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Change the way new layout assignations are computed.

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The function now computes an optimal assignation (with respect to partition size) that minimizes the distance to the former assignation, using flow algorithms.

This commit was written by Mendes Oulamara <mendes.oulamara@pm.me>
This commit is contained in:
Alex Auvolat 2022-05-01 09:54:19 +02:00
parent c9ef3e461b
commit c1d1646c4d
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GPG key ID: 09EC5284AA804D3C
4 changed files with 806 additions and 413 deletions
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1
src/rpc/Cargo.toml
View file

@ -23,6 +23,7 @@ gethostname = "0.2"
hex = "0.4" hex = "0.4"
tracing = "0.1.30" tracing = "0.1.30"
rand = "0.8" rand = "0.8"
itertools="0.10"
sodiumoxide = { version = "0.2.5-0", package = "kuska-sodiumoxide" } sodiumoxide = { version = "0.2.5-0", package = "kuska-sodiumoxide" }
async-trait = "0.1.7" async-trait = "0.1.7"

801
src/rpc/layout.rs
View file

@ -1,10 +1,14 @@
use std::cmp::Ordering; use std::cmp::Ordering;
use std::collections::{HashMap, HashSet}; use std::cmp::{min};
use std::collections::{HashMap};
use serde::{Deserialize, Serialize}; use serde::{Deserialize, Serialize};
use garage_util::crdt::{AutoCrdt, Crdt, LwwMap}; use garage_util::crdt::{AutoCrdt, Crdt, LwwMap};
use garage_util::data::*; use garage_util::data::*;
use garage_util::bipartite::*;
use rand::prelude::SliceRandom;
use crate::ring::*; use crate::ring::*;
@ -164,445 +168,454 @@ impl ClusterLayout {
true true
} }
/// Calculate an assignation of partitions to nodes
pub fn calculate_partition_assignation(&mut self) -> bool {
let (configured_nodes, zones) = self.configured_nodes_and_zones();
let n_zones = zones.len();
println!("Calculating updated partition assignation, this may take some time..."); /// This function calculates a new partition-to-node assignation.
println!(); /// The computed assignation maximizes the capacity of a
/// partition (assuming all partitions have the same size).
/// Among such optimal assignation, it minimizes the distance to
/// the former assignation (if any) to minimize the amount of
/// data to be moved. A heuristic ensures node triplets
/// dispersion (in garage_util::bipartite::optimize_matching()).
pub fn calculate_partition_assignation(&mut self) -> bool {
// Get old partition assignation //The nodes might have been updated, some might have been deleted.
let old_partitions = self.parse_assignation_data(); //So we need to first update the list of nodes and retrieve the
//assignation.
let old_node_assignation = self.update_nodes_and_ring();
// Start new partition assignation with nodes from old assignation where it is relevant let (node_zone, _) = self.get_node_zone_capacity();
let mut partitions = old_partitions
.iter()
.map(|old_part| {
let mut new_part = PartitionAss::new();
for node in old_part.nodes.iter() {
if let Some(role) = node.1 {
if role.capacity.is_some() {
new_part.add(None, n_zones, node.0, role);
}
}
}
new_part
})
.collect::<Vec<_>>();
// In various cases, not enough nodes will have been added for all partitions //We compute the optimal number of partition to assign to
// in the step above (e.g. due to node removals, or new zones being added). //every node and zone.
// Here we add more nodes to make a complete (but sub-optimal) assignation, if let Some((part_per_nod, part_per_zone)) = self.optimal_proportions(){
// using an initial partition assignation that is calculated using the multi-dc maglev trick //We collect part_per_zone in a vec to not rely on the
match self.initial_partition_assignation() { //arbitrary order in which elements are iterated in
Some(initial_partitions) => { //Hashmap::iter()
for (part, ipart) in partitions.iter_mut().zip(initial_partitions.iter()) { let part_per_zone_vec = part_per_zone.iter()
for (id, info) in ipart.nodes.iter() { .map(|(x,y)| (x.clone(),*y))
if part.nodes.len() < self.replication_factor { .collect::<Vec<(String,usize)>>();
part.add(None, n_zones, id, info.unwrap()); //We create an indexing of the zones
} let mut zone_id = HashMap::<String,usize>::new();
} for i in 0..part_per_zone_vec.len(){
assert!(part.nodes.len() == self.replication_factor); zone_id.insert(part_per_zone_vec[i].0.clone(), i);
} }
}
None => {
// Not enough nodes in cluster to build a correct assignation.
// Signal it by returning an error.
return false;
}
}
// Calculate how many partitions each node should ideally store, //We compute a candidate for the new partition to zone
// and how many partitions they are storing with the current assignation //assignation.
// This defines our target for which we will optimize in the following loop. let nb_zones = part_per_zone.len();
let total_capacity = configured_nodes let nb_nodes = part_per_nod.len();
.iter() let nb_partitions = 1<<PARTITION_BITS;
.map(|(_, info)| info.capacity.unwrap_or(0)) let left_cap_vec = vec![self.replication_factor as u32 ; nb_partitions];
.sum::<u32>() as usize; let right_cap_vec = part_per_zone_vec.iter().map(|(_,y)| *y as u32)
let total_partitions = self.replication_factor * (1 << PARTITION_BITS); .collect();
let target_partitions_per_node = configured_nodes let mut zone_assignation =
.iter() dinic_compute_matching(left_cap_vec, right_cap_vec);
.map(|(id, info)| {
(
*id,
info.capacity.unwrap_or(0) as usize * total_partitions / total_capacity,
)
})
.collect::<HashMap<&Uuid, usize>>();
let mut partitions_per_node = self.partitions_per_node(&partitions[..]);
println!("Target number of partitions per node:"); //We create the structure for the partition-to-node assignation.
for (node, npart) in target_partitions_per_node.iter() { let mut node_assignation =
println!("{:?}\t{}", node, npart); vec![vec![None; self.replication_factor ];nb_partitions];
} //We will decrement part_per_nod to keep track of the number
println!(); //of partitions that we still have to associate.
let mut part_per_nod = part_per_nod.clone();
// Shuffle partitions between nodes so that nodes will reach (or better approach) //We minimize the distance to the former assignation(if any)
// their target number of stored partitions
loop {
let mut option = None;
for (i, part) in partitions.iter_mut().enumerate() {
for (irm, (idrm, _)) in part.nodes.iter().enumerate() {
let errratio = |node, parts| {
let tgt = *target_partitions_per_node.get(node).unwrap() as f32;
(parts - tgt) / tgt
};
let square = |x| x * x;
let partsrm = partitions_per_node.get(*idrm).cloned().unwrap_or(0) as f32; //We get the id of the zones of the former assignation
//(and the id no_zone if there is no node assignated)
let no_zone = part_per_zone_vec.len();
let old_zone_assignation : Vec<Vec<usize>> =
old_node_assignation.iter().map(|x| x.iter().map(
|id| match *id { Some(i) => zone_id[&node_zone[i]] ,
None => no_zone }
).collect()).collect();
for (idadd, infoadd) in configured_nodes.iter() { //We minimize the distance to the former zone assignation
// skip replacing a node by itself zone_assignation = optimize_matching(
// and skip replacing by gateway nodes &old_zone_assignation, &zone_assignation, nb_zones+1); //+1 for no_zone
if idadd == idrm || infoadd.capacity.is_none() {
continue;
}
// We want to try replacing node idrm by node idadd //We need to assign partitions to nodes in their zone
// if that brings us close to our goal. //We first put the nodes assignation that can stay the same
let partsadd = partitions_per_node.get(*idadd).cloned().unwrap_or(0) as f32; for i in 0..nb_partitions{
let oldcost = square(errratio(*idrm, partsrm) - errratio(*idadd, partsadd)); for j in 0..self.replication_factor {
let newcost = if let Some(Some(former_node)) = old_node_assignation[i].iter().find(
square(errratio(*idrm, partsrm - 1.) - errratio(*idadd, partsadd + 1.)); |x| if let Some(id) = x {
if newcost >= oldcost { zone_id[&node_zone[*id]] == zone_assignation[i][j]
// not closer to our goal }
continue; else {false}
} )
let gain = oldcost - newcost; {
if part_per_nod[*former_node] > 0 {
node_assignation[i][j] = Some(*former_node);
part_per_nod[*former_node] -= 1;
}
}
}
}
let mut newpart = part.clone();
newpart.nodes.remove(irm); //We complete the assignation of partitions to nodes
if !newpart.add(None, n_zones, idadd, infoadd) { let mut rng = rand::thread_rng();
continue; for i in 0..nb_partitions {
} for j in 0..self.replication_factor {
assert!(newpart.nodes.len() == self.replication_factor); if node_assignation[i][j] == None {
let possible_nodes : Vec<usize> = (0..nb_nodes)
.filter(
|id| zone_id[&node_zone[*id]] == zone_assignation[i][j]
&& part_per_nod[*id] > 0).collect();
assert!(possible_nodes.len()>0);
//We randomly pick a node
if let Some(nod) = possible_nodes.choose(&mut rng){
node_assignation[i][j] = Some(*nod);
part_per_nod[*nod] -= 1;
}
}
}
}
if !old_partitions[i] //We write the assignation in the 1D table
.is_valid_transition_to(&newpart, self.replication_factor) self.ring_assignation_data = Vec::<CompactNodeType>::new();
{ for i in 0..nb_partitions{
continue; for j in 0..self.replication_factor {
} if let Some(id) = node_assignation[i][j] {
self.ring_assignation_data.push(id as CompactNodeType);
}
else {assert!(false)}
}
}
if option true
.as_ref() }
.map(|(old_gain, _, _, _, _)| gain > *old_gain) else { false }
.unwrap_or(true) }
{
option = Some((gain, i, idadd, idrm, newpart));
}
}
}
}
if let Some((_gain, i, idadd, idrm, newpart)) = option {
*partitions_per_node.entry(idadd).or_insert(0) += 1;
*partitions_per_node.get_mut(idrm).unwrap() -= 1;
partitions[i] = newpart;
} else {
break;
}
}
// Check we completed the assignation correctly /// The LwwMap of node roles might have changed. This function updates the node_id_vec
// (this is a set of checks for the algorithm's consistency) /// and returns the assignation given by ring, with the new indices of the nodes, and
assert!(partitions.len() == (1 << PARTITION_BITS)); /// None of the node is not present anymore.
assert!(partitions /// We work with the assumption that only this function and calculate_new_assignation
.iter() /// do modify assignation_ring and node_id_vec.
.all(|p| p.nodes.len() == self.replication_factor)); fn update_nodes_and_ring(&mut self) -> Vec<Vec<Option<usize>>> {
let nb_partitions = 1usize<<PARTITION_BITS;
let mut node_assignation =
vec![vec![None; self.replication_factor ];nb_partitions];
let rf = self.replication_factor;
let ring = &self.ring_assignation_data;
let new_partitions_per_node = self.partitions_per_node(&partitions[..]); let new_node_id_vec : Vec::<Uuid> = self.roles.items().iter()
assert!(new_partitions_per_node == partitions_per_node); .map(|(k, _, _)| *k)
.collect();
// Show statistics if ring.len() == rf*nb_partitions {
println!("New number of partitions per node:"); for i in 0..nb_partitions {
for (node, npart) in partitions_per_node.iter() { for j in 0..self.replication_factor {
let tgt = *target_partitions_per_node.get(node).unwrap(); node_assignation[i][j] = new_node_id_vec.iter()
let pct = 100f32 * (*npart as f32) / (tgt as f32); .position(|id| *id == self.node_id_vec[ring[i*rf + j] as usize]);
println!("{:?}\t{}\t({}% of {})", node, npart, pct as i32, tgt); }
} }
println!(); }
let mut diffcount = HashMap::new(); self.node_id_vec = new_node_id_vec;
for (oldpart, newpart) in old_partitions.iter().zip(partitions.iter()) { self.ring_assignation_data = vec![];
let nminus = oldpart.txtplus(newpart); return node_assignation;
let nplus = newpart.txtplus(oldpart); }
if nminus != "[...]" || nplus != "[...]" {
let tup = (nminus, nplus);
*diffcount.entry(tup).or_insert(0) += 1;
}
}
if diffcount.is_empty() {
println!("No data will be moved between nodes.");
} else {
let mut diffcount = diffcount.into_iter().collect::<Vec<_>>();
diffcount.sort();
println!("Number of partitions that move:");
for ((nminus, nplus), npart) in diffcount {
println!("\t{}\t{} -> {}", npart, nminus, nplus);
}
}
println!();
// Calculate and save new assignation data ///This function compute the number of partition to assign to
let (nodes, assignation_data) = ///every node and zone, so that every partition is replicated
self.compute_assignation_data(&configured_nodes[..], &partitions[..]); ///self.replication_factor times and the capacity of a partition
///is maximized.
fn optimal_proportions(&mut self) -> Option<(Vec<usize>, HashMap<String, usize>)> {
self.node_id_vec = nodes; let mut zone_capacity :HashMap<String, u32>= HashMap::new();
self.ring_assignation_data = assignation_data;
true let (node_zone, node_capacity) = self.get_node_zone_capacity();
} let nb_nodes = self.node_id_vec.len();
fn initial_partition_assignation(&self) -> Option<Vec<PartitionAss<'_>>> { for i in 0..nb_nodes
let (configured_nodes, zones) = self.configured_nodes_and_zones(); {
let n_zones = zones.len(); if zone_capacity.contains_key(&node_zone[i]) {
zone_capacity.insert(node_zone[i].clone(), zone_capacity[&node_zone[i]] + node_capacity[i]);
}
else{
zone_capacity.insert(node_zone[i].clone(), node_capacity[i]);
}
}
// Create a vector of partition indices (0 to 2**PARTITION_BITS-1) //Compute the optimal number of partitions per zone
let partitions_idx = (0usize..(1usize << PARTITION_BITS)).collect::<Vec<_>>(); let sum_capacities: u32 =zone_capacity.values().sum();
// Prepare ring if sum_capacities <= 0 {
let mut partitions: Vec<PartitionAss> = partitions_idx println!("No storage capacity in the network.");
.iter() return None;
.map(|_i| PartitionAss::new()) }
.collect::<Vec<_>>();
// Create MagLev priority queues for each node let nb_partitions = 1<<PARTITION_BITS;
let mut queues = configured_nodes
.iter()
.filter(|(_id, info)| info.capacity.is_some())
.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 = configured_nodes //Initially we would like to use zones porportionally to
.iter() //their capacity.
.filter_map(|(_, node_info)| node_info.capacity) //However, a large zone can be associated to at most
.fold(0, std::cmp::max); //nb_partitions to ensure replication of the date.
//So we take the min with nb_partitions:
let mut part_per_zone : HashMap<String, usize> =
zone_capacity.iter()
.map(|(k, v)| (k.clone(), min(nb_partitions,
(self.replication_factor*nb_partitions
**v as usize)/sum_capacities as usize) ) ).collect();
// Fill up ring //The replication_factor-1 upper bounds the number of
for rep in 0..self.replication_factor { //part_per_zones that are greater than nb_partitions
queues.sort_by_key(|(ni, _np, _q, _p)| { for _ in 1..self.replication_factor {
let queue_data = [&u16::to_be_bytes(rep as u16)[..], ni.as_slice()].concat(); //The number of partitions that are not assignated to
fasthash(&queue_data[..]) //a zone that takes nb_partitions.
}); let sum_capleft : u32 = zone_capacity.keys()
.filter(| k | {part_per_zone[*k] < nb_partitions} )
.map(|k| zone_capacity[k]).sum();
for (_, _, _, pos) in queues.iter_mut() { //The number of replication of the data that we need
*pos = 0; //to ensure.
} let repl_left = self.replication_factor
- part_per_zone.values()
.filter(|x| {**x == nb_partitions})
.count();
if repl_left == 0 {
break;
}
let mut remaining = partitions_idx.len(); for k in zone_capacity.keys() {
while remaining > 0 { if part_per_zone[k] != nb_partitions
let remaining0 = remaining; {
for i_round in 0..max_capacity { part_per_zone.insert(k.to_string() , min(nb_partitions,
for (node_id, node_info, q, pos) in queues.iter_mut() { (nb_partitions*zone_capacity[k] as usize
if i_round >= node_info.capacity.unwrap() { *repl_left)/sum_capleft as usize));
continue; }
} }
for (pos2, &qv) in q.iter().enumerate().skip(*pos) { }
if partitions[qv].add(Some(rep + 1), n_zones, node_id, node_info) {
remaining -= 1;
*pos = pos2 + 1;
break;
}
}
}
}
if remaining == remaining0 {
// No progress made, exit
return None;
}
}
}
Some(partitions) //Now we divide the zone's partition share proportionally
} //between their nodes.
fn configured_nodes_and_zones(&self) -> (Vec<(&Uuid, &NodeRole)>, HashSet<&str>) { let mut part_per_nod : Vec<usize> = (0..nb_nodes).map(
let configured_nodes = self |i| (part_per_zone[&node_zone[i]]*node_capacity[i] as usize)/zone_capacity[&node_zone[i]] as usize
.roles )
.items() .collect();
.iter()
.filter(|(_id, _, info)| info.0.is_some())
.map(|(id, _, info)| (id, info.0.as_ref().unwrap()))
.collect::<Vec<(&Uuid, &NodeRole)>>();
let zones = configured_nodes //We must update the part_per_zone to make it correspond to
.iter() //part_per_nod (because of integer rounding)
.filter(|(_id, info)| info.capacity.is_some()) part_per_zone = part_per_zone.iter().map(|(k,_)|
.map(|(_id, info)| info.zone.as_str()) (k.clone(), 0))
.collect::<HashSet<&str>>(); .collect();
for i in 0..nb_nodes {
part_per_zone.insert(
node_zone[i].clone() ,
part_per_zone[&node_zone[i]] + part_per_nod[i]);
}
(configured_nodes, zones) //Because of integer rounding, the total sum of part_per_nod
} //might not be replication_factor*nb_partitions.
// We need at most to add 1 to every non maximal value of
// part_per_nod. The capacity of a partition will be bounded
// by the minimal value of
// node_capacity_vec[i]/part_per_nod[i]
// so we try to maximize this minimal value, keeping the
// part_per_zone capped
fn compute_assignation_data<'a>( let discrepancy : usize =
&self, nb_partitions*self.replication_factor
configured_nodes: &[(&'a Uuid, &'a NodeRole)], - part_per_nod.iter().sum::<usize>();
partitions: &[PartitionAss<'a>],
) -> (Vec<Uuid>, Vec<CompactNodeType>) {
assert!(partitions.len() == (1 << PARTITION_BITS));
// Make a canonical order for nodes //We use a stupid O(N^2) algorithm. If the number of nodes
let mut nodes = configured_nodes //is actually expected to be high, one should optimize this.
.iter()
.filter(|(_id, info)| info.capacity.is_some())
.map(|(id, _)| **id)
.collect::<Vec<_>>();
let nodes_rev = nodes
.iter()
.enumerate()
.map(|(i, id)| (*id, i as CompactNodeType))
.collect::<HashMap<Uuid, CompactNodeType>>();
let mut assignation_data = vec![]; for _ in 0..discrepancy {
for partition in partitions.iter() { if let Some(idmax) = (0..nb_nodes)
assert!(partition.nodes.len() == self.replication_factor); .filter(|i| part_per_zone[&node_zone[*i]] < nb_partitions)
for (id, _) in partition.nodes.iter() { .max_by( |i,j|
assignation_data.push(*nodes_rev.get(id).unwrap()); (node_capacity[*i]*(part_per_nod[*j]+1) as u32)
} .cmp(&(node_capacity[*j]*(part_per_nod[*i]+1) as u32))
} )
{
part_per_nod[idmax] += 1;
part_per_zone.insert(node_zone[idmax].clone(),part_per_zone[&node_zone[idmax]]+1);
}
}
nodes.extend( //We check the algorithm consistency
configured_nodes
.iter()
.filter(|(_id, info)| info.capacity.is_none())
.map(|(id, _)| **id),
);
(nodes, assignation_data) let discrepancy : usize =
} nb_partitions*self.replication_factor
- part_per_nod.iter().sum::<usize>();
assert!(discrepancy == 0);
assert!(if let Some(v) = part_per_zone.values().max()
{*v <= nb_partitions} else {false} );
fn parse_assignation_data(&self) -> Vec<PartitionAss<'_>> { Some((part_per_nod, part_per_zone))
if self.ring_assignation_data.len() == self.replication_factor * (1 << PARTITION_BITS) { }
// If the previous assignation data is correct, use that
let mut partitions = vec![];
for i in 0..(1 << PARTITION_BITS) {
let mut part = PartitionAss::new();
for node_i in self.ring_assignation_data
[i * self.replication_factor..(i + 1) * self.replication_factor]
.iter()
{
let node_id = &self.node_id_vec[*node_i as usize];
if let Some(NodeRoleV(Some(info))) = self.roles.get(node_id) {
part.nodes.push((node_id, Some(info)));
} else {
part.nodes.push((node_id, None));
}
}
partitions.push(part);
}
partitions
} else {
// Otherwise start fresh
(0..(1 << PARTITION_BITS))
.map(|_| PartitionAss::new())
.collect()
}
}
fn partitions_per_node<'a>(&self, partitions: &[PartitionAss<'a>]) -> HashMap<&'a Uuid, usize> { //Returns vectors of zone and capacity; indexed by the same (temporary)
let mut partitions_per_node = HashMap::<&Uuid, usize>::new(); //indices as node_id_vec.
for p in partitions.iter() { fn get_node_zone_capacity(& self) -> (Vec<String> , Vec<u32>) {
for (id, _) in p.nodes.iter() {
*partitions_per_node.entry(*id).or_insert(0) += 1; let node_zone = self.node_id_vec.iter().map(
} |id_nod| match self.node_role(id_nod) {
} Some(NodeRole{zone,capacity:_,tags:_}) => zone.clone() ,
partitions_per_node _ => "".to_string()
} }
).collect();
let node_capacity = self.node_id_vec.iter().map(
|id_nod| match self.node_role(id_nod) {
Some(NodeRole{zone:_,capacity,tags:_}) =>
if let Some(c)=capacity
{*c}
else {0},
_ => 0
}
).collect();
(node_zone,node_capacity)
}
} }
// ---- Internal structs for partition assignation in layout ----
#[derive(Clone)]
struct PartitionAss<'a> { #[cfg(test)]
nodes: Vec<(&'a Uuid, Option<&'a NodeRole>)>, mod tests {
use super::*;
use itertools::Itertools;
fn check_assignation(cl : &ClusterLayout) {
//Check that input data has the right format
let nb_partitions = 1usize<<PARTITION_BITS;
assert!([1,2,3].contains(&cl.replication_factor));
assert!(cl.ring_assignation_data.len() == nb_partitions*cl.replication_factor);
let (node_zone, node_capacity) = cl.get_node_zone_capacity();
//Check that is is a correct assignation with zone redundancy
let rf = cl.replication_factor;
for i in 0..nb_partitions{
assert!( rf ==
cl.ring_assignation_data[rf*i..rf*(i+1)].iter()
.map(|nod| node_zone[*nod as usize].clone())
.unique()
.count() );
}
let nb_nodes = cl.node_id_vec.len();
//Check optimality
let node_nb_part =(0..nb_nodes).map(|i| cl.ring_assignation_data
.iter()
.filter(|x| **x==i as u8)
.count())
.collect::<Vec::<_>>();
let zone_vec = node_zone.iter().unique().collect::<Vec::<_>>();
let zone_nb_part = zone_vec.iter().map( |z| cl.ring_assignation_data.iter()
.filter(|x| node_zone[**x as usize] == **z)
.count()
).collect::<Vec::<_>>();
//Check optimality of the zone assignation : would it be better for the
//node_capacity/node_partitions ratio to change the assignation of a partition
if let Some(idmin) = (0..nb_nodes).min_by(
|i,j| (node_capacity[*i]*node_nb_part[*j] as u32)
.cmp(&(node_capacity[*j]*node_nb_part[*i] as u32))
){
if let Some(idnew) = (0..nb_nodes)
.filter( |i| if let Some(p) = zone_vec.iter().position(|z| **z==node_zone[*i])
{zone_nb_part[p] < nb_partitions }
else { false })
.max_by(
|i,j| (node_capacity[*i]*(node_nb_part[*j]as u32+1))
.cmp(&(node_capacity[*j]*(node_nb_part[*i] as u32+1)))
){
assert!(node_capacity[idmin]*(node_nb_part[idnew] as u32+1) >=
node_capacity[idnew]*node_nb_part[idmin] as u32);
}
}
//In every zone, check optimality of the nod assignation
for z in zone_vec {
let node_of_z_iter = (0..nb_nodes).filter(|id| node_zone[*id] == *z );
if let Some(idmin) = node_of_z_iter.clone().min_by(
|i,j| (node_capacity[*i]*node_nb_part[*j] as u32)
.cmp(&(node_capacity[*j]*node_nb_part[*i] as u32))
){
if let Some(idnew) = node_of_z_iter.min_by(
|i,j| (node_capacity[*i]*(node_nb_part[*j] as u32+1))
.cmp(&(node_capacity[*j]*(node_nb_part[*i] as u32+1)))
){
assert!(node_capacity[idmin]*(node_nb_part[idnew] as u32+1) >=
node_capacity[idnew]*node_nb_part[idmin] as u32);
}
}
}
}
fn update_layout(cl : &mut ClusterLayout, node_id_vec : &Vec<u8>,
node_capacity_vec : &Vec<u32> , node_zone_vec : &Vec<String>) {
for i in 0..node_id_vec.len(){
if let Some(x) = FixedBytes32::try_from(&[i as u8;32]) {
cl.node_id_vec.push(x);
}
let update = cl.roles.update_mutator(cl.node_id_vec[i] ,
NodeRoleV(Some(NodeRole{
zone : (node_zone_vec[i].to_string()),
capacity : (Some(node_capacity_vec[i])),
tags : (vec![])})));
cl.roles.merge(&update);
}
}
#[test]
fn test_assignation() {
let mut node_id_vec = vec![1,2,3];
let mut node_capacity_vec = vec![4000,1000,2000];
let mut node_zone_vec= vec!["A", "B", "C"].into_iter().map(|x| x.to_string()).collect();
let mut cl = ClusterLayout {
node_id_vec: vec![],
roles : LwwMap::new(),
replication_factor: 3,
ring_assignation_data : vec![],
version:0,
staging: LwwMap::new(),
staging_hash: sha256sum(&[1;32]),
};
update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
cl.calculate_partition_assignation();
check_assignation(&cl);
node_id_vec = vec![1,2,3, 4, 5, 6, 7, 8, 9];
node_capacity_vec = vec![4000,1000,1000, 3000, 1000, 1000, 2000, 10000, 2000];
node_zone_vec= vec!["A", "B", "C", "C", "C", "B", "G", "H", "I"].into_iter().map(|x| x.to_string()).collect();
update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
cl.calculate_partition_assignation();
check_assignation(&cl);
node_capacity_vec = vec![4000,1000,2000, 7000, 1000, 1000, 2000, 10000, 2000];
update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
cl.calculate_partition_assignation();
check_assignation(&cl);
node_capacity_vec = vec![4000,4000,2000, 7000, 1000, 9000, 2000, 10, 2000];
update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec);
cl.calculate_partition_assignation();
check_assignation(&cl);
}
} }
impl<'a> PartitionAss<'a> {
fn new() -> Self {
Self { nodes: Vec::new() }
}
fn nplus(&self, other: &PartitionAss<'a>) -> usize {
self.nodes
.iter()
.filter(|x| !other.nodes.contains(x))
.count()
}
fn txtplus(&self, other: &PartitionAss<'a>) -> String {
let mut nodes = self
.nodes
.iter()
.filter(|x| !other.nodes.contains(x))
.map(|x| format!("{:?}", x.0))
.collect::<Vec<_>>();
nodes.sort();
if self.nodes.iter().any(|x| other.nodes.contains(x)) {
nodes.push("...".into());
}
format!("[{}]", nodes.join(" "))
}
fn is_valid_transition_to(&self, other: &PartitionAss<'a>, replication_factor: usize) -> bool {
let min_keep_nodes_per_part = (replication_factor + 1) / 2;
let n_removed = self.nplus(other);
if self.nodes.len() <= min_keep_nodes_per_part {
n_removed == 0
} else {
n_removed <= self.nodes.len() - min_keep_nodes_per_part
}
}
// add is a key function in creating a PartitionAss, i.e. the list of nodes
// to which a partition is assigned. It tries to add a certain node id to the
// assignation, but checks that doing so is compatible with the NECESSARY
// condition that the partition assignation must be dispersed over different
// zones (datacenters) if enough zones exist. This is why it takes a n_zones
// parameter, which is the total number of zones that have existing nodes:
// if nodes in the assignation already cover all n_zones zones, then any node
// that is not yet in the assignation can be added. Otherwise, only nodes
// that are in a new zone can be added.
fn add(
&mut self,
target_len: Option<usize>,
n_zones: usize,
node: &'a Uuid,
role: &'a NodeRole,
) -> bool {
if let Some(tl) = target_len {
if self.nodes.len() != tl - 1 {
return false;
}
}
let p_zns = self
.nodes
.iter()
.map(|(_id, info)| info.unwrap().zone.as_str())
.collect::<HashSet<&str>>();
if (p_zns.len() < n_zones && !p_zns.contains(&role.zone.as_str()))
|| (p_zns.len() == n_zones && !self.nodes.iter().any(|(id, _)| *id == node))
{
self.nodes.push((node, Some(role)));
true
} else {
false
}
}
}

378
src/util/bipartite.rs Normal file
View file

@ -0,0 +1,378 @@
/*
* This module deals with graph algorithm in complete bipartite
* graphs. It is used in layout.rs to build the partition to node
* assignation.
* */
use std::cmp::{min,max};
use std::collections::VecDeque;
use rand::prelude::SliceRandom;
//Graph data structure for the flow algorithm.
#[derive(Clone,Copy,Debug)]
struct EdgeFlow{
c : i32,
flow : i32,
v : usize,
rev : usize,
}
//Graph data structure for the detection of positive cycles.
#[derive(Clone,Copy,Debug)]
struct WeightedEdge{
w : i32,
u : usize,
v : usize,
}
/* This function takes two matchings (old_match and new_match) in a
* complete bipartite graph. It returns a matching that has the
* same degree as new_match at every vertex, and that is as close
* as possible to old_match.
* */
pub fn optimize_matching( old_match : &Vec<Vec<usize>> ,
new_match : &Vec<Vec<usize>> ,
nb_right : usize )
-> Vec<Vec<usize>> {
let nb_left = old_match.len();
let ed = WeightedEdge{w:-1,u:0,v:0};
let mut edge_vec = vec![ed ; nb_left*nb_right];
//We build the complete bipartite graph structure, represented
//by the list of all edges.
for i in 0..nb_left {
for j in 0..nb_right{
edge_vec[i*nb_right + j].u = i;
edge_vec[i*nb_right + j].v = nb_left+j;
}
}
for i in 0..edge_vec.len() {
//We add the old matchings
if old_match[edge_vec[i].u].contains(&(edge_vec[i].v-nb_left)) {
edge_vec[i].w *= -1;
}
//We add the new matchings
if new_match[edge_vec[i].u].contains(&(edge_vec[i].v-nb_left)) {
(edge_vec[i].u,edge_vec[i].v) =
(edge_vec[i].v,edge_vec[i].u);
edge_vec[i].w *= -1;
}
}
//Now edge_vec is a graph where edges are oriented LR if we
//can add them to new_match, and RL otherwise. If
//adding/removing them makes the matching closer to old_match
//they have weight 1; and -1 otherwise.
//We shuffle the edge list so that there is no bias depending in
//partitions/zone label in the triplet dispersion
let mut rng = rand::thread_rng();
edge_vec.shuffle(&mut rng);
//Discovering and flipping a cycle with positive weight in this
//graph will make the matching closer to old_match.
//We use Bellman Ford algorithm to discover positive cycles
loop{
if let Some(cycle) = positive_cycle(&edge_vec, nb_left, nb_right) {
for i in cycle {
//We flip the edges of the cycle.
(edge_vec[i].u,edge_vec[i].v) =
(edge_vec[i].v,edge_vec[i].u);
edge_vec[i].w *= -1;
}
}
else {
//If there is no cycle, we return the optimal matching.
break;
}
}
//The optimal matching is build from the graph structure.
let mut matching = vec![Vec::<usize>::new() ; nb_left];
for e in edge_vec {
if e.u > e.v {
matching[e.v].push(e.u-nb_left);
}
}
matching
}
//This function finds a positive cycle in a bipartite wieghted graph.
fn positive_cycle( edge_vec : &Vec<WeightedEdge>, nb_left : usize,
nb_right : usize) -> Option<Vec<usize>> {
let nb_side_min = min(nb_left, nb_right);
let nb_vertices = nb_left+nb_right;
let weight_lowerbound = -((nb_left +nb_right) as i32) -1;
let mut accessed = vec![false ; nb_left];
//We try to find a positive cycle accessible from the left
//vertex i.
for i in 0..nb_left{
if accessed[i] {
continue;
}
let mut weight =vec![weight_lowerbound ; nb_vertices];
let mut prev =vec![ edge_vec.len() ; nb_vertices];
weight[i] = 0;
//We compute largest weighted paths from i.
//Since the graph is bipartite, any simple cycle has length
//at most 2*nb_side_min. In the general Bellman-Ford
//algorithm, the bound here is the number of vertices. Since
//the number of partitions can be much larger than the
//number of nodes, we optimize that.
for _ in 0..(2*nb_side_min) {
for j in 0..edge_vec.len() {
let e = edge_vec[j];
if weight[e.v] < weight[e.u]+e.w {
weight[e.v] = weight[e.u]+e.w;
prev[e.v] = j;
}
}
}
//We update the accessed table
for i in 0..nb_left {
if weight[i] > weight_lowerbound {
accessed[i] = true;
}
}
//We detect positive cycle
for e in edge_vec {
if weight[e.v] < weight[e.u]+e.w {
//it means e is on a path branching from a positive cycle
let mut was_seen = vec![false ; nb_vertices];
let mut curr = e.u;
//We track back with prev until we reach the cycle.
while !was_seen[curr]{
was_seen[curr] = true;
curr = edge_vec[prev[curr]].u;
}
//Now curr is on the cycle. We collect the edges ids.
let mut cycle = Vec::<usize>::new();
cycle.push(prev[curr]);
let mut cycle_vert = edge_vec[prev[curr]].u;
while cycle_vert != curr {
cycle.push(prev[cycle_vert]);
cycle_vert = edge_vec[prev[cycle_vert]].u;
}
return Some(cycle);
}
}
}
None
}
// This function takes two arrays of capacity and computes the
// maximal matching in the complete bipartite graph such that the
// left vertex i is matched to left_cap_vec[i] right vertices, and
// the right vertex j is matched to right_cap_vec[j] left vertices.
// To do so, we use Dinic's maximum flow algorithm.
pub fn dinic_compute_matching( left_cap_vec : Vec<u32>,
right_cap_vec : Vec<u32>) -> Vec< Vec<usize> >
{
let mut graph = Vec::<Vec::<EdgeFlow> >::new();
let ed = EdgeFlow{c:0,flow:0,v:0, rev:0};
// 0 will be the source
graph.push(vec![ed ; left_cap_vec.len()]);
for i in 0..left_cap_vec.len()
{
graph[0][i].c = left_cap_vec[i] as i32;
graph[0][i].v = i+2;
graph[0][i].rev = 0;
}
//1 will be the sink
graph.push(vec![ed ; right_cap_vec.len()]);
for i in 0..right_cap_vec.len()
{
graph[1][i].c = right_cap_vec[i] as i32;
graph[1][i].v = i+2+left_cap_vec.len();
graph[1][i].rev = 0;
}
//we add left vertices
for i in 0..left_cap_vec.len() {
graph.push(vec![ed ; 1+right_cap_vec.len()]);
graph[i+2][0].c = 0; //directed
graph[i+2][0].v = 0;
graph[i+2][0].rev = i;
for j in 0..right_cap_vec.len() {
graph[i+2][j+1].c = 1;
graph[i+2][j+1].v = 2+left_cap_vec.len()+j;
graph[i+2][j+1].rev = i+1;
}
}
//we add right vertices
for i in 0..right_cap_vec.len() {
let lft_ln = left_cap_vec.len();
graph.push(vec![ed ; 1+lft_ln]);
graph[i+lft_ln+2][0].c = graph[1][i].c;
graph[i+lft_ln+2][0].v = 1;
graph[i+lft_ln+2][0].rev = i;
for j in 0..left_cap_vec.len() {
graph[i+2+lft_ln][j+1].c = 0; //directed
graph[i+2+lft_ln][j+1].v = j+2;
graph[i+2+lft_ln][j+1].rev = i+1;
}
}
//To ensure the dispersion of the triplets generated by the
//assignation, we shuffle the neighbours of the nodes. Hence,
//left vertices do not consider the right ones in the same order.
let mut rng = rand::thread_rng();
for i in 0..graph.len() {
graph[i].shuffle(&mut rng);
//We need to update the ids of the reverse edges.
for j in 0..graph[i].len() {
let target_v = graph[i][j].v;
let target_rev = graph[i][j].rev;
graph[target_v][target_rev].rev = j;
}
}
let nb_vertices = graph.len();
//We run Dinic's max flow algorithm
loop{
//We build the level array from Dinic's algorithm.
let mut level = vec![-1; nb_vertices];
let mut fifo = VecDeque::new();
fifo.push_back((0,0));
while !fifo.is_empty() {
if let Some((id,lvl)) = fifo.pop_front(){
if level[id] == -1 {
level[id] = lvl;
for e in graph[id].iter(){
if e.c-e.flow > 0{
fifo.push_back((e.v,lvl+1));
}
}
}
}
}
if level[1] == -1 {
//There is no residual flow
break;
}
//Now we run DFS respecting the level array
let mut next_nbd = vec![0; nb_vertices];
let mut lifo = VecDeque::new();
let flow_upper_bound;
if let Some(x) = left_cap_vec.iter().max() {
flow_upper_bound=*x as i32;
}
else {
flow_upper_bound = 0;
assert!(false);
}
lifo.push_back((0,flow_upper_bound));
loop
{
if let Some((id_tmp, f_tmp)) = lifo.back() {
let id = *id_tmp;
let f = *f_tmp;
if id == 1 {
//The DFS reached the sink, we can add a
//residual flow.
lifo.pop_back();
while !lifo.is_empty() {
if let Some((id,_)) = lifo.pop_back(){
let nbd=next_nbd[id];
graph[id][nbd].flow += f;
let id_v = graph[id][nbd].v;
let nbd_v = graph[id][nbd].rev;
graph[id_v][nbd_v].flow -= f;
}
}
lifo.push_back((0,flow_upper_bound));
continue;
}
//else we did not reach the sink
let nbd = next_nbd[id];
if nbd >= graph[id].len() {
//There is nothing to explore from id anymore
lifo.pop_back();
if let Some((parent, _)) = lifo.back(){
next_nbd[*parent] +=1;
}
continue;
}
//else we can try to send flow from id to its nbd
let new_flow = min(f,graph[id][nbd].c
- graph[id][nbd].flow);
if level[graph[id][nbd].v] <= level[id] ||
new_flow == 0 {
//We cannot send flow to nbd.
next_nbd[id] += 1;
continue;
}
//otherwise, we send flow to nbd.
lifo.push_back((graph[id][nbd].v, new_flow));
}
else {
break;
}
}
}
//We return the association
let assoc_table = (0..left_cap_vec.len()).map(
|id| graph[id+2].iter()
.filter(|e| e.flow > 0)
.map( |e| e.v-2-left_cap_vec.len())
.collect()).collect();
//consistency check
//it is a flow
for i in 3..graph.len(){
assert!( graph[i].iter().map(|e| e.flow).sum::<i32>() == 0);
for e in graph[i].iter(){
assert!(e.flow + graph[e.v][e.rev].flow == 0);
}
}
//it solves the matching problem
for i in 0..left_cap_vec.len(){
assert!(left_cap_vec[i] as i32 ==
graph[i+2].iter().map(|e| max(0,e.flow)).sum::<i32>());
}
for i in 0..right_cap_vec.len(){
assert!(right_cap_vec[i] as i32 ==
graph[i+2+left_cap_vec.len()].iter()
.map(|e| max(0,e.flow)).sum::<i32>());
}
assoc_table
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_flow() {
let left_vec = vec![3;8];
let right_vec = vec![0,4,8,4,8];
//There are asserts in the function that computes the flow
let _ = dinic_compute_matching(left_vec, right_vec);
}
//maybe add tests relative to the matching optilization ?
}

1
src/util/lib.rs
View file

@ -4,6 +4,7 @@
extern crate tracing; extern crate tracing;
pub mod background; pub mod background;
pub mod bipartite;
pub mod config; pub mod config;
pub mod crdt; pub mod crdt;
pub mod data; pub mod data;