Tweak peer set metrics.

- Add a total peers metric to prevent races between measurements of
  ready/unready peers (which can cause the sum to be wrong).
- Add an outbound request counter.

zebra-network/src/peer/handshake.rs

@@ -199,6 +199,7 @@ where
 
             let peer_tx = peer_tx.with(move |msg: Message| {
                 // Add a metric for outbound messages.
+                // XXX add a dimension tagging message metrics by type
                 metrics::counter!("peer.outbound_messages", 1, "addr" => addr.to_string());
                 // We need to use future::ready rather than an async block here,
                 // because we need the sink to be Unpin, and the With<Fut, ...>
@@ -213,6 +214,7 @@ where
                     let mut timestamp_collector = timestamp_collector.clone();
                     async move {
                         if msg.is_ok() {
+                            // XXX add a dimension tagging message metrics by type
                             metrics::counter!(
                                 "inbound_messages",
                                 1,

zebra-network/src/peer_set/set.rs

@@ -209,7 +209,7 @@ where
 impl<D> Service<Request> for PeerSet<D>
 where
     D: Discover + Unpin,
-    D::Key: Clone + Debug,
+    D::Key: Clone + Debug + ToString,
     D::Service: Service<Request, Response = Response> + Load,
     D::Error: Into<BoxedStdError>,
     <D::Service as Service<Request>>::Error: Into<BoxedStdError> + 'static,
@@ -227,17 +227,13 @@ where
 
         // Poll unready services to drive them to readiness.
         self.poll_unready(cx);
-        trace!(
-            num_ready = self.ready_services.len(),
-            num_unready = self.unready_services.len(),
-        );
+        let num_ready = self.ready_services.len();
+        let num_unready = self.unready_services.len();
+        metrics::gauge!("pool.num_ready", num_ready.try_into().unwrap(),);
+        metrics::gauge!("pool.num_unready", num_unready.try_into().unwrap(),);
         metrics::gauge!(
-            "pool.num_ready",
-            self.ready_services.len().try_into().unwrap()
-        );
-        metrics::gauge!(
-            "pool.num_unready",
-            self.unready_services.len().try_into().unwrap()
+            "pool.num_peers",
+            (num_ready + num_unready).try_into().unwrap(),
         );
 
         loop {
@@ -291,6 +287,13 @@ where
             .swap_remove_index(index)
             .expect("preselected index must be valid");
 
+        // XXX add a dimension tagging request metrics by type
+        metrics::counter!(
+            "outbound_requests",
+            1,
+            "key" => key.to_string(),
+        );
+
         let fut = svc.call(req);
         self.push_unready(key, svc);