[feat] Added logger into nanovllm.

nanovllm/utils/logger.py

@@ -0,0 +1,123 @@
+"""
+Global logger for nano-vllm with colored output.
+
+Usage:
+    from nanovllm.utils.logger import logger
+
+    logger.debug("Debug message")    # Gray
+    logger.info("Info message")      # Blue
+    logger.warning("Warning message") # Yellow
+    logger.error("Error message")    # Red
+
+Control log level via environment variable:
+    NANOVLLM_LOG_LEVEL=DEBUG python your_script.py
+    NANOVLLM_LOG_LEVEL=INFO python your_script.py  (default)
+    NANOVLLM_LOG_LEVEL=WARNING python your_script.py
+"""
+import os
+import sys
+import logging
+from typing import Optional
+
+
+# ANSI color codes
+class Colors:
+    RESET = "\033[0m"
+    GRAY = "\033[90m"
+    BLUE = "\033[94m"
+    YELLOW = "\033[93m"
+    RED = "\033[91m"
+    BOLD = "\033[1m"
+
+
+# Level -> Color mapping
+LEVEL_COLORS = {
+    logging.DEBUG: Colors.GRAY,
+    logging.INFO: Colors.BLUE,
+    logging.WARNING: Colors.YELLOW,
+    logging.ERROR: Colors.RED,
+    logging.CRITICAL: Colors.RED + Colors.BOLD,
+}
+
+
+class ColoredFormatter(logging.Formatter):
+    """Formatter that adds colors to log levels."""
+
+    def __init__(self, fmt: str, datefmt: str = None, use_colors: bool = True):
+        super().__init__(fmt, datefmt)
+        self.use_colors = use_colors
+
+    def format(self, record: logging.LogRecord) -> str:
+        if self.use_colors:
+            color = LEVEL_COLORS.get(record.levelno, Colors.RESET)
+            # Color the level name
+            record.levelname = f"{color}{record.levelname}{Colors.RESET}"
+            # Color the message
+            record.msg = f"{color}{record.msg}{Colors.RESET}"
+        return super().format(record)
+
+
+# Log level from environment variable
+_LOG_LEVEL = os.environ.get("NANOVLLM_LOG_LEVEL", "INFO").upper()
+
+# Global logger instance
+_logger: Optional[logging.Logger] = None
+
+
+def _setup_logger() -> logging.Logger:
+    """Setup and return the global logger."""
+    log = logging.getLogger("nanovllm")
+
+    # Avoid duplicate handlers if called multiple times
+    if log.handlers:
+        return log
+
+    # Set level from environment
+    level = getattr(logging, _LOG_LEVEL, logging.INFO)
+    log.setLevel(level)
+
+    # Create handler (stderr)
+    handler = logging.StreamHandler(sys.stderr)
+    handler.setLevel(level)
+
+    # Check if terminal supports colors
+    use_colors = hasattr(sys.stderr, "isatty") and sys.stderr.isatty()
+
+    # Format: [TIME] [LEVEL] [MODULE] message
+    formatter = ColoredFormatter(
+        fmt="[%(asctime)s] [%(levelname)s] [%(name)s] %(message)s",
+        datefmt="%H:%M:%S",
+        use_colors=use_colors,
+    )
+    handler.setFormatter(formatter)
+
+    log.addHandler(handler)
+
+    # Don't propagate to root logger
+    log.propagate = False
+
+    return log
+
+
+def get_logger(name: Optional[str] = None) -> logging.Logger:
+    """
+    Get a logger instance.
+
+    Args:
+        name: Optional sub-logger name. If provided, creates a child logger
+              like 'nanovllm.attention'. If None, returns the root nanovllm logger.
+
+    Returns:
+        Logger instance
+    """
+    global _logger
+    if _logger is None:
+        _logger = _setup_logger()
+
+    if name:
+        return _logger.getChild(name)
+    return _logger
+
+
+# Convenience: direct access to the root logger
+logger = get_logger()