layou: implement ack locking

1 files changed, 68 insertions, 6 deletions

diff --git a/src/rpc/layout/manager.rs b/src/rpc/layout/manager.rs
index e270ad21..4e073d1f 100644
--- a/src/rpc/layout/manager.rs
+++ b/src/rpc/layout/manager.rs
@@ -1,5 +1,5 @@
 use std::collections::HashMap;
-use std::sync::{Arc, Mutex, RwLock, RwLockReadGuard};
+use std::sync::{atomic::Ordering, Arc, Mutex, RwLock, RwLockReadGuard};
 use std::time::Duration;
 
 use serde::{Deserialize, Serialize};
@@ -74,8 +74,8 @@ impl LayoutManager {
 			}
 		};
 
-		let mut cluster_layout = LayoutHelper::new(cluster_layout);
-		cluster_layout.update_trackers_of(node_id.into());
+		let mut cluster_layout = LayoutHelper::new(cluster_layout, Default::default());
+		cluster_layout.update_trackers(node_id.into());
 
 		let layout = Arc::new(RwLock::new(cluster_layout));
 		let change_notify = Arc::new(Notify::new());
@@ -139,13 +139,36 @@ impl LayoutManager {
 
 		let mut layout = self.layout.write().unwrap();
 		if layout.update(|l| l.update_trackers.sync_map.set_max(self.node_id, sync_until)) {
-			debug!("sync_until updated to {}", sync_until);
+			info!("sync_until updated to {}", sync_until);
 			self.broadcast_update(SystemRpc::AdvertiseClusterLayoutTrackers(
 				layout.update_trackers.clone(),
 			));
 		}
 	}
 
+	fn ack_new_version(self: &Arc<Self>) {
+		let mut layout = self.layout.write().unwrap();
+		if layout.ack_max_free(self.node_id) {
+			self.broadcast_update(SystemRpc::AdvertiseClusterLayoutTrackers(
+				layout.update_trackers.clone(),
+			));
+		}
+	}
+
+	// ---- ACK LOCKING ----
+
+	pub fn write_sets_of(self: &Arc<Self>, position: &Hash) -> WriteLock<Vec<Vec<Uuid>>> {
+		let layout = self.layout();
+		let version = layout.current().version;
+		let nodes = layout.write_sets_of(position);
+		layout
+			.ack_lock
+			.get(&version)
+			.unwrap()
+			.fetch_add(1, Ordering::Relaxed);
+		WriteLock::new(version, self, nodes)
+	}
+
 	// ---- INTERNALS ---
 
 	fn merge_layout(&self, adv: &LayoutHistory) -> Option<LayoutHistory> {
@@ -154,7 +177,7 @@ impl LayoutManager {
 
 		if !prev_layout_check || adv.check().is_ok() {
 			if layout.update(|l| l.merge(adv)) {
-				layout.update_trackers_of(self.node_id);
+				layout.update_trackers(self.node_id);
 				if prev_layout_check && layout.check().is_err() {
 					panic!("Merged two correct layouts and got an incorrect layout.");
 				}
@@ -168,7 +191,7 @@ impl LayoutManager {
 		let mut layout = self.layout.write().unwrap();
 		if layout.update_trackers != *adv {
 			if layout.update(|l| l.update_trackers.merge(adv)) {
-				layout.update_trackers_of(self.node_id);
+				layout.update_trackers(self.node_id);
 				return Some(layout.update_trackers.clone());
 			}
 		}
@@ -317,3 +340,42 @@ impl LayoutManager {
 		Ok(SystemRpc::Ok)
 	}
 }
+
+// ---- ack lock ----
+
+pub struct WriteLock<T> {
+	layout_version: u64,
+	layout_manager: Arc<LayoutManager>,
+	value: T,
+}
+
+impl<T> WriteLock<T> {
+	fn new(version: u64, layout_manager: &Arc<LayoutManager>, value: T) -> Self {
+		Self {
+			layout_version: version,
+			layout_manager: layout_manager.clone(),
+			value,
+		}
+	}
+}
+
+impl<T> AsRef<T> for WriteLock<T> {
+	fn as_ref(&self) -> &T {
+		&self.value
+	}
+}
+
+impl<T> Drop for WriteLock<T> {
+	fn drop(&mut self) {
+		let layout = self.layout_manager.layout(); // acquire read lock
+		if let Some(counter) = layout.ack_lock.get(&self.layout_version) {
+			let prev_lock = counter.fetch_sub(1, Ordering::Relaxed);
+			if prev_lock == 1 && layout.current().version > self.layout_version {
+				drop(layout); // release read lock, write lock will be acquired
+				self.layout_manager.ack_new_version();
+			}
+		} else {
+			error!("Could not find ack lock counter for layout version {}. This probably indicates a bug in Garage.", self.layout_version);
+		}
+	}
+}