python 使用多線程效果提升不高，因為只會占用一個cpu核，為了提升，需要使用多進程（比如 uwsgi 做服務）
這時候，在日志更新時就會出問題，通常日志更新是按天的，這時候多個進程就會重新去更新，比如：
進程a切換到 log.2020.06.22,進程b在切換的時候發現這個文件存在了就會去刪除，導致舊的數據被刪除。解決方式，
修改
logging.handlers.TimedRotatingFileHandler
的類，使得進程b在切換的時候發現這個文件存在了（說明其他進程創建了）就不刪除舊的，同時新建的時候，文件writemode 采用 a+ 而不是w（用w會刪除已經有的文件，導致進程a打的日志丟失），
參考：https://www.jianshu.com/p/d615bf01e37b
創建新類繼承 TimedRotatingFileHandler
class SafeRotatingFileHandler(TimedRotatingFileHandler): def __init__(self, filename, when='h', interval=1, backupCount=0, encoding=None, delay=False, utc=False): TimedRotatingFileHandler.__init__(self, filename, when, interval, backupCount, encoding, delay, utc) """ Override doRollover lines commanded by "##" is changed by cc """ 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. Override, 1. if dfn not exist then do rename 2. _open with "a" model """ if self.stream: self.stream.close() self.stream = None # get the time that this sequence started at and make it a TimeTuple currentTime = int(time.time()) dstNow = time.localtime(currentTime)[-1] t = self.rolloverAt - self.interval if self.utc: timeTuple = time.gmtime(t) else: timeTuple = time.localtime(t) dstThen = timeTuple[-1] if dstNow != dstThen: if dstNow: addend = 3600 else: addend = -3600 timeTuple = time.localtime(t + addend) dfn = self.baseFilename + "." + time.strftime(self.suffix, timeTuple) ## if os.path.exists(dfn): ## os.remove(dfn) # Issue 18940: A file may not have been created if delay is True. ## if os.path.exists(self.baseFilename): if not os.path.exists(dfn) and os.path.exists(self.baseFilename): os.rename(self.baseFilename, dfn) if self.backupCount > 0: for s in self.getFilesToDelete(): os.remove(s) if not self.delay: self.mode = "a" self.stream = self._open() 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: dstAtRollover = time.localtime(newRolloverAt)[-1] if dstNow != dstAtRollover: if not dstNow: # DST kicks in before next rollover, so we need to deduct an hour addend = -3600 else: # DST bows out before next rollover, so we need to add an hour addend = 3600 newRolloverAt += addend self.rolloverAt = newRolloverAt