Simpler Merkle & sync

src/rpc/ring.rs

@@ -5,6 +5,11 @@ use serde::{Deserialize, Serialize};
 
 use garage_util::data::*;
 
+// A partition number is encoded on 16 bits,
+// i.e. we have up to 2**16 partitions.
+// (in practice we have exactly 2**PARTITION_BITS partitions)
+pub type Partition = u16;
+
 // TODO: make this constant parametrizable in the config file
 // For deployments with many nodes it might make sense to bump
 // it up to 10.
@@ -17,6 +22,7 @@ const PARTITION_MASK_U16: u16 = ((1 << PARTITION_BITS) - 1) << (16 - PARTITION_B
 // (most deployments use a replication factor of 3, so...)
 pub const MAX_REPLICATION: usize = 3;
 
+
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct NetworkConfig {
 	pub members: HashMap<UUID, NetworkConfigEntry>,
@@ -170,11 +176,24 @@ impl Ring {
 		Self { config, ring }
 	}
 
-	pub fn partition_of(&self, from: &Hash) -> u16 {
+	pub fn partition_of(&self, from: &Hash) -> Partition {
 		let top = u16::from_be_bytes(from.as_slice()[0..2].try_into().unwrap());
 		top >> (16 - PARTITION_BITS)
 	}
 
+	pub fn partitions(&self) -> Vec<(Partition, Hash)> {
+		let mut ret = vec![];
+
+		for (i, entry) in self.ring.iter().enumerate() {
+			ret.push((i as u16, entry.location));
+		}
+		if ret.len() > 0 {
+			assert_eq!(ret[0].1, [0u8; 32].into());
+		}
+
+		ret
+	}
+
 	pub fn walk_ring(&self, from: &Hash, n: usize) -> Vec<UUID> {
 		if self.ring.len() != 1 << PARTITION_BITS {
 			warn!("Ring not yet ready, read/writes will be lost!");

src/table/merkle.rs

@@ -1,4 +1,3 @@
-use std::convert::TryInto;
 use std::sync::Arc;
 use std::time::Duration;
 
@@ -15,22 +14,12 @@ use garage_util::background::BackgroundRunner;
 use garage_util::data::*;
 use garage_util::error::Error;
 
+use garage_rpc::ring::*;
+
 use crate::data::*;
 use crate::replication::*;
 use crate::schema::*;
 
-pub type MerklePartition = [u8; 2];
-
-pub fn hash_of_merkle_partition(p: MerklePartition) -> Hash {
-	let mut partition_pos = [0u8; 32];
-	partition_pos[0..2].copy_from_slice(&p[..]);
-	partition_pos.into()
-}
-
-pub fn hash_of_merkle_partition_opt(p: Option<MerklePartition>) -> Hash {
-	p.map(hash_of_merkle_partition)
-		.unwrap_or([0xFFu8; 32].into())
-}
 
 // This modules partitions the data in 2**16 partitions, based on the top
 // 16 bits (two bytes) of item's partition keys' hashes.
@@ -57,8 +46,8 @@ pub struct MerkleUpdater<F: TableSchema, R: TableReplication> {
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct MerkleNodeKey {
-	// partition: first 16 bits (two bytes) of the partition_key's hash
-	pub partition: [u8; 2],
+	// partition number
+	pub partition: Partition,
 
 	// prefix: a prefix for the hash of full keys, i.e. hash(hash(partition_key)+sort_key)
 	#[serde(with = "serde_bytes")]
@@ -143,7 +132,7 @@ where
 		};
 
 		let key = MerkleNodeKey {
-			partition: k[0..2].try_into().unwrap(),
+			partition: self.data.replication.partition_of(&Hash::try_from(&k[0..32]).unwrap()),
 			prefix: vec![],
 		};
 		self.data
@@ -325,7 +314,7 @@ where
 impl MerkleNodeKey {
 	fn encode(&self) -> Vec<u8> {
 		let mut ret = Vec::with_capacity(2 + self.prefix.len());
-		ret.extend(&self.partition[..]);
+		ret.extend(&u16::to_be_bytes(self.partition)[..]);
 		ret.extend(&self.prefix[..]);
 		ret
 	}
@@ -443,3 +432,9 @@ fn test_intermediate_aux() {
 		]
 	);
 }
+
+impl MerkleNode {
+	pub fn is_empty(&self) -> bool {
+		*self == MerkleNode::Empty
+	}
+}

src/table/replication/fullcopy.rs

@@ -1,7 +1,7 @@
 use std::sync::Arc;
 
 use garage_rpc::membership::System;
-use garage_rpc::ring::Ring;
+use garage_rpc::ring::*;
 use garage_util::data::*;
 
 use crate::replication::*;
@@ -19,10 +19,6 @@ impl TableReplication for TableFullReplication {
 	// Advantage: do all reads locally, extremely fast
 	// Inconvenient: only suitable to reasonably small tables
 
-	fn partition_of(&self, _hash: &Hash) -> u16 {
-		0u16
-	}
-
 	fn read_nodes(&self, _hash: &Hash) -> Vec<UUID> {
 		vec![self.system.id]
 	}
@@ -46,9 +42,10 @@ impl TableReplication for TableFullReplication {
 		self.max_faults
 	}
 
-	fn split_points(&self, _ring: &Ring) -> Vec<Hash> {
-		let mut ret = vec![];
-		ret.push([0u8; 32].into());
-		ret
+	fn partition_of(&self, _hash: &Hash) -> Partition {
+		0u16
+	}
+	fn partitions(&self) -> Vec<(Partition, Hash)> {
+		vec![(0u16, [0u8; 32].into())]
 	}
 }

src/table/replication/parameters.rs

@@ -1,4 +1,4 @@
-use garage_rpc::ring::Ring;
+use garage_rpc::ring::*;
 
 use garage_util::data::*;
 
@@ -6,9 +6,6 @@ pub trait TableReplication: Send + Sync {
 	// See examples in table_sharded.rs and table_fullcopy.rs
 	// To understand various replication methods
 
-	// Partition number of data item (for Merkle tree)
-	fn partition_of(&self, hash: &Hash) -> u16;
-
 	// Which nodes to send reads from
 	fn read_nodes(&self, hash: &Hash) -> Vec<UUID>;
 	fn read_quorum(&self) -> usize;
@@ -18,6 +15,7 @@ pub trait TableReplication: Send + Sync {
 	fn write_quorum(&self) -> usize;
 	fn max_write_errors(&self) -> usize;
 
-	// Get partition boundaries
-	fn split_points(&self, ring: &Ring) -> Vec<Hash>;
+	// Accessing partitions, for Merkle tree & sync
+	fn partition_of(&self, hash: &Hash) -> Partition;
+	fn partitions(&self) -> Vec<(Partition, Hash)>;
 }

src/table/replication/sharded.rs

@@ -1,7 +1,7 @@
 use std::sync::Arc;
 
 use garage_rpc::membership::System;
-use garage_rpc::ring::Ring;
+use garage_rpc::ring::*;
 use garage_util::data::*;
 
 use crate::replication::*;
@@ -22,10 +22,6 @@ impl TableReplication for TableShardedReplication {
 	// - reads are done on all of the nodes that replicate the data
 	// - writes as well
 
-	fn partition_of(&self, hash: &Hash) -> u16 {
-		self.system.ring.borrow().partition_of(hash)
-	}
-
 	fn read_nodes(&self, hash: &Hash) -> Vec<UUID> {
 		let ring = self.system.ring.borrow().clone();
 		ring.walk_ring(&hash, self.replication_factor)
@@ -45,16 +41,10 @@ impl TableReplication for TableShardedReplication {
 		self.replication_factor - self.write_quorum
 	}
 
-	fn split_points(&self, ring: &Ring) -> Vec<Hash> {
-		let mut ret = vec![];
-
-		for entry in ring.ring.iter() {
-			ret.push(entry.location);
+	fn partition_of(&self, hash: &Hash) -> Partition {
+		self.system.ring.borrow().partition_of(hash)
 	}
-		if ret.len() > 0 {
-			assert_eq!(ret[0], [0u8; 32].into());
-		}
-
-		ret
+	fn partitions(&self) -> Vec<(Partition, Hash)> {
+		self.system.ring.borrow().partitions()
 	}
 }

src/table/sync.rs

@@ -1,5 +1,4 @@
 use std::collections::VecDeque;
-use std::convert::TryInto;
 use std::sync::{Arc, Mutex};
 use std::time::{Duration, Instant};
 
@@ -15,7 +14,7 @@ use garage_util::data::*;
 use garage_util::error::Error;
 
 use garage_rpc::membership::System;
-use garage_rpc::ring::Ring;
+use garage_rpc::ring::*;
 use garage_rpc::rpc_client::*;
 use garage_rpc::rpc_server::*;
 
@@ -38,20 +37,10 @@ pub struct TableSyncer<F: TableSchema, R: TableReplication> {
 	rpc_client: Arc<RpcClient<SyncRPC>>,
 }
 
-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<MerklePartition>,
-}
-
 #[derive(Serialize, Deserialize)]
 pub(crate) enum SyncRPC {
-	RootCkHash(PartitionRange, Hash),
-	RootCkList(PartitionRange, RootCk),
-	CkNoDifference,
+	RootCkHash(Partition, Hash),
+	RootCkDifferent(bool),
 	GetNode(MerkleNodeKey),
 	Node(MerkleNodeKey, MerkleNode),
 	Items(Vec<Arc<ByteBuf>>),
@@ -66,7 +55,9 @@ struct SyncTodo {
 
 #[derive(Debug, Clone)]
 struct TodoPartition {
-	range: PartitionRange,
+	partition: Partition,
+	begin: Hash,
+	end: Hash,
 
 	// Are we a node that stores this partition or not?
 	retain: bool,
@@ -222,7 +213,7 @@ where
 			let nodes = self
 				.data
 				.replication
-				.write_nodes(&hash_of_merkle_partition(partition.range.begin))
+				.write_nodes(&partition.begin)
 				.into_iter()
 				.filter(|node| *node != my_id)
 				.collect::<Vec<_>>();
@@ -254,8 +245,8 @@ where
 			}
 		} else {
 			self.offload_partition(
-				&hash_of_merkle_partition(partition.range.begin),
-				&hash_of_merkle_partition_opt(partition.range.end),
+				&partition.begin,
+				&partition.end,
 				must_exit,
 			)
 			.await?;
@@ -364,30 +355,13 @@ where
 	// 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<RootCk, Error> {
-		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 {
+	fn get_root_ck(&self, partition: Partition) -> Result<(MerkleNodeKey, MerkleNode), Error> {
 		let key = MerkleNodeKey {
-				partition: u16::to_be_bytes(i),
+			partition,
 			prefix: vec![],
 		};
-			match self.merkle.read_node(&key)? {
-				MerkleNode::Empty => (),
-				x => {
-					ret.push((key.partition, hash_of(&x)?));
-				}
-			}
-		}
-		Ok(ret)
+		let node = self.merkle.read_node(&key)?;
+		Ok((key, node))
 	}
 
 	async fn do_sync_with(
@@ -396,7 +370,7 @@ where
 		who: UUID,
 		must_exit: watch::Receiver<bool>,
 	) -> Result<(), Error> {
-		let root_ck = self.get_root_ck(partition.range)?;
+		let (root_ck_key, root_ck) = self.get_root_ck(partition.partition)?;
 		if root_ck.is_empty() {
 			debug!(
 				"({}) Sync {:?} with {:?}: partition is empty.",
@@ -404,51 +378,29 @@ where
 			);
 			return Ok(());
 		}
+		let root_ck_hash = hash_of::<MerkleNode>(&root_ck)?;
 
-		let root_ck_hash = hash_of(&root_ck)?;
-
-		// If their root checksum has level > than us, use that as a reference
+		// Check if they have the same root checksum
+		// If so, do nothing.
 		let root_resp = self
 			.rpc_client
 			.call(
 				who,
-				SyncRPC::RootCkHash(partition.range, root_ck_hash),
+				SyncRPC::RootCkHash(partition.partition, root_ck_hash),
 				TABLE_SYNC_RPC_TIMEOUT,
 			)
 			.await?;
 
 		let mut todo = match root_resp {
-			SyncRPC::CkNoDifference => {
+			SyncRPC::RootCkDifferent(false) => {
 				debug!(
 					"({}) Sync {:?} with {:?}: no difference",
 					self.data.name, partition, who
 				);
 				return Ok(());
 			}
-			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
+			SyncRPC::RootCkDifferent(true) => {
+				VecDeque::from(vec![root_ck_key])
 			}
 			x => {
 				return Err(Error::Message(format!(
@@ -565,13 +517,9 @@ where
 	async fn handle_rpc(self: &Arc<Self>, message: &SyncRPC) -> Result<SyncRPC, Error> {
 		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))
-				}
+				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)?;
@@ -596,39 +544,31 @@ impl SyncTodo {
 
 		self.todo.clear();
 
-		let ring = system.ring.borrow().clone();
-		let split_points = data.replication.split_points(&ring);
+		let partitions = data.replication.partitions();
 
-		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()
-			};
+		for i in 0..partitions.len() {
+			let begin = partitions[i].1;
 
-			let end: Option<MerklePartition> = 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())
+			let end = if i + 1 < partitions.len() {
+				partitions[i+1].1
 			} else {
-				None
+				[0xFFu8; 32].into()
 			};
 
-			let begin_hash = hash_of_merkle_partition(begin);
-			let end_hash = hash_of_merkle_partition_opt(end);
-
-			let nodes = data.replication.write_nodes(&begin_hash);
+			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_hash..end_hash).next().is_none() {
+				if data.store.range(begin..end).next().is_none() {
 					continue;
 				}
 			}
 
 			self.todo.push(TodoPartition {
-				range: PartitionRange { begin, end },
+				partition: partitions[i].0,
+				begin,
+				end,
 				retain,
 			});
 		}