fix: worker to graceful shutdown after finishing in-flight requests (#4838)

Signed-off-by: hongkuanz <hongkuanz@nvidia.com>
Co-authored-by: Biswa Panda <biswa.panda@gmail.com>

lib/llm/src/mocker/engine.rs

@@ -60,7 +60,11 @@ impl MockVllmEngine {
     }
 
     pub async fn start(&self, component: Component) -> Result<()> {
-        let cancel_token = component.drt().runtime().child_token();
+        // Use primary_token() instead of child_token() so the mocker continues running
+        // during graceful shutdown (Phase 1/2) and only stops in Phase 3.
+        // child_token() is a child of endpoint_shutdown_token which is cancelled in Phase 1.
+        // primary_token() is only cancelled in Phase 3, after waiting for inflight requests.
+        let cancel_token = component.drt().primary_token();
 
         // Simulate engine startup time if configured
         if let Some(startup_time_secs) = self.engine_args.startup_time {
@@ -143,6 +147,11 @@ impl MockVllmEngine {
                             }
                         }
                         _ = cancel_token_cloned.cancelled() => {
+                            tracing::info!("Scheduler output task cancelled, clearing active requests");
+                            // Clear all active requests to unblock waiting request handlers
+                            // This will cause their request_rx.recv() to return None
+                            let mut active = active_requests_clone.lock().await;
+                            active.clear();
                             break;
                         }
                     }

lib/runtime/src/pipeline/network/ingress/http_endpoint.rs

@@ -105,7 +105,27 @@ impl SharedHttpServer {
                 .system_health
                 .lock()
                 .set_endpoint_health_status(endpoint_name, HealthStatus::NotReady);
-            tracing::debug!("Unregistered endpoint handler for subject: {}", subject);
+            tracing::debug!(
+                endpoint_name = %endpoint_name,
+                subject = %subject,
+                "Unregistered HTTP endpoint handler"
+            );
+
+            let inflight_count = handler.inflight.load(Ordering::SeqCst);
+            if inflight_count > 0 {
+                tracing::info!(
+                    endpoint_name = %endpoint_name,
+                    inflight_count = inflight_count,
+                    "Waiting for inflight HTTP requests to complete"
+                );
+                while handler.inflight.load(Ordering::SeqCst) > 0 {
+                    handler.notify.notified().await;
+                }
+                tracing::info!(
+                    endpoint_name = %endpoint_name,
+                    "All inflight HTTP requests completed"
+                );
+            }
         }
     }
 

lib/runtime/src/pipeline/network/ingress/nats_server.rs

@@ -32,6 +32,7 @@ pub struct NatsMultiplexedServer {
 
 struct EndpointTask {
     cancel_token: CancellationToken,
+    join_handle: tokio::task::JoinHandle<()>,
     _endpoint_name: String,
 }
 
@@ -145,7 +146,7 @@ impl super::unified_server::RequestPlaneServer for NatsMultiplexedServer {
         // Spawn task to handle this endpoint using PushEndpoint
         // Note: PushEndpoint::start() is a blocking loop that runs until cancelled
         let endpoint_name_clone = endpoint_name.clone();
-        tokio::spawn(async move {
+        let join_handle = tokio::spawn(async move {
             if let Err(e) = push_endpoint
                 .start(
                     service_endpoint,
@@ -180,6 +181,7 @@ impl super::unified_server::RequestPlaneServer for NatsMultiplexedServer {
             endpoint_name.clone(),
             EndpointTask {
                 cancel_token: endpoint_cancel,
+                join_handle,
                 _endpoint_name: endpoint_name,
             },
         );
@@ -193,7 +195,25 @@ impl super::unified_server::RequestPlaneServer for NatsMultiplexedServer {
                 endpoint_name = %endpoint_name,
                 "Unregistering NATS endpoint"
             );
+            // Cancel the token to trigger graceful shutdown
             task.cancel_token.cancel();
+
+            // Wait for the endpoint task to complete (which includes waiting for inflight requests)
+            tracing::debug!(
+                endpoint_name = %endpoint_name,
+                "Waiting for NATS endpoint task to complete"
+            );
+            if let Err(e) = task.join_handle.await {
+                tracing::warn!(
+                    endpoint_name = %endpoint_name,
+                    error = %e,
+                    "NATS endpoint task panicked during shutdown"
+                );
+            }
+            tracing::info!(
+                endpoint_name = %endpoint_name,
+                "NATS endpoint unregistration complete"
+            );
         }
         Ok(())
     }

lib/runtime/src/pipeline/network/ingress/push_endpoint.rs

@@ -135,16 +135,26 @@ impl PushEndpoint {
 
         // await for all inflight requests to complete if graceful shutdown
         if self.graceful_shutdown {
-            tracing::info!(
-                "Waiting for {} inflight requests to complete",
-                inflight.load(Ordering::SeqCst)
-            );
-            while inflight.load(Ordering::SeqCst) > 0 {
-                notify.notified().await;
+            let inflight_count = inflight.load(Ordering::SeqCst);
+            if inflight_count > 0 {
+                tracing::info!(
+                    endpoint_name = endpoint_name_local.as_str(),
+                    inflight_count = inflight_count,
+                    "Waiting for inflight NATS requests to complete"
+                );
+                while inflight.load(Ordering::SeqCst) > 0 {
+                    notify.notified().await;
+                }
+                tracing::info!(
+                    endpoint_name = endpoint_name_local.as_str(),
+                    "All inflight NATS requests completed"
+                );
             }
-            tracing::info!("All inflight requests completed");
         } else {
-            tracing::info!("Skipping graceful shutdown, not waiting for inflight requests");
+            tracing::info!(
+                endpoint_name = endpoint_name_local.as_str(),
+                "Skipping graceful shutdown, not waiting for inflight requests"
+            );
         }
 
         Ok(())

lib/runtime/src/pipeline/network/ingress/shared_tcp_endpoint.rs

@@ -100,11 +100,33 @@ impl SharedTcpServer {
     }
 
     pub async fn unregister_endpoint(&self, endpoint_path: &str, endpoint_name: &str) {
-        self.handlers.remove(endpoint_path);
-        tracing::info!(
-            "Unregistered endpoint '{}' from shared TCP server",
-            endpoint_name
-        );
+        if let Some((_, handler)) = self.handlers.remove(endpoint_path) {
+            handler
+                .system_health
+                .lock()
+                .set_endpoint_health_status(endpoint_name, crate::HealthStatus::NotReady);
+            tracing::info!(
+                endpoint_name = %endpoint_name,
+                endpoint_path = %endpoint_path,
+                "Unregistered TCP endpoint handler"
+            );
+
+            let inflight_count = handler.inflight.load(Ordering::SeqCst);
+            if inflight_count > 0 {
+                tracing::info!(
+                    endpoint_name = %endpoint_name,
+                    inflight_count = inflight_count,
+                    "Waiting for inflight TCP requests to complete"
+                );
+                while handler.inflight.load(Ordering::SeqCst) > 0 {
+                    handler.notify.notified().await;
+                }
+                tracing::info!(
+                    endpoint_name = %endpoint_name,
+                    "All inflight TCP requests completed"
+                );
+            }
+        }
     }
 
     pub async fn start(self: Arc<Self>) -> Result<()> {