[peer-metrics] Add metrics for cluster health, like GetClusterHealth admin API

src/rpc/system.rs

@@ -104,7 +104,7 @@ pub struct System {
 	#[cfg(feature = "kubernetes-discovery")]
 	kubernetes_discovery: Option<KubernetesDiscoveryConfig>,
 
-	_metrics: SystemMetrics,
+	metrics: SystemMetrics,
 
 	replication_mode: ReplicationMode,
 	replication_factor: usize,
@@ -168,7 +168,7 @@ pub struct ClusterHealth {
 	pub partitions_all_ok: usize,
 }
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub enum ClusterHealthStatus {
 	/// All nodes are available
 	Healthy,
@@ -376,7 +376,7 @@ impl System {
 			consul_discovery,
 			#[cfg(feature = "kubernetes-discovery")]
 			kubernetes_discovery: config.kubernetes_discovery.clone(),
-			_metrics: metrics,
+			metrics,
 
 			ring,
 			update_ring: Mutex::new(update_ring),
@@ -698,7 +698,13 @@ impl System {
 		while !*stop_signal.borrow() {
 			let restart_at = Instant::now() + STATUS_EXCHANGE_INTERVAL;
 
+			// Update local node status that is exchanged.
+			// Status variables are exported into Prometheus in SystemMetrics,
+			// so we take the opportunity to also update here the health status
+			// that is reported in those metrics.
 			self.update_local_status();
+			*self.metrics.health.write().unwrap() = Some(self.health());
+
 			let local_status: NodeStatus = self.local_status.read().unwrap().clone();
 			let _ = self
 				.rpc

src/rpc/system_metrics.rs

@@ -2,22 +2,40 @@ use std::sync::{Arc, RwLock};
 
 use opentelemetry::{global, metrics::*, KeyValue};
 
-use crate::system::NodeStatus;
+use crate::system::{ClusterHealth, ClusterHealthStatus, NodeStatus};
 
 /// TableMetrics reference all counter used for metrics
 pub struct SystemMetrics {
+	pub(crate) health: Arc<RwLock<Option<ClusterHealth>>>,
+
+	// Static values
 	pub(crate) _garage_build_info: ValueObserver<u64>,
 	pub(crate) _replication_factor: ValueObserver<u64>,
+
+	// Disk space values from System::local_status
 	pub(crate) _disk_avail: ValueObserver<u64>,
 	pub(crate) _disk_total: ValueObserver<u64>,
+
+	// Health report from System::health()
+	pub(crate) _cluster_healthy: ValueObserver<u64>,
+	pub(crate) _cluster_available: ValueObserver<u64>,
+	pub(crate) _known_nodes: ValueObserver<u64>,
+	pub(crate) _connected_nodes: ValueObserver<u64>,
+	pub(crate) _storage_nodes: ValueObserver<u64>,
+	pub(crate) _storage_nodes_ok: ValueObserver<u64>,
+	pub(crate) _partitions: ValueObserver<u64>,
+	pub(crate) _partitions_quorum: ValueObserver<u64>,
+	pub(crate) _partitions_all_ok: ValueObserver<u64>,
 }
 
 impl SystemMetrics {
 	pub fn new(replication_factor: usize, local_status: Arc<RwLock<NodeStatus>>) -> Self {
 		let meter = global::meter("garage_system");
-		let st1 = local_status.clone();
-		let st2 = local_status.clone();
+		let health = Arc::new(RwLock::new(None));
 		Self {
+			health: health.clone(),
+
+			// Static values
 			_garage_build_info: meter
 				.u64_value_observer("garage_build_info", move |observer| {
 					observer.observe(
@@ -36,9 +54,13 @@ impl SystemMetrics {
 				})
 				.with_description("Garage replication factor setting")
 				.init(),
-			_disk_avail: meter
+
+			// Disk space values from System::local_status
+			_disk_avail: {
+				let status = local_status.clone();
+				meter
 					.u64_value_observer("garage_local_disk_avail", move |observer| {
-					let st = st1.read().unwrap();
+						let st = status.read().unwrap();
 						if let Some((avail, _total)) = st.data_disk_avail {
 							observer.observe(avail, &[KeyValue::new("volume", "data")]);
 						}
@@ -47,10 +69,13 @@ impl SystemMetrics {
 						}
 					})
 					.with_description("Garage available disk space on each node")
-				.init(),
-			_disk_total: meter
+					.init()
+			},
+			_disk_total: {
+				let status = local_status.clone();
+				meter
 					.u64_value_observer("garage_local_disk_total", move |observer| {
-					let st = st2.read().unwrap();
+						let st = status.read().unwrap();
 						if let Some((_avail, total)) = st.data_disk_avail {
 							observer.observe(total, &[KeyValue::new("volume", "data")]);
 						}
@@ -59,7 +84,120 @@ impl SystemMetrics {
 						}
 					})
 					.with_description("Garage total disk space on each node")
-				.init(),
+					.init()
+			},
+
+			// Health report from System::health()
+			_cluster_healthy: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_healthy", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							if h.status == ClusterHealthStatus::Healthy {
+								observer.observe(1, &[]);
+							} else {
+								observer.observe(0, &[]);
+							}
+						}
+					})
+					.with_description("Whether all storage nodes are connected")
+					.init()
+			},
+			_cluster_available: {
+				let health = health.clone();
+				meter.u64_value_observer("cluster_available", move |observer| {
+					if let Some(h) = health.read().unwrap().as_ref() {
+						if h.status != ClusterHealthStatus::Unavailable {
+							observer.observe(1, &[]);
+						} else {
+							observer.observe(0, &[]);
+						}
+					}
+				})
+				.with_description("Whether all requests can be served, even if some storage nodes are disconnected")
+				.init()
+			},
+			_known_nodes: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_known_nodes", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							observer.observe(h.known_nodes as u64, &[]);
+						}
+					})
+					.with_description("Number of nodes already seen once in the cluster")
+					.init()
+			},
+			_connected_nodes: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_connected_nodes", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							observer.observe(h.connected_nodes as u64, &[]);
+						}
+					})
+					.with_description("Number of nodes currently connected")
+					.init()
+			},
+			_storage_nodes: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_storage_nodes", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							observer.observe(h.storage_nodes as u64, &[]);
+						}
+					})
+					.with_description("Number of storage nodes declared in the current layout")
+					.init()
+			},
+			_storage_nodes_ok: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_storage_nodes_ok", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							observer.observe(h.storage_nodes_ok as u64, &[]);
+						}
+					})
+					.with_description("Number of storage nodes currently connected")
+					.init()
+			},
+			_partitions: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_partitions", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							observer.observe(h.partitions as u64, &[]);
+						}
+					})
+					.with_description("Number of partitions in the layout")
+					.init()
+			},
+			_partitions_quorum: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_partitions_quorum", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							observer.observe(h.partitions_quorum as u64, &[]);
+						}
+					})
+					.with_description(
+						"Number of partitions for which we have a quorum of connected nodes",
+					)
+					.init()
+			},
+			_partitions_all_ok: {
+				let health = health.clone();
+				meter
+					.u64_value_observer("cluster_partitions_all_ok", move |observer| {
+						if let Some(h) = health.read().unwrap().as_ref() {
+							observer.observe(h.partitions_all_ok as u64, &[]);
+						}
+					})
+					.with_description(
+						"Number of partitions for which all storage nodes are connected",
+					)
+					.init()
+			},
 		}
 	}
 }