diff --git a/ctl/src/balancer/mod.rs b/ctl/src/balancer/mod.rs
index 66d06ff..8d9d68c 100644
--- a/ctl/src/balancer/mod.rs
+++ b/ctl/src/balancer/mod.rs
@@ -28,21 +28,34 @@ use proto::{
 };
 use utils::http::{self, OptionExt as _, ResultExt as _};
 
+#[derive(Default)]
 pub struct InstanceBag {
     pub instances: Vec<(InstanceId, IpAddr)>,
     pub count: AtomicUsize,
 }
 
 #[derive(Clone)]
-pub struct Balancer {
+pub struct BalancerState {
     pub addrs: Arc<Mutex<HashMap<ServiceId, InstanceBag>>>,
+    pub client: Client<HttpConnector, Body>,
 }
 
-impl Balancer {
-    pub fn new() -> Self {
-        Balancer {
-            addrs: Arc::new(Mutex::new(HashMap::default())),
-        }
+impl BalancerState {
+    #[must_use]
+    pub fn new() -> (Self, BalancerHandle) {
+        let map = Arc::new(Mutex::new(HashMap::default()));
+        (
+            BalancerState {
+                addrs: map.clone(),
+                client: {
+                    let mut connector = HttpConnector::new();
+                    connector.set_keepalive(Some(Duration::from_secs(60)));
+                    connector.set_nodelay(true);
+                    Client::builder(TokioExecutor::new()).build::<_, Body>(connector)
+                },
+            },
+            BalancerHandle { addrs: map },
+        )
     }
 
     pub fn next(&self, service: &ServiceId) -> (InstanceId, IpAddr) {
@@ -53,35 +66,37 @@ impl Balancer {
     }
 }
 
-#[derive(Clone)]
-pub struct BalancerState {
-    pub balancer: Balancer,
-    pub client: Client<HttpConnector, Body>,
+pub struct BalancerHandle {
+    pub addrs: Arc<Mutex<HashMap<ServiceId, InstanceBag>>>,
 }
 
-impl BalancerState {
-    #[must_use]
-    pub fn new() -> Self {
-        BalancerState {
-            balancer: Balancer::new(),
-            client: {
-                let mut connector = HttpConnector::new();
-                connector.set_keepalive(Some(Duration::from_secs(60)));
-                connector.set_nodelay(true);
-                Client::builder(TokioExecutor::new()).build::<_, Body>(connector)
-            },
-        }
+impl BalancerHandle {
+    #[allow(dead_code)]
+    pub fn add_instance(&mut self, id: ServiceId, at: (InstanceId, IpAddr)) {
+        let mut map = self.addrs.lock().unwrap();
+        let bag = map.entry(id).or_default();
+        bag.instances.push(at);
+    }
+
+    #[allow(dead_code)]
+    pub fn drop_instance(&mut self, id: &ServiceId, at: (InstanceId, IpAddr)) {
+        let mut map = self.addrs.lock().unwrap();
+        let Some(bag) = map.get_mut(id) else {
+            return;
+        };
+        bag.instances
+            .retain(|(inst, addr)| inst == &at.0 && addr == &at.1);
     }
 }
 
 pub async fn proxy(
     ConnectInfo(addr): ConnectInfo<SocketAddr>,
-    State(state): State<BalancerState>,
+    State(balancer): State<BalancerState>,
     mut req: Request,
 ) -> http::Result<impl IntoResponse> {
     let service = extract_service_id(&mut req)?;
 
-    let (instance, server_addr) = state.balancer.next(&service);
+    let (instance, server_addr) = balancer.next(&service);
 
     *req.uri_mut() = {
         let uri = req.uri();
@@ -100,7 +115,7 @@ pub async fn proxy(
         HeaderValue::from_str(&addr.ip().to_string()).unwrap(),
     );
 
-    state
+    balancer
         .client
         .request(req)
         .await
diff --git a/ctl/src/main.rs b/ctl/src/main.rs
index 915bf95..6bd0962 100644
--- a/ctl/src/main.rs
+++ b/ctl/src/main.rs
@@ -45,10 +45,10 @@ async fn main() -> eyre::Result<()> {
         worker_mgr.run().await;
     });
 
-    let balancer_state = BalancerState::new();
+    let (balancer, _balancer_handle) = BalancerState::new();
     bag.spawn(async move {
         let app = balancer::proxy
-            .with_state(balancer_state)
+            .with_state(balancer)
             .into_make_service_with_connect_info::<SocketAddr>();
         info!("balancer http listening at {ANY_IP}:{CTL_BALANCER_PORT}");
         axum::serve(balancer_listener, app).await.unwrap();