[V1][BugFix] Exit properly if engine core fails during startup (#16137)

Signed-off-by: Nick Hill <nhill@redhat.com>

tests/v1/engine/test_engine_core_client.py

@@ -3,8 +3,10 @@
 import asyncio
 import time
 import uuid
+from threading import Thread
 from typing import Optional
 
+import psutil
 import pytest
 from transformers import AutoTokenizer
 
@@ -245,3 +247,42 @@ async def test_engine_core_client_asyncio(monkeypatch: pytest.MonkeyPatch):
             await core_client.call_utility_async("echo", None, "help!")
 
         assert str(e_info.value) == "Call to echo method failed: help!"
+
+
+@pytest.mark.timeout(10)
+def test_startup_failure(monkeypatch: pytest.MonkeyPatch):
+
+    with monkeypatch.context() as m, pytest.raises(Exception) as e_info:
+        m.setenv("VLLM_USE_V1", "1")
+
+        engine_args = EngineArgs(model=MODEL_NAME)
+        vllm_config = engine_args.create_engine_config(
+            usage_context=UsageContext.UNKNOWN_CONTEXT)
+        executor_class = Executor.get_class(vllm_config)
+
+        # Start another thread to wait for engine core process to start
+        # and kill it - simulate fatal uncaught process exit.
+        this_proc = psutil.Process()
+        children_before = set(this_proc.children())
+
+        def kill_first_child():
+            while True:
+                time.sleep(0.5)
+                children = set(this_proc.children()) - children_before
+                if children:
+                    child = children.pop()
+                    print("Killing child core process", child.pid)
+                    child.kill()
+                    break
+
+        Thread(target=kill_first_child, daemon=True).start()
+
+        _core_client = EngineCoreClient.make_client(
+            multiprocess_mode=True,
+            asyncio_mode=True,
+            vllm_config=vllm_config,
+            executor_class=executor_class,
+            log_stats=True,
+        )
+
+    assert "Engine core initialization failed" in str(e_info.value)