path: root/src/rpc/system.rs

//! Module containing structs related to membership management
use std::collections::HashMap;
use std::io::{Read, Write};
use std::net::{IpAddr, SocketAddr};
use std::path::{Path, PathBuf};
use std::sync::{Arc, RwLock};
use std::time::{Duration, Instant};

use arc_swap::ArcSwap;
use async_trait::async_trait;
use futures::{join, select};
use futures_util::future::*;
use serde::{Deserialize, Serialize};
use sodiumoxide::crypto::sign::ed25519;
use tokio::sync::watch;
use tokio::sync::Mutex;

use netapp::endpoint::{Endpoint, EndpointHandler};
use netapp::message::*;
use netapp::peering::fullmesh::FullMeshPeeringStrategy;
use netapp::util::parse_and_resolve_peer_addr_async;
use netapp::{NetApp, NetworkKey, NodeID, NodeKey};

use garage_util::background::BackgroundRunner;
use garage_util::config::Config;
#[cfg(feature = "kubernetes-discovery")]
use garage_util::config::KubernetesDiscoveryConfig;
use garage_util::data::*;
use garage_util::error::*;
use garage_util::persister::Persister;
use garage_util::time::*;

#[cfg(feature = "consul-discovery")]
use crate::consul::ConsulDiscovery;
#[cfg(feature = "kubernetes-discovery")]
use crate::kubernetes::*;
use crate::layout::*;
use crate::replication_mode::*;
use crate::ring::*;
use crate::rpc_helper::*;

const DISCOVERY_INTERVAL: Duration = Duration::from_secs(60);
const STATUS_EXCHANGE_INTERVAL: Duration = Duration::from_secs(10);

/// Version tag used for version check upon Netapp connection.
/// Cluster nodes with different version tags are deemed
/// incompatible and will refuse to connect.
pub const GARAGE_VERSION_TAG: u64 = 0x6761726167650008; // garage 0x0008

/// RPC endpoint used for calls related to membership
pub const SYSTEM_RPC_PATH: &str = "garage_rpc/membership.rs/SystemRpc";

pub const CONNECT_ERROR_MESSAGE: &str = "Error establishing RPC connection to remote node. This can happen if the remote node is not reachable on the network, but also if the two nodes are not configured with the same rpc_secret";

/// RPC messages related to membership
#[derive(Debug, Serialize, Deserialize, Clone)]
pub enum SystemRpc {
	/// Response to successfull advertisements
	Ok,
	/// Request to connect to a specific node (in <pubkey>@<host>:<port> format)
	Connect(String),
	/// Ask other node its cluster layout. Answered with AdvertiseClusterLayout
	PullClusterLayout,
	/// Advertise Garage status. Answered with another AdvertiseStatus.
	/// Exchanged with every node on a regular basis.
	AdvertiseStatus(NodeStatus),
	/// Advertisement of cluster layout. Sent spontanously or in response to PullClusterLayout
	AdvertiseClusterLayout(ClusterLayout),
	/// Get known nodes states
	GetKnownNodes,
	/// Return known nodes
	ReturnKnownNodes(Vec<KnownNodeInfo>),
}

impl Rpc for SystemRpc {
	type Response = Result<SystemRpc, Error>;
}

/// This node's membership manager
pub struct System {
	/// The id of this node
	pub id: Uuid,

	persist_cluster_layout: Persister<ClusterLayout>,
	persist_peer_list: Persister<Vec<(Uuid, SocketAddr)>>,

	local_status: ArcSwap<NodeStatus>,
	node_status: RwLock<HashMap<Uuid, (u64, NodeStatus)>>,

	pub netapp: Arc<NetApp>,
	fullmesh: Arc<FullMeshPeeringStrategy>,
	pub rpc: RpcHelper,

	system_endpoint: Arc<Endpoint<SystemRpc, System>>,

	rpc_listen_addr: SocketAddr,
	#[cfg(any(feature = "consul-discovery", feature = "kubernetes-discovery"))]
	rpc_public_addr: Option<SocketAddr>,
	bootstrap_peers: Vec<String>,

	#[cfg(feature = "consul-discovery")]
	consul_discovery: Option<ConsulDiscovery>,
	#[cfg(feature = "kubernetes-discovery")]
	kubernetes_discovery: Option<KubernetesDiscoveryConfig>,

	replication_mode: ReplicationMode,
	replication_factor: usize,

	/// The ring
	pub ring: watch::Receiver<Arc<Ring>>,
	update_ring: Mutex<watch::Sender<Arc<Ring>>>,

	/// The job runner of this node
	pub background: Arc<BackgroundRunner>,

	/// Path to metadata directory
	pub metadata_dir: PathBuf,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NodeStatus {
	/// Hostname of the node
	pub hostname: String,
	/// Replication factor configured on the node
	pub replication_factor: usize,
	/// Cluster layout version
	pub cluster_layout_version: u64,
	/// Hash of cluster layout staging data
	pub cluster_layout_staging_hash: Hash,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct KnownNodeInfo {
	pub id: Uuid,
	pub addr: SocketAddr,
	pub is_up: bool,
	pub last_seen_secs_ago: Option<u64>,
	pub status: NodeStatus,
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub struct ClusterHealth {
	/// The current health status of the cluster (see below)
	pub status: ClusterHealthStatus,
	/// Number of nodes already seen once in the cluster
	pub known_nodes: usize,
	/// Number of nodes currently connected
	pub connected_nodes: usize,
	/// Number of storage nodes declared in the current layout
	pub storage_nodes: usize,
	/// Number of storage nodes currently connected
	pub storage_nodes_ok: usize,
	/// Number of partitions in the layout
	pub partitions: usize,
	/// Number of partitions for which we have a quorum of connected nodes
	pub partitions_quorum: usize,
	/// Number of partitions for which all storage nodes are connected
	pub partitions_all_ok: usize,
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub enum ClusterHealthStatus {
	/// All nodes are available
	Healthy,
	/// Some storage nodes are unavailable, but quorum is stil
	/// achieved for all partitions
	Degraded,
	/// Quorum is not available for some partitions
	Unavailable,
}

pub fn read_node_id(metadata_dir: &Path) -> Result<NodeID, Error> {
	let mut pubkey_file = metadata_dir.to_path_buf();
	pubkey_file.push("node_key.pub");

	let mut f = std::fs::File::open(pubkey_file.as_path())?;
	let mut d = vec![];
	f.read_to_end(&mut d)?;
	if d.len() != 32 {
		return Err(Error::Message("Corrupt node_key.pub file".to_string()));
	}

	let mut key = [0u8; 32];
	key.copy_from_slice(&d[..]);
	Ok(NodeID::from_slice(&key[..]).unwrap())
}

pub fn gen_node_key(metadata_dir: &Path) -> Result<NodeKey, Error> {
	let mut key_file = metadata_dir.to_path_buf();
	key_file.push("node_key");
	if key_file.as_path().exists() {
		let mut f = std::fs::File::open(key_file.as_path())?;
		let mut d = vec![];
		f.read_to_end(&mut d)?;
		if d.len() != 64 {
			return Err(Error::Message("Corrupt node_key file".to_string()));
		}

		let mut key = [0u8; 64];
		key.copy_from_slice(&d[..]);
		Ok(NodeKey::from_slice(&key[..]).unwrap())
	} else {
		if !metadata_dir.exists() {
			info!("Metadata directory does not exist, creating it.");
			std::fs::create_dir(&metadata_dir)?;
		}

		info!("Generating new node key pair.");
		let (pubkey, key) = ed25519::gen_keypair();

		{
			use std::os::unix::fs::PermissionsExt;
			let mut f = std::fs::File::create(key_file.as_path())?;
			let mut perm = f.metadata()?.permissions();
			perm.set_mode(0o600);
			std::fs::set_permissions(key_file.as_path(), perm)?;
			f.write_all(&key[..])?;
		}

		{
			let mut pubkey_file = metadata_dir.to_path_buf();
			pubkey_file.push("node_key.pub");
			let mut f2 = std::fs::File::create(pubkey_file.as_path())?;
			f2.write_all(&pubkey[..])?;
		}

		Ok(key)
	}
}

impl System {
	/// Create this node's membership manager
	pub fn new(
		network_key: NetworkKey,
		background: Arc<BackgroundRunner>,
		replication_mode: ReplicationMode,
		config: &Config,
	) -> Result<Arc<Self>, Error> {
		let replication_factor = replication_mode.replication_factor();

		let node_key =
			gen_node_key(&config.metadata_dir).expect("Unable to read or generate node ID");
		info!(
			"Node ID of this node: {}",
			hex::encode(&node_key.public_key()[..8])
		);

		let persist_cluster_layout: Persister<ClusterLayout> =
			Persister::new(&config.metadata_dir, "cluster_layout");
		let persist_peer_list = Persister::new(&config.metadata_dir, "peer_list");

		let cluster_layout = match persist_cluster_layout.load() {
			Ok(x) => {
				if x.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.replication_factor,
						replication_factor
					)));
				}
				x
			}
			Err(e) => {
				info!(
					"No valid previous cluster layout stored ({}), starting fresh.",
					e
				);
				ClusterLayout::new(replication_factor)
			}
		};

		let local_status = NodeStatus {
			hostname: gethostname::gethostname()
				.into_string()
				.unwrap_or_else(|_| "<invalid utf-8>".to_string()),
			replication_factor,
			cluster_layout_version: cluster_layout.version,
			cluster_layout_staging_hash: cluster_layout.staging_hash,
		};

		let ring = Ring::new(cluster_layout, replication_factor);
		let (update_ring, ring) = watch::channel(Arc::new(ring));

		let rpc_public_addr = match &config.rpc_public_addr {
			Some(a_str) => {
				use std::net::ToSocketAddrs;
				match a_str.to_socket_addrs() {
					Err(e) => {
						error!(
							"Cannot resolve rpc_public_addr {} from config file: {}.",
							a_str, e
						);
						None
					}
					Ok(a) => {
						let a = a.collect::<Vec<_>>();
						if a.is_empty() {
							error!("rpc_public_addr {} resolve to no known IP address", a_str);
						}
						if a.len() > 1 {
							warn!("Multiple possible resolutions for rpc_public_addr: {:?}. Taking the first one.", a);
						}
						a.into_iter().next()
					}
				}
			}
			None => {
				let addr =
					get_default_ip().map(|ip| SocketAddr::new(ip, config.rpc_bind_addr.port()));
				if let Some(a) = addr {
					warn!("Using autodetected rpc_public_addr: {}. Consider specifying it explicitly in configuration file if possible.", a);
				}
				addr
			}
		};
		if rpc_public_addr.is_none() {
			warn!("This Garage node does not know its publicly reachable RPC address, this might hamper intra-cluster communication.");
		}

		let netapp = NetApp::new(GARAGE_VERSION_TAG, network_key, node_key);
		let fullmesh = FullMeshPeeringStrategy::new(netapp.clone(), vec![], rpc_public_addr);
		if let Some(ping_timeout) = config.rpc_ping_timeout_msec {
			fullmesh.set_ping_timeout_millis(ping_timeout);
		}

		let system_endpoint = netapp.endpoint(SYSTEM_RPC_PATH.into());

		#[cfg(feature = "consul-discovery")]
		let consul_discovery = match &config.consul_discovery {
			Some(cfg) => Some(
				ConsulDiscovery::new(cfg.clone())
					.ok_or_message("Invalid Consul discovery configuration")?,
			),
			None => None,
		};
		#[cfg(not(feature = "consul-discovery"))]
		if config.consul_discovery.is_some() {
			warn!("Consul discovery is not enabled in this build.");
		}

		#[cfg(not(feature = "kubernetes-discovery"))]
		if config.kubernetes_discovery.is_some() {
			warn!("Kubernetes discovery is not enabled in this build.");
		}

		let sys = Arc::new(System {
			id: netapp.id.into(),
			persist_cluster_layout,
			persist_peer_list,
			local_status: ArcSwap::new(Arc::new(local_status)),
			node_status: RwLock::new(HashMap::new()),
			netapp: netapp.clone(),
			fullmesh: fullmesh.clone(),
			rpc: RpcHelper::new(
				netapp.id.into(),
				fullmesh,
				background.clone(),
				ring.clone(),
				config.rpc_timeout_msec.map(Duration::from_millis),
			),
			system_endpoint,
			replication_mode,
			replication_factor,
			rpc_listen_addr: config.rpc_bind_addr,
			#[cfg(any(feature = "consul-discovery", feature = "kubernetes-discovery"))]
			rpc_public_addr,
			bootstrap_peers: config.bootstrap_peers.clone(),
			#[cfg(feature = "consul-discovery")]
			consul_discovery,
			#[cfg(feature = "kubernetes-discovery")]
			kubernetes_discovery: config.kubernetes_discovery.clone(),

			ring,
			update_ring: Mutex::new(update_ring),
			background,
			metadata_dir: config.metadata_dir.clone(),
		});
		sys.system_endpoint.set_handler(sys.clone());
		Ok(sys)
	}

	/// Perform bootstraping, starting the ping loop
	pub async fn run(self: Arc<Self>, must_exit: watch::Receiver<bool>) {
		join!(
			self.netapp
				.clone()
				.listen(self.rpc_listen_addr, None, must_exit.clone()),
			self.fullmesh.clone().run(must_exit.clone()),
			self.discovery_loop(must_exit.clone()),
			self.status_exchange_loop(must_exit.clone()),
		);
	}

	// ---- Administrative operations (directly available and
	//      also available through RPC) ----

	pub fn get_known_nodes(&self) -> Vec<KnownNodeInfo> {
		let node_status = self.node_status.read().unwrap();
		let known_nodes = self
			.fullmesh
			.get_peer_list()
			.iter()
			.map(|n| KnownNodeInfo {
				id: n.id.into(),
				addr: n.addr,
				is_up: n.is_up(),
				last_seen_secs_ago: n
					.last_seen
					.map(|t| (Instant::now().saturating_duration_since(t)).as_secs()),
				status: node_status
					.get(&n.id.into())
					.cloned()
					.map(|(_, st)| st)
					.unwrap_or(NodeStatus {
						hostname: "?".to_string(),
						replication_factor: 0,
						cluster_layout_version: 0,
						cluster_layout_staging_hash: Hash::from([0u8; 32]),
					}),
			})
			.collect::<Vec<_>>();
		known_nodes
	}

	pub fn get_cluster_layout(&self) -> ClusterLayout {
		self.ring.borrow().layout.clone()
	}

	pub async fn update_cluster_layout(
		self: &Arc<Self>,
		layout: &ClusterLayout,
	) -> Result<(), Error> {
		self.handle_advertise_cluster_layout(layout).await?;
		Ok(())
	}

	pub async fn connect(&self, node: &str) -> Result<(), Error> {
		let (pubkey, addrs) = parse_and_resolve_peer_addr_async(node)
			.await
			.ok_or_else(|| {
				Error::Message(format!(
					"Unable to parse or resolve node specification: {}",
					node
				))
			})?;
		let mut errors = vec![];
		for ip in addrs.iter() {
			match self
				.netapp
				.clone()
				.try_connect(*ip, pubkey)
				.await
				.err_context(CONNECT_ERROR_MESSAGE)
			{
				Ok(()) => return Ok(()),
				Err(e) => {
					errors.push((*ip, e));
				}
			}
		}
		if errors.len() == 1 {
			Err(Error::Message(errors[0].1.to_string()))
		} else {
			Err(Error::Message(format!("{:?}", errors)))
		}
	}

	pub fn health(&self) -> ClusterHealth {
		let ring: Arc<_> = self.ring.borrow().clone();
		let quorum = self.replication_mode.write_quorum();
		let replication_factor = self.replication_factor;

		let nodes = self
			.get_known_nodes()
			.into_iter()
			.map(|n| (n.id, n))
			.collect::<HashMap<Uuid, _>>();
		let connected_nodes = nodes.iter().filter(|(_, n)| n.is_up).count();

		let storage_nodes = ring
			.layout
			.roles
			.items()
			.iter()
			.filter(|(_, _, v)| matches!(v, NodeRoleV(Some(r)) if r.capacity.is_some()))
			.collect::<Vec<_>>();
		let storage_nodes_ok = storage_nodes
			.iter()
			.filter(|(x, _, _)| nodes.get(x).map(|n| n.is_up).unwrap_or(false))
			.count();

		let partitions = ring.partitions();
		let partitions_n_up = partitions
			.iter()
			.map(|(_, h)| {
				let pn = ring.get_nodes(h, ring.replication_factor);
				pn.iter()
					.filter(|x| nodes.get(x).map(|n| n.is_up).unwrap_or(false))
					.count()
			})
			.collect::<Vec<usize>>();
		let partitions_all_ok = partitions_n_up
			.iter()
			.filter(|c| **c == replication_factor)
			.count();
		let partitions_quorum = partitions_n_up.iter().filter(|c| **c >= quorum).count();

		let status =
			if partitions_quorum == partitions.len() && storage_nodes_ok == storage_nodes.len() {
				ClusterHealthStatus::Healthy
			} else if partitions_quorum == partitions.len() {
				ClusterHealthStatus::Degraded
			} else {
				ClusterHealthStatus::Unavailable
			};

		ClusterHealth {
			status,
			known_nodes: nodes.len(),
			connected_nodes,
			storage_nodes: storage_nodes.len(),
			storage_nodes_ok,
			partitions: partitions.len(),
			partitions_quorum,
			partitions_all_ok,
		}
	}

	// ---- INTERNALS ----

	#[cfg(feature = "consul-discovery")]
	async fn advertise_to_consul(self: Arc<Self>) -> Result<(), Error> {
		let c = match &self.consul_discovery {
			Some(c) => c,
			_ => return Ok(()),
		};

		let rpc_public_addr = match self.rpc_public_addr {
			Some(addr) => addr,
			None => {
				warn!("Not advertising to Consul because rpc_public_addr is not defined in config file and could not be autodetected.");
				return Ok(());
			}
		};

		c.publish_consul_service(
			self.netapp.id,
			&self.local_status.load_full().hostname,
			rpc_public_addr,
		)
		.await
		.err_context("Error while publishing Consul service")
	}

	#[cfg(feature = "kubernetes-discovery")]
	async fn advertise_to_kubernetes(self: Arc<Self>) -> Result<(), Error> {
		let k = match &self.kubernetes_discovery {
			Some(k) => k,
			_ => return Ok(()),
		};

		let rpc_public_addr = match self.rpc_public_addr {
			Some(addr) => addr,
			None => {
				warn!("Not advertising to Kubernetes because rpc_public_addr is not defined in config file and could not be autodetected.");
				return Ok(());
			}
		};

		publish_kubernetes_node(
			k,
			self.netapp.id,
			&self.local_status.load_full().hostname,
			rpc_public_addr,
		)
		.await
		.err_context("Error while publishing node to kubernetes")
	}

	/// Save network configuration to disc
	async fn save_cluster_layout(self: Arc<Self>) -> Result<(), Error> {
		let ring: Arc<Ring> = self.ring.borrow().clone();
		self.persist_cluster_layout
			.save_async(&ring.layout)
			.await
			.expect("Cannot save current cluster layout");
		Ok(())
	}

	fn update_local_status(&self) {
		let mut new_si: NodeStatus = self.local_status.load().as_ref().clone();

		let ring = self.ring.borrow();
		new_si.cluster_layout_version = ring.layout.version;
		new_si.cluster_layout_staging_hash = ring.layout.staging_hash;
		self.local_status.swap(Arc::new(new_si));
	}

	// --- RPC HANDLERS ---

	async fn handle_connect(&self, node: &str) -> Result<SystemRpc, Error> {
		self.connect(node).await?;
		Ok(SystemRpc::Ok)
	}

	fn handle_pull_cluster_layout(&self) -> SystemRpc {
		let ring = self.ring.borrow().clone();
		SystemRpc::AdvertiseClusterLayout(ring.layout.clone())
	}

	fn handle_get_known_nodes(&self) -> SystemRpc {
		let known_nodes = self.get_known_nodes();
		SystemRpc::ReturnKnownNodes(known_nodes)
	}

	async fn handle_advertise_status(
		self: &Arc<Self>,
		from: Uuid,
		info: &NodeStatus,
	) -> Result<SystemRpc, Error> {
		let local_info = self.local_status.load();

		if local_info.replication_factor < info.replication_factor {
			error!("Some node have a higher replication factor ({}) than this one ({}). This is not supported and will lead to data corruption. Shutting down for safety.",
				info.replication_factor,
				local_info.replication_factor);
			std::process::exit(1);
		}

		if info.cluster_layout_version > local_info.cluster_layout_version
			|| info.cluster_layout_staging_hash != local_info.cluster_layout_staging_hash
		{
			let self2 = self.clone();
			self.background.spawn_cancellable(async move {
				self2.pull_cluster_layout(from).await;
				Ok(())
			});
		}

		self.node_status
			.write()
			.unwrap()
			.insert(from, (now_msec(), info.clone()));

		Ok(SystemRpc::Ok)
	}

	async fn handle_advertise_cluster_layout(
		self: &Arc<Self>,
		adv: &ClusterLayout,
	) -> Result<SystemRpc, Error> {
		if adv.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.replication_factor,
				self.replication_factor
			);
			error!("{}", msg);
			return Err(Error::Message(msg));
		}

		let update_ring = self.update_ring.lock().await;
		let mut layout: ClusterLayout = self.ring.borrow().layout.clone();

		let prev_layout_check = layout.check();
		if layout.merge(adv) {
			if prev_layout_check && !layout.check() {
				error!("New cluster layout is invalid, discarding.");
				return Err(Error::Message(
					"New cluster layout is invalid, discarding.".into(),
				));
			}

			let ring = Ring::new(layout.clone(), self.replication_factor);
			update_ring.send(Arc::new(ring))?;
			drop(update_ring);

			let self2 = self.clone();
			self.background.spawn_cancellable(async move {
				self2
					.rpc
					.broadcast(
						&self2.system_endpoint,
						SystemRpc::AdvertiseClusterLayout(layout),
						RequestStrategy::with_priority(PRIO_HIGH),
					)
					.await?;
				Ok(())
			});
			self.background.spawn(self.clone().save_cluster_layout());
		}

		Ok(SystemRpc::Ok)
	}

	async fn status_exchange_loop(&self, mut stop_signal: watch::Receiver<bool>) {
		while !*stop_signal.borrow() {
			let restart_at = tokio::time::sleep(STATUS_EXCHANGE_INTERVAL);

			self.update_local_status();
			let local_status: NodeStatus = self.local_status.load().as_ref().clone();
			let _ = self
				.rpc
				.broadcast(
					&self.system_endpoint,
					SystemRpc::AdvertiseStatus(local_status),
					RequestStrategy::with_priority(PRIO_HIGH),
				)
				.await;

			select! {
				_ = restart_at.fuse() => {},
				_ = stop_signal.changed().fuse() => {},
			}
		}
	}

	async fn discovery_loop(self: &Arc<Self>, mut stop_signal: watch::Receiver<bool>) {
		while !*stop_signal.borrow() {
			let not_configured = !self.ring.borrow().layout.check();
			let no_peers = self.fullmesh.get_peer_list().len() < self.replication_factor;
			let expected_n_nodes = self.ring.borrow().layout.num_nodes();
			let bad_peers = self
				.fullmesh
				.get_peer_list()
				.iter()
				.filter(|p| p.is_up())
				.count() != expected_n_nodes;

			if not_configured || no_peers || bad_peers {
				info!("Doing a bootstrap/discovery step (not_configured: {}, no_peers: {}, bad_peers: {})", not_configured, no_peers, bad_peers);

				let mut ping_list = resolve_peers(&self.bootstrap_peers).await;

				// Add peer list from list stored on disk
				if let Ok(peers) = self.persist_peer_list.load_async().await {
					ping_list.extend(peers.iter().map(|(id, addr)| ((*id).into(), *addr)))
				}

				// Fetch peer list from Consul
				#[cfg(feature = "consul-discovery")]
				if let Some(c) = &self.consul_discovery {
					match c.get_consul_nodes().await {
						Ok(node_list) => {
							ping_list.extend(node_list);
						}
						Err(e) => {
							warn!("Could not retrieve node list from Consul: {}", e);
						}
					}
				}

				// Fetch peer list from Kubernetes
				#[cfg(feature = "kubernetes-discovery")]
				if let Some(k) = &self.kubernetes_discovery {
					if !k.skip_crd {
						match create_kubernetes_crd().await {
							Ok(()) => (),
							Err(e) => {
								error!("Failed to create kubernetes custom resource: {}", e)
							}
						};
					}

					match get_kubernetes_nodes(k).await {
						Ok(node_list) => {
							ping_list.extend(node_list);
						}
						Err(e) => {
							warn!("Could not retrieve node list from Kubernetes: {}", e);
						}
					}
				}

				for (node_id, node_addr) in ping_list {
					tokio::spawn(
						self.netapp
							.clone()
							.try_connect(node_addr, node_id)
							.map(|r| r.err_context(CONNECT_ERROR_MESSAGE)),
					);
				}
			}

			if let Err(e) = self.save_peer_list().await {
				warn!("Could not save peer list to file: {}", e);
			}

			#[cfg(feature = "consul-discovery")]
			self.background.spawn(self.clone().advertise_to_consul());

			#[cfg(feature = "kubernetes-discovery")]
			self.background
				.spawn(self.clone().advertise_to_kubernetes());

			let restart_at = tokio::time::sleep(DISCOVERY_INTERVAL);
			select! {
				_ = restart_at.fuse() => {},
				_ = stop_signal.changed().fuse() => {},
			}
		}
	}

	async fn save_peer_list(&self) -> Result<(), Error> {
		// Prepare new peer list to save to file
		// It is a vec of tuples (node ID as Uuid, node SocketAddr)
		let mut peer_list = self
			.fullmesh
			.get_peer_list()
			.iter()
			.map(|n| (n.id.into(), n.addr))
			.collect::<Vec<_>>();

		// Before doing it, we read the current peer list file (if it exists)
		// and append it to the list we are about to save,
		// so that no peer ID gets lost in the process.
		if let Ok(mut prev_peer_list) = self.persist_peer_list.load_async().await {
			prev_peer_list.retain(|(id, _ip)| peer_list.iter().all(|(id2, _ip2)| id2 != id));
			peer_list.extend(prev_peer_list);
		}

		// Save new peer list to file
		self.persist_peer_list.save_async(&peer_list).await
	}

	async fn pull_cluster_layout(self: Arc<Self>, peer: Uuid) {
		let resp = self
			.rpc
			.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;
		}
	}
}

#[async_trait]
impl EndpointHandler<SystemRpc> for System {
	async fn handle(self: &Arc<Self>, msg: &SystemRpc, from: NodeID) -> Result<SystemRpc, Error> {
		match msg {
			SystemRpc::Connect(node) => self.handle_connect(node).await,
			SystemRpc::PullClusterLayout => Ok(self.handle_pull_cluster_layout()),
			SystemRpc::AdvertiseStatus(adv) => self.handle_advertise_status(from.into(), adv).await,
			SystemRpc::AdvertiseClusterLayout(adv) => {
				self.clone().handle_advertise_cluster_layout(adv).await
			}
			SystemRpc::GetKnownNodes => Ok(self.handle_get_known_nodes()),
			m => Err(Error::unexpected_rpc_message(m)),
		}
	}
}

fn get_default_ip() -> Option<IpAddr> {
	pnet_datalink::interfaces()
		.iter()
		.find(|e| e.is_up() && !e.is_loopback() && !e.ips.is_empty())
		.and_then(|e| e.ips.first())
		.map(|a| a.ip())
}

async fn resolve_peers(peers: &[String]) -> Vec<(NodeID, SocketAddr)> {
	let mut ret = vec![];

	for peer in peers.iter() {
		match parse_and_resolve_peer_addr_async(peer).await {
			Some((pubkey, addrs)) => {
				for ip in addrs {
					ret.push((pubkey, ip));
				}
			}
			None => {
				warn!("Unable to parse and/or resolve peer hostname {}", peer);
			}
		}
	}

	ret
}