Python入门之——logging日志模块通过gppylib.gplog学习logging模块使用

港控/mmm° 2022-12-03 11:26 220阅读 0赞

gppylib.gplog在文件lib/python/gppylib/gplog.py下。该模块包含一些建立python内建logging模块的帮助函数。主要是方便tool、helper等模块建立各自的Logger（setup\_helper\_tool\_logging和setup\_tool\_logging函数）。我们通过一个例子来对该文件中相关函数进行分析。

from gppylib import gplog
      logger = gplog.setup_tool_logging(EXECNAME, hostname, username, logdir)
      if options.verbose:
        gplog.enable_verbose_logging()
      if options.quiet:
        gplog.quiet_stdout_logging()
      logger.info("Start myTool")
      ...

首先是调用setup\_tool\_logging函数，参数是EXECNAME, hostname, username, logdir。该函数返回单例模式的logger，可用于向stdout和文件中输出记录。主要是个性化定制logger的名字name，向SOUT\_HANDLER和FILE\_HANDLER设置Formatter，并使用个性化的格式化字符串。

def setup_tool_logging(appName, hostname, userName, logdir=None, nonuser=False):
        """ Returns a singleton logger for standard Greenplum tools: - Logs output to stdout - Logs output to a file, typically in ~/gpAdminLogs """
        global _DEFAULT_FORMATTER
        global _APP_NAME_FOR_DEFAULT_FORMAT
        logger_name = "%s:%s" % (hostname, userName)
        if nonuser:
            appName = appName + "_" + logger_name
        _APP_NAME_FOR_DEFAULT_FORMAT = appName
        _enable_gpadmin_logging(appName, logdir)
        #
        # now reset the default formatter (someone may have called get_default_logger before calling setup_tool_logging)
        #
        logger = get_default_logger()
        logger.name = logger_name
        _DEFAULT_FORMATTER = None
        f = _get_default_formatter()
        _SOUT_HANDLER.setFormatter(f)
        _FILE_HANDLER.setFormatter(f)
        return logger

该函数用于为default logger设置文件输出handler，验证log的目录的正确性和存在性，最后通过调用\_set\_file\_logging添加file handler。stream handler是在get\_default\_logger中加入logger的。

def _enable_gpadmin_logging(name, logdir=None):
        """ Sets up the file output handler for the default logger. - if logdir is not specified it uses ~/gpAdminLogs - the file is constructed as appended with "<logdir>/<name>_<date>.log" NOTE: internal use only """
        global _FILE_HANDLER
        get_default_logger()
        now = datetime.date.today()
        if logdir is None:
            home_dir = os.path.expanduser("~")
            gpadmin_logs_dir = home_dir + "/gpAdminLogs"
        else:
            gpadmin_logs_dir = logdir
        if not os.path.exists(gpadmin_logs_dir):
            os.mkdir(gpadmin_logs_dir)
        filename = "%s/%s_%s.log" % (gpadmin_logs_dir, name, now.strftime("%Y%m%d"))
        _set_file_logging(filename)

get\_default\_logger单例模式返回默认logger，值创建stream handle也就是项stdout输出记录，并设置file handler。

def get_default_logger():
        """ Return the singleton default logger. If a logger has not yet been established it creates one that: - Logs output to stdout - Does not setup file logging. Typical usage would be to call one of the setup_*_logging() functions at the beginning of a script in order to establish the exact type of logging desired, after which later calls to get_default_logger() can be used to return a reference to the logger. """
        global _LOGGER, _SOUT_HANDLER
        if _LOGGER is None:
            _LOGGER = logging.getLogger('default')
            f = _get_default_formatter()
            _SOUT_HANDLER = EncodingStreamHandler(sys.stdout)
            _SOUT_HANDLER.setFormatter(f)
            _LOGGER.addHandler(_SOUT_HANDLER)
            _LOGGER.setLevel(logging.INFO)
        return _LOGGER

自定义的Handler类，继承自logging.StreamHandler，主要用于确保message的编码为utf-8。在重写的emit函数中进行处理，最终还需调用父类的emit的函数对记录进行处理（写到Stream中）

class EncodingStreamHandler(logging.StreamHandler):
        """This handler makes sure that the encoding of the message is utf-8 before passing it along to the StreamHandler. This will prevent encode/decode errors later on."""
    
        def __init__(self, strm=None):
            logging.StreamHandler.__init__(self, strm)
    
        def emit(self, record):
            if not isinstance(record.msg, str) and not isinstance(record.msg, unicode):
                record.msg = str(record.msg)
            if not isinstance(record.msg, unicode):
                record.msg = unicode(record.msg, 'utf-8')
            logging.StreamHandler.emit(self, record)

同样这里设置file handle，用于向文件中输入记录，其中的EncodingFileHandler继承ogging.FileHandler，也是确保message的编码为utf-8。

def _set_file_logging(filename):
        """ Establishes a file output HANDLER for the default formatter. NOTE: internal use only """
        global _LOGGER, _SOUT_HANDLER, _FILENAME, _FILE_HANDLER
        _FILENAME = filename
        _FILE_HANDLER = EncodingFileHandler(filename, 'a')
        _FILE_HANDLER.setFormatter(_get_default_formatter())
        _LOGGER.addHandler(_FILE_HANDLER)
    
    class EncodingFileHandler(logging.FileHandler):
        """This handler makes sure that the encoding of the message is utf-8 before passing it along to the FileHandler. This will prevent encode/decode errors later on."""
        def __init__(self, filename, mode='a', encoding=None, delay=0):
            logging.FileHandler.__init__(self, filename, mode, encoding, delay)
        def emit(self, record):
            if not isinstance(record.msg, str) and not isinstance(record.msg, unicode):
                record.msg = str(record.msg)
            if not isinstance(record.msg, unicode):
                record.msg = unicode(record.msg, 'utf-8')
            logging.FileHandler.emit(self, record)

\_get\_default\_formatter函数用于对formatter中的格式化进行定制后，返回Formatter对象。

def _get_default_formatter():
        """ Returns the default formatter, constructing it if needed. The default formatter formats things using Greenplum standard logging: <date>:<pid> <programname>:<hostname>:<username>:[LEVEL]:-message NOTE: internal use only """
        global _DEFAULT_FORMATTER
        global _APP_NAME_FOR_DEFAULT_FORMAT
        if _DEFAULT_FORMATTER is None:
            format_str = "%(asctime)s:%(programname)s:%(name)s-[%(levelname)-s]:-%(message)s"
            app_name = _APP_NAME_FOR_DEFAULT_FORMAT.replace("%", "")  # to make sure we don't produce a format string
            format_str = format_str.replace("%(programname)s", "%06d %s" % (os.getpid(), app_name))
            _DEFAULT_FORMATTER = logging.Formatter(format_str, "%Y%m%d:%H:%M:%S")
        return _DEFAULT_FORMATTER

enable\_verbose\_logging和quiet\_stdout\_logging调用Logger对象的setLevel函数用于设置输出记录的级别阈值

def enable_verbose_logging():
        """ Increases the log level to be verbose. - Applies to all logging handlers (stdout/file). """
        _LOGGER.setLevel(logging.DEBUG)
    
    def quiet_stdout_logging():
        """ Reduce log level for stdout logging """
        global _SOUT_HANDLER
        _SOUT_HANDLER.setLevel(logging.WARN)