重写 Python logging 的 TimedRotatingFileHandler doRollover 方法，解决多进程切割日志的问题。

parallel_timed_rotating_handler.py

#!/bin/env python
# -*- coding: utf-8 -*-

import os
import time
import logging
from logging.handlers import TimedRotatingFileHandler


LOG_DIR = "/tmp/"
LOG_NAME = "test"


if not os.path.isdir(LOG_DIR):
    os.makedirs(LOG_DIR)
    

class ParallelTimedRotatingHandler(TimedRotatingFileHandler):
    def doRollover(self):
        """ 
        do a rollover; in this case, a date/time stamp is appended to the 
        filename when the rollover happens.  However, you want the file to
        be named for the start of the interval, not the current time.  
        If there is a backup count, then we have to get a list of matching 
        filenames, sort them and remove the one with the oldest suffix.
        """
        if self.stream:
            self.stream.close()
        # get the time that this sequence started at and make it a TimeTuple
        t = self.rolloverAt - self.interval
        if self.utc:
            timeTuple = time.gmtime(t)
        else:
            timeTuple = time.localtime(t)
        dfn = self.baseFilename + "." + time.strftime(self.suffix, timeTuple)
        if not os.path.exists(dfn):
            os.rename(self.baseFilename, dfn)
        if self.backupCount > 0:
            # find the oldest log file and delete it
            for s in self.getFilesToDelete():
                os.remove(s)
        self.mode = 'a'
        self.stream = self._open()
        currentTime = int(time.time())
        newRolloverAt = self.computeRollover(currentTime)
        while newRolloverAt <= currentTime:
            newRolloverAt = newRolloverAt + self.interval
        #If DST changes and midnight or weekly rollover, adjust for this.
        if (self.when == 'MIDNIGHT' or self.when.startswith('W'))\
                and not self.utc:
            dstNow = time.localtime(currentTime)[-1]
            dstAtRollover = time.localtime(newRolloverAt)[-1]
            if dstNow != dstAtRollover:
             # DST kicks in before next rollover, so we need to deduct an hour
                if not dstNow:  
                    newRolloverAt = newRolloverAt - 3600
             # DST bows out before next rollover, so we need to add an hour
                else:           
                    newRolloverAt = newRolloverAt + 3600
        self.rolloverAt = newRolloverAt


def singleton(cls):
    instances = {}
    def _singleton(*args, **kw):
        if cls not in instances:
            instances[cls] = cls(*args, **kw)
        return instances[cls]
    return _singleton


@singleton
class LogHandler(object):
    WHEN = "midnight"
    BACKUPCOUNT = 7

    logger = logging.getLogger()
    logger.setLevel(logging.DEBUG)
    
    # 格式.
    formatter = logging.Formatter(
        '[%(asctime)s] [%(levelname)-8s] [%(name)-16s] [%(filename)s] [%(funcName)s] [%(lineno)d] %(message)s',
        '%Y-%m-%d %H:%M:%S',)

    # info 日志.
    info_handler = ParallelTimedRotatingHandler(LOG_DIR + LOG_NAME + "-info.log",
                                                WHEN, backupCount=BACKUPCOUNT)
    info_handler.propagate = 0
    info_handler.setFormatter(formatter)
    info_handler.setLevel(logging.INFO)
    logger.addHandler(info_handler)

    # warning 日志.
    warning_handler = ParallelTimedRotatingHandler(LOG_DIR + LOG_NAME + "-warning.log",
                                                   WHEN, backupCount=BACKUPCOUNT)
    info_handler.propagate = 0
    warning_handler.setFormatter(formatter)
    warning_handler.setLevel(logging.WARNING)
    logger.addHandler(warning_handler)

你好，我目前也遇到了多进程切割日志的问题，对比了源码和你的修改以后，发现主要是这句self.mode = 'a'，源码里面是 self.mode = 'w'，请问为什么要这么改呢？还有你的代码里面singleton是用来干什么的呢？