Add support for fully replicated tables with epidemic dissemination of updates

src/main.rs

@@ -4,6 +4,7 @@ mod error;
 mod background;
 mod membership;
 mod table;
+mod table_fullcopy;
 mod table_sharded;
 mod table_sync;
 

src/table.rs

@@ -427,6 +427,8 @@ where
 		self: &Arc<Self>,
 		mut entries: Vec<Arc<ByteBuf>>,
 	) -> Result<(), Error> {
+		let mut epidemic_propagate = vec![];
+
 		for update_bytes in entries.drain(..) {
 			let update = rmp_serde::decode::from_read_ref::<_, F::E>(update_bytes.as_slice())?;
 
@@ -449,16 +451,28 @@ where
 					.map_err(Error::RMPEncode)
 					.map_err(sled::ConflictableTransactionError::Abort)?;
 				db.insert(tree_key.clone(), new_bytes)?;
-				Ok((old_entry, Some(new_entry)))
+				Ok((old_entry, new_entry))
 			})?;
 
-			if old_entry != new_entry {
-				self.instance.updated(old_entry, new_entry).await;
+			if old_entry.as_ref() != Some(&new_entry) {
+				if self.replication.epidemic_writes() {
+					epidemic_propagate.push(new_entry.clone());
+				}
+
+				self.instance.updated(old_entry, Some(new_entry)).await;
 
 				let syncer = self.syncer.load_full().unwrap();
 				self.system.background.spawn(syncer.invalidate(tree_key));
 			}
 		}
+
+		if epidemic_propagate.len() > 0 {
+			let self2 = self.clone();
+			self.system
+				.background
+				.spawn(async move { self2.insert_many(&epidemic_propagate[..]).await });
+		}
+
 		Ok(())
 	}
 

src/table_fullcopy.rs

@@ -0,0 +1,100 @@
+use arc_swap::ArcSwapOption;
+use std::sync::Arc;
+
+use crate::data::*;
+use crate::membership::{Ring, System};
+use crate::table::*;
+
+#[derive(Clone)]
+pub struct TableFullReplication {
+	pub write_factor: usize,
+	pub write_quorum: usize,
+
+	neighbors: ArcSwapOption<Neighbors>,
+}
+
+#[derive(Clone)]
+struct Neighbors {
+	ring: Arc<Ring>,
+	neighbors: Vec<UUID>,
+}
+
+impl TableFullReplication {
+	pub fn new(write_factor: usize, write_quorum: usize) -> Self {
+		TableFullReplication {
+			write_factor,
+			write_quorum,
+			neighbors: ArcSwapOption::from(None),
+		}
+	}
+
+	fn get_neighbors(&self, system: &System) -> Vec<UUID> {
+		let neighbors = self.neighbors.load_full();
+		if let Some(n) = neighbors {
+			if Arc::ptr_eq(&n.ring, &system.ring.borrow()) {
+				return n.neighbors.clone();
+			}
+		}
+
+		// Recalculate neighbors
+		let ring = system.ring.borrow().clone();
+		let my_id = system.id.clone();
+
+		let mut nodes = vec![];
+		for (node, _) in ring.config.members.iter() {
+			let node_ranking = hash(&[node.as_slice(), my_id.as_slice()].concat());
+			nodes.push((node.clone(), node_ranking));
+		}
+		nodes.sort_by(|(_, rank1), (_, rank2)| rank1.cmp(rank2));
+		let mut neighbors = nodes
+			.drain(..)
+			.map(|(node, _)| node)
+			.filter(|node| *node != my_id)
+			.take(self.write_factor)
+			.collect::<Vec<_>>();
+		neighbors.push(my_id);
+		self.neighbors.swap(Some(Arc::new(Neighbors {
+			ring,
+			neighbors: neighbors.clone(),
+		})));
+		neighbors
+	}
+}
+
+impl TableReplication for TableFullReplication {
+	// 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
+
+	fn read_nodes(&self, _hash: &Hash, system: &System) -> Vec<UUID> {
+		vec![system.id.clone()]
+	}
+	fn read_quorum(&self) -> usize {
+		1
+	}
+
+	fn write_nodes(&self, _hash: &Hash, system: &System) -> Vec<UUID> {
+		self.get_neighbors(system)
+	}
+	fn write_quorum(&self) -> usize {
+		self.write_quorum
+	}
+	fn max_write_errors(&self) -> usize {
+		self.write_factor - self.write_quorum
+	}
+	fn epidemic_writes(&self) -> bool {
+		true
+	}
+
+	fn replication_nodes(&self, _hash: &Hash, ring: &Ring) -> Vec<UUID> {
+		ring.config.members.keys().cloned().collect::<Vec<_>>()
+	}
+	fn split_points(&self, _ring: &Ring) -> Vec<Hash> {
+		let mut ret = vec![];
+		ret.push([0u8; 32].into());
+		ret.push([0xFFu8; 32].into());
+		ret
+	}
+}

src/table_sharded.rs

@@ -1,5 +1,5 @@
 use crate::data::*;
-use crate::membership::{System, Ring};
+use crate::membership::{Ring, System};
 use crate::table::*;
 
 #[derive(Clone)]

src/table_sync.rs

@@ -604,7 +604,7 @@ impl SyncTodo {
 		for i in 0..split_points.len() - 1 {
 			let begin = split_points[i].clone();
 			let end = split_points[i + 1].clone();
-			let nodes = table.replication.write_nodes_from_ring(&begin, &ring);
+			let nodes = table.replication.replication_nodes(&begin, &ring);
 
 			let retain = nodes.contains(&my_id);
 			if !retain {
@@ -650,11 +650,11 @@ impl SyncTodo {
 			let end = all_points[i + 1].clone();
 			let was_ours = table
 				.replication
-				.write_nodes_from_ring(&begin, &old_ring)
+				.replication_nodes(&begin, &old_ring)
 				.contains(&my_id);
 			let is_ours = table
 				.replication
-				.write_nodes_from_ring(&begin, &new_ring)
+				.replication_nodes(&begin, &new_ring)
 				.contains(&my_id);
 
 			let was_todo = match old_todo.binary_search_by(|x| x.begin.cmp(&begin)) {