feat: add metrics for dropped outgoing messages (#10225)

Co-authored-by: Matthias Seitz <[email protected]>

crates/net/network/src/metrics.rs

@@ -83,6 +83,8 @@ pub struct NetworkMetrics {
 pub struct SessionManagerMetrics {
     /// Number of successful outgoing dial attempts.
     pub(crate) total_dial_successes: Counter,
+    /// Number of dropped outgoing peer messages.
+    pub(crate) total_outgoing_peer_messages_dropped: Counter,
 }
 
 /// Metrics for the [`TransactionsManager`](crate::transactions::TransactionsManager).

crates/net/network/src/session/mod.rs

@@ -41,7 +41,7 @@ use secp256k1::SecretKey;
 use tokio::{
     io::{AsyncRead, AsyncWrite},
     net::TcpStream,
-    sync::{mpsc, oneshot},
+    sync::{mpsc, mpsc::error::TrySendError, oneshot},
 };
 use tokio_stream::wrappers::ReceiverStream;
 use tokio_util::sync::PollSender;
@@ -346,7 +346,18 @@ impl SessionManager {
     /// Sends a message to the peer's session
     pub fn send_message(&mut self, peer_id: &PeerId, msg: PeerMessage) {
         if let Some(session) = self.active_sessions.get_mut(peer_id) {
-            let _ = session.commands_to_session.try_send(SessionCommand::Message(msg));
+            let _ = session.commands_to_session.try_send(SessionCommand::Message(msg)).inspect_err(
+                |e| {
+                    if let TrySendError::Full(_) = e {
+                        debug!(
+                            target: "net::session",
+                            ?peer_id,
+                            "session command buffer full, dropping message"
+                        );
+                        self.metrics.total_outgoing_peer_messages_dropped.increment(1);
+                    }
+                },
+            );
         }
     }