Keep network status & ring in a tokio::sync::watch

advantages
- reads don't prevent preparing writes
- can be followed from other parts of the system by cloning the receiver

src/api_server.rs

@@ -212,9 +212,9 @@ async fn put_block_meta(
 async fn put_block(garage: Arc<Garage>, hash: Hash, data: Vec<u8>) -> Result<(), Error> {
 	let who = garage
 		.system
-		.members
-		.read()
-		.await
+		.ring
+		.borrow()
+		.clone()
 		.walk_ring(&hash, garage.system.config.meta_replication_factor);
 	rpc_try_call_many(
 		garage.system.clone(),
@@ -359,9 +359,9 @@ async fn handle_get(
 async fn get_block(garage: Arc<Garage>, hash: &Hash) -> Result<Vec<u8>, Error> {
 	let who = garage
 		.system
-		.members
-		.read()
-		.await
+		.ring
+		.borrow()
+		.clone()
 		.walk_ring(&hash, garage.system.config.meta_replication_factor);
 	let resps = rpc_try_call_many(
 		garage.system.clone(),

src/block.rs

@@ -1,15 +1,14 @@
 use std::path::PathBuf;
 
+use futures_util::future::*;
 use tokio::fs;
 use tokio::prelude::*;
 use tokio::sync::Mutex;
-use futures_util::future::*;
 
+use crate::background::*;
 use crate::data::*;
 use crate::error::Error;
 use crate::proto::*;
-use crate::background::*;
-
 
 pub struct BlockManager {
 	pub data_dir: PathBuf,
@@ -19,7 +18,8 @@ pub struct BlockManager {
 
 impl BlockManager {
 	pub fn new(db: &sled::Db, data_dir: PathBuf) -> Self {
-		let rc = db.open_tree("block_local_rc")
+		let rc = db
+			.open_tree("block_local_rc")
 			.expect("Unable to open block_local_rc tree");
 		rc.set_merge_operator(rc_merge);
 		Self {
@@ -81,18 +81,20 @@ impl BlockManager {
 				background.spawn(tokio::fs::remove_file(path).map_err(Into::into));
 				Ok(())
 			}
-			Some(_) => Ok(())
+			Some(_) => Ok(()),
 		}
 	}
 }
 
 fn rc_merge(_key: &[u8], old: Option<&[u8]>, new: &[u8]) -> Option<Vec<u8>> {
-	let old = old.map(|x| {
+	let old = old
+		.map(|x| {
 			assert!(x.len() == 8);
 			let mut x8 = [0u8; 8];
 			x8.copy_from_slice(x);
 			u64::from_be_bytes(x8)
-	}).unwrap_or(0);
+		})
+		.unwrap_or(0);
 	assert!(new.len() == 1);
 	let new = match new[0] {
 		0 => {

src/block_ref_table.rs

@@ -55,8 +55,11 @@ impl TableFormat for BlockRefTable {
 			}
 		}
 		if was_before && !is_after {
-			if let Err(e) = garage.block_manager.block_decref(&new.block, &garage.background) {
-				eprintln!("Failed to decref or delete block {:?}: {}", &new.block, e);
+			if let Err(e) = garage
+				.block_manager
+				.block_decref(&new.block, &garage.background)
+			{
+				eprintln!("Failed to decref block {:?}: {}", &new.block, e);
 			}
 		}
 	}

src/membership.rs

@@ -13,7 +13,7 @@ use futures_util::future::*;
 use sha2::{Digest, Sha256};
 use tokio::prelude::*;
 use tokio::sync::watch;
-use tokio::sync::RwLock;
+use tokio::sync::Mutex;
 
 use crate::background::BackgroundRunner;
 use crate::data::*;
@@ -32,36 +32,44 @@ pub struct System {
 
 	pub rpc_client: RpcClient,
 
-	pub members: RwLock<Members>,
+	pub status: watch::Receiver<Arc<Status>>,
+	pub ring: watch::Receiver<Arc<Ring>>,
+
+	update_lock: Mutex<(watch::Sender<Arc<Status>>, watch::Sender<Arc<Ring>>)>,
 
 	pub background: Arc<BackgroundRunner>,
 }
 
-pub struct Members {
-	pub status: HashMap<UUID, NodeStatus>,
-	pub status_hash: Hash,
-
-	pub config: NetworkConfig,
-	pub ring: Vec<RingEntry>,
-	pub n_datacenters: usize,
+#[derive(Debug, Clone)]
+pub struct Status {
+	pub nodes: HashMap<UUID, NodeStatus>,
+	pub hash: Hash,
 }
 
+#[derive(Debug, Clone)]
 pub struct NodeStatus {
 	pub addr: SocketAddr,
 	pub remaining_ping_attempts: usize,
 }
 
-#[derive(Debug)]
+#[derive(Clone)]
+pub struct Ring {
+	pub config: NetworkConfig,
+	pub ring: Vec<RingEntry>,
+	pub n_datacenters: usize,
+}
+
+#[derive(Clone, Debug)]
 pub struct RingEntry {
 	pub location: Hash,
 	pub node: UUID,
 	pub datacenter: u64,
 }
 
-impl Members {
+impl Status {
 	fn handle_ping(&mut self, ip: IpAddr, info: &PingMessage) -> bool {
 		let addr = SocketAddr::new(ip, info.rpc_port);
-		let old_status = self.status.insert(
+		let old_status = self.nodes.insert(
 			info.id.clone(),
 			NodeStatus {
 				addr: addr.clone(),
@@ -77,8 +85,8 @@ impl Members {
 		}
 	}
 
-	fn recalculate_status_hash(&mut self) {
-		let mut nodes = self.status.iter().collect::<Vec<_>>();
+	fn recalculate_hash(&mut self) {
+		let mut nodes = self.nodes.iter().collect::<Vec<_>>();
 		nodes.sort_unstable_by_key(|(id, _status)| *id);
 
 		let mut hasher = Sha256::new();
@@ -88,11 +96,13 @@ impl Members {
 			hasher.input(format!("{} {}\n", hex::encode(&id), status.addr));
 		}
 		eprintln!("END --");
-		self.status_hash
+		self.hash
 			.as_slice_mut()
 			.copy_from_slice(&hasher.result()[..]);
 	}
+}
 
+impl Ring {
 	fn rebuild_ring(&mut self) {
 		let mut new_ring = vec![];
 		let mut datacenters = vec![];
@@ -201,20 +211,28 @@ impl System {
 				}
 			}
 		};
-		let mut members = Members {
-			status: HashMap::new(),
-			status_hash: Hash::default(),
+		let mut status = Status {
+			nodes: HashMap::new(),
+			hash: Hash::default(),
+		};
+		status.recalculate_hash();
+		let (update_status, status) = watch::channel(Arc::new(status));
+
+		let mut ring = Ring {
 			config: net_config,
 			ring: Vec::new(),
 			n_datacenters: 0,
 		};
-		members.recalculate_status_hash();
-		members.rebuild_ring();
+		ring.rebuild_ring();
+		let (update_ring, ring) = watch::channel(Arc::new(ring));
+
 		System {
 			config,
 			id,
 			rpc_client: RpcClient::new(),
-			members: RwLock::new(members),
+			status,
+			ring,
+			update_lock: Mutex::new((update_status, update_ring)),
 			background,
 		}
 	}
@@ -223,37 +241,33 @@ impl System {
 		let mut path = self.config.metadata_dir.clone();
 		path.push("network_config");
 
-		let members = self.members.read().await;
-		let data =
-			rmp_to_vec_all_named(&members.config)?;
-		drop(members);
+		let ring = self.ring.borrow().clone();
+		let data = rmp_to_vec_all_named(&ring.config)?;
 
-		let mut f = tokio::fs::File::create(path.as_path())
-			.await?;
-		f.write_all(&data[..])
-			.await?;
+		let mut f = tokio::fs::File::create(path.as_path()).await?;
+		f.write_all(&data[..]).await?;
 		Ok(())
 	}
 
-	pub async fn make_ping(&self) -> Message {
-		let members = self.members.read().await;
+	pub fn make_ping(&self) -> Message {
+		let status = self.status.borrow().clone();
+		let ring = self.ring.borrow().clone();
 		Message::Ping(PingMessage {
 			id: self.id.clone(),
 			rpc_port: self.config.rpc_port,
-			status_hash: members.status_hash.clone(),
-			config_version: members.config.version,
+			status_hash: status.hash.clone(),
+			config_version: ring.config.version,
 		})
 	}
 
 	pub async fn broadcast(self: Arc<Self>, msg: Message, timeout: Duration) {
-		let members = self.members.read().await;
-		let to = members
-			.status
+		let status = self.status.borrow().clone();
+		let to = status
+			.nodes
 			.keys()
 			.filter(|x| **x != self.id)
 			.cloned()
 			.collect::<Vec<_>>();
-		drop(members);
 		rpc_call_many(self.clone(), &to[..], &msg, timeout).await;
 	}
 
@@ -273,7 +287,7 @@ impl System {
 	}
 
 	pub async fn ping_nodes(self: Arc<Self>, peers: Vec<(SocketAddr, Option<UUID>)>) {
-		let ping_msg = self.make_ping().await;
+		let ping_msg = self.make_ping();
 		let ping_resps = join_all(peers.iter().map(|(addr, id_option)| {
 			let sys = self.clone();
 			let ping_msg_ref = &ping_msg;
@@ -287,14 +301,16 @@ impl System {
 		}))
 		.await;
 
-		let mut members = self.members.write().await;
+		let update_locked = self.update_lock.lock().await;
+		let mut status: Status = self.status.borrow().as_ref().clone();
+		let ring = self.ring.borrow().clone();
 
 		let mut has_changes = false;
 		let mut to_advertise = vec![];
 
 		for (id_option, addr, ping_resp) in ping_resps {
 			if let Ok(Message::Ping(info)) = ping_resp {
-				let is_new = members.handle_ping(addr.ip(), &info);
+				let is_new = status.handle_ping(addr.ip(), &info);
 				if is_new {
 					has_changes = true;
 					to_advertise.push(AdvertisedNode {
@@ -302,17 +318,17 @@ impl System {
 						addr: addr.clone(),
 					});
 				}
-				if is_new || members.status_hash != info.status_hash {
+				if is_new || status.hash != info.status_hash {
 					self.background
 						.spawn_cancellable(self.clone().pull_status(info.id.clone()).map(Ok));
 				}
-				if is_new || members.config.version < info.config_version {
+				if is_new || ring.config.version < info.config_version {
 					self.background
 						.spawn_cancellable(self.clone().pull_config(info.id.clone()).map(Ok));
 				}
 			} else if let Some(id) = id_option {
-				let remaining_attempts = members
-					.status
+				let remaining_attempts = status
+					.nodes
 					.get(id)
 					.map(|x| x.remaining_ping_attempts)
 					.unwrap_or(0);
@@ -321,19 +337,22 @@ impl System {
 						"Removing node {} after too many failed pings",
 						hex::encode(&id)
 					);
-					members.status.remove(&id);
+					status.nodes.remove(&id);
 					has_changes = true;
 				} else {
-					if let Some(st) = members.status.get_mut(id) {
+					if let Some(st) = status.nodes.get_mut(id) {
 						st.remaining_ping_attempts = remaining_attempts - 1;
 					}
 				}
 			}
 		}
 		if has_changes {
-			members.recalculate_status_hash();
+			status.recalculate_hash();
 		}
-		drop(members);
+		if let Err(e) = update_locked.0.broadcast(Arc::new(status)) {
+			eprintln!("In ping_nodes: could not save status update ({})", e);
+		}
+		drop(update_locked);
 
 		if to_advertise.len() > 0 {
 			self.broadcast(Message::AdvertiseNodesUp(to_advertise), PING_TIMEOUT)
@@ -346,29 +365,35 @@ impl System {
 		from: &SocketAddr,
 		ping: &PingMessage,
 	) -> Result<Message, Error> {
-		let mut members = self.members.write().await;
-		let is_new = members.handle_ping(from.ip(), ping);
+		let update_locked = self.update_lock.lock().await;
+		let mut status: Status = self.status.borrow().as_ref().clone();
+
+		let is_new = status.handle_ping(from.ip(), ping);
 		if is_new {
-			members.recalculate_status_hash();
+			status.recalculate_hash();
 		}
-		let status_hash = members.status_hash.clone();
-		let config_version = members.config.version;
-		drop(members);
+		let status_hash = status.hash.clone();
+		let config_version = self.ring.borrow().config.version;
+
+		update_locked.0.broadcast(Arc::new(status))?;
+		drop(update_locked);
 
 		if is_new || status_hash != ping.status_hash {
-			self.background.spawn_cancellable(self.clone().pull_status(ping.id.clone()).map(Ok));
+			self.background
+				.spawn_cancellable(self.clone().pull_status(ping.id.clone()).map(Ok));
 		}
 		if is_new || config_version < ping.config_version {
-			self.background.spawn_cancellable(self.clone().pull_config(ping.id.clone()).map(Ok));
+			self.background
+				.spawn_cancellable(self.clone().pull_config(ping.id.clone()).map(Ok));
 		}
 
-		Ok(self.make_ping().await)
+		Ok(self.make_ping())
 	}
 
-	pub async fn handle_pull_status(&self) -> Result<Message, Error> {
-		let members = self.members.read().await;
+	pub fn handle_pull_status(&self) -> Result<Message, Error> {
+		let status = self.status.borrow().clone();
 		let mut mem = vec![];
-		for (node, status) in members.status.iter() {
+		for (node, status) in status.nodes.iter() {
 			mem.push(AdvertisedNode {
 				id: node.clone(),
 				addr: status.addr.clone(),
@@ -377,9 +402,9 @@ impl System {
 		Ok(Message::AdvertiseNodesUp(mem))
 	}
 
-	pub async fn handle_pull_config(&self) -> Result<Message, Error> {
-		let members = self.members.read().await;
-		Ok(Message::AdvertiseConfig(members.config.clone()))
+	pub fn handle_pull_config(&self) -> Result<Message, Error> {
+		let ring = self.ring.borrow().clone();
+		Ok(Message::AdvertiseConfig(ring.config.clone()))
 	}
 
 	pub async fn handle_advertise_nodes_up(
@@ -388,14 +413,15 @@ impl System {
 	) -> Result<Message, Error> {
 		let mut to_ping = vec![];
 
-		let mut members = self.members.write().await;
+		let update_lock = self.update_lock.lock().await;
+		let mut status: Status = self.status.borrow().as_ref().clone();
 		let mut has_changed = false;
 
 		for node in adv.iter() {
 			if node.id == self.id {
 				// learn our own ip address
 				let self_addr = SocketAddr::new(node.addr.ip(), self.config.rpc_port);
-				let old_self = members.status.insert(
+				let old_self = status.nodes.insert(
 					node.id.clone(),
 					NodeStatus {
 						addr: self_addr,
@@ -406,17 +432,19 @@ impl System {
 					None => true,
 					Some(x) => x.addr != self_addr,
 				};
-			} else if !members.status.contains_key(&node.id) {
+			} else if !status.nodes.contains_key(&node.id) {
 				to_ping.push((node.addr.clone(), Some(node.id.clone())));
 			}
 		}
 		if has_changed {
-			members.recalculate_status_hash();
+			status.recalculate_hash();
 		}
-		drop(members);
+		update_lock.0.broadcast(Arc::new(status))?;
+		drop(update_lock);
 
 		if to_ping.len() > 0 {
-			self.background.spawn_cancellable(self.clone().ping_nodes(to_ping).map(Ok));
+			self.background
+				.spawn_cancellable(self.clone().ping_nodes(to_ping).map(Ok));
 		}
 
 		Ok(Message::Ok)
@@ -426,10 +454,14 @@ impl System {
 		self: Arc<Self>,
 		adv: &NetworkConfig,
 	) -> Result<Message, Error> {
-		let mut members = self.members.write().await;
-		if adv.version > members.config.version {
-			members.config = adv.clone();
-			members.rebuild_ring();
+		let mut ring: Ring = self.ring.borrow().as_ref().clone();
+		let update_lock = self.update_lock.lock().await;
+
+		if adv.version > ring.config.version {
+			ring.config = adv.clone();
+			ring.rebuild_ring();
+			update_lock.1.broadcast(Arc::new(ring))?;
+			drop(update_lock);
 
 			self.background.spawn_cancellable(
 				self.clone()
@@ -446,14 +478,13 @@ impl System {
 		loop {
 			let restart_at = tokio::time::delay_for(PING_INTERVAL);
 
-			let members = self.members.read().await;
-			let ping_addrs = members
-				.status
+			let status = self.status.borrow().clone();
+			let ping_addrs = status
+				.nodes
 				.iter()
 				.filter(|(id, _)| **id != self.id)
 				.map(|(id, status)| (status.addr.clone(), Some(id.clone())))
 				.collect::<Vec<_>>();
-			drop(members);
 
 			self.clone().ping_nodes(ping_addrs).await;
 

src/rpc_client.rs

@@ -79,8 +79,8 @@ pub async fn rpc_call(
 	timeout: Duration,
 ) -> Result<Message, Error> {
 	let addr = {
-		let members = sys.members.read().await;
-		match members.status.get(to) {
+		let status = sys.status.borrow().clone();
+		match status.nodes.get(to) {
 			Some(status) => status.addr.clone(),
 			None => return Err(Error::Message(format!("Peer ID not found"))),
 		}

src/rpc_server.rs

@@ -59,8 +59,8 @@ async fn handler(
 	let resp = err_to_msg(match &msg {
 		Message::Ping(ping) => sys.handle_ping(&addr, ping).await,
 
-		Message::PullStatus => sys.handle_pull_status().await,
-		Message::PullConfig => sys.handle_pull_config().await,
+		Message::PullStatus => sys.handle_pull_status(),
+		Message::PullConfig => sys.handle_pull_config(),
 		Message::AdvertiseNodesUp(adv) => sys.handle_advertise_nodes_up(adv).await,
 		Message::AdvertiseConfig(adv) => sys.handle_advertise_config(adv).await,
 

src/server.rs

@@ -10,8 +10,8 @@ use tokio::sync::RwLock;
 
 use crate::api_server;
 use crate::background::*;
-use crate::data::*;
 use crate::block::*;
+use crate::data::*;
 use crate::error::Error;
 use crate::membership::System;
 use crate::proto::*;

src/table.rs

@@ -3,9 +3,9 @@ use std::sync::Arc;
 use std::time::Duration;
 
 use async_trait::async_trait;
+use futures::stream::*;
 use serde::{Deserialize, Serialize};
 use serde_bytes::ByteBuf;
-use futures::stream::*;
 
 use crate::data::*;
 use crate::error::Error;
@@ -150,9 +150,9 @@ impl<F: TableFormat + 'static> Table<F> {
 		let hash = e.partition_key().hash();
 		let who = self
 			.system
-			.members
-			.read()
-			.await
+			.ring
+			.borrow()
+			.clone()
 			.walk_ring(&hash, self.param.replication_factor);
 		eprintln!("insert who: {:?}", who);
 
@@ -171,9 +171,9 @@ impl<F: TableFormat + 'static> Table<F> {
 			let hash = entry.partition_key().hash();
 			let who = self
 				.system
-				.members
-				.read()
-				.await
+				.ring
+				.borrow()
+				.clone()
 				.walk_ring(&hash, self.param.replication_factor);
 			let e_enc = Arc::new(ByteBuf::from(rmp_to_vec_all_named(entry)?));
 			for node in who {
@@ -184,18 +184,12 @@ impl<F: TableFormat + 'static> Table<F> {
 			}
 		}
 
-		let call_futures = call_list.drain()
-			.map(|(node, entries)| async move {
+		let call_futures = call_list.drain().map(|(node, entries)| async move {
 			let rpc = TableRPC::<F>::Update(entries);
 			let rpc_bytes = rmp_to_vec_all_named(&rpc)?;
 			let message = Message::TableRPC(self.name.to_string(), rpc_bytes);
 
-				let resp = rpc_call(
-					self.system.clone(),
-					&node,
-					&message,
-					self.param.timeout
-				).await?;
+			let resp = rpc_call(self.system.clone(), &node, &message, self.param.timeout).await?;
 			Ok::<_, Error>((node, resp))
 		});
 		let mut resps = call_futures.collect::<FuturesUnordered<_>>();
@@ -217,9 +211,9 @@ impl<F: TableFormat + 'static> Table<F> {
 		let hash = partition_key.hash();
 		let who = self
 			.system
-			.members
-			.read()
-			.await
+			.ring
+			.borrow()
+			.clone()
 			.walk_ring(&hash, self.param.replication_factor);
 		eprintln!("get who: {:?}", who);
 
@@ -259,10 +253,7 @@ impl<F: TableFormat + 'static> Table<F> {
 
 	async fn repair_on_read(&self, who: &[UUID], what: &F::E) -> Result<(), Error> {
 		let what_enc = Arc::new(ByteBuf::from(rmp_to_vec_all_named(what)?));
-		self.rpc_try_call_many(&who[..],
-			&TableRPC::<F>::Update(vec![what_enc]),
-			who.len(),
-		)
+		self.rpc_try_call_many(&who[..], &TableRPC::<F>::Update(vec![what_enc]), who.len())
 			.await
 			.map(|_| ())
 	}

src/version_table.rs

@@ -69,14 +69,19 @@ impl TableFormat for VersionTable {
 			// Propagate deletion of version blocks
 			if let Some(old_v) = old {
 				if new.deleted && !old_v.deleted {
-					let deleted_block_refs = old_v.blocks.iter()
+					let deleted_block_refs = old_v
+						.blocks
+						.iter()
 						.map(|vb| BlockRef {
 							block: vb.hash.clone(),
 							version: old_v.uuid.clone(),
 							deleted: true,
 						})
 						.collect::<Vec<_>>();
-					garage.block_ref_table.insert_many(&deleted_block_refs[..]).await?;
+					garage
+						.block_ref_table
+						.insert_many(&deleted_block_refs[..])
+						.await?;
 				}
 			}
 			Ok(())