Tiny extract select_worker_min_load (#14648)

sgl-model-gateway/src/policies/cache_aware.rs

@@ -210,6 +210,63 @@ impl CacheAwarePolicy {
             );
         }
     }
+
+    fn select_worker_min_load(
+        &self,
+        workers: &[Arc<dyn Worker>],
+        request_text: &Option<&str>,
+        healthy_indices: &[usize],
+        model_id: &str,
+        // TODO may skip passing this arg (and compute inside function) if this is not bottleneck
+        max_load: usize,
+        min_load: usize,
+    ) -> Option<usize> {
+        // Log load balancing trigger
+        // TODO may use `&str`
+        let worker_loads: Vec<(String, usize)> = workers
+            .iter()
+            .map(|w| (w.url().to_string(), w.load()))
+            .collect();
+
+        // TODO may change text
+        debug!(
+            "Load balancing triggered | max: {} | min: {} | workers: {:?}",
+            max_load, min_load, worker_loads
+        );
+
+        RouterMetrics::record_load_balancing_event();
+        RouterMetrics::set_load_range(max_load, min_load);
+
+        // Use shortest queue when imbalanced
+        let min_load_idx = healthy_indices
+            .iter()
+            .min_by_key(|&&idx| workers[idx].load())
+            .copied()?;
+
+        // Even in imbalanced mode, update the tree to maintain cache state
+        if let Some(text) = request_text {
+            // Get the tree reference without locking the entire HashMap
+            // DashMap only locks the specific shard containing this key
+            let tree = self.trees.get(model_id).map(|entry| entry.value().clone());
+
+            if let Some(tree) = tree {
+                // Now we can work with the tree without holding the HashMap lock
+                tree.insert(text, workers[min_load_idx].url());
+            } else {
+                debug!(
+                    "Warning: No tree found for model '{}', skipping cache update",
+                    model_id
+                );
+            }
+        }
+
+        // Increment processed counter
+        workers[min_load_idx].increment_processed();
+        RouterMetrics::record_processed_request(workers[min_load_idx].url());
+        RouterMetrics::record_policy_decision(self.name(), workers[min_load_idx].url());
+
+        Some(min_load_idx)
+    }
 }
 
 impl LoadBalancingPolicy for CacheAwarePolicy {
@@ -245,49 +302,14 @@ impl LoadBalancingPolicy for CacheAwarePolicy {
             && (max_load as f32) > (min_load as f32 * self.config.balance_rel_threshold);
 
         if is_imbalanced {
-            // Log load balancing trigger
-            let worker_loads: Vec<(String, usize)> = workers
-                .iter()
-                .map(|w| (w.url().to_string(), w.load()))
-                .collect();
-
-            debug!(
-                "Load balancing triggered | max: {} | min: {} | workers: {:?}",
-                max_load, min_load, worker_loads
+            return self.select_worker_min_load(
+                workers,
+                &request_text,
+                &healthy_indices,
+                model_id,
+                max_load,
+                min_load,
             );
-
-            RouterMetrics::record_load_balancing_event();
-            RouterMetrics::set_load_range(max_load, min_load);
-
-            // Use shortest queue when imbalanced
-            let min_load_idx = healthy_indices
-                .iter()
-                .min_by_key(|&&idx| workers[idx].load())
-                .copied()?;
-
-            // Even in imbalanced mode, update the tree to maintain cache state
-            if let Some(text) = request_text {
-                // Get the tree reference without locking the entire HashMap
-                // DashMap only locks the specific shard containing this key
-                let tree = self.trees.get(model_id).map(|entry| entry.value().clone());
-
-                if let Some(tree) = tree {
-                    // Now we can work with the tree without holding the HashMap lock
-                    tree.insert(text, workers[min_load_idx].url());
-                } else {
-                    debug!(
-                        "Warning: No tree found for model '{}', skipping cache update",
-                        model_id
-                    );
-                }
-            }
-
-            // Increment processed counter
-            workers[min_load_idx].increment_processed();
-            RouterMetrics::record_processed_request(workers[min_load_idx].url());
-            RouterMetrics::record_policy_decision(self.name(), workers[min_load_idx].url());
-
-            return Some(min_load_idx);
         }
 
         // Use cache-aware routing when balanced