Add support for fully replicated tables with epidemic dissemination of updates

This commit is contained in:
Alex Auvolat 2020-04-19 15:14:23 +02:00
parent 7131553c53
commit 302502f4c1
5 changed files with 122 additions and 7 deletions

View file

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

View file

@ -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(())
}

100
src/table_fullcopy.rs Normal file
View file

@ -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
}
}

View file

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

View file

@ -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)) {