Refactor code for apply/revert, implement Update/Apply/RevertLayout

src/rpc/Cargo.toml

@@ -19,6 +19,7 @@ garage_util = { version = "0.7.0", path = "../util" }
 arc-swap = "1.0"
 bytes = "1.0"
 gethostname = "0.2"
+git-version = "0.3.4"
 hex = "0.4"
 tracing = "0.1.30"
 rand = "0.8"

src/rpc/layout.rs

@@ -5,6 +5,7 @@ use serde::{Deserialize, Serialize};
 
 use garage_util::crdt::{AutoCrdt, Crdt, LwwMap};
 use garage_util::data::*;
+use garage_util::error::*;
 
 use crate::ring::*;
 
@@ -100,6 +101,61 @@ impl ClusterLayout {
 		}
 	}
 
+	pub fn apply_staged_changes(mut self, version: Option<u64>) -> Result<Self, Error> {
+		match version {
+			None => {
+				let error = r#"
+Please pass the new layout version number to ensure that you are writing the correct version of the cluster layout.
+To know the correct value of the new layout version, invoke `garage layout show` and review the proposed changes.
+				"#;
+				return Err(Error::Message(error.into()));
+			}
+			Some(v) => {
+				if v != self.version + 1 {
+					return Err(Error::Message("Invalid new layout version".into()));
+				}
+			}
+		}
+
+		self.roles.merge(&self.staging);
+		self.roles.retain(|(_, _, v)| v.0.is_some());
+
+		if !self.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()));
+		}
+
+		self.staging.clear();
+		self.staging_hash = blake2sum(&rmp_to_vec_all_named(&self.staging).unwrap()[..]);
+
+		self.version += 1;
+
+		Ok(self)
+	}
+
+	pub fn revert_staged_changes(mut self, version: Option<u64>) -> Result<Self, Error> {
+		match version {
+			None => {
+				let error = r#"
+Please pass the new layout version number to ensure that you are writing the correct version of the cluster layout.
+To know the correct value of the new layout version, invoke `garage layout show` and review the proposed changes.
+				"#;
+				return Err(Error::Message(error.into()));
+			}
+			Some(v) => {
+				if v != self.version + 1 {
+					return Err(Error::Message("Invalid new layout version".into()));
+				}
+			}
+		}
+
+		self.staging.clear();
+		self.staging_hash = blake2sum(&rmp_to_vec_all_named(&self.staging).unwrap()[..]);
+
+		self.version += 1;
+
+		Ok(self)
+	}
+
 	/// Returns a list of IDs of nodes that currently have
 	/// a role in the cluster
 	pub fn node_ids(&self) -> &[Uuid] {

src/rpc/system.rs

@@ -315,6 +315,14 @@ impl System {
 	// ---- Administrative operations (directly available and
 	//      also available through RPC) ----
 
+	pub fn garage_version(&self) -> &'static str {
+		option_env!("GIT_VERSION").unwrap_or(git_version::git_version!(
+			prefix = "git:",
+			cargo_prefix = "cargo:",
+			fallback = "unknown"
+		))
+	}
+
 	pub fn get_known_nodes(&self) -> Vec<KnownNodeInfo> {
 		let node_status = self.node_status.read().unwrap();
 		let known_nodes = self
@@ -345,6 +353,14 @@ impl System {
 		self.ring.borrow().layout.clone()
 	}
 
+	pub async fn update_cluster_layout(
+		self: &Arc<Self>,
+		layout: &ClusterLayout,
+	) -> Result<(), Error> {
+		self.handle_advertise_cluster_layout(layout).await?;
+		Ok(())
+	}
+
 	pub async fn connect(&self, node: &str) -> Result<(), Error> {
 		let (pubkey, addrs) = parse_and_resolve_peer_addr(node).ok_or_else(|| {
 			Error::Message(format!(
@@ -495,7 +511,7 @@ impl System {
 	}
 
 	async fn handle_advertise_cluster_layout(
-		self: Arc<Self>,
+		self: &Arc<Self>,
 		adv: &ClusterLayout,
 	) -> Result<SystemRpc, Error> {
 		let update_ring = self.update_ring.lock().await;