From de6889946bd10045f2ee79b252e75d8f3e323956 Mon Sep 17 00:00:00 2001
From: "wang.yuqi" <yuqi.wang@daocloud.io>
Date: Tue, 25 Nov 2025 19:00:44 +0800
Subject: [PATCH] [Misc] Suppress log outputs when constructing the default
 vllm config. (#29291)

Signed-off-by: wang.yuqi <yuqi.wang@daocloud.io>
Signed-off-by: wang.yuqi <noooop@126.com>
Signed-off-by: Cyrus Leung <cyrus.tl.leung@gmail.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Cyrus Leung <cyrus.tl.leung@gmail.com>
Co-authored-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
---
 vllm/engine/arg_utils.py | 14 ++++++++------
 vllm/logger.py           | 11 ++++++++++-
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/vllm/engine/arg_utils.py b/vllm/engine/arg_utils.py
index 8338e54d4fd85..6b5c8ba87ecbf 100644
--- a/vllm/engine/arg_utils.py
+++ b/vllm/engine/arg_utils.py
@@ -77,7 +77,7 @@ from vllm.config.observability import DetailedTraceModules
 from vllm.config.parallel import DistributedExecutorBackend, ExpertPlacementStrategy
 from vllm.config.scheduler import SchedulerPolicy
 from vllm.config.utils import get_field
-from vllm.logger import init_logger
+from vllm.logger import init_logger, suppress_logging
 from vllm.platforms import CpuArchEnum, current_platform
 from vllm.plugins import load_general_plugins
 from vllm.ray.lazy_utils import is_in_ray_actor, is_ray_initialized
@@ -247,11 +247,13 @@ def _compute_kwargs(cls: ConfigType) -> dict[str, dict[str, Any]]:
             default = field.default
             # Handle pydantic.Field defaults
             if isinstance(default, FieldInfo):
-                default = (
-                    default.default
-                    if default.default_factory is None
-                    else default.default_factory()
-                )
+                if default.default_factory is None:
+                    default = default.default
+                else:
+                    # VllmConfig's Fields have default_factory set to config classes.
+                    # These could emit logs on init, which would be confusing.
+                    with suppress_logging():
+                        default = default.default_factory()
         elif field.default_factory is not MISSING:
             default = field.default_factory()
 
diff --git a/vllm/logger.py b/vllm/logger.py
index 772e36497b45e..ad3123c0f0149 100644
--- a/vllm/logger.py
+++ b/vllm/logger.py
@@ -7,7 +7,8 @@ import json
 import logging
 import os
 import sys
-from collections.abc import Hashable
+from collections.abc import Generator, Hashable
+from contextlib import contextmanager
 from functools import lru_cache, partial
 from logging import Logger
 from logging.config import dictConfig
@@ -212,6 +213,14 @@ def init_logger(name: str) -> _VllmLogger:
     return cast(_VllmLogger, logger)
 
 
+@contextmanager
+def suppress_logging(level: int = logging.INFO) -> Generator[None, Any, None]:
+    current_level = logging.root.manager.disable
+    logging.disable(level)
+    yield
+    logging.disable(current_level)
+
+
 # The root logger is initialized when the module is imported.
 # This is thread-safe as the module is only imported once,
 # guaranteed by the Python GIL.