id)
 				.map(|node| {
 					self.clone()
-						.do_sync_with(partition.clone(), *node, must_exit.clone())
+						.do_sync_with(&partition, *node, must_exit.clone())
 				})
 				.collect::<FuturesUnordered<_>>();
 
@@ -147,14 +132,14 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 					warn!("({}) Sync error: {}", F::TABLE_NAME, e);
 				}
 			}
-			if n_errors > self.data.replication.max_write_errors() {
+			if n_errors > 0 {
 				return Err(Error::Message(format!(
-					"Sync failed with too many nodes (should have been: {:?}).",
-					nodes
+					"Sync failed with {} nodes.",
+					n_errors
 				)));
 			}
 		} else {
-			self.offload_partition(&partition.begin, &partition.end, must_exit)
+			self.offload_partition(&partition.first_hash, &partition.last_hash, must_exit)
 				.await?;
 		}
 
@@ -285,7 +270,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 
 	async fn do_sync_with(
 		self: Arc<Self>,
-		partition: TodoPartition,
+		partition: &SyncPartition,
 		who: Uuid,
 		must_exit: watch::Receiver<bool>,
 	) -> Result<(), Error> {
@@ -492,76 +477,23 @@ impl<F: TableSchema, R: TableReplication> EndpointHandler<SyncRpc> for TableSync
 
 struct SyncWorker<F: TableSchema, R: TableReplication> {
 	syncer: Arc<TableSyncer<F, R>>,
+
 	layout_notify: Arc<Notify>,
-	layout_version: u64,
+	layout_versions: (u64, u64, u64),
+
 	add_full_sync_rx: mpsc::UnboundedReceiver<()>,
-	todo: Vec<TodoPartition>,
 	next_full_sync: Instant,
+
+	todo: Option<SyncPartitions>,
 }
 
 impl<F: TableSchema, R: TableReplication> SyncWorker<F, R> {
 	fn add_full_sync(&mut self) {
-		let system = &self.syncer.system;
-		let data = &self.syncer.data;
-
-		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
-				match data.store.range(begin..end) {
-					Ok(mut iter) => {
-						if iter.next().is_none() {
-							continue;
-						}
-					}
-					Err(e) => {
-						warn!("DB error in add_full_sync: {}", e);
-						continue;
-					}
-				}
-			}
-
-			self.todo.push(TodoPartition {
-				partition: partitions[i].0,
-				begin,
-				end,
-				retain,
-			});
-		}
-
+		let mut partitions = self.syncer.data.replication.sync_partitions();
+		partitions.partitions.shuffle(&mut thread_rng());
+		self.todo = Some(partitions);
 		self.next_full_sync = Instant::now() + ANTI_ENTROPY_INTERVAL;
 	}
-
-	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)
-		}
-	}
 }
 
 #[async_trait]
@@ -572,18 +504,46 @@ impl<F: TableSchema, R: TableReplication> Worker for SyncWorker<F, R> {
 
 	fn status(&self) -> WorkerStatus {
 		WorkerStatus {
-			queue_length: Some(self.todo.len() as u64),
+			queue_length: Some(self.todo.as_ref().map(|x| x.partitions.len()).unwrap_or(0) as u64),
 			..Default::default()
 		}
 	}
 
 	async fn work(&mut self, must_exit: &mut watch::Receiver<bool>) -> Result<WorkerState, Error> {
-		if let Some(partition) = self.pop_task() {
-			self.syncer.sync_partition(&partition, must_exit).await?;
-			Ok(WorkerState::Busy)
-		} else {
-			Ok(WorkerState::Idle)
+		if let Some(todo) = &mut self.todo {
+			let partition = todo.partitions.pop().unwrap();
+
+			// process partition
+			if let Err(e) = self.syncer.sync_partition(&partition, must_exit).await {
+				error!(
+					"{}: Failed to sync partition {:?}: {}",
+					F::TABLE_NAME,
+					partition,
+					e
+				);
+				// if error, put partition back at the other side of the queue,
+				// so that other partitions will be tried in the meantime
+				todo.partitions.insert(0, partition);
+				// TODO: returning an error here will cause the background job worker
+				// to delay this task for some time, but maybe we don't want to
+				// delay it if there are lots of failures from nodes that are gone
+				// (we also don't want zero delays as that will cause lots of useless retries)
+				return Err(e);
+			}
+
+			// done
+			if !todo.partitions.is_empty() {
+				return Ok(WorkerState::Busy);
+			}
+
+			self.syncer
+				.system
+				.layout_manager
+				.sync_table_until(F::TABLE_NAME, todo.layout_version);
 		}
+
+		self.todo = None;
+		Ok(WorkerState::Idle)
 	}
 
 	async fn wait_for_work(&mut self) -> WorkerState {
@@ -594,10 +554,16 @@ impl<F: TableSchema, R: TableReplication> Worker for SyncWorker<F, R> {
 				}
 			},
 			_ = self.layout_notify.notified() => {
-				let new_version = self.syncer.system.cluster_layout().current().version;
-				if new_version > self.layout_version {
-					self.layout_version = new_version;
-					debug!("({}) Layout changed, adding full sync to syncer todo list", F::TABLE_NAME);
+				let layout_versions = self.syncer.system.cluster_layout().sync_versions();
+				if layout_versions != self.layout_versions {
+					self.layout_versions = layout_versions;
+					debug!(
+						"({}) Layout versions changed (max={}, ack={}, min stored={}), adding full sync to syncer todo list",
+						F::TABLE_NAME,
+						layout_versions.0,
+						layout_versions.1,
+						layout_versions.2
+					);
 					self.add_full_sync();
 				}
 			},
@@ -605,9 +571,9 @@ impl<F: TableSchema, R: TableReplication> Worker for SyncWorker<F, R> {
 				self.add_full_sync();
 			}
 		}
-		match self.todo.is_empty() {
-			false => WorkerState::Busy,
-			true => WorkerState::Idle,
+		match self.todo.is_some() {
+			true => WorkerState::Busy,
+			false => WorkerState::Idle,
 		}
 	}
 }