Python日志轮转策略

# Python 日志轮转策略 — FileHandler / TimedRotating / logrotate
# 生产环境日志管理方案，避免磁盘写满

import logging
from logging.handlers import RotatingFileHandler, TimedRotatingFileHandler, WatchedFileHandler
import os

LOG_DIR = "/var/log/python-app"
os.makedirs(LOG_DIR, exist_ok=True)

# 1. RotatingFileHandler — 按大小轮转（10MB，保留 5 个备份）
rotating_handler = RotatingFileHandler(
filename=os.path.join(LOG_DIR, "app.log"),
mode="a",
maxBytes=10 * 1024 * 1024,
backupCount=5,
encoding="utf-8",
)
# app.log -> app.log.1 -> ... app.log.5（丢弃最旧）

# 2. TimedRotatingFileHandler — 按时间轮转（午夜，保留 30 天）
timed_handler = TimedRotatingFileHandler(
filename=os.path.join(LOG_DIR, "app-timed.log"),
when="midnight",
interval=1,
backupCount=30,
encoding="utf-8",
utc=True,
)
# when: "S"秒 "M"分 "H"时 "D"天 "midnight"午夜 "W0"~"W6"每周

# 3. WatchedFileHandler — 配合外部 logrotate
watched_handler = WatchedFileHandler(
filename=os.path.join(LOG_DIR, "app-watched.log"),
mode="a",
encoding="utf-8",
)

# 格式化与配置
formatter = logging.Formatter(
fmt="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
datefmt="%Y-%m-%d %H:%M:%S",
)
for h in [rotating_handler, timed_handler, watched_handler]:
h.setFormatter(formatter)

logger = logging.getLogger(__name__)
for h in [rotating_handler, timed_handler, watched_handler]:
logger.addHandler(h)
logger.setLevel(logging.DEBUG)
logger.info("日志系统已初始化，支持大小轮转、时间轮转和外部 logrotate")

# ========== 系统 logrotate 配置（/etc/logrotate.d/python-app）==========
# /var/log/python-app/*.log {
# daily # 每天轮转
# rotate 30 # 保留 30 天
# compress # gzip 压缩
# delaycompress # 延迟一天
# missingok # 文件缺失不报错
# copytruncate # 复制并截断（无需重启应用）
# size 100M # 超过 100M 也触发
# }

# 测试：logrotate -d /etc/logrotate.d/python-app
# 强制：logrotate -f /etc/logrotate.d/python-app

# copytruncate：logrotate 复制文件 -> 截断原文件 ->
# Python 继续写入原 inode，无需信号通知

# ========== 完整生产配置（字典模式）==========
def setup_logging():
config = {
"version": 1,
"formatters": {
"standard": {"format": "%(asctime)s [%(levelname)s] %(name)s: %(message)s"},
"json": {"format": '{"time":"%(asctime)s","level":"%(levelname)s","message":"%(message)s"}'},
},
"handlers": {
"rotating": {
"class": "logging.handlers.RotatingFileHandler",
"filename": os.path.join(LOG_DIR, "app.log"),
"maxBytes": 10 * 1024 * 1024,
"backupCount": 5,
"formatter": "json",
},
"error": {
"class": "logging.handlers.TimedRotatingFileHandler",
"filename": os.path.join(LOG_DIR, "error.log"),
"when": "midnight",
"backupCount": 90,
"level": "ERROR",
"formatter": "standard",
},
},
"loggers": {
"": {"handlers": ["rotating", "error"], "level": "DEBUG"},
"sqlalchemy": {"level": "WARNING"},
},
}
logging.config.dictConfig(config)

# ========== 关键要点 ==========
# RotatingFileHandler：按大小轮转，maxBytes + backupCount 控制总空间。
# TimedRotatingFileHandler：按时间轮转，适合合规保留要求。
# WatchedFileHandler：配合外部 logrotate，无需重启应用。
# 系统 logrotate：独立轮转方案，copytruncate 无需信号通知。
# 分层配置：不同级别分离，不同格式（可读 vs JSON）。