[router] refactor router and worker management 4/n (#10756)

Co-authored-by: Chang Su <chang.s.su@oracle.com>

sgl-router/src/routers/http/pd_router.rs

@@ -41,6 +41,7 @@ pub struct PDRouter {
     pub prefill_client: Client,
     pub retry_config: RetryConfig,
     pub api_key: Option<String>,
+    pub enable_igw: bool,
     prefill_drain_tx: mpsc::Sender<reqwest::Response>,
 }
 
@@ -317,6 +318,7 @@ impl PDRouter {
             prefill_drain_tx,
             retry_config: ctx.router_config.effective_retry_config(),
             api_key: ctx.router_config.api_key.clone(),
+            enable_igw: ctx.router_config.enable_igw,
         })
     }
 
@@ -849,7 +851,14 @@ impl PDRouter {
         request_text: Option<&str>,
         model_id: Option<&str>,
     ) -> Result<(Arc<dyn Worker>, Arc<dyn Worker>), String> {
-        let prefill_workers = if let Some(model) = model_id {
+        let effective_model_id = if !self.enable_igw { None } else { model_id };
+
+        debug!(
+            "Selecting PD pair: enable_igw={}, model_id={:?}, effective_model_id={:?}",
+            self.enable_igw, model_id, effective_model_id
+        );
+
+        let prefill_workers = if let Some(model) = effective_model_id {
             self.worker_registry
                 .get_by_model_fast(model)
                 .into_iter()
@@ -859,7 +868,7 @@ impl PDRouter {
             self.worker_registry.get_prefill_workers()
         };
 
-        let decode_workers = if let Some(model) = model_id {
+        let decode_workers = if let Some(model) = effective_model_id {
             self.worker_registry
                 .get_by_model_fast(model)
                 .into_iter()
@@ -1797,6 +1806,7 @@ mod tests {
             prefill_drain_tx: mpsc::channel(100).0,
             retry_config: RetryConfig::default(),
             api_key: Some("test_api_key".to_string()),
+            enable_igw: false,
         }
     }
 

sgl-router/src/routers/http/router.rs

@@ -35,6 +35,7 @@ pub struct Router {
     policy_registry: Arc<PolicyRegistry>,
     client: Client,
     dp_aware: bool,
+    enable_igw: bool,
     retry_config: RetryConfig,
     _worker_loads: Arc<tokio::sync::watch::Receiver<HashMap<String, isize>>>,
     _load_monitor_handle: Option<Arc<tokio::task::JoinHandle<()>>>,
@@ -93,6 +94,7 @@ impl Router {
             policy_registry: ctx.policy_registry.clone(),
             client: ctx.client.clone(),
             dp_aware: ctx.router_config.dp_aware,
+            enable_igw: ctx.router_config.enable_igw,
             retry_config: ctx.router_config.effective_retry_config(),
             _worker_loads: worker_loads,
             _load_monitor_handle: load_monitor_handle,
@@ -162,9 +164,11 @@ impl Router {
         model_id: Option<&str>,
         text: Option<&str>,
     ) -> Option<Arc<dyn Worker>> {
+        let effective_model_id = if !self.enable_igw { None } else { model_id };
+
         // Get workers for the specified model O(1), filtered by connection mode
         let workers = self.worker_registry.get_workers_filtered(
-            model_id,
+            effective_model_id,
             Some(WorkerType::Regular),
             Some(ConnectionMode::Http),
             false, // get all workers, we'll filter by is_available() next
@@ -1106,6 +1110,7 @@ mod tests {
             retry_config: RetryConfig::default(),
             _worker_loads: Arc::new(rx),
             _load_monitor_handle: None,
+            enable_igw: false,
         }
     }