From b868493da9b7cf6e5703ee5d068ae34938fbff34 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Tue, 20 Feb 2024 14:49:08 +0100
Subject: [peer-metrics] add basic cluster node status metrics (fix #545)

---
 src/rpc/system_metrics.rs | 94 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)

diff --git a/src/rpc/system_metrics.rs b/src/rpc/system_metrics.rs
index ad4aca2f..ffbef6df 100644
--- a/src/rpc/system_metrics.rs
+++ b/src/rpc/system_metrics.rs
@@ -3,6 +3,7 @@ use std::time::{Duration, Instant};
 
 use opentelemetry::{global, metrics::*, KeyValue};
 
+use crate::ring::Ring;
 use crate::system::{ClusterHealthStatus, System};
 
 /// TableMetrics reference all counter used for metrics
@@ -25,6 +26,10 @@ pub struct SystemMetrics {
 	pub(crate) _partitions: ValueObserver<u64>,
 	pub(crate) _partitions_quorum: ValueObserver<u64>,
 	pub(crate) _partitions_all_ok: ValueObserver<u64>,
+
+	// Status report for individual cluster nodes
+	pub(crate) _layout_node_connected: ValueObserver<u64>,
+	pub(crate) _layout_node_disconnected_time: ValueObserver<u64>,
 }
 
 impl SystemMetrics {
@@ -204,6 +209,95 @@ impl SystemMetrics {
 					)
 					.init()
 			},
+
+			// Status report for individual cluster nodes
+			_layout_node_connected: {
+				let system = system.clone();
+				meter
+					.u64_value_observer("cluster_layout_node_connected", move |observer| {
+						let ring: Arc<Ring> = system.ring.borrow().clone();
+						let nodes = system.get_known_nodes();
+						for (id, _, config) in ring.layout.roles.items().iter() {
+							if let Some(role) = &config.0 {
+								let mut kv = vec![
+									KeyValue::new("id", format!("{:?}", id)),
+									KeyValue::new("role_zone", role.zone.clone()),
+								];
+								match role.capacity {
+									Some(cap) => {
+										kv.push(KeyValue::new("role_capacity", cap as i64));
+										kv.push(KeyValue::new("role_gateway", 0));
+									}
+									None => {
+										kv.push(KeyValue::new("role_gateway", 1));
+									}
+								}
+
+								let value;
+								if let Some(node) = nodes.iter().find(|n| n.id == *id) {
+									value = if node.is_up { 1 } else { 0 };
+								// TODO: if we add address and hostname, and those change, we
+								// get duplicate metrics, due to bad otel aggregation :(
+								// Can probably be fixed when we upgrade opentelemetry
+								// kv.push(KeyValue::new("address", node.addr.to_string()));
+								// kv.push(KeyValue::new(
+								// 	"hostname",
+								// 	node.status.hostname.clone(),
+								// ));
+								} else {
+									value = 0;
+								}
+
+								observer.observe(value, &kv);
+							}
+						}
+					})
+					.with_description("Connection status for nodes in the cluster layout")
+					.init()
+			},
+			_layout_node_disconnected_time: {
+				let system = system.clone();
+				meter
+					.u64_value_observer("cluster_layout_node_disconnected_time", move |observer| {
+						let ring: Arc<Ring> = system.ring.borrow().clone();
+						let nodes = system.get_known_nodes();
+						for (id, _, config) in ring.layout.roles.items().iter() {
+							if let Some(role) = &config.0 {
+								let mut kv = vec![
+									KeyValue::new("id", format!("{:?}", id)),
+									KeyValue::new("role_zone", role.zone.clone()),
+								];
+								match role.capacity {
+									Some(cap) => {
+										kv.push(KeyValue::new("role_capacity", cap as i64));
+										kv.push(KeyValue::new("role_gateway", 0));
+									}
+									None => {
+										kv.push(KeyValue::new("role_gateway", 1));
+									}
+								}
+
+								if let Some(node) = nodes.iter().find(|n| n.id == *id) {
+									// TODO: see comment above
+									// kv.push(KeyValue::new("address", node.addr.to_string()));
+									// kv.push(KeyValue::new(
+									// 	"hostname",
+									// 	node.status.hostname.clone(),
+									// ));
+									if node.is_up {
+										observer.observe(0, &kv);
+									} else if let Some(secs) = node.last_seen_secs_ago {
+										observer.observe(secs, &kv);
+									}
+								}
+							}
+						}
+					})
+					.with_description(
+						"Time (in seconds) since last connection to nodes in the cluster layout",
+					)
+					.init()
+			},
 		}
 	}
 }
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