[router] add different policies for p node and d node (#8395)

sgl-router/src/routers/factory.rs

@@ -17,7 +17,16 @@ impl RouterFactory {
             RoutingMode::PrefillDecode {
                 prefill_urls,
                 decode_urls,
-            } => Self::create_pd_router(prefill_urls, decode_urls, &config.policy, config),
+                prefill_policy,
+                decode_policy,
+            } => Self::create_pd_router(
+                prefill_urls,
+                decode_urls,
+                prefill_policy.as_ref(),
+                decode_policy.as_ref(),
+                &config.policy,
+                config,
+            ),
         }
     }
 
@@ -45,18 +54,23 @@ impl RouterFactory {
     fn create_pd_router(
         prefill_urls: &[(String, Option<u16>)],
         decode_urls: &[String],
-        policy_config: &PolicyConfig,
+        prefill_policy_config: Option<&PolicyConfig>,
+        decode_policy_config: Option<&PolicyConfig>,
+        main_policy_config: &PolicyConfig,
         router_config: &RouterConfig,
     ) -> Result<Box<dyn RouterTrait>, String> {
-        // Create policy directly from PolicyConfig
-        // All policies now support PD mode through the select_worker_pair method
-        let policy = PolicyFactory::create_from_config(policy_config);
+        // Create policies - use specific policies if provided, otherwise fall back to main policy
+        let prefill_policy =
+            PolicyFactory::create_from_config(prefill_policy_config.unwrap_or(main_policy_config));
+        let decode_policy =
+            PolicyFactory::create_from_config(decode_policy_config.unwrap_or(main_policy_config));
 
-        // Create PD router with injected policy
+        // Create PD router with separate policies
         let router = PDRouter::new(
             prefill_urls.to_vec(),
             decode_urls.to_vec(),
-            policy,
+            prefill_policy,
+            decode_policy,
             router_config.worker_startup_timeout_secs,
             router_config.worker_startup_check_interval_secs,
         )?;