[Perf][CLI] Improve overall startup time (#19941)

vllm/entrypoints/cli/main.py

@@ -1,27 +1,15 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+'''The CLI entrypoints of vLLM
 
-# The CLI entrypoint to vLLM.
+Note that all future modules must be lazily loaded within main
+to avoid certain eager import breakage.'''
+from __future__ import annotations
+
+import importlib.metadata
 import signal
 import sys
 
-import vllm.entrypoints.cli.benchmark.main
-import vllm.entrypoints.cli.collect_env
-import vllm.entrypoints.cli.openai
-import vllm.entrypoints.cli.run_batch
-import vllm.entrypoints.cli.serve
-import vllm.version
-from vllm.entrypoints.utils import VLLM_SUBCMD_PARSER_EPILOG, cli_env_setup
-from vllm.utils import FlexibleArgumentParser
-
-CMD_MODULES = [
-    vllm.entrypoints.cli.openai,
-    vllm.entrypoints.cli.serve,
-    vllm.entrypoints.cli.benchmark.main,
-    vllm.entrypoints.cli.collect_env,
-    vllm.entrypoints.cli.run_batch,
-]
-
 
 def register_signal_handlers():
 
@@ -33,16 +21,34 @@ def register_signal_handlers():
 
 
 def main():
+    import vllm.entrypoints.cli.benchmark.main
+    import vllm.entrypoints.cli.collect_env
+    import vllm.entrypoints.cli.openai
+    import vllm.entrypoints.cli.run_batch
+    import vllm.entrypoints.cli.serve
+    from vllm.entrypoints.utils import VLLM_SUBCMD_PARSER_EPILOG, cli_env_setup
+    from vllm.utils import FlexibleArgumentParser
+
+    CMD_MODULES = [
+        vllm.entrypoints.cli.openai,
+        vllm.entrypoints.cli.serve,
+        vllm.entrypoints.cli.benchmark.main,
+        vllm.entrypoints.cli.collect_env,
+        vllm.entrypoints.cli.run_batch,
+    ]
+
     cli_env_setup()
 
     parser = FlexibleArgumentParser(
         description="vLLM CLI",
         epilog=VLLM_SUBCMD_PARSER_EPILOG,
     )
-    parser.add_argument('-v',
-                        '--version',
-                        action='version',
-                        version=vllm.version.__version__)
+    parser.add_argument(
+        '-v',
+        '--version',
+        action='version',
+        version=importlib.metadata.version('vllm'),
+    )
     subparsers = parser.add_subparsers(required=False, dest="subparser")
     cmds = {}
     for cmd_module in CMD_MODULES: