garage/src/table/replication/sharded.rs
Alex Auvolat b490ebc7f6
Many improvements on ring/replication and its configuration:
- Explicit "replication_mode" configuration parameters that takes
  either "none", "2" or "3" as values, instead of letting user configure
  replication factor themselves. These are presets whose corresponding
  replication/quorum values can be found in replication/mode.rs

- Explicit support for single-node and two-node deployments
  (number of nodes must be at least "replication_mode", with "none"
  we can have only one node)

- Ring is now stored much more compactly with 256*8 + n*32 bytes,
  instead of 256*32 bytes

- Support for gateway-only nodes that do not store data
  (these nodes still need a metadata_directory to store the list
  of bucket and keys since those are stored on all nodes; it also
  technically needs a data_directory to start but it will stay
  empty unless we have bugs)
2021-05-28 14:07:36 +02:00

53 lines
1.5 KiB
Rust

use std::sync::Arc;
use garage_rpc::membership::System;
use garage_rpc::ring::*;
use garage_util::data::*;
use crate::replication::*;
/// Sharded replication schema:
/// - based on the ring of nodes, a certain set of neighbors
/// store entries, given as a function of the position of the
/// entry's hash in the ring
/// - reads are done on all of the nodes that replicate the data
/// - writes as well
#[derive(Clone)]
pub struct TableShardedReplication {
/// The membership manager of this node
pub system: Arc<System>,
/// How many time each data should be replicated
pub replication_factor: usize,
/// How many nodes to contact for a read, should be at most `replication_factor`
pub read_quorum: usize,
/// How many nodes to contact for a write, should be at most `replication_factor`
pub write_quorum: usize,
}
impl TableReplication for TableShardedReplication {
fn read_nodes(&self, hash: &Hash) -> Vec<Uuid> {
let ring = self.system.ring.borrow();
ring.get_nodes(&hash, self.replication_factor)
}
fn read_quorum(&self) -> usize {
self.read_quorum
}
fn write_nodes(&self, hash: &Hash) -> Vec<Uuid> {
let ring = self.system.ring.borrow();
ring.get_nodes(&hash, self.replication_factor)
}
fn write_quorum(&self) -> usize {
self.write_quorum
}
fn max_write_errors(&self) -> usize {
self.replication_factor - self.write_quorum
}
fn partition_of(&self, hash: &Hash) -> Partition {
self.system.ring.borrow().partition_of(hash)
}
fn partitions(&self) -> Vec<(Partition, Hash)> {
self.system.ring.borrow().partitions()
}
}