feat: add metrics for inflight get pooled tx requests (#4547)

crates/net/network/src/metrics.rs

@@ -67,6 +67,8 @@ pub struct TransactionsManagerMetrics {
     pub(crate) messages_with_already_seen_transactions: Counter,
     /// Number of transactions about to be imported into the pool.
     pub(crate) pending_pool_imports: Gauge,
+    /// Currently active outgoing GetPooledTransactions requests.
+    pub(crate) inflight_transaction_requests: Gauge,
     /// How often we failed to send a request to the peer because the channel was full.
     pub(crate) egress_peer_channel_full: Counter,
 }

crates/net/network/src/transactions.rs

@@ -174,10 +174,16 @@ where
         TransactionsHandle { manager_tx: self.command_tx.clone() }
     }
 
+    #[inline]
     fn update_import_metrics(&self) {
         self.metrics.pending_pool_imports.set(self.pool_imports.len() as f64);
     }
 
+    #[inline]
+    fn update_request_metrics(&self) {
+        self.metrics.inflight_transaction_requests.set(self.inflight_requests.len() as f64);
+    }
+
     /// Request handler for an incoming request for transactions
     fn on_get_pooled_transactions(
         &mut self,
@@ -591,6 +597,8 @@ where
             this.on_network_tx_event(event);
         }
 
+        this.update_request_metrics();
+
         // Advance all requests.
         while let Poll::Ready(Some(GetPooledTxResponse { peer_id, result })) =
             this.inflight_requests.poll_next_unpin(cx)
@@ -609,6 +617,7 @@ where
             }
         }
 
+        this.update_request_metrics();
         this.update_import_metrics();
 
         // Advance all imports