From 8a2b1dd422fb57abe611d8c1cf3cb0b55f487189 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Thu, 9 Nov 2023 12:55:36 +0100
Subject: wip: split out layout management from System into separate
 LayoutManager

---
 src/rpc/layout/manager.rs | 177 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 177 insertions(+)
 create mode 100644 src/rpc/layout/manager.rs

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

diff --git a/src/rpc/layout/manager.rs b/src/rpc/layout/manager.rs
new file mode 100644
index 00000000..a8a77139
--- /dev/null
+++ b/src/rpc/layout/manager.rs
@@ -0,0 +1,177 @@
+use std::sync::Arc;
+use std::time::Duration;
+
+use tokio::sync::watch;
+use tokio::sync::Mutex;
+
+use netapp::endpoint::Endpoint;
+use netapp::peering::fullmesh::FullMeshPeeringStrategy;
+use netapp::NodeID;
+
+use garage_util::config::Config;
+use garage_util::data::*;
+use garage_util::error::*;
+use garage_util::persister::Persister;
+
+use super::*;
+use crate::rpc_helper::*;
+use crate::system::*;
+
+pub struct LayoutManager {
+	replication_factor: usize,
+	persist_cluster_layout: Persister<LayoutHistory>,
+
+	pub layout_watch: watch::Receiver<Arc<LayoutHistory>>,
+	update_layout: Mutex<watch::Sender<Arc<LayoutHistory>>>,
+
+	pub(crate) rpc_helper: RpcHelper,
+	system_endpoint: Arc<Endpoint<SystemRpc, System>>,
+}
+
+impl LayoutManager {
+	pub fn new(
+		config: &Config,
+		node_id: NodeID,
+		system_endpoint: Arc<Endpoint<SystemRpc, System>>,
+		fullmesh: Arc<FullMeshPeeringStrategy>,
+		replication_factor: usize,
+	) -> Result<Self, Error> {
+		let persist_cluster_layout: Persister<LayoutHistory> =
+			Persister::new(&config.metadata_dir, "cluster_layout");
+
+		let cluster_layout = match persist_cluster_layout.load() {
+			Ok(x) => {
+				if x.current().replication_factor != replication_factor {
+					return Err(Error::Message(format!(
+						"Prevous cluster layout has replication factor {}, which is different than the one specified in the config file ({}). The previous cluster layout can be purged, if you know what you are doing, simply by deleting the `cluster_layout` file in your metadata directory.",
+						x.current().replication_factor,
+						replication_factor
+					)));
+				}
+				x
+			}
+			Err(e) => {
+				info!(
+					"No valid previous cluster layout stored ({}), starting fresh.",
+					e
+				);
+				LayoutHistory::new(replication_factor)
+			}
+		};
+
+		let (update_layout, layout_watch) = watch::channel(Arc::new(cluster_layout));
+
+		let rpc_helper = RpcHelper::new(
+			node_id.into(),
+			fullmesh,
+			layout_watch.clone(),
+			config.rpc_timeout_msec.map(Duration::from_millis),
+		);
+
+		Ok(Self {
+			replication_factor,
+			persist_cluster_layout,
+			layout_watch,
+			update_layout: Mutex::new(update_layout),
+			system_endpoint,
+			rpc_helper,
+		})
+	}
+
+	// ---- PUBLIC INTERFACE ----
+
+	pub async fn update_cluster_layout(&self, layout: &LayoutHistory) -> Result<(), Error> {
+		self.handle_advertise_cluster_layout(layout).await?;
+		Ok(())
+	}
+
+	pub fn history(&self) -> watch::Ref<Arc<LayoutHistory>> {
+		self.layout_watch.borrow()
+	}
+
+	pub(crate) async fn pull_cluster_layout(&self, peer: Uuid) {
+		let resp = self
+			.rpc_helper
+			.call(
+				&self.system_endpoint,
+				peer,
+				SystemRpc::PullClusterLayout,
+				RequestStrategy::with_priority(PRIO_HIGH),
+			)
+			.await;
+		if let Ok(SystemRpc::AdvertiseClusterLayout(layout)) = resp {
+			let _: Result<_, _> = self.handle_advertise_cluster_layout(&layout).await;
+		}
+	}
+
+	// ---- INTERNALS ---
+
+	/// Save network configuration to disc
+	async fn save_cluster_layout(&self) -> Result<(), Error> {
+		let layout: Arc<LayoutHistory> = self.layout_watch.borrow().clone();
+		self.persist_cluster_layout
+			.save_async(&layout)
+			.await
+			.expect("Cannot save current cluster layout");
+		Ok(())
+	}
+
+	// ---- RPC HANDLERS ----
+
+	pub(crate) fn handle_pull_cluster_layout(&self) -> SystemRpc {
+		let layout = self.layout_watch.borrow().as_ref().clone();
+		SystemRpc::AdvertiseClusterLayout(layout)
+	}
+
+	pub(crate) async fn handle_advertise_cluster_layout(
+		&self,
+		adv: &LayoutHistory,
+	) -> Result<SystemRpc, Error> {
+		if adv.current().replication_factor != self.replication_factor {
+			let msg = format!(
+				"Received a cluster layout from another node with replication factor {}, which is different from what we have in our configuration ({}). Discarding the cluster layout we received.",
+				adv.current().replication_factor,
+				self.replication_factor
+			);
+			error!("{}", msg);
+			return Err(Error::Message(msg));
+		}
+
+		let update_layout = self.update_layout.lock().await;
+		// TODO: don't clone each time an AdvertiseClusterLayout is received
+		let mut layout: LayoutHistory = self.layout_watch.borrow().as_ref().clone();
+
+		let prev_layout_check = layout.check().is_ok();
+		if layout.merge(adv) {
+			if prev_layout_check && layout.check().is_err() {
+				error!("New cluster layout is invalid, discarding.");
+				return Err(Error::Message(
+					"New cluster layout is invalid, discarding.".into(),
+				));
+			}
+
+			update_layout.send(Arc::new(layout.clone()))?;
+			drop(update_layout);
+
+			/* TODO
+			tokio::spawn(async move {
+				if let Err(e) = system
+					.rpc_helper()
+					.broadcast(
+						&system.system_endpoint,
+						SystemRpc::AdvertiseClusterLayout(layout),
+						RequestStrategy::with_priority(PRIO_HIGH),
+					)
+					.await
+				{
+					warn!("Error while broadcasting new cluster layout: {}", e);
+				}
+			});
+			*/
+
+			self.save_cluster_layout().await?;
+		}
+
+		Ok(SystemRpc::Ok)
+	}
+}
-- 
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