Add parachain_desired_peer_count metric (#3035)

polkadot/node/network/bridge/src/lib.rs

@@ -131,13 +131,22 @@ impl Metrics {
 				.inc_by((size * to_peers) as u64);
 		}
 	}
+
+	fn note_desired_peer_count(&self, peer_set: PeerSet, size: usize) {
+		self.0.as_ref().map(|metrics| metrics
+			.desired_peer_count
+			.with_label_values(&[peer_set.get_protocol_name_static()])
+			.set(size as u64)
+		);
+	}
 }
 
 #[derive(Clone)]
 struct MetricsInner {
 	peer_count: prometheus::GaugeVec<prometheus::U64>,
 	connected_events: prometheus::CounterVec<prometheus::U64>,
 	disconnected_events: prometheus::CounterVec<prometheus::U64>,
+	desired_peer_count: prometheus::GaugeVec<prometheus::U64>,
 
 	notifications_received: prometheus::CounterVec<prometheus::U64>,
 	notifications_sent: prometheus::CounterVec<prometheus::U64>,
@@ -181,6 +190,16 @@ impl metrics::Metrics for Metrics {
 				)?,
 				registry,
 			)?,
+			desired_peer_count: prometheus::register(
+				prometheus::GaugeVec::new(
+					prometheus::Opts::new(
+						"parachain_desired_peer_count",
+						"The number of peers that the local node is expected to connect to on a parachain-related peer-set",
+					),
+					&["protocol"]
+				)?,
+				registry,
+			)?,
 			notifications_received: prometheus::register(
 				prometheus::CounterVec::new(
 					prometheus::Opts::new(
@@ -519,6 +538,8 @@ where
 							"Received a validator connection request",
 						);
 
+						metrics.note_desired_peer_count(peer_set, validator_ids.len());
+
 						let (ns, ads) = validator_discovery.on_request(
 							validator_ids,
 							peer_set,