[router] consolidate worker load monitoring (#10894)

sgl-router/src/policies/registry.rs

@@ -257,6 +257,47 @@ impl PolicyRegistry {
             .unwrap_or_else(|| self.get_default_policy())
     }
 
+    /// Get all PowerOfTwo policies that need load updates
+    pub fn get_all_power_of_two_policies(&self) -> Vec<Arc<dyn LoadBalancingPolicy>> {
+        let mut power_of_two_policies = Vec::new();
+
+        if self.default_policy.name() == "power_of_two" {
+            power_of_two_policies.push(Arc::clone(&self.default_policy));
+        }
+
+        if let Some(ref policy) = *self.prefill_policy.read().unwrap() {
+            if policy.name() == "power_of_two" && !Arc::ptr_eq(policy, &self.default_policy) {
+                power_of_two_policies.push(Arc::clone(policy));
+            }
+        }
+
+        if let Some(ref policy) = *self.decode_policy.read().unwrap() {
+            if policy.name() == "power_of_two"
+                && !Arc::ptr_eq(policy, &self.default_policy)
+                && !self
+                    .prefill_policy
+                    .read()
+                    .unwrap()
+                    .as_ref()
+                    .is_some_and(|p| Arc::ptr_eq(p, policy))
+            {
+                power_of_two_policies.push(Arc::clone(policy));
+            }
+        }
+
+        let model_policies = self.model_policies.read().unwrap();
+        for policy in model_policies.values() {
+            if policy.name() == "power_of_two" {
+                let already_added = power_of_two_policies.iter().any(|p| Arc::ptr_eq(p, policy));
+                if !already_added {
+                    power_of_two_policies.push(Arc::clone(policy));
+                }
+            }
+        }
+
+        power_of_two_policies
+    }
+
     /// Initialize cache-aware policy with workers if applicable
     /// This should be called after workers are registered for a model
     pub fn init_cache_aware_policy(&self, model_id: &str, workers: &[Arc<dyn Worker>]) {