Add metric for unfeasbile update to unknown subnet

Signed-off-by: Lee Smet <lee.smet@hotmail.com>

mycelium-metrics/src/prometheus.rs

@@ -29,6 +29,7 @@ pub struct PrometheusExporter {
     router_propage_selected_peers_time_spent: IntCounter,
     router_update_skipped_route_selection: IntCounter,
     router_update_denied_by_filter: IntCounter,
+    router_update_not_interested: IntCounter,
     peer_manager_peer_added: IntCounterVec,
     peer_manager_known_peers: IntGauge,
     peer_manager_connection_attemps: IntCounterVec,
@@ -137,6 +138,11 @@ impl PrometheusExporter {
                 "Updates which were received and immediately denied by a configured filter",
             )
             .expect("Can register an int counter in default registry"),
+            router_update_not_interested: register_int_counter!(
+                "mycelium_router_update_not_interested",
+                "Updates which were allowed by the configured filters, but not of interest as they were either not feasible, or retractions, for an unknown subnet",
+            )
+            .expect("Can register an int counter in default registry"),
             peer_manager_peer_added: register_int_counter_vec!(
                 opts!(
                     "mycelium_peer_manager_peers_added",
@@ -385,6 +391,11 @@ impl Metrics for PrometheusExporter {
         self.router_update_denied_by_filter.inc()
     }
 
+    #[inline]
+    fn router_update_not_interested(&self) {
+        self.router_update_not_interested.inc()
+    }
+
     #[inline]
     fn peer_manager_peer_added(&self, pt: mycelium::peer_manager::PeerType) {
         let label = match pt {

mycelium/src/metrics.rs

@@ -163,6 +163,11 @@ pub trait Metrics {
     #[inline]
     fn router_update_denied_by_filter(&self) {}
 
+    /// An update was accepted by the router filters, but was otherwise unfeasible or a retraction,
+    /// for an unknown subnet.
+    #[inline]
+    fn router_update_not_interested(&self) {}
+
     /// A new [`Peer`](crate::peer::Peer) was added to the
     /// [`PeerManager`](crate::peer_manager::PeerManager) while it is running.
     #[inline]

mycelium/src/router.rs

@@ -989,6 +989,7 @@ where
             } else {
                 if !update_feasible || metric.is_infinite() {
                     debug!(%subnet, "Ignore unfeasible update | retraction for unknown subnet");
+                    self.metrics.router_update_not_interested();
                     return;
                 }
                 let ss = self.node_keypair.0.shared_secret(&router_id.to_pubkey());