fix(518): Label connected clients metric by database (#523)

Fixes #518.

Author: joshua-spacetime

crates/core/src/client/client_connection.rs

@@ -113,6 +113,8 @@ impl ClientConnection {
         // Buffer up to 64 client messages
         let (sendtx, sendrx) = mpsc::channel::<DataMessage>(64);
 
+        let db = module.info().address;
+
         let sender = ClientConnectionSender { id, protocol, sendtx };
         let this = Self {
             sender,
@@ -121,7 +123,7 @@ impl ClientConnection {
         };
 
         let actor_fut = actor(this.clone(), sendrx);
-        let gauge_guard = WORKER_METRICS.connected_clients.inc_scope();
+        let gauge_guard = WORKER_METRICS.connected_clients.with_label_values(&db).inc_scope();
         tokio::spawn(actor_fut.map(|()| drop(gauge_guard)));
 
         Ok(this)

crates/core/src/worker_metrics/mod.rs

@@ -1,13 +1,14 @@
 use crate::util::typed_prometheus::metrics_group;
 use once_cell::sync::Lazy;
-use prometheus::{Gauge, GaugeVec, HistogramVec, IntCounterVec, IntGauge, IntGaugeVec};
+use prometheus::{Gauge, GaugeVec, HistogramVec, IntCounterVec, IntGaugeVec};
 use spacetimedb_lib::{Address, Hash, Identity};
 
 metrics_group!(
     pub struct WorkerMetrics {
         #[name = spacetime_worker_connected_clients]
         #[help = "Number of clients connected to the worker."]
-        pub connected_clients: IntGauge,
+        #[labels(database_address: Address)]
+        pub connected_clients: IntGaugeVec,
 
         #[name = spacetime_websocket_requests]
         #[help = "Number of websocket request messages"]