[Misc] add logging level env var (#5045)

.github/ISSUE_TEMPLATE/400-bug report.yml

@@ -59,6 +59,8 @@ body:
 
       Please also paste or describe the results you observe instead of the expected results. If you observe an error, please paste the error message including the **full** traceback of the exception. It may be relevant to wrap error messages in ```` ```triple quotes blocks``` ````.
 
+      Please set the environment variable `export VLLM_LOGGING_LEVEL=DEBUG` to turn on more logging to help debugging potential issues.
+
       If you experienced crashes or hangs, it would be helpful to run vllm with `export VLLM_TRACE_FUNCTION=1` . All the function calls in vllm will be recorded. Inspect these log files, and tell which function crashes or hangs.
     placeholder: |
       A clear and concise description of what the bug is.

vllm/envs.py

@@ -22,6 +22,7 @@ if TYPE_CHECKING:
     VLLM_DO_NOT_TRACK: bool = False
     VLLM_USAGE_SOURCE: str = ""
     VLLM_CONFIGURE_LOGGING: int = 1
+    VLLM_LOGGING_LEVEL: str = "INFO"
     VLLM_LOGGING_CONFIG_PATH: Optional[str] = None
     VLLM_TRACE_FUNCTION: int = 0
     VLLM_ATTENTION_BACKEND: Optional[str] = None
@@ -178,6 +179,10 @@ environment_variables: Dict[str, Callable[[], Any]] = {
     "VLLM_LOGGING_CONFIG_PATH":
     lambda: os.getenv("VLLM_LOGGING_CONFIG_PATH"),
 
+    # this is used for configuring the default logging level
+    "VLLM_LOGGING_LEVEL":
+    lambda: os.getenv("VLLM_LOGGING_LEVEL", "INFO"),
+
     # Trace function calls
     # If set to 1, vllm will trace function calls
     # Useful for debugging

vllm/logger.py

@@ -14,6 +14,7 @@ import vllm.envs as envs
 
 VLLM_CONFIGURE_LOGGING = envs.VLLM_CONFIGURE_LOGGING
 VLLM_LOGGING_CONFIG_PATH = envs.VLLM_LOGGING_CONFIG_PATH
+VLLM_LOGGING_LEVEL = envs.VLLM_LOGGING_LEVEL
 
 _FORMAT = "%(levelname)s %(asctime)s %(filename)s:%(lineno)d] %(message)s"
 _DATE_FORMAT = "%m-%d %H:%M:%S"
@@ -30,7 +31,7 @@ DEFAULT_LOGGING_CONFIG = {
         "vllm": {
             "class": "logging.StreamHandler",
             "formatter": "vllm",
-            "level": "INFO",
+            "level": VLLM_LOGGING_LEVEL,
             "stream": "ext://sys.stdout",
         },
     },