Several changes in table_sync:

- separate path for case of offloading a partition we don't store
- use sync::Mutex instead of tokio::Mutex, make less fn's async

src/table/table.rs

@@ -435,7 +435,7 @@ where
 		let syncer = self.syncer.load_full().unwrap();
 
 		debug!("({}) Deleting range {:?} - {:?}", self.name, begin, end);
-		let mut count = 0;
+		let mut count: usize = 0;
 		while let Some((key, _value)) = self.store.get_lt(end.as_slice())? {
 			if key.as_ref() < begin.as_slice() {
 				break;

src/table/table_sync.rs

@@ -1,15 +1,14 @@
 use rand::Rng;
 use std::collections::{BTreeMap, VecDeque};
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 use std::time::{Duration, Instant};
 
-use futures::future::BoxFuture;
+use futures::future::join_all;
 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 garage_rpc::ring::Ring;
@@ -33,7 +32,7 @@ pub struct TableSyncer<F: TableSchema, R: TableReplication> {
 pub enum SyncRPC {
 	GetRootChecksumRange(Hash, Hash),
 	RootChecksumRange(SyncRange),
-	Checksums(Vec<RangeChecksum>, bool),
+	Checksums(Vec<RangeChecksum>),
 	Difference(Vec<SyncRange>, Vec<Arc<ByteBuf>>),
 }
 
@@ -43,8 +42,11 @@ pub struct SyncTodo {
 
 #[derive(Debug, Clone)]
 struct TodoPartition {
+	// Partition consists in hashes between begin included and end excluded
 	begin: Hash,
 	end: Hash,
+
+	// Are we a node that stores this partition or not?
 	retain: bool,
 }
 
@@ -161,7 +163,7 @@ where
 				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);
+						self.todo.lock().unwrap().add_ring_difference(&self.table, &prev_ring, &new_ring);
 						prev_ring = new_ring;
 					}
 				}
@@ -194,7 +196,7 @@ where
 	}
 
 	pub async fn add_full_scan(&self) {
-		self.todo.lock().await.add_full_scan(&self.table);
+		self.todo.lock().unwrap().add_full_scan(&self.table);
 	}
 
 	async fn syncer_task(
@@ -203,7 +205,8 @@ where
 		busy_tx: mpsc::UnboundedSender<bool>,
 	) -> Result<(), Error> {
 		while !*must_exit.borrow() {
-			if let Some(partition) = self.todo.lock().await.pop_task() {
+			let task = self.todo.lock().unwrap().pop_task();
+			if let Some(partition) = task {
 				busy_tx.send(true)?;
 				let res = self
 					.clone()
@@ -228,6 +231,7 @@ where
 		partition: &TodoPartition,
 		must_exit: &mut watch::Receiver<bool>,
 	) -> Result<(), Error> {
+		if partition.retain {
 			let my_id = self.table.system.id;
 			let nodes = self
 				.table
@@ -241,9 +245,7 @@ where
 				"({}) Preparing to sync {:?} with {:?}...",
 				self.table.name, partition, nodes
 			);
-		let root_cks = self
+			let root_cks = self.root_checksum(&partition.begin, &partition.end, must_exit)?;
-			.root_checksum(&partition.begin, &partition.end, must_exit)
-			.await?;
 
 			let mut sync_futures = nodes
 				.iter()
@@ -252,7 +254,6 @@ where
 						partition.clone(),
 						root_cks.clone(),
 						*node,
-					partition.retain,
 						must_exit.clone(),
 					)
 				})
@@ -271,33 +272,111 @@ where
 					nodes
 				)));
 			}
-
+		} else {
-		if !partition.retain {
+			self.offload_partition(&partition.begin, &partition.end, must_exit)
-			self.table
-				.delete_range(&partition.begin, &partition.end)
 				.await?;
 		}
 
 		Ok(())
 	}
 
-	async fn root_checksum(
+	// 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.table.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
+					.table
+					.replication
+					.write_nodes(&begin, &self.table.system)
+					.into_iter()
+					.collect::<Vec<_>>();
+				if nodes.contains(&self.table.system.id) {
+					warn!("Interrupting offload as partitions seem to have changed");
+					break;
+				}
+
+				counter += 1;
+				debug!("Offloading items from {:?}..{:?} ({})", 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<_>>();
+		let update_msg = Arc::new(TableRPC::<F>::Update(values));
+
+		for res in join_all(nodes.iter().map(|to| {
+			self.table
+				.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
+		for (k, v) in items.iter() {
+			self.table.store.transaction(|tx_db| {
+				if let Some(curv) = tx_db.get(k)? {
+					if curv == &v[..] {
+						tx_db.remove(&k[..])?;
+					}
+				}
+				Ok(())
+			})?;
+		}
+
+		Ok(())
+	}
+
+	fn root_checksum(
 		self: &Arc<Self>,
 		begin: &Hash,
 		end: &Hash,
 		must_exit: &mut watch::Receiver<bool>,
 	) -> Result<RangeChecksum, Error> {
 		for i in 1..MAX_DEPTH {
-			let rc = self
+			let rc = self.range_checksum(
-				.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);
 			}
@@ -307,7 +386,7 @@ where
 		)))
 	}
 
-	async fn range_checksum(
+	fn range_checksum(
 		self: &Arc<Self>,
 		range: &SyncRange,
 		must_exit: &mut watch::Receiver<bool>,
@@ -357,9 +436,7 @@ where
 			};
 			let mut time = Instant::now();
 			while !*must_exit.borrow() {
-				let sub_ck = self
+				let sub_ck = self.range_checksum_cached_hash(&sub_range, must_exit)?;
-					.range_checksum_cached_hash(&sub_range, must_exit)
-					.await?;
 
 				if let Some(hash) = sub_ck.hash {
 					children.push((sub_range.clone(), hash));
@@ -397,22 +474,22 @@ where
 		}
 	}
 
-	fn range_checksum_cached_hash<'a>(
+	fn range_checksum_cached_hash(
-		self: &'a Arc<Self>,
+		self: &Arc<Self>,
-		range: &'a SyncRange,
+		range: &SyncRange,
-		must_exit: &'a mut watch::Receiver<bool>,
+		must_exit: &mut watch::Receiver<bool>,
-	) -> BoxFuture<'a, Result<RangeChecksumCache, Error>> {
+	) -> Result<RangeChecksumCache, Error> {
-		async move {
+		{
-			let mut cache = self.cache[range.level].lock().await;
+			let mut cache = self.cache[range.level].lock().unwrap();
 			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?;
+		let v = self.range_checksum(&range, must_exit)?;
 		trace!(
 			"({}) New checksum calculated for {}-{}/{}, {} children",
 			self.table.name,
@@ -436,19 +513,16 @@ where
 			time: v.time,
 		};
 
-			let mut cache = self.cache[range.level].lock().await;
+		let mut cache = self.cache[range.level].lock().unwrap();
 		cache.insert(range.clone(), cache_entry.clone());
 		Ok(cache_entry)
 	}
-		.boxed()
-	}
 
 	async fn do_sync_with(
 		self: Arc<Self>,
 		partition: TodoPartition,
 		root_ck: RangeChecksum,
 		who: UUID,
-		retain: bool,
 		mut must_exit: watch::Receiver<bool>,
 	) -> Result<(), Error> {
 		let mut todo = VecDeque::new();
@@ -468,7 +542,7 @@ where
 			.await?;
 		if let TableRPC::<F>::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?;
+				let their_root_range_ck = self.range_checksum(&range, &mut must_exit)?;
 				todo.push_back(their_root_range_ck);
 			} else {
 				todo.push_back(root_ck);
@@ -498,7 +572,7 @@ where
 				.rpc_client
 				.call(
 					who,
-					TableRPC::<F>::SyncRPC(SyncRPC::Checksums(step, retain)),
+					TableRPC::<F>::SyncRPC(SyncRPC::Checksums(step)),
 					TABLE_SYNC_RPC_TIMEOUT,
 				)
 				.await?;
@@ -519,11 +593,11 @@ where
 					if differing.level == 0 {
 						items_to_send.push(differing.begin);
 					} else {
-						let checksum = self.range_checksum(&differing, &mut must_exit).await?;
+						let checksum = self.range_checksum(&differing, &mut must_exit)?;
 						todo.push_back(checksum);
 					}
 				}
-				if retain && diff_items.len() > 0 {
+				if diff_items.len() > 0 {
 					self.table.handle_update(&diff_items[..]).await?;
 				}
 				if items_to_send.len() > 0 {
@@ -575,11 +649,11 @@ where
 	) -> Result<SyncRPC, Error> {
 		match message {
 			SyncRPC::GetRootChecksumRange(begin, end) => {
-				let root_cks = self.root_checksum(&begin, &end, &mut must_exit).await?;
+				let root_cks = self.root_checksum(&begin, &end, &mut must_exit)?;
 				Ok(SyncRPC::RootChecksumRange(root_cks.bounds))
 			}
-			SyncRPC::Checksums(checksums, retain) => {
+			SyncRPC::Checksums(checksums) => {
-				self.handle_checksums_rpc(&checksums[..], *retain, &mut must_exit)
+				self.handle_checksums_rpc(&checksums[..], &mut must_exit)
 					.await
 			}
 			_ => Err(Error::Message(format!("Unexpected sync RPC"))),
@@ -589,14 +663,13 @@ where
 	async fn handle_checksums_rpc(
 		self: &Arc<Self>,
 		checksums: &[RangeChecksum],
-		retain: bool,
 		must_exit: &mut watch::Receiver<bool>,
 	) -> Result<SyncRPC, Error> {
 		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?;
+			let our_ckr = self.range_checksum(&their_ckr.bounds, must_exit)?;
 			for (their_range, their_hash) in their_ckr.children.iter() {
 				let differs = match our_ckr
 					.children
@@ -604,9 +677,8 @@ where
 				{
 					Err(_) => {
 						if their_range.level >= 1 {
-							let cached_hash = self
+							let cached_hash =
-								.range_checksum_cached_hash(&their_range, must_exit)
+								self.range_checksum_cached_hash(&their_range, must_exit)?;
-								.await?;
 							cached_hash.hash.map(|h| h != *their_hash).unwrap_or(true)
 						} else {
 							true
@@ -616,7 +688,7 @@ where
 				};
 				if differs {
 					ret_ranges.push(their_range.clone());
-					if retain && their_range.level == 0 {
+					if their_range.level == 0 {
 						if let Some(item_bytes) =
 							self.table.store.get(their_range.begin.as_slice())?
 						{
@@ -640,7 +712,7 @@ where
 					if our_range.level > 0 {
 						ret_ranges.push(our_range.clone());
 					}
-					if retain && our_range.level == 0 {
+					if our_range.level == 0 {
 						if let Some(item_bytes) =
 							self.table.store.get(our_range.begin.as_slice())?
 						{
@@ -673,7 +745,7 @@ where
 				end: vec![],
 				level: i,
 			};
-			let mut cache = self.cache[i].lock().await;
+			let mut cache = self.cache[i].lock().unwrap();
 			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();