Config management & ring

src/data.rs

@@ -15,6 +15,7 @@ pub struct NetworkConfig {
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct NetworkConfigEntry {
+	pub datacenter: String,
 	pub n_tokens: u32,
 }
 

src/main.rs

@@ -55,6 +55,9 @@ pub struct ConfigureOpt {
 	/// Node to configure (prefix of hexadecimal node id)
 	node_id: String,
 
+	/// Location (datacenter) of the node
+	datacenter: String,
+
 	/// Number of tokens
 	n_tokens: u32,
 }
@@ -100,7 +103,7 @@ async fn cmd_status(rpc_cli: RpcClient, rpc_host: SocketAddr) -> Result<(), Erro
 	println!("Healthy nodes:");
 	for adv in status.iter() {
 		if let Some(cfg) = config.members.get(&adv.id) {
-			println!("{}\t{}\t{}\t{}", hex::encode(adv.id), adv.addr, adv.datacenter, cfg.n_tokens);
+			println!("{}\t{}\t{}\t{}", hex::encode(adv.id), cfg.datacenter, cfg.n_tokens, adv.addr);
 		}
 	}
 
@@ -109,7 +112,7 @@ async fn cmd_status(rpc_cli: RpcClient, rpc_host: SocketAddr) -> Result<(), Erro
 		println!("\nFailed nodes:");
 		for (id, cfg) in config.members.iter() {
 			if !status.iter().any(|x| x.id == *id) {
-				println!("{}\t{}", hex::encode(id), cfg.n_tokens);
+				println!("{}\t{}\t{}", hex::encode(id), cfg.datacenter, cfg.n_tokens);
 			}
 		}
 	}
@@ -118,7 +121,7 @@ async fn cmd_status(rpc_cli: RpcClient, rpc_host: SocketAddr) -> Result<(), Erro
 		println!("\nUnconfigured nodes:");
 		for adv in status.iter() {
 			if !config.members.contains_key(&adv.id) {
-				println!("{}\t{}\t{}", hex::encode(adv.id), adv.addr, adv.datacenter);
+				println!("{}\t{}", hex::encode(adv.id), adv.addr);
 			}
 		}
 	}
@@ -153,6 +156,7 @@ async fn cmd_configure(rpc_cli: RpcClient, rpc_host: SocketAddr, args: Configure
 
 	config.members.insert(candidates[0].clone(),
 						  NetworkConfigEntry{
+							  datacenter: args.datacenter,
 							  n_tokens: args.n_tokens,
 						  });
 	config.version += 1;

src/membership.rs

@@ -1,4 +1,6 @@
 use std::sync::Arc;
+use std::hash::Hash as StdHash;
+use std::hash::Hasher;
 use std::path::PathBuf;
 use std::io::{Read};
 use std::collections::HashMap;
@@ -34,6 +36,19 @@ pub struct Members {
 	pub status_hash: Hash,
 
 	pub config: NetworkConfig,
+    pub ring: Vec<RingEntry>,
+    pub n_datacenters: usize,
+}
+
+pub struct NodeStatus {
+	pub addr: SocketAddr,
+	pub remaining_ping_attempts: usize,
+}
+
+pub struct RingEntry {
+    pub location: Hash,
+    pub node: UUID,
+    pub datacenter: u64,
 }
 
 impl Members {
@@ -43,7 +58,6 @@ impl Members {
 			NodeStatus{
 				addr: addr.clone(),
 				remaining_ping_attempts: MAX_FAILED_PINGS,
-				datacenter: info.datacenter.clone(),
 			});
 		match old_status {
 			None => {
@@ -61,18 +75,78 @@ impl Members {
 		let mut hasher = Sha256::new();
 		eprintln!("Current set of pingable nodes: --");
 		for (id, status) in nodes {
-			eprintln!("{} {} ({})", hex::encode(id), status.addr, status.datacenter);
+			eprintln!("{} {}", hex::encode(id), status.addr);
 			hasher.input(format!("{} {}\n", hex::encode(id), status.addr));
 		}
 		eprintln!("END --");
 		self.status_hash.copy_from_slice(&hasher.result()[..]);
 	}
-}
 
-pub struct NodeStatus {
-	pub addr: SocketAddr,
-	pub datacenter: String,
-	pub remaining_ping_attempts: usize,
+    fn rebuild_ring(&mut self) {
+        let mut new_ring = vec![];
+        let mut datacenters = vec![];
+
+        for (id, config) in self.config.members.iter() {
+            let mut dc_hasher = std::collections::hash_map::DefaultHasher::new();
+            config.datacenter.hash(&mut dc_hasher);
+            let datacenter = dc_hasher.finish();
+
+            if !datacenters.contains(&datacenter) {
+                datacenters.push(datacenter);
+            }
+
+            for i in 0..config.n_tokens {
+                let mut location_hasher = Sha256::new();
+                location_hasher.input(format!("{} {}", hex::encode(id), i));
+                let mut location = [0u8; 32];
+                location.copy_from_slice(&location_hasher.result()[..]);
+
+                new_ring.push(RingEntry{
+                    location,
+                    node: id.clone(),
+                    datacenter,
+                })
+            }
+        }
+
+        new_ring.sort_by_key(|x| x.location);
+        self.ring = new_ring;
+        self.n_datacenters = datacenters.len();
+    }
+
+    fn walk_ring(&self, from: &Hash, n: usize) -> Vec<UUID> {
+        if n >= self.config.members.len() {
+            return self.config.members.keys().cloned().collect::<Vec<_>>();
+        }
+
+        let start = match self.ring.binary_search_by_key(from, |x| x.location) {
+            Ok(i) => i,
+            Err(i) => if i == 0 {
+                self.ring.len() - 1
+            } else {
+                i - 1
+            }
+        };
+        let mut ret = vec![];
+        let mut datacenters = vec![];
+
+        for delta in 0..self.ring.len() {
+            if ret.len() == n {
+                break;
+            }
+
+            let i = (start + delta) % self.ring.len();
+
+            if datacenters.len() == self.n_datacenters && !ret.contains(&self.ring[i].node) {
+                ret.push(self.ring[i].node.clone());
+            } else if !datacenters.contains(&self.ring[i].datacenter) {
+                ret.push(self.ring[i].node.clone());
+                datacenters.push(self.ring[i].datacenter);
+            }
+        }
+
+        ret
+    }
 }
 
 fn read_network_config(metadata_dir: &PathBuf) -> Result<NetworkConfig, Error> {
@@ -106,8 +180,11 @@ impl System {
 				status: HashMap::new(),
 				status_hash: [0u8; 32],
 				config: net_config,
+                ring: Vec::new(),
+                n_datacenters: 0,
         };
 		members.recalculate_status_hash();
+        members.rebuild_ring();
 		System{
 			config,
 			id,
@@ -135,7 +212,6 @@ impl System {
 		let members = self.members.read().await;
 		Message::Ping(PingMessage{
 			id: self.id,
-			datacenter: self.config.datacenter.clone(),
 			rpc_port: self.config.rpc_port,
 			status_hash: members.status_hash.clone(),
 			config_version: members.config.version,
@@ -184,7 +260,6 @@ impl System {
 					to_advertise.push(AdvertisedNode{
 						id: info.id.clone(),
 						addr: addr.clone(),
-                        datacenter: info.datacenter.clone(),
 					});
 				}
 				if is_new || members.status_hash != info.status_hash {
@@ -247,7 +322,6 @@ impl System {
 			mem.push(AdvertisedNode{
 				id: node.clone(),
 				addr: status.addr.clone(),
-                datacenter: status.datacenter.clone(),
 			});
 		}
 		Ok(Message::AdvertiseNodesUp(mem))
@@ -274,7 +348,6 @@ impl System {
 				let old_self = members.status.insert(node.id.clone(),
 					NodeStatus{
 						addr: self_addr,
-						datacenter: self.config.datacenter.clone(),
 						remaining_ping_attempts: MAX_FAILED_PINGS,
 					});
 				has_changed = match old_self {
@@ -303,9 +376,11 @@ impl System {
 	{
 		let mut members = self.members.write().await;
 		if adv.version > members.config.version {
-			members.config = adv.clone();
 			tokio::spawn(self.clone().broadcast(Message::AdvertiseConfig(adv.clone()), PING_TIMEOUT));
+
+			members.config = adv.clone();
             self.save_network_config().await;
+            members.rebuild_ring();
 		}
 
 		Ok(Message::Ok)

src/proto.rs

@@ -21,7 +21,6 @@ pub enum Message {
 #[derive(Debug, Serialize, Deserialize)]
 pub struct PingMessage {
 	pub id: UUID,
-	pub datacenter: String,
 	pub rpc_port: u16,
 
 	pub status_hash: Hash,
@@ -32,5 +31,4 @@ pub struct PingMessage {
 pub struct AdvertisedNode {
 	pub id: UUID,
 	pub addr: SocketAddr,
-	pub datacenter: String,
 }

src/server.rs

@@ -14,8 +14,6 @@ use crate::rpc_server;
 
 #[derive(Deserialize, Debug)]
 pub struct Config {
-	pub datacenter: String,
-
 	pub metadata_dir: PathBuf,
 	pub data_dir: PathBuf,