Work & TODO

TODO

@@ -0,0 +1,29 @@
+Object table
+------------
+
+
+Rename version table to object table
+In value handle the different versions
+
+So that the table becomes (bucket, key) -> CRDT(list of versions)
+
+CRDT merge rule:
+- keep one complete version (the one with the highest timestamp)
+- keep all incomplete versions with timestamps higher than the complete version
+
+Cleanup rule: remove incomplete versions after a given delay (say 24h)
+
+
+Block table
+-----------
+
+Table is version_UUID -> BTreeMap<(offset, block hash)> OR Deleted (= CRDT top)
+
+
+Block reference table
+---------------------
+
+Table is block_Hash + Sort key: version_UUID -> boolean (true when deleted)
+
+Since the hash key is the same as for the blocks themselves,
+we can simply consider the updates to this table as events that increase/decrease a reference counter.

src/data.rs

@@ -67,6 +67,9 @@ impl FixedBytes32 {
 	pub fn as_slice_mut(&mut self) -> &mut [u8] {
 		&mut self.0[..]
 	}
+	pub fn to_vec(&self) -> Vec<u8> {
+		self.0.to_vec()
+	}
 }
 
 pub type UUID = FixedBytes32;

src/error.rs

@@ -35,9 +35,6 @@ pub enum Error {
 	#[error(display = "{}", _0)]
 	BadRequest(String),
 
-	#[error(display = "Entry not found")]
-	NotFound,
-
 	#[error(display = "{}", _0)]
 	Message(String),
 }

src/table.rs

@@ -2,7 +2,6 @@ use std::time::Duration;
 use std::sync::Arc;
 use serde::{Serialize, Deserialize};
 use async_trait::async_trait;
-use reduce::Reduce;
 
 use crate::error::Error;
 use crate::proto::*;
@@ -52,7 +51,10 @@ impl<F: TableFormat + 'static> TableRpcHandler for TableRpcHandlerAdapter<F> {
 #[derive(Serialize, Deserialize)]
 pub enum TableRPC<F: TableFormat> {
 	Ok,
-	Read(Vec<F::K>),
+
+	ReadEntry(F::K, Vec<u8>),
+	ReadEntryResponse(Option<F::V>),
+
 	Update(Vec<(F::K, F::V)>),
 }
 
@@ -62,18 +64,19 @@ pub struct Partition {
 	pub other_nodes: Vec<UUID>,
 }
 
-pub trait KeyHash {
+pub trait TableKey {
 	fn hash(&self) -> Hash;
 }
 
-pub trait ValueMerge {
+pub trait TableValue {
+	fn sort_key(&self) -> Vec<u8>;
 	fn merge(&mut self, other: &Self);
 }
 
 #[async_trait]
 pub trait TableFormat: Send + Sync {
-	type K: Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + KeyHash + Send + Sync;
-	type V: Clone + Serialize + for<'de> Deserialize<'de> + ValueMerge + Send + Sync;
+	type K: Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + TableKey + Send + Sync;
+	type V: Clone + Serialize + for<'de> Deserialize<'de> + TableValue + Send + Sync;
 
 	async fn updated(&self, key: &Self::K, old: Option<&Self::V>, new: &Self::V);
 }
@@ -109,33 +112,34 @@ impl<F: TableFormat + 'static> Table<F> {
 		Ok(())
 	}
 
-	pub async fn get(&self, k: &F::K) -> Result<F::V, Error> {
+	pub async fn get(&self, k: &F::K, sort_key: &[u8]) -> Result<Option<F::V>, Error> {
 		let hash = k.hash();
 		let who = self.system.members.read().await
 			.walk_ring(&hash, self.param.replication_factor);
 
-		let rpc = &TableRPC::<F>::Read(vec![k.clone()]);
+		let rpc = &TableRPC::<F>::ReadEntry(k.clone(), sort_key.to_vec());
 		let resps = self.rpc_try_call_many(&who[..],
 										   &rpc,
 										   self.param.read_quorum)
 			.await?;
 
-		let mut values = vec![];
+		let mut ret = None;
 		for resp in resps {
-			if let TableRPC::Update(mut pairs) = resp {
-				if pairs.len() == 0 {
-					continue;
-				} else if pairs.len() == 1 && pairs[0].0 == *k {
-					values.push(pairs.drain(..).next().unwrap().1);
-					continue;
+			if let TableRPC::ReadEntryResponse(value) = resp {
+				if let Some(v) = value {
+					ret = match ret {
+						None => Some(v),
+						Some(mut x) => {
+							x.merge(&v);
+							Some(x)
 						}
 					}
+				}
+			} else {
 				return Err(Error::Message(format!("Invalid return value to read")));
 			}
-		values.drain(..)
-			.reduce(|mut x, y| { x.merge(&y); x })
-			.map(Ok)
-			.unwrap_or(Err(Error::NotFound))
+		}
+		Ok(ret)
 	}
 
 	async fn rpc_try_call_many(&self, who: &[UUID], rpc: &TableRPC<F>, quorum: usize) -> Result<Vec<TableRPC<F>>, Error> {
@@ -163,33 +167,35 @@ impl<F: TableFormat + 'static> Table<F> {
 
 	async fn handle(&self, msg: TableRPC<F>) -> Result<TableRPC<F>, Error> {
 		match msg {
-			TableRPC::Read(keys) => {
-				Ok(TableRPC::Update(self.handle_read(&keys)?))
+			TableRPC::ReadEntry(key, sort_key) => {
+				let value = self.handle_read_entry(&key, &sort_key)?;
+				Ok(TableRPC::ReadEntryResponse(value))
 			}
 			TableRPC::Update(pairs) => {
-				self.handle_write(pairs).await?;
+				self.handle_update(pairs).await?;
 				Ok(TableRPC::Ok)
 			}
 			_ => Err(Error::RPCError(format!("Unexpected table RPC")))
 		}
 	}
 
-	fn handle_read(&self, keys: &[F::K]) -> Result<Vec<(F::K, F::V)>, Error> {
-		let mut results = vec![];
-		for key in keys.iter() {
-			if let Some(bytes) = self.store.get(&key.hash())? {
-				let pair = rmp_serde::decode::from_read_ref::<_, (F::K, F::V)>(bytes.as_ref())?;
-				results.push(pair);
+	fn handle_read_entry(&self, key: &F::K, sort_key: &[u8]) -> Result<Option<F::V>, Error> {
+		let mut tree_key = key.hash().to_vec();
+		tree_key.extend(sort_key);
+		if let Some(bytes) = self.store.get(&tree_key)? {
+			let (_, v) = rmp_serde::decode::from_read_ref::<_, (F::K, F::V)>(&bytes)?;
+			Ok(Some(v))
+		} else {
+			Ok(None)
 		}
 	}
-		Ok(results)
-	}
 
-	async fn handle_write(&self, mut pairs: Vec<(F::K, F::V)>) -> Result<(), Error> {
+	async fn handle_update(&self, mut pairs: Vec<(F::K, F::V)>) -> Result<(), Error> {
 		for mut pair in pairs.drain(..) {
-			let hash = pair.0.hash();
+			let mut tree_key = pair.0.hash().to_vec();
+			tree_key.extend(pair.1.sort_key());
 
-			let old_val = match self.store.get(&hash)? {
+			let old_val = match self.store.get(&tree_key)? {
 				Some(prev_bytes) => {
 					let (_, old_val) = rmp_serde::decode::from_read_ref::<_, (F::K, F::V)>(&prev_bytes)?;
 					pair.1.merge(&old_val);
@@ -199,7 +205,7 @@ impl<F: TableFormat + 'static> Table<F> {
 			};
 
 			let new_bytes = rmp_serde::encode::to_vec_named(&pair)?;
-			self.store.insert(&hash, new_bytes)?;
+			self.store.insert(&tree_key, new_bytes)?;
 
 			self.instance.updated(&pair.0, old_val.as_ref(), &pair.1).await;
 		}

src/version_table.rs

@@ -37,13 +37,16 @@ pub struct VersionTable {
 	pub garage: RwLock<Option<Arc<Garage>>>,
 }
 
-impl KeyHash for VersionMetaKey {
+impl TableKey for VersionMetaKey {
 	fn hash(&self) -> Hash {
 		hash(self.bucket.as_bytes())
 	}
 }
 
-impl ValueMerge for VersionMetaValue {
+impl TableValue for VersionMetaValue {
+	fn sort_key(&self) -> Vec<u8> {
+		vec![]
+	}
 	fn merge(&mut self, other: &Self) {
 		unimplemented!()
 	}