1 files changed, 170 insertions, 0 deletions
diff --git a/src/rpc/layout/history.rs b/src/rpc/layout/history.rs
new file mode 100644
index 00000000..b3019f58
--- /dev/null
+++ b/src/rpc/layout/history.rs
@@ -0,0 +1,170 @@
+use std::cmp::Ordering;
+use std::sync::Arc;
+
+use garage_util::crdt::{Crdt, Lww, LwwMap};
+use garage_util::data::*;
+use garage_util::encode::nonversioned_encode;
+use garage_util::error::*;
+
+use super::schema::*;
+use super::*;
+
+impl LayoutHistory {
+	pub fn new(replication_factor: usize) -> Self {
+		let version = LayoutVersion::new(replication_factor);
+
+		let staging_parameters = Lww::<LayoutParameters>::new(version.parameters);
+		let empty_lwwmap = LwwMap::new();
+
+		let mut ret = LayoutHistory {
+			versions: vec![version].into_boxed_slice().into(),
+			update_trackers: Default::default(),
+			staging_parameters,
+			staging_roles: empty_lwwmap,
+			staging_hash: [0u8; 32].into(),
+		};
+		ret.staging_hash = ret.calculate_staging_hash();
+		ret
+	}
+
+	pub fn current(&self) -> &LayoutVersion {
+		self.versions.last().as_ref().unwrap()
+	}
+
+	pub(crate) fn calculate_staging_hash(&self) -> Hash {
+		let hashed_tuple = (&self.staging_roles, &self.staging_parameters);
+		blake2sum(&nonversioned_encode(&hashed_tuple).unwrap()[..])
+	}
+
+	// ================== updates to layout, public interface ===================
+
+	pub fn merge(&mut self, other: &LayoutHistory) -> bool {
+		let mut changed = false;
+
+		// Merge staged layout changes
+		match other.current().version.cmp(&self.current().version) {
+			Ordering::Greater => {
+				self.staging_parameters = other.staging_parameters.clone();
+				self.staging_roles = other.staging_roles.clone();
+				self.staging_hash = other.staging_hash;
+				changed = true;
+			}
+			Ordering::Equal => {
+				self.staging_parameters.merge(&other.staging_parameters);
+				self.staging_roles.merge(&other.staging_roles);
+
+				let new_staging_hash = self.calculate_staging_hash();
+				if new_staging_hash != self.staging_hash {
+					changed = true;
+				}
+
+				self.staging_hash = new_staging_hash;
+			}
+			Ordering::Less => (),
+		}
+
+		// Add any new versions to history
+		let mut versions = self.versions.to_vec();
+		for v2 in other.versions.iter() {
+			if let Some(v1) = versions.iter().find(|v| v.version == v2.version) {
+				if v1 != v2 {
+					error!("Inconsistent layout histories: different layout compositions for version {}. Your cluster will be broken as long as this layout version is not replaced.", v2.version);
+				}
+			} else if versions.iter().all(|v| v.version != v2.version - 1) {
+				error!(
+					"Cannot receive new layout version {}, version {} is missing",
+					v2.version,
+					v2.version - 1
+				);
+			} else {
+				versions.push(v2.clone());
+				changed = true;
+			}
+		}
+		self.versions = Arc::from(versions.into_boxed_slice());
+
+		// Merge trackers
+		self.update_trackers.merge(&other.update_trackers);
+
+		changed
+	}
+
+	pub fn apply_staged_changes(mut self, version: Option<u64>) -> Result<(Self, Message), 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.current().version + 1 {
+					return Err(Error::Message("Invalid new layout version".into()));
+				}
+			}
+		}
+
+		let mut new_version = self.current().clone();
+		new_version.version += 1;
+
+		new_version.roles.merge(&self.staging_roles);
+		new_version.roles.retain(|(_, _, v)| v.0.is_some());
+		new_version.parameters = *self.staging_parameters.get();
+
+		self.staging_roles.clear();
+		self.staging_hash = self.calculate_staging_hash();
+
+		let msg = new_version.calculate_partition_assignment()?;
+
+		let mut versions = self.versions.to_vec();
+		versions.push(new_version);
+		self.versions = Arc::from(versions.into_boxed_slice());
+
+		Ok((self, msg))
+	}
+
+	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.current().version + 1 {
+					return Err(Error::Message("Invalid new layout version".into()));
+				}
+			}
+		}
+
+		self.staging_roles.clear();
+		self.staging_parameters.update(self.current().parameters);
+		self.staging_hash = self.calculate_staging_hash();
+
+		// TODO this is stupid, we should have a separate version counter/LWW
+		// for the staging params
+		let mut new_version = self.current().clone();
+		new_version.version += 1;
+
+		let mut versions = self.versions.to_vec();
+		versions.push(new_version);
+		self.versions = Arc::from(versions.into_boxed_slice());
+
+		Ok(self)
+	}
+
+	pub fn check(&self) -> Result<(), String> {
+		// Check that the hash of the staging data is correct
+		let staging_hash = self.calculate_staging_hash();
+		if staging_hash != self.staging_hash {
+			return Err("staging_hash is incorrect".into());
+		}
+
+		// TODO: anythign more ?
+
+		self.current().check()
+	}
+}