[Bugfix] set VLLM_WORKER_MULTIPROC_METHOD=spawn for vllm.entrypoionts.openai.api_server (#15700)

Signed-off-by: Jinzhen Lin <linjinzhen@hotmail.com>

vllm/entrypoints/cli/main.py

@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 
 # The CLI entrypoint to vLLM.
-import os
 import signal
 import sys
 
@@ -9,11 +8,9 @@ import vllm.entrypoints.cli.benchmark.main
 import vllm.entrypoints.cli.openai
 import vllm.entrypoints.cli.serve
 import vllm.version
-from vllm.logger import init_logger
+from vllm.entrypoints.utils import cli_env_setup
 from vllm.utils import FlexibleArgumentParser
 
-logger = init_logger(__name__)
-
 CMD_MODULES = [
     vllm.entrypoints.cli.openai,
     vllm.entrypoints.cli.serve,
@@ -30,29 +27,8 @@ def register_signal_handlers():
     signal.signal(signal.SIGTSTP, signal_handler)
 
 
-def env_setup():
-    # The safest multiprocessing method is `spawn`, as the default `fork` method
-    # is not compatible with some accelerators. The default method will be
-    # changing in future versions of Python, so we should use it explicitly when
-    # possible.
-    #
-    # We only set it here in the CLI entrypoint, because changing to `spawn`
-    # could break some existing code using vLLM as a library. `spawn` will cause
-    # unexpected behavior if the code is not protected by
-    # `if __name__ == "__main__":`.
-    #
-    # References:
-    # - https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods
-    # - https://pytorch.org/docs/stable/notes/multiprocessing.html#cuda-in-multiprocessing
-    # - https://pytorch.org/docs/stable/multiprocessing.html#sharing-cuda-tensors
-    # - https://docs.habana.ai/en/latest/PyTorch/Getting_Started_with_PyTorch_and_Gaudi/Getting_Started_with_PyTorch.html?highlight=multiprocessing#torch-multiprocessing-for-dataloaders
-    if "VLLM_WORKER_MULTIPROC_METHOD" not in os.environ:
-        logger.debug("Setting VLLM_WORKER_MULTIPROC_METHOD to 'spawn'")
-        os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
-
-
 def main():
-    env_setup()
+    cli_env_setup()
 
     parser = FlexibleArgumentParser(description="vLLM CLI")
     parser.add_argument('-v',