openstack日志模块

一、简单的python日志模块介绍

http://www.cnblogs.com/tuzkee/p/3974193.html

http://blog.csdn.net/jgood/article/details/4340740

二、日志的配置

　　openstack服务程序在启动的时候都会对日志系统进行设置，这里以nova-api为例，在它的的启动代码里：

nova/cmd/api.py

def main():
    config.parse_args(sys.argv)
    logging.setup("nova")
    ...

　　由于在/etc/init.d/openstack-nova-api控制脚本里已经传入参数，所以sys.argv为['/usr/bin/nova-api', '--logfile', '/var/log/nova/api.log']，即在配置参数里面设置了日志系统的文件记录地址。接着看日志的设置代码如下:

nova/openstack/common/log.py

def setup(product_name):
    if CONF.log_config:
        _load_log_config(CONF.log_config)
    else:
        _setup_logging_from_conf()
    sys.excepthook = _create_logging_excepthook(product_name)

def _setup_logging_from_conf():
    """
    获取根logger，此后创建的所有logger都继承了它的配置，所以此后创建的logger基本不需要配置就可以直接使用
    """
    log_root = getLogger(None).logger
    for handler in log_root.handlers:
            log_root.removeHandler(handler)

    if CONF.use_syslog:
        facility = _find_facility_from_conf()
        syslog = logging.handlers.SysLogHandler(address='/dev/log',
                                                facility=facility)
        log_root.addHandler(syslog)
    """设置日志输出位置"""
    logpath = _get_log_file_path()#获取刚刚设置的日志文件路径
    if logpath:
        filelog = logging.handlers.WatchedFileHandler(logpath)
        log_root.addHandler(filelog)

    if CONF.use_stderr:
        streamlog = ColorHandler()
        log_root.addHandler(streamlog)

    elif not CONF.log_file:
        streamlog = logging.StreamHandler(sys.stdout)
        log_root.addHandler(streamlog)

    if CONF.publish_errors:
        handler = importutils.import_object(
            "nova.openstack.common.log_handler.PublishErrorsHandler",
            logging.ERROR)
        log_root.addHandler(handler)
    """设置日志格式"""
    datefmt = CONF.log_date_format
    for handler in log_root.handlers:
        if CONF.log_format:
            handler.setFormatter(logging.Formatter(fmt=CONF.log_format,
                                                   datefmt=datefmt))
            log_root.info('Deprecated: log_format is now deprecated and will '
                          'be removed in the next release')
        else:
            handler.setFormatter(ContextFormatter(datefmt=datefmt))
    """设置日志级别"""
    if CONF.debug:
        log_root.setLevel(logging.DEBUG)
    elif CONF.verbose:
        log_root.setLevel(logging.INFO)
    else:
        log_root.setLevel(logging.WARNING)

    for pair in CONF.default_log_levels:
        mod, _sep, level_name = pair.partition('=')
        level = logging.getLevelName(level_name)
        logger = logging.getLogger(mod)
        logger.setLevel(level)

三、日志的使用

　　首先导入并获取logger

from nova.openstack.common import log as logging
LOG = logging.getLogger(__name__)

　　其中的LOG是经过openstack定制的logger，可见如下代码：

def getLogger(name='unknown', version='unknown'):
    if name not in _loggers:
        _loggers[name] = ContextAdapter(logging.getLogger(name),
                                        name,
                                        version)
    return _loggers[name]

class ContextAdapter(BaseLoggerAdapter):
    warn = logging.LoggerAdapter.warning

    def __init__(self, logger, project_name, version_string):
        self.logger = logger
        self.project = project_name
        self.version = version_string

　　接着就可以使用logger了，例如：

LOG.error(xxx)