micropelago/garage
3
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Small change to partition assignation algorithm

Browse Source 
This change helps ensure that nodes for each partition are spread
over all datacenters, a property that wasn't ensured previously
when going from a 2 DC deployment to a 3 DC deployment
This commit is contained in:
Alex Auvolat 2022-02-10 16:10:21 +01:00
parent 43945234ae
commit 413ab0eaed
No known key found for this signature in database
GPG Key ID: 0E496D15096376BE
2 changed files with 37 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
src/garage/cli/layout.rs
View File

@ -196,6 +196,15 @@ pub async fn cmd_apply_layout(
) -> Result<(), Error> {
let mut layout = fetch_layout(rpc_cli, rpc_host).await?;
layout.roles.merge(&layout.staging);
if !layout.calculate_partition_assignation() {
return Err(Error::Message("Could not calculate new assignation of partitions to nodes. This can happen if there are less nodes than the desired number of copies of your data (see the replication_mode configuration parameter).".into()));
}
layout.staging.clear();
layout.staging_hash = blake2sum(&rmp_to_vec_all_named(&layout.staging).unwrap()[..]);
match apply_opt.version {
None => {
println!("Please pass the --version flag to ensure that you are writing the correct version of the cluster layout.");
@ -209,15 +218,6 @@ pub async fn cmd_apply_layout(
}
}
layout.roles.merge(&layout.staging);
if !layout.calculate_partition_assignation() {
return Err(Error::Message("Could not calculate new assignation of partitions to nodes. This can happen if there are less nodes than the desired number of copies of your data (see the replication_mode configuration parameter).".into()));
}
layout.staging.clear();
layout.staging_hash = blake2sum(&rmp_to_vec_all_named(&layout.staging).unwrap()[..]);
layout.version += 1;
send_layout(rpc_cli, rpc_host, layout).await?;

28
src/rpc/layout.rs
View File

@ -172,12 +172,38 @@ impl ClusterLayout {
println!("Calculating updated partition assignation, this may take some time...");
println!();
// Get old partition assignation
let old_partitions = self.parse_assignation_data();
// Create new partition assignation starting from old one
let mut partitions = old_partitions.clone();
// Cleanup steps in new partition assignation:
let min_keep_nodes_per_part = (self.replication_factor + 1) / 2;
for part in partitions.iter_mut() {
// - remove from assignation nodes that don't have a role in the layout anymore
part.nodes
.retain(|(_, info)| info.map(|x| x.capacity.is_some()).unwrap_or(false));
// - remove from assignation some nodes that are in the same datacenter
// if we can, so that the later steps can ensure datacenter variety
// as much as possible (but still under the constraint that each partition
// should not move from at least a certain number of nodes that is
// min_keep_nodes_per_part)
'rmloop: while part.nodes.len() > min_keep_nodes_per_part {
let mut zns_c = HashMap::<&str, usize>::new();
for (_id, info) in part.nodes.iter() {
*zns_c.entry(info.unwrap().zone.as_str()).or_insert(0) += 1;
}
for i in 0..part.nodes.len() {
if zns_c[part.nodes[i].1.unwrap().zone.as_str()] > 1 {
part.nodes.remove(i);
continue 'rmloop;
}
}
break;
}
}
// When nodes are removed, or when bootstraping an assignation from
@ -196,6 +222,8 @@ impl ClusterLayout {
}
}
None => {
// Not enough nodes in cluster to build a correct assignation.
// Signal it by returning an error.
return false;
}
}