WIP

TODOs:
- ensure sync goes both way
- finish sending blocks to other nodes when they need them before deleting

7 files changed, 234 insertions, 112 deletions

diff --git a/src/block.rs b/src/block.rs
index e898ad19..25a10910 100644
--- a/src/block.rs
+++ b/src/block.rs
@@ -6,6 +6,7 @@ use futures::stream::*;
 use tokio::fs;
 use tokio::prelude::*;
 use tokio::sync::{watch, Mutex};
+use arc_swap::ArcSwapOption;
 
 use crate::data;
 use crate::data::*;
@@ -13,6 +14,7 @@ use crate::error::Error;
 use crate::membership::System;
 use crate::proto::*;
 use crate::rpc_client::*;
+use crate::server::Garage;
 
 pub struct BlockManager {
 	pub data_dir: PathBuf,
@@ -20,10 +22,11 @@ pub struct BlockManager {
 	pub resync_queue: sled::Tree,
 	pub lock: Mutex<()>,
 	pub system: Arc<System>,
+	pub garage: ArcSwapOption<Garage>,
 }
 
 impl BlockManager {
-	pub async fn new(db: &sled::Db, data_dir: PathBuf, system: Arc<System>) -> Arc<Self> {
+	pub fn new(db: &sled::Db, data_dir: PathBuf, system: Arc<System>) -> Arc<Self> {
 		let rc = db
 			.open_tree("block_local_rc")
 			.expect("Unable to open block_local_rc tree");
@@ -33,20 +36,23 @@ impl BlockManager {
 			.open_tree("block_local_resync_queue")
 			.expect("Unable to open block_local_resync_queue tree");
 
-		let block_manager = Arc::new(Self {
+		Arc::new(Self {
 			rc,
 			resync_queue,
 			data_dir,
 			lock: Mutex::new(()),
 			system,
-		});
-		let bm2 = block_manager.clone();
-		block_manager
+			garage: ArcSwapOption::from(None),
+		})
+	}
+
+	pub async fn spawn_background_worker(self: Arc<Self>) {
+		let bm2 = self.clone();
+		self
 			.system
 			.background
 			.spawn_worker(move |must_exit| bm2.resync_loop(must_exit))
 			.await;
-		block_manager
 	}
 
 	pub async fn write_block(&self, hash: &Hash, data: &[u8]) -> Result<Message, Error> {
@@ -80,7 +86,7 @@ impl BlockManager {
 			let _lock = self.lock.lock().await;
 			eprintln!("Block {:?} is corrupted. Deleting and resyncing.", hash);
 			fs::remove_file(path).await?;
-			self.resync_queue.insert(hash.to_vec(), vec![1u8])?;
+			self.put_to_resync(&hash, 0)?;
 			return Err(Error::CorruptData(hash.clone()));
 		}
 
@@ -98,38 +104,55 @@ impl BlockManager {
 	}
 
 	pub fn block_incref(&self, hash: &Hash) -> Result<(), Error> {
-		self.rc.merge(&hash, vec![1])?;
+		let new_rc = self.rc.merge(&hash, vec![1])?;
+		if new_rc.map(|x| u64_from_bytes(&x[..]) == 0).unwrap_or(true) {
+			self.put_to_resync(&hash, BLOCK_RW_TIMEOUT.as_millis() as u64)?;
+		}
 		Ok(())
 	}
 
 	pub fn block_decref(&self, hash: &Hash) -> Result<(), Error> {
-		if self.rc.merge(&hash, vec![0])?.is_none() {
-			self.resync_queue.insert(hash.to_vec(), vec![1u8])?;
+		let new_rc = self.rc.merge(&hash, vec![0])?;
+		if new_rc.is_none() {
+			self.put_to_resync(&hash, 2 * BLOCK_RW_TIMEOUT.as_millis() as u64)?;
 		}
 		Ok(())
 	}
 
+	fn put_to_resync(&self, hash: &Hash, delay_millis: u64) -> Result<(), Error> {
+		let when = now_msec() + delay_millis;
+		eprintln!("Put resync_queue: {} {:?}", when, hash);
+		let mut key = u64::to_be_bytes(when).to_vec();
+		key.extend(hash.as_ref());
+		self.resync_queue.insert(key, hash.as_ref())?;
+		Ok(())
+	}
+
 	async fn resync_loop(self: Arc<Self>, must_exit: watch::Receiver<bool>) -> Result<(), Error> {
 		while !*must_exit.borrow() {
-			if let Some((hash_bytes, _v)) = self.resync_queue.get_gt(&[])? {
-				let mut hash = [0u8; 32];
-				hash.copy_from_slice(hash_bytes.as_ref());
-				let hash = Hash::from(hash);
-
-				match self.resync_iter(&hash).await {
-					Ok(_) => {
-						self.resync_queue.remove(&hash_bytes)?;
-					}
-					Err(e) => {
-						eprintln!(
-							"Failed to resync hash {:?}, leaving it in queue: {}",
-							hash, e
-						);
+			if let Some((time_bytes, hash_bytes)) = self.resync_queue.get_gt(&[])? {
+				let time_msec = u64_from_bytes(&time_bytes[0..8]);
+				eprintln!("First in resync queue: {} (now = {})", time_msec, now_msec());
+				if now_msec() >= time_msec {
+					let mut hash = [0u8; 32];
+					hash.copy_from_slice(hash_bytes.as_ref());
+					let hash = Hash::from(hash);
+
+					match self.resync_iter(&hash).await {
+						Ok(_) => {
+							self.resync_queue.remove(&hash_bytes)?;
+						}
+						Err(e) => {
+							eprintln!(
+								"Failed to resync hash {:?}, leaving it in queue: {}",
+								hash, e
+							);
+						}
 					}
+					continue;
 				}
-			} else {
-				tokio::time::delay_for(Duration::from_secs(1)).await;
 			}
+			tokio::time::delay_for(Duration::from_secs(1)).await;
 		}
 		Ok(())
 	}
@@ -145,14 +168,23 @@ impl BlockManager {
 			.map(|x| u64_from_bytes(x.as_ref()) > 0)
 			.unwrap_or(false);
 
+		eprintln!("Resync block {:?}: exists {}, needed {}", hash, exists, needed);
+
 		if exists && !needed {
-			// TODO: verify that other nodes that might need it have it ?
+			let garage = self.garage.load_full().unwrap();
+			let active_refs = garage.block_ref_table.get_range(&hash, &[0u8; 32].into(), Some(()), 1).await?;
+			let needed_by_others = !active_refs.is_empty();
+			if needed_by_others {
+				// TODO check they have it and send it if not
+			}
 			fs::remove_file(path).await?;
 			self.resync_queue.remove(&hash)?;
 		}
 
 		if needed && !exists {
 			// TODO find a way to not do this if they are sending it to us
+			// Let's suppose this isn't an issue for now with the BLOCK_RW_TIMEOUT delay
+			// between the RC being incremented and this part being called.
 			let block_data = rpc_get_block(&self.system, &hash).await?;
 			self.write_block(hash, &block_data[..]).await?;
 		}
@@ -190,11 +222,8 @@ fn rc_merge(_key: &[u8], old: Option<&[u8]>, new: &[u8]) -> Option<Vec<u8>> {
 }
 
 pub async fn rpc_get_block(system: &Arc<System>, hash: &Hash) -> Result<Vec<u8>, Error> {
-	let who = system
-		.ring
-		.borrow()
-		.clone()
-		.walk_ring(&hash, system.config.data_replication_factor);
+	let ring = system.ring.borrow().clone();
+	let who = ring.walk_ring(&hash, system.config.data_replication_factor);
 	let msg = Message::GetBlock(hash.clone());
 	let mut resp_stream = who
 		.iter()
@@ -215,11 +244,8 @@ pub async fn rpc_get_block(system: &Arc<System>, hash: &Hash) -> Result<Vec<u8>,
 }
 
 pub async fn rpc_put_block(system: &Arc<System>, hash: Hash, data: Vec<u8>) -> Result<(), Error> {
-	let who = system
-		.ring
-		.borrow()
-		.clone()
-		.walk_ring(&hash, system.config.data_replication_factor);
+	let ring = system.ring.borrow().clone();
+	let who = ring.walk_ring(&hash, system.config.data_replication_factor);
 	rpc_try_call_many(
 		system.clone(),
 		&who[..],
diff --git a/src/block_ref_table.rs b/src/block_ref_table.rs
index cf24fea7..5f6ce21b 100644
--- a/src/block_ref_table.rs
+++ b/src/block_ref_table.rs
@@ -44,6 +44,7 @@ impl TableSchema for BlockRefTable {
 	type P = Hash;
 	type S = UUID;
 	type E = BlockRef;
+	type Filter = ();
 
 	async fn updated(&self, old: Option<Self::E>, new: Option<Self::E>) {
 		let block = &old.as_ref().or(new.as_ref()).unwrap().block;
@@ -60,4 +61,8 @@ impl TableSchema for BlockRefTable {
 			}
 		}
 	}
+
+	fn matches_filter(entry: &Self::E, _filter: &Self::Filter) -> bool {
+		!entry.deleted
+	}
 }
diff --git a/src/object_table.rs b/src/object_table.rs
index fbacf2dc..880543e1 100644
--- a/src/object_table.rs
+++ b/src/object_table.rs
@@ -96,6 +96,7 @@ impl TableSchema for ObjectTable {
 	type P = String;
 	type S = String;
 	type E = Object;
+	type Filter = ();
 
 	async fn updated(&self, old: Option<Self::E>, new: Option<Self::E>) {
 		let version_table = self.version_table.clone();
@@ -122,4 +123,9 @@ impl TableSchema for ObjectTable {
 			});
 		}
 	}
+
+	fn matches_filter(_entry: &Self::E, _filter: &Self::Filter) -> bool {
+		// TODO
+		true
+	}
 }
diff --git a/src/server.rs b/src/server.rs
index 287b4386..591a7bf9 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -1,10 +1,11 @@
-pub use futures_util::future::FutureExt;
-use serde::Deserialize;
 use std::collections::HashMap;
 use std::io::{Read, Write};
 use std::net::SocketAddr;
 use std::path::PathBuf;
 use std::sync::Arc;
+
+pub use futures_util::future::FutureExt;
+use serde::Deserialize;
 use tokio::sync::watch;
 
 use crate::api_server;
@@ -66,9 +67,11 @@ impl Garage {
 		db: sled::Db,
 		background: Arc<BackgroundRunner>,
 	) -> Arc<Self> {
+		println!("Initialize membership management system...");
 		let system = Arc::new(System::new(config.clone(), id, background.clone()));
 
-		let block_manager = BlockManager::new(&db, config.data_dir.clone(), system.clone()).await;
+		println!("Initialize block manager...");
+		let block_manager = BlockManager::new(&db, config.data_dir.clone(), system.clone());
 
 		let data_rep_param = TableReplicationParams {
 			replication_factor: system.config.data_replication_factor,
@@ -84,6 +87,7 @@ impl Garage {
 			timeout: DEFAULT_TIMEOUT,
 		};
 
+		println!("Initialize block_ref_table...");
 		let block_ref_table = Table::new(
 			BlockRefTable {
 				background: background.clone(),
@@ -95,6 +99,8 @@ impl Garage {
 			data_rep_param.clone(),
 		)
 		.await;
+
+		println!("Initialize version_table...");
 		let version_table = Table::new(
 			VersionTable {
 				background: background.clone(),
@@ -106,6 +112,8 @@ impl Garage {
 			meta_rep_param.clone(),
 		)
 		.await;
+
+		println!("Initialize object_table...");
 		let object_table = Table::new(
 			ObjectTable {
 				background: background.clone(),
@@ -118,6 +126,7 @@ impl Garage {
 		)
 		.await;
 
+		println!("Initialize Garage...");
 		let mut garage = Self {
 			db,
 			system: system.clone(),
@@ -142,7 +151,13 @@ impl Garage {
 			garage.block_ref_table.clone().rpc_handler(),
 		);
 
-		Arc::new(garage)
+		let garage = Arc::new(garage);
+
+		println!("Start block manager background thread...");
+		garage.block_manager.garage.swap(Some(garage.clone()));
+		garage.block_manager.clone().spawn_background_worker().await;
+
+		garage
 	}
 }
 
@@ -206,20 +221,25 @@ async fn wait_from(mut chan: watch::Receiver<bool>) -> () {
 }
 
 pub async fn run_server(config_file: PathBuf) -> Result<(), Error> {
+	println!("Loading configuration...");
 	let config = read_config(config_file).expect("Unable to read config file");
 
+	let id = gen_node_id(&config.metadata_dir).expect("Unable to read or generate node ID");
+	println!("Node ID: {}", hex::encode(&id));
+
+	println!("Opening database...");
 	let mut db_path = config.metadata_dir.clone();
 	db_path.push("db");
 	let db = sled::open(db_path).expect("Unable to open DB");
 
-	let id = gen_node_id(&config.metadata_dir).expect("Unable to read or generate node ID");
-	println!("Node ID: {}", hex::encode(&id));
-
 	let (send_cancel, watch_cancel) = watch::channel(false);
 
+	println!("Initializing background runner...");
 	let background = BackgroundRunner::new(8, watch_cancel.clone());
+
 	let garage = Garage::new(config, id, db, background.clone()).await;
 
+	println!("Initializing RPC and API servers...");
 	let rpc_server = rpc_server::run_rpc_server(garage.clone(), wait_from(watch_cancel.clone()));
 	let api_server = api_server::run_api_server(garage.clone(), wait_from(watch_cancel.clone()));
 
diff --git a/src/table.rs b/src/table.rs
index 6892c9f5..40114aec 100644
--- a/src/table.rs
+++ b/src/table.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, BTreeMap};
 use std::sync::Arc;
 use std::time::Duration;
 
@@ -60,10 +60,11 @@ pub enum TableRPC<F: TableSchema> {
 	ReadEntry(F::P, F::S),
 	ReadEntryResponse(Option<ByteBuf>),
 
+	ReadRange(F::P, F::S, Option<F::Filter>, usize),
+
 	Update(Vec<Arc<ByteBuf>>),
 
-	SyncChecksums(Vec<RangeChecksum>),
-	SyncDifferentSet(Vec<SyncRange>),
+	SyncRPC(SyncRPC),
 }
 
 pub trait PartitionKey {
@@ -118,11 +119,15 @@ pub trait TableSchema: Send + Sync {
 	type P: PartitionKey + Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + Send + Sync;
 	type S: SortKey + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync;
 	type E: Entry<Self::P, Self::S>;
+	type Filter: Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync;
 
 	async fn updated(&self, old: Option<Self::E>, new: Option<Self::E>);
+	fn matches_filter(_entry: &Self::E, _filter: &Self::Filter) -> bool { true }
 }
 
 impl<F: TableSchema + 'static> Table<F> {
+	// =============== PUBLIC INTERFACE FUNCTIONS (new, insert, get, etc) ===============
+
 	pub async fn new(
 		instance: F,
 		system: Arc<System>,
@@ -144,18 +149,10 @@ impl<F: TableSchema + 'static> Table<F> {
 		table
 	}
 
-	pub fn rpc_handler(self: Arc<Self>) -> Box<dyn TableRpcHandler + Send + Sync> {
-		Box::new(TableRpcHandlerAdapter::<F> { table: self })
-	}
-
 	pub async fn insert(&self, e: &F::E) -> Result<(), Error> {
 		let hash = e.partition_key().hash();
-		let who = self
-			.system
-			.ring
-			.borrow()
-			.clone()
-			.walk_ring(&hash, self.param.replication_factor);
+		let ring = self.system.ring.borrow().clone();
+		let who = ring.walk_ring(&hash, self.param.replication_factor);
 		eprintln!("insert who: {:?}", who);
 
 		let e_enc = Arc::new(ByteBuf::from(rmp_to_vec_all_named(e)?));
@@ -171,12 +168,8 @@ impl<F: TableSchema + 'static> Table<F> {
 
 		for entry in entries.iter() {
 			let hash = entry.partition_key().hash();
-			let who = self
-				.system
-				.ring
-				.borrow()
-				.clone()
-				.walk_ring(&hash, self.param.replication_factor);
+			let ring = self.system.ring.borrow().clone();
+			let who = ring.walk_ring(&hash, self.param.replication_factor);
 			let e_enc = Arc::new(ByteBuf::from(rmp_to_vec_all_named(entry)?));
 			for node in who {
 				if !call_list.contains_key(&node) {
@@ -215,12 +208,8 @@ impl<F: TableSchema + 'static> Table<F> {
 		sort_key: &F::S,
 	) -> Result<Option<F::E>, Error> {
 		let hash = partition_key.hash();
-		let who = self
-			.system
-			.ring
-			.borrow()
-			.clone()
-			.walk_ring(&hash, self.param.replication_factor);
+		let ring = self.system.ring.borrow().clone();
+		let who = ring.walk_ring(&hash, self.param.replication_factor);
 		eprintln!("get who: {:?}", who);
 
 		let rpc = &TableRPC::<F>::ReadEntry(partition_key.clone(), sort_key.clone());
@@ -251,15 +240,76 @@ impl<F: TableSchema + 'static> Table<F> {
 		}
 		if let Some(ret_entry) = &ret {
 			if not_all_same {
+				let self2 = self.clone();
+				let ent2 = ret_entry.clone();
 				self.system
 					.background
-					.spawn(self.clone().repair_on_read(who, ret_entry.clone()));
+					.spawn(async move {
+						self2.repair_on_read(&who[..], ent2).await
+					});
 			}
 		}
 		Ok(ret)
 	}
 
-	async fn repair_on_read(self: Arc<Self>, who: Vec<UUID>, what: F::E) -> Result<(), Error> {
+	pub async fn get_range(
+		self: &Arc<Self>,
+		partition_key: &F::P,
+		begin_sort_key: &F::S,
+		filter: Option<F::Filter>,
+		limit: usize,
+	) -> Result<Vec<F::E>, Error> {
+		let hash = partition_key.hash();
+		let ring = self.system.ring.borrow().clone();
+		let who = ring.walk_ring(&hash, self.param.replication_factor);
+
+		let rpc = &TableRPC::<F>::ReadRange(partition_key.clone(), begin_sort_key.clone(), filter, limit);
+		let resps = self
+			.rpc_try_call_many(&who[..], &rpc, self.param.read_quorum)
+			.await?;
+
+		let mut ret = BTreeMap::new();
+		let mut to_repair = BTreeMap::new();
+		for resp in resps {
+			if let TableRPC::Update(entries) = resp {
+				for entry_bytes in entries.iter() {
+					let entry = rmp_serde::decode::from_read_ref::<_, F::E>(entry_bytes.as_slice())?;
+					let entry_key = self.tree_key(entry.partition_key(), entry.sort_key());
+					match ret.remove(&entry_key) {
+						None => {
+							ret.insert(entry_key, Some(entry));
+						}
+						Some(Some(mut prev)) => {
+							let must_repair = prev != entry;
+							prev.merge(&entry);
+							if must_repair {
+								to_repair.insert(entry_key.clone(), Some(prev.clone()));
+							}
+							ret.insert(entry_key, Some(prev));
+						}
+						Some(None) => unreachable!(),
+					}
+				}
+			}
+		}
+		if !to_repair.is_empty() {
+			let self2 = self.clone();
+			self.system
+				.background
+				.spawn(async move {
+					for (_, v) in to_repair.iter_mut() {
+						self2.repair_on_read(&who[..], v.take().unwrap()).await?;
+					}
+					Ok(())
+				});
+		}
+		let ret_vec = ret.iter_mut().take(limit).map(|(_k, v)| v.take().unwrap()).collect::<Vec<_>>();
+		Ok(ret_vec)
+	}
+
+	// =============== UTILITY FUNCTION FOR CLIENT OPERATIONS ===============
+
+	async fn repair_on_read(&self, who: &[UUID], what: F::E) -> Result<(), Error> {
 		let what_enc = Arc::new(ByteBuf::from(rmp_to_vec_all_named(&what)?));
 		self.rpc_try_call_many(&who[..], &TableRPC::<F>::Update(vec![what_enc]), who.len())
 			.await?;
@@ -322,6 +372,12 @@ impl<F: TableSchema + 'static> Table<F> {
 		)))
 	}
 
+	// =============== HANDLERS FOR RPC OPERATIONS (SERVER SIDE) ==============
+
+	pub fn rpc_handler(self: Arc<Self>) -> Box<dyn TableRpcHandler + Send + Sync> {
+		Box::new(TableRpcHandlerAdapter::<F> { table: self })
+	}
+
 	async fn handle(self: &Arc<Self>, msg: TableRPC<F>) -> Result<TableRPC<F>, Error> {
 		match msg {
 			TableRPC::ReadEntry(key, sort_key) => {
@@ -332,12 +388,12 @@ impl<F: TableSchema + 'static> Table<F> {
 				self.handle_update(pairs).await?;
 				Ok(TableRPC::Ok)
 			}
-			TableRPC::SyncChecksums(checksums) => {
+			TableRPC::SyncRPC(rpc) => {
 				let syncer = self.syncer.read().await.as_ref().unwrap().clone();
-				let differing = syncer
-					.handle_checksum_rpc(&checksums[..], self.system.background.stop_signal.clone())
+				let response = syncer
+					.handle_rpc(&rpc, self.system.background.stop_signal.clone())
 					.await?;
-				Ok(TableRPC::SyncDifferentSet(differing))
+				Ok(TableRPC::SyncRPC(response))
 			}
 			_ => Err(Error::RPCError(format!("Unexpected table RPC"))),
 		}
diff --git a/src/table_sync.rs b/src/table_sync.rs
index 8eb08074..5ef13d6d 100644
--- a/src/table_sync.rs
+++ b/src/table_sync.rs
@@ -27,6 +27,12 @@ pub struct TableSyncer<F: TableSchema> {
 	pub cache: Vec<Mutex<BTreeMap<SyncRange, RangeChecksum>>>,
 }
 
+#[derive(Serialize, Deserialize)]
+pub enum SyncRPC {
+	Checksums(Vec<RangeChecksum>),
+	DifferentSet(Vec<SyncRange>),
+}
+
 pub struct SyncTodo {
 	pub todo: Vec<Partition>,
 }
@@ -166,13 +172,8 @@ impl<F: TableSchema + 'static> TableSyncer<F> {
 			.root_checksum(&partition.begin, &partition.end, must_exit)
 			.await?;
 
-		let nodes = self
-			.table
-			.system
-			.ring
-			.borrow()
-			.clone()
-			.walk_ring(&partition.begin, self.table.param.replication_factor);
+		let ring = self.table.system.ring.borrow().clone();
+		let nodes = ring.walk_ring(&partition.begin, self.table.param.replication_factor);
 		let mut sync_futures = nodes
 			.iter()
 			.map(|node| {
@@ -361,9 +362,9 @@ impl<F: TableSchema + 'static> TableSyncer<F> {
 
 			let rpc_resp = self
 				.table
-				.rpc_call(&who, &TableRPC::<F>::SyncChecksums(step))
+				.rpc_call(&who, &TableRPC::<F>::SyncRPC(SyncRPC::Checksums(step)))
 				.await?;
-			if let TableRPC::<F>::SyncDifferentSet(mut s) = rpc_resp {
+			if let TableRPC::<F>::SyncRPC(SyncRPC::DifferentSet(mut s)) = rpc_resp {
 				let mut items = vec![];
 				for differing in s.drain(..) {
 					if differing.level == 0 {
@@ -381,7 +382,7 @@ impl<F: TableSchema + 'static> TableSyncer<F> {
 				}
 			} else {
 				return Err(Error::Message(format!(
-					"Unexpected response to RPC SyncChecksums: {}",
+					"Unexpected response to sync RPC checksums: {}",
 					debug_serialize(&rpc_resp)
 				)));
 			}
@@ -417,41 +418,44 @@ impl<F: TableSchema + 'static> TableSyncer<F> {
 		}
 	}
 
-	pub async fn handle_checksum_rpc(
+	pub async fn handle_rpc(
 		self: &Arc<Self>,
-		checksums: &[RangeChecksum],
+		message: &SyncRPC,
 		mut must_exit: watch::Receiver<bool>,
-	) -> Result<Vec<SyncRange>, Error> {
-		let mut ret = vec![];
-		for ckr in checksums.iter() {
-			let our_ckr = self.range_checksum(&ckr.bounds, &mut must_exit).await?;
-			for (range, hash) in ckr.children.iter() {
-				match our_ckr
-					.children
-					.binary_search_by(|(our_range, _)| our_range.begin.cmp(&range.begin))
-				{
-					Err(_) => {
-						ret.push(range.clone());
-					}
-					Ok(i) => {
-						if our_ckr.children[i].1 != *hash {
+	) -> Result<SyncRPC, Error> {
+		if let SyncRPC::Checksums(checksums) = message {
+			let mut ret = vec![];
+			for ckr in checksums.iter() {
+				let our_ckr = self.range_checksum(&ckr.bounds, &mut must_exit).await?;
+				for (range, hash) in ckr.children.iter() {
+					match our_ckr
+						.children
+						.binary_search_by(|(our_range, _)| our_range.begin.cmp(&range.begin))
+					{
+						Err(_) => {
 							ret.push(range.clone());
 						}
+						Ok(i) => {
+							if our_ckr.children[i].1 != *hash {
+								ret.push(range.clone());
+							}
+						}
 					}
 				}
 			}
+			let n_checksums = checksums
+				.iter()
+				.map(|x| x.children.len())
+				.fold(0, |x, y| x + y);
+			eprintln!(
+				"({}) Checksum comparison RPC: {} different out of {}",
+				self.table.name,
+				ret.len(),
+				n_checksums
+			);
+			return Ok(SyncRPC::DifferentSet(ret));
 		}
-		let n_checksums = checksums
-			.iter()
-			.map(|x| x.children.len())
-			.fold(0, |x, y| x + y);
-		eprintln!(
-			"({}) Checksum comparison RPC: {} different out of {}",
-			self.table.name,
-			ret.len(),
-			n_checksums
-		);
-		Ok(ret)
+		Err(Error::Message(format!("Unexpected sync RPC")))
 	}
 
 	pub async fn invalidate(self: Arc<Self>, item_key: Vec<u8>) -> Result<(), Error> {
diff --git a/src/version_table.rs b/src/version_table.rs
index 77a7560d..22290fd7 100644
--- a/src/version_table.rs
+++ b/src/version_table.rs
@@ -62,6 +62,7 @@ impl TableSchema for VersionTable {
 	type P = Hash;
 	type S = EmptySortKey;
 	type E = Version;
+	type Filter = ();
 
 	async fn updated(&self, old: Option<Self::E>, new: Option<Self::E>) {
 		let block_ref_table = self.block_ref_table.clone();
@@ -84,4 +85,8 @@ impl TableSchema for VersionTable {
 			});
 		}
 	}
+
+	fn matches_filter(entry: &Self::E, _filter: &Self::Filter) -> bool {
+		!entry.deleted
+	}
 }