Python使用logging搭建工程级日志系统的最佳实践

import logging

# 最简配置（同时输出到终端和文件）
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
    handlers=[
        logging.StreamHandler(),                    # 终端
        logging.FileHandler("app.log", encoding="utf-8"),  # 文件
    ],
)

log = logging.getLogger(__name__)

log.info("服务启动成功")
log.warning("磁盘使用率超过 80%%")
log.error("数据库连接超时", exc_info=True)  # 自动打印堆栈

from logging.handlers import RotatingFileHandler

handler = RotatingFileHandler(
    "app.log",
    maxBytes=10 * 1024 * 1024,  # 10MB
    backupCount=5,              # 保留 5 个备份
    encoding="utf-8",
)
handler.setFormatter(logging.Formatter(
    "%(asctime)s [%(levelname)s] %(name)s: %(message)s"
))

# utils/db.py
logger = logging.getLogger("app.db")

# utils/http.py
logger = logging.getLogger("app.http")

import json
import logging


class JsonFormatter(logging.Formatter):
    def format(self, record: logging.LogRecord) -> str:
        log_obj = {
            "time": self.formatTime(record, self.datefmt),
            "level": record.levelname,
            "logger": record.name,
            "message": record.getMessage(),
        }
        if record.exc_info and record.exc_info[0]:
            log_obj["exception"] = self.formatException(record.exc_info)
        return json.dumps(log_obj, ensure_ascii=False)

import logging
import logging.handlers
import sys
from pathlib import Path


def setup_logger(
    name: str = __name__,
    level: str = "INFO",
    log_file: str | None = None,
) -> logging.Logger:
    logger = logging.getLogger(name)
    if logger.handlers:
        return logger  # 防止重复添加

    logger.setLevel(getattr(logging, level.upper(), logging.INFO))

    fmt = logging.Formatter(
        "%(asctime)s [%(levelname)s] %(name)s:%(lineno)d: %(message)s"
    )

    # 终端 Handler（始终输出 >= WARNING）
    console = logging.StreamHandler(sys.stdout)
    console.setLevel(logging.WARNING)
    console.setFormatter(fmt)
    logger.addHandler(console)

    # 文件 Handler 带轮转（输出全部级别）
    if log_file:
        Path(log_file).parent.mkdir(parents=True, exist_ok=True)
        handler = logging.handlers.RotatingFileHandler(
            log_file, maxBytes=10 << 20, backupCount=5, encoding="utf-8"
        )
        handler.setLevel(logging.DEBUG)
        handler.setFormatter(fmt)
        logger.addHandler(handler)

    return logger


# 使用
log = setup_logger("my_app", level="DEBUG", log_file="logs/my_app.log")
log.info("✅ Logger 初始化完成")