From a2d87a012d2452177da37d159f1367f17eba7d9c Mon Sep 17 00:00:00 2001
From: Yureka <yuka@yuka.dev>
Date: Sun, 20 Apr 2025 20:56:04 +0200
Subject: [PATCH] refactor: use replication factor of the layout versions in
 calculate_sync_map_min_with_quorum

---
 src/rpc/layout/helper.rs  |  7 +------
 src/rpc/layout/history.rs | 26 +++++++++++++++-----------
 src/rpc/layout/manager.rs |  8 ++------
 3 files changed, 18 insertions(+), 23 deletions(-)

diff --git a/src/rpc/layout/helper.rs b/src/rpc/layout/helper.rs
index 35746851..088ffb2f 100644
--- a/src/rpc/layout/helper.rs
+++ b/src/rpc/layout/helper.rs
@@ -28,7 +28,6 @@ pub struct SyncLayoutDigest {
 }
 
 pub struct LayoutHelper {
-	replication_factor: ReplicationFactor,
 	consistency_mode: ConsistencyMode,
 	layout: Option<LayoutHistory>,
 
@@ -51,7 +50,6 @@ pub struct LayoutHelper {
 
 impl LayoutHelper {
 	pub fn new(
-		replication_factor: ReplicationFactor,
 		consistency_mode: ConsistencyMode,
 		mut layout: LayoutHistory,
 		mut ack_lock: HashMap<u64, AtomicUsize>,
@@ -97,8 +95,7 @@ impl LayoutHelper {
 		// consistency on those).
 		// This value is calculated using quorums to allow progress even
 		// if not all nodes have successfully completed a sync.
-		let sync_map_min =
-			layout.calculate_sync_map_min_with_quorum(replication_factor, &all_nongateway_nodes);
+		let sync_map_min = layout.calculate_sync_map_min_with_quorum(&all_nongateway_nodes);
 
 		let trackers_hash = layout.calculate_trackers_hash();
 		let staging_hash = layout.calculate_staging_hash();
@@ -111,7 +108,6 @@ impl LayoutHelper {
 		let is_check_ok = layout.check().is_ok();
 
 		LayoutHelper {
-			replication_factor,
 			consistency_mode,
 			layout: Some(layout),
 			ack_map_min,
@@ -134,7 +130,6 @@ impl LayoutHelper {
 		let changed = f(self.layout.as_mut().unwrap());
 		if changed {
 			*self = Self::new(
-				self.replication_factor,
 				self.consistency_mode,
 				self.layout.take().unwrap(),
 				std::mem::take(&mut self.ack_lock),
diff --git a/src/rpc/layout/history.rs b/src/rpc/layout/history.rs
index 1e6bc84b..79f4e3c0 100644
--- a/src/rpc/layout/history.rs
+++ b/src/rpc/layout/history.rs
@@ -123,13 +123,9 @@ impl LayoutHistory {
 		}
 	}
 
-	pub(crate) fn calculate_sync_map_min_with_quorum(
-		&self,
-		replication_factor: ReplicationFactor,
-		all_nongateway_nodes: &[Uuid],
-	) -> u64 {
-		// This function calculates the minimum layout version from which
-		// it is safe to read if we want to maintain read-after-write consistency.
+	/// This function calculates the minimum layout version from which
+	/// it is safe to read if we want to maintain read-after-write consistency.
+	pub(crate) fn calculate_sync_map_min_with_quorum(&self, all_nongateway_nodes: &[Uuid]) -> u64 {
 		// In the general case the computation can be a bit expensive so
 		// we try to optimize it in several ways.
 
@@ -139,8 +135,6 @@ impl LayoutHistory {
 			return self.current().version;
 		}
 
-		let quorum = replication_factor.write_quorum(ConsistencyMode::Consistent);
-
 		let min_version = self.min_stored();
 		let global_min = self
 			.update_trackers
@@ -153,7 +147,16 @@ impl LayoutHistory {
 		// This is represented by reading from the layout with version
 		// number global_min, the smallest layout version for which all nodes
 		// have completed a sync.
-		if quorum == self.current().replication_factor {
+		//
+		// While we currently do not support changing the replication factor
+		// between layout versions, this calculation is future-proofing for the
+		// case where this might be possible.
+		if self
+			.versions
+			.iter()
+			.filter(|v| v.version >= global_min)
+			.all(|v| v.write_quorum(ConsistencyMode::Consistent) == v.replication_factor)
+		{
 			return global_min;
 		}
 
@@ -195,7 +198,8 @@ impl LayoutHistory {
 					.map(|x| self.update_trackers.sync_map.get(x, min_version))
 					.collect::<Vec<_>>();
 				sync_values.sort();
-				let set_min = sync_values[sync_values.len() - quorum];
+				let set_min =
+					sync_values[sync_values.len() - v.write_quorum(ConsistencyMode::Consistent)];
 				if set_min < current_min {
 					current_min = set_min;
 				}
diff --git a/src/rpc/layout/manager.rs b/src/rpc/layout/manager.rs
index 789603b5..c5bba0b6 100644
--- a/src/rpc/layout/manager.rs
+++ b/src/rpc/layout/manager.rs
@@ -64,12 +64,8 @@ impl LayoutManager {
 			}
 		};
 
-		let mut cluster_layout = LayoutHelper::new(
-			replication_factor,
-			consistency_mode,
-			cluster_layout,
-			Default::default(),
-		);
+		let mut cluster_layout =
+			LayoutHelper::new(consistency_mode, cluster_layout, Default::default());
 		cluster_layout.update_update_trackers(node_id.into());
 
 		let layout = Arc::new(RwLock::new(cluster_layout));