[frontend] spawn engine process from api server process (#7484)

tests/entrypoints/openai/test_mp_api_server.py

@@ -0,0 +1,37 @@
+import pytest
+
+from vllm.entrypoints.openai.api_server import build_async_engine_client
+from vllm.entrypoints.openai.cli_args import make_arg_parser
+from vllm.utils import FlexibleArgumentParser
+
+
+@pytest.mark.asyncio
+async def test_mp_crash_detection():
+
+    with pytest.raises(RuntimeError) as excinfo:
+        parser = FlexibleArgumentParser(
+            description="vLLM's remote OpenAI server.")
+        parser = make_arg_parser(parser)
+        args = parser.parse_args([])
+        # use an invalid tensor_parallel_size to trigger the
+        # error in the server
+        args.tensor_parallel_size = 65536
+
+        async with build_async_engine_client(args):
+            pass
+    assert "The server process died before responding to the readiness probe"\
+          in str(excinfo.value)
+
+
+@pytest.mark.asyncio
+async def test_mp_cuda_init():
+    # it should not crash, when cuda is initialized
+    # in the API server process
+    import torch
+    torch.cuda.init()
+    parser = FlexibleArgumentParser(description="vLLM's remote OpenAI server.")
+    parser = make_arg_parser(parser)
+    args = parser.parse_args([])
+
+    async with build_async_engine_client(args):
+        pass