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new layout: make zone_redundancy optionnal (if not set, is maximum)

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This commit is contained in:
Alex 2023-09-18 11:57:36 +02:00
parent 2e229d4430
commit 015ccb39aa
3 changed files with 120 additions and 52 deletions
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37
src/garage/cli/layout.rs
View file

@ -261,28 +261,35 @@ pub async fn cmd_config_layout(
let mut did_something = false;
match config_opt.redundancy {
None => (),
Some(r) => {
if r > layout.replication_factor {
println!(
"The zone redundancy must be smaller or equal to the \
replication factor ({}).",
layout.replication_factor
);
} else if r < 1 {
println!("The zone redundancy must be at least 1.");
} else {
layout
.staging_parameters
.update(LayoutParameters { zone_redundancy: r });
println!("The new zone redundancy has been saved ({}).", r);
Some(r_str) => {
let r = r_str
.parse::<ZoneRedundancy>()
.ok_or_message("invalid zone redundancy value")?;
if let ZoneRedundancy::AtLeast(r_int) = r {
if r_int > layout.replication_factor {
return Err(Error::Message(format!(
"The zone redundancy must be smaller or equal to the \
replication factor ({}).",
layout.replication_factor
)));
} else if r_int < 1 {
return Err(Error::Message(
"The zone redundancy must be at least 1.".into(),
));
}
}
layout
.staging_parameters
.update(LayoutParameters { zone_redundancy: r });
println!("The new zone redundancy has been saved ({}).", r);
did_something = true;
}
}
if !did_something {
return Err(Error::Message(
"Please specify an action for `garage layout config` to do".into(),
"Please specify an action for `garage layout config`".into(),
));
}

4
src/garage/cli/structs.rs
View file

@ -143,9 +143,9 @@ pub struct RemoveRoleOpt {
#[derive(StructOpt, Debug)]
pub struct ConfigLayoutOpt {
/// Zone redundancy parameter
/// Zone redundancy parameter ('none'/'max' or integer)
#[structopt(short = "r", long = "redundancy")]
pub(crate) redundancy: Option<usize>,
pub(crate) redundancy: Option<String>,
}
#[derive(StructOpt, Debug)]

131
src/rpc/layout.rs
View file

@ -1,6 +1,7 @@
use std::cmp::Ordering;
use std::collections::HashMap;
use std::collections::HashSet;
use std::fmt;
use bytesize::ByteSize;
use itertools::Itertools;
@ -115,7 +116,16 @@ mod v09 {
/// algorithm. It is stored as a Crdt.
#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug, Serialize, Deserialize)]
pub struct LayoutParameters {
pub zone_redundancy: usize,
pub zone_redundancy: ZoneRedundancy,
}
/// Zone redundancy: if set to AtLeast(x), the layout calculation will aim to store copies
/// of each partition on at least that number of different zones.
/// If None, copies will be stored on the maximum possible number of zones.
#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug, Serialize, Deserialize)]
pub enum ZoneRedundancy {
AtLeast(usize),
Maximum,
}
impl garage_util::migrate::Migrate for ClusterLayout {
@ -125,7 +135,6 @@ mod v09 {
fn migrate(previous: Self::Previous) -> Self {
use itertools::Itertools;
use std::collections::HashSet;
// In the old layout, capacities are in an arbitrary unit,
// but in the new layout they are in bytes.
@ -152,17 +161,10 @@ mod v09 {
.min()
.unwrap_or(0);
// Determine zone redundancy parameter
let zone_redundancy = std::cmp::min(
previous.replication_factor,
roles
.items()
.iter()
.filter_map(|(_, _, r)| r.0.as_ref().map(|p| p.zone.as_str()))
.collect::<HashSet<&str>>()
.len(),
);
let parameters = LayoutParameters { zone_redundancy };
// By default, zone_redundancy is None (i.e. maximum possible value)
let parameters = LayoutParameters {
zone_redundancy: ZoneRedundancy::Maximum,
};
let mut res = Self {
version: previous.version,
@ -224,13 +226,37 @@ impl NodeRole {
}
}
impl fmt::Display for ZoneRedundancy {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
ZoneRedundancy::Maximum => write!(f, "maximum"),
ZoneRedundancy::AtLeast(x) => write!(f, "{}", x),
}
}
}
impl core::str::FromStr for ZoneRedundancy {
type Err = &'static str;
fn from_str(s: &str) -> Result<Self, Self::Err> {
match s {
"none" | "max" | "maximum" => Ok(ZoneRedundancy::Maximum),
x => {
let v = x
.parse::<usize>()
.map_err(|_| "zone redundancy must be 'none'/'max' or an integer")?;
Ok(ZoneRedundancy::AtLeast(v))
}
}
}
}
// Implementation of the ClusterLayout methods unrelated to the assignment algorithm.
impl ClusterLayout {
pub fn new(replication_factor: usize) -> Self {
// We set the default zone redundancy to be equal to the replication factor,
// i.e. as strict as possible.
// We set the default zone redundancy to be None, meaning that the maximum
// possible value will be used depending on the cluster topology
let parameters = LayoutParameters {
zone_redundancy: replication_factor,
zone_redundancy: ZoneRedundancy::Maximum,
};
let staging_parameters = Lww::<LayoutParameters>::new(parameters.clone());
@ -418,6 +444,23 @@ To know the correct value of the new layout version, invoke `garage layout show`
Ok(total_capacity)
}
/// Returns the effective value of the zone_redundancy parameter
fn effective_zone_redundancy(&self) -> usize {
match self.parameters.zone_redundancy {
ZoneRedundancy::AtLeast(v) => v,
ZoneRedundancy::Maximum => {
let n_zones = self
.roles
.items()
.iter()
.filter_map(|(_, _, role)| role.0.as_ref().map(|x| x.zone.as_str()))
.collect::<HashSet<&str>>()
.len();
std::cmp::min(n_zones, self.replication_factor)
}
}
}
/// Check a cluster layout for internal consistency
/// (assignment, roles, parameters, partition size)
/// returns true if consistent, false if error
@ -471,6 +514,7 @@ To know the correct value of the new layout version, invoke `garage layout show`
}
// Check that every partition is associated to distinct nodes
let zone_redundancy = self.effective_zone_redundancy();
let rf = self.replication_factor;
for p in 0..(1 << PARTITION_BITS) {
let nodes_of_p = self.ring_assignment_data[rf * p..rf * (p + 1)].to_vec();
@ -485,11 +529,10 @@ To know the correct value of the new layout version, invoke `garage layout show`
.expect("Zone not found.")
})
.collect::<Vec<_>>();
let redundancy = self.parameters.zone_redundancy;
if zones_of_p.iter().unique().count() < redundancy {
if zones_of_p.iter().unique().count() < zone_redundancy {
return Err(format!(
"nodes of partition are in less than {} distinct zones",
redundancy
zone_redundancy
));
}
}
@ -518,7 +561,7 @@ To know the correct value of the new layout version, invoke `garage layout show`
// algorithm.
let cl2 = self.clone();
let (_, zone_to_id) = cl2.generate_nongateway_zone_ids().unwrap();
match cl2.compute_optimal_partition_size(&zone_to_id) {
match cl2.compute_optimal_partition_size(&zone_to_id, zone_redundancy) {
Ok(s) if s != self.partition_size => {
return Err(format!(
"partition_size ({}) is different than optimal value ({})",
@ -533,6 +576,8 @@ To know the correct value of the new layout version, invoke `garage layout show`
}
}
// ====================================================================================
// Implementation of the ClusterLayout methods related to the assignment algorithm.
impl ClusterLayout {
/// This function calculates a new partition-to-node assignment.
@ -549,13 +594,15 @@ impl ClusterLayout {
// changes in the layout. We retrieve the old_assignment reframed with new ids
let old_assignment_opt = self.update_node_id_vec()?;
let zone_redundancy = self.effective_zone_redundancy();
let mut msg = Message::new();
msg.push("==== COMPUTATION OF A NEW PARTITION ASSIGNATION ====".into());
msg.push("".into());
msg.push(format!(
"Partitions are \
replicated {} times on at least {} distinct zones.",
self.replication_factor, self.parameters.zone_redundancy
self.replication_factor, zone_redundancy
));
// We generate for once numerical ids for the zones of non gateway nodes,
@ -570,12 +617,12 @@ impl ClusterLayout {
nb_nongateway_nodes, self.replication_factor
)));
}
if id_to_zone.len() < self.parameters.zone_redundancy {
if id_to_zone.len() < zone_redundancy {
return Err(Error::Message(format!(
"The number of zones with non-gateway \
nodes ({}) is smaller than the redundancy parameter ({})",
id_to_zone.len(),
self.parameters.zone_redundancy
zone_redundancy
)));
}
@ -583,7 +630,7 @@ impl ClusterLayout {
// Capacities should be given in a unit so that partition size is at least 100.
// In this case, integer rounding plays a marginal role in the percentages of
// optimality.
let partition_size = self.compute_optimal_partition_size(&zone_to_id)?;
let partition_size = self.compute_optimal_partition_size(&zone_to_id, zone_redundancy)?;
msg.push("".into());
if old_assignment_opt != None {
@ -610,7 +657,8 @@ impl ClusterLayout {
// We compute a first flow/assignment that is heuristically close to the previous
// assignment
let mut gflow = self.compute_candidate_assignment(&zone_to_id, &old_assignment_opt)?;
let mut gflow =
self.compute_candidate_assignment(&zone_to_id, &old_assignment_opt, zone_redundancy)?;
if let Some(assoc) = &old_assignment_opt {
// We minimize the distance to the previous assignment.
self.minimize_rebalance_load(&mut gflow, &zone_to_id, assoc)?;
@ -735,9 +783,10 @@ impl ClusterLayout {
fn compute_optimal_partition_size(
&self,
zone_to_id: &HashMap<String, usize>,
zone_redundancy: usize,
) -> Result<u64, Error> {
let empty_set = HashSet::<(usize, usize)>::new();
let mut g = self.generate_flow_graph(1, zone_to_id, &empty_set)?;
let mut g = self.generate_flow_graph(1, zone_to_id, &empty_set, zone_redundancy)?;
g.compute_maximal_flow()?;
if g.get_flow_value()? < (NB_PARTITIONS * self.replication_factor) as i64 {
return Err(Error::Message(
@ -750,7 +799,12 @@ impl ClusterLayout {
let mut s_down = 1;
let mut s_up = self.get_total_capacity()?;
while s_down + 1 < s_up {
g = self.generate_flow_graph((s_down + s_up) / 2, zone_to_id, &empty_set)?;
g = self.generate_flow_graph(
(s_down + s_up) / 2,
zone_to_id,
&empty_set,
zone_redundancy,
)?;
g.compute_maximal_flow()?;
if g.get_flow_value()? < (NB_PARTITIONS * self.replication_factor) as i64 {
s_up = (s_down + s_up) / 2;
@ -789,18 +843,18 @@ impl ClusterLayout {
partition_size: u64,
zone_to_id: &HashMap<String, usize>,
exclude_assoc: &HashSet<(usize, usize)>,
zone_redundancy: usize,
) -> Result<Graph<FlowEdge>, Error> {
let vertices =
ClusterLayout::generate_graph_vertices(zone_to_id.len(), self.nongateway_nodes().len());
let mut g = Graph::<FlowEdge>::new(&vertices);
let nb_zones = zone_to_id.len();
let redundancy = self.parameters.zone_redundancy;
for p in 0..NB_PARTITIONS {
g.add_edge(Vertex::Source, Vertex::Pup(p), redundancy as u64)?;
g.add_edge(Vertex::Source, Vertex::Pup(p), zone_redundancy as u64)?;
g.add_edge(
Vertex::Source,
Vertex::Pdown(p),
(self.replication_factor - redundancy) as u64,
(self.replication_factor - zone_redundancy) as u64,
)?;
for z in 0..nb_zones {
g.add_edge(Vertex::Pup(p), Vertex::PZ(p, z), 1)?;
@ -829,6 +883,7 @@ impl ClusterLayout {
&self,
zone_to_id: &HashMap<String, usize>,
prev_assign_opt: &Option<Vec<Vec<usize>>>,
zone_redundancy: usize,
) -> Result<Graph<FlowEdge>, Error> {
// We list the (partition,node) associations that are not used in the
// previous assignment
@ -846,7 +901,12 @@ impl ClusterLayout {
}
// We compute the best flow using only the edges used in the previous assignment
let mut g = self.generate_flow_graph(self.partition_size, zone_to_id, &exclude_edge)?;
let mut g = self.generate_flow_graph(
self.partition_size,
zone_to_id,
&exclude_edge,
zone_redundancy,
)?;
g.compute_maximal_flow()?;
// We add the excluded edges and compute the maximal flow with the full graph.
@ -997,7 +1057,7 @@ impl ClusterLayout {
if *prev_assign_opt == None {
new_partitions = stored_partitions.clone();
new_partitions_zone = stored_partitions_zone.clone();
//new_partitions_zone = stored_partitions_zone.clone();
}
// We display the statistics
@ -1124,7 +1184,7 @@ mod tests {
let mut curr_zone = 0;
let redundancy = cl.parameters.zone_redundancy;
let redundancy = cl.effective_zone_redundancy();
for replic in 0..cl.replication_factor {
for p in 0..NB_PARTITIONS {
@ -1176,8 +1236,9 @@ mod tests {
);
cl.staging_roles.merge(&update);
}
cl.staging_parameters
.update(LayoutParameters { zone_redundancy });
cl.staging_parameters.update(LayoutParameters {
zone_redundancy: ZoneRedundancy::AtLeast(zone_redundancy),
});
cl.staging_hash = cl.calculate_staging_hash();
}