[diffusion] fix: shut down diffusion workers on serve exit (#30110)

python/sglang/multimodal_gen/runtime/launch_server.py

@@ -6,6 +6,7 @@ import os
 import signal
 import sys
 import threading
+import time
 
 import psutil
 import uvicorn
@@ -15,7 +16,9 @@ from sglang.multimodal_gen.runtime.disaggregation.orchestrator import (
 )
 from sglang.multimodal_gen.runtime.disaggregation.roles import RoleType
 from sglang.multimodal_gen.runtime.entrypoints.http_server import create_app
+from sglang.multimodal_gen.runtime.entrypoints.utils import ShutdownReq
 from sglang.multimodal_gen.runtime.managers.gpu_worker import run_scheduler_process
+from sglang.multimodal_gen.runtime.scheduler_client import SchedulerClient
 from sglang.multimodal_gen.runtime.server_args import (
     ServerArgs,
     prepare_server_args,
@@ -24,6 +27,12 @@ from sglang.multimodal_gen.runtime.server_args import (
 from sglang.multimodal_gen.runtime.utils.common import is_port_available
 from sglang.multimodal_gen.runtime.utils.logging_utils import configure_logger, logger
 from sglang.multimodal_gen.runtime.utils.trace_wrapper import init_diffusion_tracing
+from sglang.multimodal_gen.utils import kill_itself_when_parent_died
+
+_SCHEDULER_SHUTDOWN_TIMEOUT_MS = 5000
+_WORKER_JOIN_TIMEOUT_S = 10
+_WORKER_TERMINATE_TIMEOUT_S = 1
+_WORKER_KILL_TIMEOUT_S = 1
 
 
 def _find_available_port(
@@ -83,6 +92,82 @@ def kill_process_tree(parent_pid, include_parent: bool = True, skip_pid: int = N
             pass
 
 
+def _process_names(processes) -> str:
+    return ", ".join(getattr(p, "name", repr(p)) for p in processes)
+
+
+def _join_processes_with_deadline(processes, timeout_s: float) -> None:
+    deadline = time.monotonic() + timeout_s
+    for process in processes:
+        remaining_s = max(0.0, deadline - time.monotonic())
+        process.join(timeout=remaining_s)
+
+
+def _terminate_alive_processes(processes, timeout_s: float) -> list:
+    alive = [p for p in processes if p.is_alive()]
+    if not alive:
+        return []
+
+    logger.warning(
+        "Worker process(es) did not exit in time; terminating: %s",
+        _process_names(alive),
+    )
+    for process in alive:
+        process.terminate()
+    _join_processes_with_deadline(alive, timeout_s)
+    return [p for p in alive if p.is_alive()]
+
+
+def _kill_alive_processes(processes, timeout_s: float) -> None:
+    alive = [p for p in processes if p.is_alive()]
+    if not alive:
+        return
+
+    logger.warning(
+        "Worker process(es) did not terminate in time; killing: %s",
+        _process_names(alive),
+    )
+    for process in alive:
+        process.kill()
+    _join_processes_with_deadline(alive, timeout_s)
+
+
+def _run_http_server_process(server_args: ServerArgs) -> None:
+    kill_itself_when_parent_died()
+    launch_http_server_only(server_args)
+
+
+def _request_monolithic_scheduler_shutdown(server_args: ServerArgs) -> None:
+    if server_args.disagg_role != RoleType.MONOLITHIC:
+        return
+
+    client = SchedulerClient()
+    try:
+        client.initialize(server_args)
+        client.forward(ShutdownReq(), timeout_ms=_SCHEDULER_SHUTDOWN_TIMEOUT_MS)
+    except Exception as e:
+        logger.warning("Failed to request graceful scheduler shutdown: %s", e)
+    finally:
+        client.close()
+
+
+def shutdown_scheduler_processes(
+    server_args: ServerArgs | None,
+    processes: list,
+    *,
+    request_shutdown: bool = True,
+) -> None:
+    if not processes:
+        return
+
+    if request_shutdown and server_args is not None:
+        _request_monolithic_scheduler_shutdown(server_args)
+
+    _join_processes_with_deadline(processes, _WORKER_JOIN_TIMEOUT_S)
+    alive = _terminate_alive_processes(processes, _WORKER_TERMINATE_TIMEOUT_S)
+    _kill_alive_processes(alive, _WORKER_KILL_TIMEOUT_S)
+
+
 def launch_server(server_args: ServerArgs, launch_http_server: bool = True):
     """
     Args:
@@ -198,14 +283,17 @@ def launch_server(server_args: ServerArgs, launch_http_server: bool = True):
         if server_args.webui:
             logger.info("Launch FastAPI server in another process because of webui.")
             http_server_process = mp.Process(
-                target=launch_http_server_only,
+                target=_run_http_server_process,
                 args=(server_args,),
                 name="sglang-diffusion-webui",
                 daemon=True,
             )
             http_server_process.start()
         else:
-            launch_http_server_only(server_args)
+            try:
+                launch_http_server_only(server_args)
+            finally:
+                shutdown_scheduler_processes(server_args, processes)
 
     return processes
 
@@ -408,7 +496,13 @@ def launch_pool_disagg_server(
             "Starting FastAPI server (connected to DiffusionServer at port %d).",
             server_args.scheduler_port,
         )
-        launch_http_server_only(server_args)
+        try:
+            launch_http_server_only(server_args)
+        finally:
+            diffusion_server.stop()
+            shutdown_scheduler_processes(
+                server_args, all_processes, request_shutdown=False
+            )
 
     return all_processes
 
@@ -538,7 +632,10 @@ def launch_disagg_server(server_args: ServerArgs):
         "Starting HTTP server (connected to DiffusionServer at port %d).",
         base_port,
     )
-    launch_http_server_only(server_args)
+    try:
+        launch_http_server_only(server_args)
+    finally:
+        diffusion_server.stop()
 
 
 def launch_disagg_role(server_args: ServerArgs):
@@ -659,6 +756,8 @@ def launch_disagg_role(server_args: ServerArgs):
             p.join()
     except KeyboardInterrupt:
         logger.info("Role %s shutting down.", role_type.value)
+    finally:
+        shutdown_scheduler_processes(role_args, processes, request_shutdown=False)
 
 
 def dispatch_launch(server_args: ServerArgs):

python/sglang/multimodal_gen/runtime/managers/gpu_worker.py

@@ -78,6 +78,7 @@ from sglang.multimodal_gen.runtime.utils.trace_wrapper import (
     init_diffusion_tracing,
     trace_slice,
 )
+from sglang.multimodal_gen.utils import kill_itself_when_parent_died
 from sglang.srt.utils.network import NetworkAddress
 
 logger = init_logger(__name__)
@@ -999,6 +1000,7 @@ def run_scheduler_process(
     Rank 0 acts as the master, handling ZMQ requests and coordinating slaves.
     Ranks > 0 act as slaves, waiting for tasks from the master.
     """
+    kill_itself_when_parent_died()
     configure_logger(server_args)
     globally_suppress_loggers()
     if current_platform.is_cuda():

python/sglang/multimodal_gen/test/unit/test_launch_server_shutdown.py

@@ -0,0 +1,83 @@
+import unittest
+from types import SimpleNamespace
+from unittest.mock import Mock, patch
+
+from sglang.multimodal_gen.runtime import launch_server as ls
+from sglang.multimodal_gen.runtime.disaggregation.roles import RoleType
+from sglang.multimodal_gen.runtime.entrypoints.utils import ShutdownReq
+
+
+class _FakeProcess:
+    name = "fake-worker"
+
+    def __init__(self, *, exit_on_join: bool = False):
+        self.alive = True
+        self.exit_on_join = exit_on_join
+        self.join_timeouts = []
+        self.terminated = False
+        self.killed = False
+
+    def join(self, timeout=None):
+        self.join_timeouts.append(timeout)
+        if self.exit_on_join:
+            self.alive = False
+
+    def is_alive(self):
+        return self.alive
+
+    def terminate(self):
+        self.terminated = True
+
+    def kill(self):
+        self.killed = True
+        self.alive = False
+
+
+class TestLaunchServerShutdown(unittest.TestCase):
+    def test_monolithic_shutdown_requests_scheduler_then_forces_worker(self):
+        process = _FakeProcess()
+        server_args = SimpleNamespace(disagg_role=RoleType.MONOLITHIC)
+        client = Mock()
+
+        with patch.object(ls, "SchedulerClient", return_value=client):
+            ls.shutdown_scheduler_processes(server_args, [process])
+
+        client.initialize.assert_called_once_with(server_args)
+        request = client.forward.call_args.args[0]
+        self.assertIsInstance(request, ShutdownReq)
+        self.assertEqual(client.forward.call_args.kwargs, {"timeout_ms": 5000})
+        client.close.assert_called_once_with()
+
+        self.assertTrue(process.terminated)
+        self.assertTrue(process.killed)
+        self.assertAlmostEqual(process.join_timeouts[0], 10, delta=0.1)
+        self.assertAlmostEqual(process.join_timeouts[1], 1, delta=0.1)
+        self.assertAlmostEqual(process.join_timeouts[2], 1, delta=0.1)
+
+    def test_scheduler_shutdown_error_still_forces_worker(self):
+        process = _FakeProcess()
+        server_args = SimpleNamespace(disagg_role=RoleType.MONOLITHIC)
+        client = Mock()
+        client.forward.side_effect = TimeoutError("blocked")
+
+        with patch.object(ls, "SchedulerClient", return_value=client):
+            ls.shutdown_scheduler_processes(server_args, [process])
+
+        client.close.assert_called_once_with()
+        self.assertTrue(process.terminated)
+        self.assertTrue(process.killed)
+
+    def test_disagg_role_does_not_send_monolithic_shutdown_request(self):
+        process = _FakeProcess(exit_on_join=True)
+        server_args = SimpleNamespace(disagg_role=RoleType.ENCODER)
+
+        with patch.object(ls, "SchedulerClient") as scheduler_client:
+            ls.shutdown_scheduler_processes(server_args, [process])
+
+        scheduler_client.assert_not_called()
+        self.assertFalse(process.terminated)
+        self.assertFalse(process.killed)
+
+
+if __name__ == "__main__":
+    unittest.main()

python/sglang/multimodal_gen/utils.py

@@ -527,21 +527,18 @@ def shallow_asdict(obj) -> dict[str, Any]:
     return {f.name: getattr(obj, f.name) for f in fields(obj)}
 
 
-# TODO: validate that this is fine
 def kill_itself_when_parent_died() -> None:
-    # if sys.platform == "linux":
+    if sys.platform != "linux":
-    # sigkill this process when parent worker manager dies
+        return
-    PR_SET_PDEATHSIG = 1
-    import platform
 
-    if platform.system() == "Linux":
+    # keep GPU workers tied to the CLI process even if the parent is SIGKILLed
-        libc = ctypes.CDLL("libc.so.6")
+    PR_SET_PDEATHSIG = 1
-        libc.prctl(PR_SET_PDEATHSIG, signal.SIGKILL)
+    libc = ctypes.CDLL("libc.so.6", use_errno=True)
-    # elif platform.system() == "Darwin":
+    if libc.prctl(PR_SET_PDEATHSIG, signal.SIGKILL) != 0:
-    #     libc = ctypes.CDLL("libc.dylib")
+        err = ctypes.get_errno()
-    #     logger.warning("kill_itself_when_parent_died is only supported in linux.")
+        raise OSError(err, os.strerror(err))
-    else:
+    if os.getppid() == 1:
-        logger.warning("kill_itself_when_parent_died is only supported in linux.")
+        os.kill(os.getpid(), signal.SIGKILL)
 
 
 def get_exception_traceback() -> str: