在使用 time-rotating 记录器创建的每个日志文件中写入一个 header

Question

我制作了一个 time-rotating 记录器，它会在午夜创建一个新的日志文件。在我的日志文件中，我想在每个文件的顶部写一个 header 。我正在寻找一种有效的方法来调用一个函数，该函数在创建文件时将 header 写入日志文件。

import logging
from logging.handlers import TimedRotatingFileHandler

# create time-rotating log handler
logHandler = TimedRotatingFileHandler(logfile, when='midnight')

# create logger
self.log = logging.getLogger('MyTimeRotatingLogger')
self.log.addHandler(logHandler)

Answer 1

我解决了！基本上所有需要做的就是覆盖 TimedRotatingFileHandler 的 doRollover 方法，在这个新的 parent class 中也需要一些代码来传递日志实例和设置 header 内容。特此为遇到类似情况的人提供一个广泛的例子。

from logging.handlers import TimedRotatingFileHandler

class MyTimedRotatingFileHandler(TimedRotatingFileHandler):
    def __init__(self, logfile, when, interval):
        super(MyTimedRotatingFileHandler, self).__init__(logfile, when, interval)
        self._header = ""
        self._log = None

    def doRollover(self):
        super(MyTimedRotatingFileHandler, self).doRollover()
        if self._log is not None and self._header != "":
            self._log.info(self._header)

    def setHeader(self, header):
        self._header = header

    def configureHeaderWriter(self, header, log):
        self._header = header
        self._log = log

# create time-rotating log handler
logHandler = MyTimedRotatingFileHandler(logfile, when='midnight')
form = '%(asctime)s %(name)s %(levelname)s: %(message)s'
logFormatter = logging.Formatter(form)
logHandler.setFormatter(logFormatter)

# create logger
log = logging.getLogger('MyLogger')
logHandler.configureHeaderWriter('test-header', log)
log.addHandler(logHandler)
log.setLevel(logging.INFO)

Answer 2

为了在第一个日志文件中也有一个 header，我建议对您的解决方案进行稍微修改的替代方案。即，在定义 header 之后立即对写入 header 的代码段进行额外调用，并在记录器设置中插入某些行（请参阅代码中的注释）：

from logging.handlers import TimedRotatingFileHandler

class MyTimedRotatingFileHandler(TimedRotatingFileHandler):
    def __init__(self, logfile, when, interval):
        super(MyTimedRotatingFileHandler, self).__init__(logfile, when, interval)
        self._header = ""
        self._log = None

    def write_header(self):
        if self._log is not None and self._header != '': 
            self._log.info(self._header)

    def doRollover(self):
        super(MyTimedRotatingFileHandler, self).doRollover()
        self.write_header()

    def configureHeaderWriter(self, header, log):
        self._header = header
        self._log = log
        self.write_header()     # WRITE HEADER TO FIRST FILE

# create time-rotating log handler
logHandler = MyTimedRotatingFileHandler(logfile, when='midnight')
form = '%(asctime)s %(name)s %(levelname)s: %(message)s'
logFormatter = logging.Formatter(form)
logHandler.setFormatter(logFormatter)

# create logger
log = logging.getLogger('MyLogger')

# CONFIGURE LOG LEVEL AND ATTACH HANDLER TO LOGGER **BEFORE** SETTING THE HEADER
log.setLevel(logging.INFO)
log.addHandler(logHandler)  

logHandler.configureHeaderWriter('test-header', log)

Answer 3

上面的解决方案涵盖了大多数用例，但如果您仍想尊重 FileHandler.delay 属性的行为，我认为最简单的解决方案是重写 _open() 方法：

class MyTimedRotatingFileHandler(TimedRotatingFileHandler):
    def __init__(self, filename, when='h', interval=1, backupCount=0, encoding=None, delay=False, utc=False, atTime=None, header=''):
        self.header = header
        super().__init__(filename, when, interval, backupCount, encoding, delay, utc, atTime)
    def _open(self):
        stream = super()._open()
        if self.header and stream.tell() == 0:
            stream.write(self.header + self.terminator)
            stream.flush()
        return stream

这样您就可以避免以仅包含 header 的“空”日志文件结束，并且您不必担心将特定记录器传递给处理程序。

在使用 time-rotating 记录器创建的每个日志文件中写入一个 header

Write a header at every logfile that is created with a time-rotating logger

python

logging