feat(gossipsub): allow whitelisting topics for metrics

protocols/gossipsub/CHANGELOG.md

@@ -1,4 +1,7 @@
 ## 0.48.1
+- Allow whitelisting topics for metrics to ensure metrics are recorded correctly for these topics.
+  See [PR 5895](https://github.com/libp2p/rust-libp2p/pull/5895)
+
 - Improve `max_messages_per_rpc` consistency by ensuring RPC control messages also adhere to the existing limits.
   See [PR 5826](https://github.com/libp2p/rust-libp2p/pull/5826)
 

protocols/gossipsub/src/behaviour.rs

@@ -3053,6 +3053,13 @@ where
             }
         }
     }
+
+    /// Register topics to ensure metrics are recorded correctly for these topics.
+    pub fn register_topics_for_metrics(&mut self, topics: Vec<TopicHash>) {
+        if let Some(metrics) = &mut self.metrics {
+            metrics.register_allowed_topics(topics);
+        }
+    }
 }
 
 fn get_ip_addr(addr: &Multiaddr) -> Option<IpAddr> {

protocols/gossipsub/src/metrics.rs

@@ -648,6 +648,13 @@ impl Metrics {
             metric.set(metric.get() - 1);
         }
     }
+
+    /// Registers a set of topics that we want to store calculate metrics for.
+    pub(crate) fn register_allowed_topics(&mut self, topics: Vec<TopicHash>) {
+        for topic_hash in topics {
+            self.topic_info.insert(topic_hash, true);
+        }
+    }
 }
 
 /// Reasons why a peer was included in the mesh.