diff --git a/backend/src/controller/judger/route/mod.rs b/backend/src/controller/judger/route/mod.rs
index c6bc7af9..0292a79d 100644
--- a/backend/src/controller/judger/route/mod.rs
+++ b/backend/src/controller/judger/route/mod.rs
@@ -4,7 +4,7 @@ pub mod swarm;
 
 use super::Error;
 use std::{
-    collections::{BTreeMap, VecDeque},
+    collections::VecDeque,
     ops::DerefMut,
     sync::{
         atomic::{AtomicIsize, Ordering},
@@ -15,7 +15,7 @@ use std::{
 
 use lockfree::{map::Map, queue::Queue, set::Set};
 use spin::Mutex;
-use tonic::{service::Interceptor,*};
+use tonic::{service::Interceptor, *};
 use uuid::Uuid;
 
 use crate::{
@@ -25,6 +25,7 @@ use crate::{
 
 // introduce routing layer error
 
+const HEALTHY_THRESHOLD: isize = 100;
 type JudgerIntercept =
     JudgerClient<service::interceptor::InterceptedService<transport::Channel, AuthInterceptor>>;
 
@@ -74,7 +75,8 @@ pub struct ConnGuard {
 
 impl ConnGuard {
     pub fn report_success(&mut self) {
-        self.upstream.healthy.fetch_add(2, Ordering::SeqCst);
+        self.upstream.healthy.fetch_add(3, Ordering::Acquire);
+        self.upstream.healthy.fetch_min(HEALTHY_THRESHOLD, Ordering::Acquire);
     }
 }
 
@@ -93,7 +95,7 @@ impl std::ops::Deref for ConnGuard {
 
 impl Drop for ConnGuard {
     fn drop(&mut self) {
-        self.upstream.healthy.fetch_add(-1, Ordering::Acquire);
+        self.upstream.healthy.fetch_add(-2, Ordering::Acquire);
         self.upstream.clients.push(self.conn.take().unwrap());
     }
 }
@@ -171,14 +173,19 @@ impl Router {
 
         let mut queue = queue.lock();
 
-        match queue.pop_front() {
-            Some(upstream) => {
-                queue.push_back(upstream.clone());
-                upstream.get().await
-            }
-            None => {
-                self.routing_table.remove(uuid);
-                Err(Error::BadArgument("lang"))
+        loop {
+            match queue.pop_front() {
+                Some(upstream) => {
+                    if upstream.is_healthy() {
+                        queue.push_back(upstream.clone());
+                        drop(queue);
+                        return upstream.get().await;
+                    }
+                }
+                None => {
+                    self.routing_table.remove(uuid);
+                    return Err(Error::BadArgument("lang"));
+                }
             }
         }
     }
@@ -186,9 +193,7 @@ impl Router {
 
 // abstraction for pipelining
 pub struct Upstream {
-    // healthy score
     healthy: AtomicIsize,
-    // if transport layer fail, spawn a new one
     clients: Queue<JudgerIntercept>,
     connection: ConnectionDetail,
 }
@@ -211,13 +216,16 @@ impl Upstream {
         }
         Ok((
             Arc::new(Self {
-                healthy: AtomicIsize::new(20),
+                healthy: AtomicIsize::new(HEALTHY_THRESHOLD),
                 clients: Queue::new(),
                 connection: detail,
             }),
             result,
         ))
     }
+    fn is_healthy(&self) -> bool {
+        self.healthy.load(Ordering::Acquire) > 0
+    }
     async fn get(self: Arc<Self>) -> Result<ConnGuard, Error> {
         let conn = match self.clients.pop() {
             Some(x) => x,
diff --git a/backend/src/controller/judger/route/swarm.rs b/backend/src/controller/judger/route/swarm.rs
index 7be9feea..3e0205cb 100644
--- a/backend/src/controller/judger/route/swarm.rs
+++ b/backend/src/controller/judger/route/swarm.rs
@@ -1,4 +1,4 @@
-use std::{collections::HashSet, net::IpAddr, sync::Arc, time::Duration};
+use std::{collections::HashSet, net::IpAddr, time::Duration};
 
 use super::{ConnectionDetail, Error};
 use crate::init::config;