layout: refactor digests and add "!=" assertions before epidemic bcast

src/rpc/layout/helper.rs

@@ -2,10 +2,24 @@ use std::collections::HashMap;
 use std::ops::Deref;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
+use serde::{Deserialize, Serialize};
+
 use garage_util::data::*;
 
 use super::schema::*;
 
+#[derive(Debug, Clone, Serialize, Deserialize, Default, PartialEq, Eq)]
+pub struct LayoutDigest {
+	/// Cluster layout version
+	pub current_version: u64,
+	/// Number of active layout versions
+	pub active_versions: usize,
+	/// Hash of cluster layout update trackers
+	pub trackers_hash: Hash,
+	/// Hash of cluster layout staging data
+	pub staging_hash: Hash,
+}
+
 pub struct LayoutHelper {
 	layout: Option<LayoutHistory>,
 
@@ -16,8 +30,8 @@ pub struct LayoutHelper {
 	all_nodes: Vec<Uuid>,
 	all_nongateway_nodes: Vec<Uuid>,
 
-	pub(crate) trackers_hash: Hash,
-	pub(crate) staging_hash: Hash,
+	trackers_hash: Hash,
+	staging_hash: Hash,
 
 	// ack lock: counts in-progress write operations for each
 	// layout version ; we don't increase the ack update tracker
@@ -152,6 +166,15 @@ impl LayoutHelper {
 		self.staging_hash
 	}
 
+	pub fn digest(&self) -> LayoutDigest {
+		LayoutDigest {
+			current_version: self.current().version,
+			active_versions: self.versions.len(),
+			trackers_hash: self.trackers_hash,
+			staging_hash: self.staging_hash,
+		}
+	}
+
 	// ------------------ helpers for update tracking ---------------
 
 	pub(crate) fn update_trackers(&mut self, local_node_id: Uuid) {

src/rpc/layout/history.rs

@@ -5,7 +5,6 @@ use garage_util::data::*;
 use garage_util::encode::nonversioned_encode;
 use garage_util::error::*;
 
-use super::schema::*;
 use super::*;
 
 impl LayoutHistory {

src/rpc/layout/manager.rs

@@ -2,8 +2,6 @@ use std::collections::HashMap;
 use std::sync::{atomic::Ordering, Arc, Mutex, RwLock, RwLockReadGuard};
 use std::time::Duration;
 
-use serde::{Deserialize, Serialize};
-
 use tokio::sync::Notify;
 
 use netapp::endpoint::Endpoint;
@@ -33,16 +31,6 @@ pub struct LayoutManager {
 	system_endpoint: Arc<Endpoint<SystemRpc, System>>,
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize, Default)]
-pub struct LayoutStatus {
-	/// Cluster layout version
-	pub cluster_layout_version: u64,
-	/// Hash of cluster layout update trackers
-	pub cluster_layout_trackers_hash: Hash,
-	/// Hash of cluster layout staging data
-	pub cluster_layout_staging_hash: Hash,
-}
-
 impl LayoutManager {
 	pub fn new(
 		config: &Config,
@@ -105,15 +93,6 @@ impl LayoutManager {
 		self.layout.read().unwrap()
 	}
 
-	pub fn status(&self) -> LayoutStatus {
-		let layout = self.layout();
-		LayoutStatus {
-			cluster_layout_version: layout.current().version,
-			cluster_layout_trackers_hash: layout.trackers_hash(),
-			cluster_layout_staging_hash: layout.staging_hash(),
-		}
-	}
-
 	pub async fn update_cluster_layout(
 		self: &Arc<Self>,
 		layout: &LayoutHistory,
@@ -173,6 +152,7 @@ impl LayoutManager {
 
 	fn merge_layout(&self, adv: &LayoutHistory) -> Option<LayoutHistory> {
 		let mut layout = self.layout.write().unwrap();
+		let prev_digest = layout.digest();
 		let prev_layout_check = layout.check().is_ok();
 
 		if !prev_layout_check || adv.check().is_ok() {
@@ -181,6 +161,7 @@ impl LayoutManager {
 				if prev_layout_check && layout.check().is_err() {
 					panic!("Merged two correct layouts and got an incorrect layout.");
 				}
+				assert!(layout.digest() != prev_digest);
 				return Some(layout.clone());
 			}
 		}
@@ -190,10 +171,12 @@ impl LayoutManager {
 
 	fn merge_layout_trackers(&self, adv: &UpdateTrackers) -> Option<UpdateTrackers> {
 		let mut layout = self.layout.write().unwrap();
+		let prev_digest = layout.digest();
 
 		if layout.update_trackers != *adv {
 			if layout.update(|l| l.update_trackers.merge(adv)) {
 				layout.update_trackers(self.node_id);
+				assert!(layout.digest() != prev_digest);
 				return Some(layout.update_trackers.clone());
 			}
 		}
@@ -269,16 +252,17 @@ impl LayoutManager {
 
 	// ---- RPC HANDLERS ----
 
-	pub(crate) fn handle_advertise_status(self: &Arc<Self>, from: Uuid, remote: &LayoutStatus) {
-		let local = self.status();
-		if remote.cluster_layout_version > local.cluster_layout_version
-			|| remote.cluster_layout_staging_hash != local.cluster_layout_staging_hash
+	pub(crate) fn handle_advertise_status(self: &Arc<Self>, from: Uuid, remote: &LayoutDigest) {
+		let local = self.layout().digest();
+		if remote.current_version > local.current_version
+			|| remote.active_versions != local.active_versions
+			|| remote.staging_hash != local.staging_hash
 		{
 			tokio::spawn({
 				let this = self.clone();
 				async move { this.pull_cluster_layout(from).await }
 			});
-		} else if remote.cluster_layout_trackers_hash != local.cluster_layout_trackers_hash {
+		} else if remote.trackers_hash != local.trackers_hash {
 			tokio::spawn({
 				let this = self.clone();
 				async move { this.pull_cluster_layout_trackers(from).await }

src/rpc/layout/mod.rs

@@ -11,7 +11,7 @@ pub mod manager;
 
 // ---- re-exports ----
 
-pub use helper::LayoutHelper;
+pub use helper::{LayoutDigest, LayoutHelper};
 pub use manager::WriteLock;
 pub use schema::*;
 pub use version::*;