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_FORMATTERenable_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)