[Bugfix] Support diffusion worker dead detect when use inline engine (#3214)

Signed-off-by: wuhang <wuhang6@huawei.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/diffusion/test_inline_stage_diffusion_client.py

@@ -5,6 +5,7 @@ from types import SimpleNamespace
 from unittest.mock import MagicMock, patch
 
 import pytest
+from vllm.v1.engine.exceptions import EngineDeadError
 
 from vllm_omni.diffusion.data import OmniDiffusionConfig
 from vllm_omni.diffusion.inline_stage_diffusion_client import InlineStageDiffusionClient
@@ -19,6 +20,10 @@ pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
 def mock_engine():
     with patch("vllm_omni.diffusion.inline_stage_diffusion_client.DiffusionEngine") as mock:
         engine_instance = MagicMock()
+        engine_instance.executor = SimpleNamespace(
+            register_failure_callback=MagicMock(),
+            check_health=MagicMock(),
+        )
         mock.make_engine.return_value = engine_instance
         yield engine_instance
 
@@ -97,6 +102,41 @@ def test_inline_shutdown(client, mock_engine):
     mock_engine.close.assert_called_once()
 
 
+def test_inline_registers_executor_failure_callback(client, mock_engine):
+    mock_engine.executor.register_failure_callback.assert_called_once()
+
+
+def test_inline_executor_failure_marks_engine_dead(client, mock_engine):
+    callback = mock_engine.executor.register_failure_callback.call_args.args[0]
+
+    callback()
+
+    assert client._engine_dead is True
+    with pytest.raises(EngineDeadError, match="inline diffusion engine is dead"):
+        client.get_diffusion_output_nowait()
+
+
+def test_inline_returns_queued_output_before_engine_dead(client, mock_engine):
+    callback = mock_engine.executor.register_failure_callback.call_args.args[0]
+    output = OmniRequestOutput.from_diffusion(request_id="req-queued", images=[])
+    client._output_queue.put_nowait(output)
+
+    callback()
+
+    assert client.get_diffusion_output_nowait() is output
+    with pytest.raises(EngineDeadError, match="inline diffusion engine is dead"):
+        client.get_diffusion_output_nowait()
+
+
+def test_inline_check_health_marks_engine_dead(client, mock_engine):
+    mock_engine.executor.check_health.side_effect = EngineDeadError()
+
+    with pytest.raises(EngineDeadError):
+        client.check_health()
+
+    assert client._engine_dead is True
+
+
 def test_inline_client_requires_replica_id(mock_engine):
     metadata = SimpleNamespace(
         stage_id=0,