Further reduce the CPU overhead of networking metrics (paritytech#10875)

* Simplify `num_connected_peers`

* Track requested peer counts

* Revert "Track requested peer counts"

This reverts commit 9f1c870.

* Remove `substrate_sub_libp2p_peerset_num_requested` metric

* Remove two unused functions that I forgot to get rid of in previous commit

client/network/src/protocol.rs

@@ -465,12 +465,6 @@ impl<B: BlockT> Protocol<B> {
 		self.behaviour.open_peers()
 	}
 
-	/// Returns the list of all the peers that the peerset currently requests us to be connected
-	/// to on the default set.
-	pub fn requested_peers(&self) -> impl Iterator<Item = &PeerId> {
-		self.behaviour.requested_peers(HARDCODED_PEERSETS_SYNC)
-	}
-
 	/// Returns the number of discovered nodes that we keep in memory.
 	pub fn num_discovered_peers(&self) -> usize {
 		self.behaviour.num_discovered_peers()
@@ -496,7 +490,7 @@ impl<B: BlockT> Protocol<B> {
 
 	/// Returns the number of peers we're connected to.
 	pub fn num_connected_peers(&self) -> usize {
-		self.peers.values().count()
+		self.peers.len()
 	}
 
 	/// Returns the number of peers we're connected to and that are being queried.

client/network/src/protocol/notifications/behaviour.rs

@@ -251,16 +251,6 @@ impl PeerState {
 			_ => None,
 		}
 	}
-
-	/// True if that node has been requested by the PSM.
-	fn is_requested(&self) -> bool {
-		matches!(
-			self,
-			Self::PendingRequest { .. } |
-				Self::Requested | Self::DisabledPendingEnable { .. } |
-				Self::Enabled { .. }
-		)
-	}
 }
 
 /// State of the handler of a single connection visible from this state machine.
@@ -560,17 +550,6 @@ impl Notifications {
 		}
 	}
 
-	/// Returns the list of all the peers that the peerset currently requests us to be connected to.
-	pub fn requested_peers<'a>(
-		&'a self,
-		set_id: sc_peerset::SetId,
-	) -> impl Iterator<Item = &'a PeerId> + 'a {
-		self.peers
-			.iter()
-			.filter(move |((_, set), state)| *set == set_id && state.is_requested())
-			.map(|((id, _), _)| id)
-	}
-
 	/// Returns the list of reserved peers.
 	pub fn reserved_peers<'a>(
 		&'a self,

client/network/src/service.rs

@@ -2108,10 +2108,6 @@ impl<B: BlockT + 'static, H: ExHashT> Future for NetworkWorker<B, H> {
 				.peerset_num_discovered
 				.set(this.network_service.behaviour_mut().user_protocol().num_discovered_peers()
 					as u64);
-			metrics.peerset_num_requested.set(
-				this.network_service.behaviour_mut().user_protocol().requested_peers().count()
-					as u64,
-			);
 			metrics.pending_connections.set(
 				Swarm::network_info(&this.network_service).connection_counters().num_pending()
 					as u64,

client/network/src/service/metrics.rs

@@ -69,7 +69,6 @@ pub struct Metrics {
 	pub notifications_streams_closed_total: CounterVec<U64>,
 	pub notifications_streams_opened_total: CounterVec<U64>,
 	pub peerset_num_discovered: Gauge<U64>,
-	pub peerset_num_requested: Gauge<U64>,
 	pub pending_connections: Gauge<U64>,
 	pub pending_connections_errors_total: CounterVec<U64>,
 	pub requests_in_failure_total: CounterVec<U64>,
@@ -204,10 +203,6 @@ impl Metrics {
 				"substrate_sub_libp2p_peerset_num_discovered",
 				"Number of nodes stored in the peerset manager",
 			)?, registry)?,
-			peerset_num_requested: prometheus::register(Gauge::new(
-				"substrate_sub_libp2p_peerset_num_requested",
-				"Number of nodes that the peerset manager wants us to be connected to",
-			)?, registry)?,
 			pending_connections: prometheus::register(Gauge::new(
 				"substrate_sub_libp2p_pending_connections",
 				"Number of connections in the process of being established",