layout: begin managing the update tracker values

src/rpc/layout/history.rs

@@ -1,3 +1,5 @@
+use std::collections::HashSet;
+
 use garage_util::crdt::{Crdt, Lww, LwwMap};
 use garage_util::data::*;
 use garage_util::encode::nonversioned_encode;
@@ -30,6 +32,14 @@ impl LayoutHistory {
 		self.versions.last().as_ref().unwrap()
 	}
 
+	pub fn all_storage_nodes(&self) -> HashSet<Uuid> {
+		self.versions
+			.iter()
+			.map(|x| x.nongateway_nodes())
+			.flatten()
+			.collect::<HashSet<_>>()
+	}
+
 	pub(crate) fn update_hashes(&mut self) {
 		self.trackers_hash = self.calculate_trackers_hash();
 		self.staging_hash = self.calculate_staging_hash();
@@ -43,6 +53,65 @@ impl LayoutHistory {
 		blake2sum(&nonversioned_encode(&self.staging).unwrap()[..])
 	}
 
+	// ------------------ update tracking ---------------
+
+	pub(crate) fn update_trackers(&mut self, node_id: Uuid) {
+		// Ensure trackers for this node's values are up-to-date
+
+		// 1. Acknowledge the last layout version in the history
+		self.ack_last(node_id);
+
+		// 2. Assume the data on this node is sync'ed up at least to
+		//    the first layout version in the history
+		self.sync_first(node_id);
+
+		// 3. Acknowledge everyone has synced up to min(self.sync_map)
+		self.sync_ack(node_id);
+
+		// 4. Cleanup layout versions that are not needed anymore
+		self.cleanup_old_versions();
+
+		info!("ack_map: {:?}", self.update_trackers.ack_map);
+		info!("sync_map: {:?}", self.update_trackers.sync_map);
+		info!("sync_ack_map: {:?}", self.update_trackers.sync_ack_map);
+
+		// Finally, update hashes
+		self.update_hashes();
+	}
+
+	pub(crate) fn ack_last(&mut self, node: Uuid) {
+		let last_version = self.current().version;
+		self.update_trackers.ack_map.set_max(node, last_version);
+	}
+
+	pub(crate) fn sync_first(&mut self, node: Uuid) {
+		let first_version = self.versions.first().as_ref().unwrap().version;
+		self.update_trackers.sync_map.set_max(node, first_version);
+	}
+
+	pub(crate) fn sync_ack(&mut self, node: Uuid) {
+		self.update_trackers.sync_ack_map.set_max(
+			node,
+			self.calculate_global_min(&self.update_trackers.sync_map),
+		);
+	}
+
+	pub(crate) fn cleanup_old_versions(&mut self) {
+		let min_sync_ack = self.calculate_global_min(&self.update_trackers.sync_ack_map);
+		while self.versions.first().as_ref().unwrap().version < min_sync_ack {
+			self.versions.remove(0);
+		}
+	}
+
+	pub(crate) fn calculate_global_min(&self, tracker: &UpdateTracker) -> u64 {
+		let storage_nodes = self.all_storage_nodes();
+		storage_nodes
+			.iter()
+			.map(|x| tracker.0.get(x).copied().unwrap_or(0))
+			.min()
+			.unwrap_or(0)
+	}
+
 	// ================== updates to layout, public interface ===================
 
 	pub fn merge(&mut self, other: &LayoutHistory) -> bool {
@@ -78,11 +147,6 @@ impl LayoutHistory {
 			changed = true;
 		}
 
-		// Update hashes if there are changes
-		if changed {
-			self.update_hashes();
-		}
-
 		changed
 	}