From 523d2ecb9511f74e144cd116b942d6c1bf0f546d Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Thu, 9 Nov 2023 11:19:43 +0100
Subject: layout: use separate CRDT for staged layout changes

---
 src/rpc/layout/schema.rs | 106 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 100 insertions(+), 6 deletions(-)

(limited to 'src/rpc/layout/schema.rs')

diff --git a/src/rpc/layout/schema.rs b/src/rpc/layout/schema.rs
index 14e797be..c5b9b1d3 100644
--- a/src/rpc/layout/schema.rs
+++ b/src/rpc/layout/schema.rs
@@ -1,3 +1,9 @@
+use std::fmt;
+
+use bytesize::ByteSize;
+
+use garage_util::crdt::{AutoCrdt, Crdt};
+
 mod v08 {
 	use crate::layout::CompactNodeType;
 	use garage_util::crdt::LwwMap;
@@ -210,6 +216,15 @@ mod v010 {
 		pub ring_assignment_data: Vec<CompactNodeType>,
 	}
 
+	/// The staged changes for the next layout version
+	#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+	pub struct LayoutStaging {
+		/// Parameters to be used in the next partition assignment computation.
+		pub parameters: Lww<LayoutParameters>,
+		/// Role changes which are staged for the next version of the layout
+		pub roles: LwwMap<Uuid, NodeRoleV>,
+	}
+
 	/// The history of cluster layouts
 	#[derive(Clone, Debug, Serialize, Deserialize)]
 	pub struct LayoutHistory {
@@ -219,10 +234,8 @@ mod v010 {
 		/// Update trackers
 		pub update_trackers: UpdateTrackers,
 
-		/// Parameters to be used in the next partition assignment computation.
-		pub staging_parameters: Lww<LayoutParameters>,
-		/// Role changes which are staged for the next version of the layout
-		pub staging_roles: LwwMap<Uuid, NodeRoleV>,
+		/// Staged changes for the next version
+		pub staging: Lww<LayoutStaging>,
 		/// Hash of the serialized staging_parameters + staging_roles
 		pub staging_hash: Hash,
 	}
@@ -265,6 +278,10 @@ mod v010 {
 					.map(|x| (*x, version.version))
 					.collect::<HashMap<Uuid, u64>>(),
 			);
+			let staging = LayoutStaging {
+				parameters: previous.staging_parameters,
+				roles: previous.staging_roles,
+			};
 			let mut ret = Self {
 				versions: vec![version],
 				update_trackers: UpdateTrackers {
@@ -272,8 +289,7 @@ mod v010 {
 					sync_map: update_tracker.clone(),
 					sync_ack_map: update_tracker.clone(),
 				},
-				staging_parameters: previous.staging_parameters,
-				staging_roles: previous.staging_roles,
+				staging: Lww::raw(previous.version, staging),
 				staging_hash: [0u8; 32].into(),
 			};
 			ret.staging_hash = ret.calculate_staging_hash();
@@ -283,3 +299,81 @@ mod v010 {
 }
 
 pub use v010::*;
+
+// ---- utility functions ----
+
+impl AutoCrdt for LayoutParameters {
+	const WARN_IF_DIFFERENT: bool = true;
+}
+
+impl AutoCrdt for NodeRoleV {
+	const WARN_IF_DIFFERENT: bool = true;
+}
+
+impl Crdt for LayoutStaging {
+	fn merge(&mut self, other: &LayoutStaging) {
+		self.parameters.merge(&other.parameters);
+		self.roles.merge(&other.roles);
+	}
+}
+
+impl NodeRole {
+	pub fn capacity_string(&self) -> String {
+		match self.capacity {
+			Some(c) => ByteSize::b(c).to_string_as(false),
+			None => "gateway".to_string(),
+		}
+	}
+
+	pub fn tags_string(&self) -> String {
+		self.tags.join(",")
+	}
+}
+
+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))
+			}
+		}
+	}
+}
+
+impl UpdateTracker {
+	fn merge(&mut self, other: &UpdateTracker) {
+		for (k, v) in other.0.iter() {
+			if let Some(v_mut) = self.0.get_mut(k) {
+				*v_mut = std::cmp::max(*v_mut, *v);
+			} else {
+				self.0.insert(*k, *v);
+			}
+		}
+	}
+
+	pub(crate) fn min(&self) -> u64 {
+		self.0.iter().map(|(_, v)| *v).min().unwrap_or(0)
+	}
+}
+
+impl UpdateTrackers {
+	pub(crate) fn merge(&mut self, other: &UpdateTrackers) {
+		self.ack_map.merge(&other.ack_map);
+		self.sync_map.merge(&other.sync_map);
+		self.sync_ack_map.merge(&other.sync_ack_map);
+	}
+}
-- 
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