fix: dummy health check server not accessible on non-zero rank nodes (#12297)

python/sglang/compile_deep_gemm.py

@@ -104,15 +104,21 @@ def launch_server_process_and_send_one_request(
             if response.status_code == 200:
                 # Rank-0 node send a request to sync with other node and then return.
                 if server_args.node_rank == 0:
-                    response = requests.post(
-                        f"{base_url}/generate",
-                        json={
+                    payload = {
                         "input_ids": [0, 1, 2, 3],
                         "sampling_params": {
                             "max_new_tokens": 8,
                             "temperature": 0,
                         },
-                        },
+                    }
+                    # In PD mode, include fake bootstrap fields so workers don't assert
+                    if server_args.disaggregation_mode != "null":
+                        payload["bootstrap_host"] = FAKE_BOOTSTRAP_HOST
+                        payload["bootstrap_room"] = 0
+
+                    response = requests.post(
+                        f"{base_url}/generate",
+                        json=payload,
                         timeout=600,
                     )
                     if response.status_code != 200:

python/sglang/srt/utils/common.py

@@ -2351,16 +2351,24 @@ def launch_dummy_health_check_server(host, port, enable_metrics):
     )
     server = uvicorn.Server(config=config)
 
+    # Run server in a background daemon thread with its own event loop
+    # This prevents blocking the main thread while still serving health checks
+    def run_server():
         try:
-        loop = asyncio.get_running_loop()
+            asyncio.run(server.serve())
+        except Exception as e:
+            logger.error(f"Dummy health check server failed to start: {e}")
+            raise
+        finally:
+            logger.info(f"Dummy health check server stopped at {host}:{port}")
+
+    thread = threading.Thread(
+        target=run_server, daemon=True, name="health-check-server"
+    )
+    thread.start()
     logger.info(
-            f"Dummy health check server scheduled on existing loop at {host}:{port}"
+        f"Dummy health check server started in background thread at {host}:{port}"
     )
-        loop.create_task(server.serve())
-
-    except RuntimeError:
-        logger.info(f"Starting dummy health check server at {host}:{port}")
-        server.run()
 
 
 def create_checksum(directory: str):