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use std::collections::{HashMap, HashSet};
use std::convert::TryInto;
use serde::{Deserialize, Serialize};
use garage_util::data::*;
// TODO: make this constant parametrizable in the config file
// For deployments with many nodes it might make sense to bump
// it up to 10.
// Maximum value : 16
pub const PARTITION_BITS: usize = 8;
const PARTITION_MASK_U16: u16 = ((1 << PARTITION_BITS) - 1) << (16 - PARTITION_BITS);
// TODO: make this constant paraetrizable in the config file
// (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>,
pub version: u64,
}
impl NetworkConfig {
pub(crate) fn new() -> Self {
Self {
members: HashMap::new(),
version: 0,
}
}
}
#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct NetworkConfigEntry {
pub datacenter: String,
pub capacity: u32,
pub tag: String,
}
#[derive(Clone)]
pub struct Ring {
pub config: NetworkConfig,
pub ring: Vec<RingEntry>,
}
#[derive(Clone, Debug)]
pub struct RingEntry {
pub location: Hash,
pub nodes: [UUID; MAX_REPLICATION],
}
impl Ring {
pub(crate) fn new(config: NetworkConfig) -> Self {
// Create a vector of partition indices (0 to 2**PARTITION_BITS-1)
let partitions_idx = (0usize..(1usize << PARTITION_BITS)).collect::<Vec<_>>();
let datacenters = config
.members
.iter()
.map(|(_id, info)| info.datacenter.as_str())
.collect::<HashSet<&str>>();
let n_datacenters = datacenters.len();
// Prepare ring
let mut partitions: Vec<Vec<(&UUID, &NetworkConfigEntry)>> = partitions_idx
.iter()
.map(|_i| Vec::new())
.collect::<Vec<_>>();
// Create MagLev priority queues for each node
let mut queues = config
.members
.iter()
.map(|(node_id, node_info)| {
let mut parts = partitions_idx
.iter()
.map(|i| {
let part_data =
[&u16::to_be_bytes(*i as u16)[..], node_id.as_slice()].concat();
(*i, fasthash(&part_data[..]))
})
.collect::<Vec<_>>();
parts.sort_by_key(|(_i, h)| *h);
let parts_i = parts.iter().map(|(i, _h)| *i).collect::<Vec<_>>();
(node_id, node_info, parts_i, 0)
})
.collect::<Vec<_>>();
let max_capacity = config
.members
.iter()
.map(|(_, node_info)| node_info.capacity)
.fold(0, std::cmp::max);
// Fill up ring
for rep in 0..MAX_REPLICATION {
queues.sort_by_key(|(ni, _np, _q, _p)| {
let queue_data = [&u16::to_be_bytes(rep as u16)[..], ni.as_slice()].concat();
fasthash(&queue_data[..])
});
for (_, _, _, pos) in queues.iter_mut() {
*pos = 0;
}
let mut remaining = partitions_idx.len();
while remaining > 0 {
let remaining0 = remaining;
for i_round in 0..max_capacity {
for (node_id, node_info, q, pos) in queues.iter_mut() {
if i_round >= node_info.capacity {
continue;
}
for pos2 in *pos..q.len() {
let qv = q[pos2];
if partitions[qv].len() != rep {
continue;
}
let p_dcs = partitions[qv]
.iter()
.map(|(_id, info)| info.datacenter.as_str())
.collect::<HashSet<&str>>();
if (p_dcs.len() < n_datacenters
&& !p_dcs.contains(&node_info.datacenter.as_str()))
|| (p_dcs.len() == n_datacenters
&& !partitions[qv].iter().any(|(id, _i)| id == node_id))
{
partitions[qv].push((node_id, node_info));
remaining -= 1;
*pos = pos2 + 1;
break;
}
}
}
}
if remaining == remaining0 {
// No progress made, exit
warn!("Could not build ring, not enough nodes configured.");
return Self {
config,
ring: vec![],
};
}
}
}
let ring = partitions
.iter()
.enumerate()
.map(|(i, nodes)| {
let top = (i as u16) << (16 - PARTITION_BITS);
let mut hash = [0u8; 32];
hash[0..2].copy_from_slice(&u16::to_be_bytes(top)[..]);
let nodes = nodes.iter().map(|(id, _info)| **id).collect::<Vec<UUID>>();
RingEntry {
location: hash.into(),
nodes: nodes.try_into().unwrap(),
}
})
.collect::<Vec<_>>();
// eprintln!("RING: --");
// for e in ring.iter() {
// eprintln!("{:?}", e);
// }
// eprintln!("END --");
Self { config, ring }
}
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!");
return vec![];
}
let top = u16::from_be_bytes(from.as_slice()[0..2].try_into().unwrap());
let partition_idx = (top >> (16 - PARTITION_BITS)) as usize;
let partition = &self.ring[partition_idx];
let partition_top =
u16::from_be_bytes(partition.location.as_slice()[0..2].try_into().unwrap());
assert_eq!(partition_top & PARTITION_MASK_U16, top & PARTITION_MASK_U16);
assert!(n <= partition.nodes.len());
partition.nodes[..n].iter().cloned().collect::<Vec<_>>()
}
}
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