flask中的日志使用方法

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1 日志应用场景

基于flask开发的应用程序通常有三类日志，按照一次HTTP请求的处理顺序依次为：

url handler处理HTTP请求时打印的地址
handler使用的类的方法打印的日志
flask的web server打印的HTTP请求和响应日志

@app.route('/')def handler_home():    logging.info('handler_home starts')    u = Util()    u.do_something()    logging.info('handler_home ends')    return 'hello world'class Util(object):    def do_something(self):        logging.info('Util do_something')INFO: 07-09 17:42:26: _internal.py:87 * 10348  * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)INFO: 07-09 17:42:30: app.py:20 * 10348 handler_home startsINFO: 07-09 17:42:30: app.py:16 * 10348 Util do_somethingINFO: 07-09 17:42:30: app.py:23 * 10348 handler_home endsINFO: 07-09 17:42:30: _internal.py:87 * 10348 127.0.0.1 - - [09/Jul/2016 17:42:30] "GET / HTTP/1

2 配置方法

在基于flask开发的应用中使用日志需要初始化两个logger：

flask的app对象自身有一个logger对象，它是用来打印HTTP请求响应日志，如果debug=True时还打印调试信息。这个日志是flask框架的内部代码自己打印的，业务代码不需要关心
业务代码（包括handler以及自己写的类中打印的日志）使用logging模块的logger对象，通过logging.{warn,info,debug}等接口打印即可。位于单独的py文件中的类，import logging即可。

例：日志handler为定时切割方式，flask和业务代码的日志也可以分别打印到不同的文件中。

import logif __name__ == '__main__':    log.init_log('./log/app') #初始化logging.logger    log.init_log('./log/app', app.logger) #初始化app.logger# log.pyimport osimport loggingimport logging.handlersdef init_log(log_path, logger=None, level=logging.INFO, when="D", backup=7,             format="%(levelname)s: %(asctime)s: %(filename)s:%(lineno)d * %(thread)d %(message)s",             datefmt="%m-%d %H:%M:%S"):    """    init_log - initialize log module    Args:      log_path      - Log file path prefix.                      Log data will go to two files: log_path.log and log_path.log.wf                      Any non-exist parent directories will be created automatically      logger        - default using logging.getLogger()      level         - msg above the level will be displayed                      DEBUG < INFO < WARNING < ERROR < CRITICAL                      the default value is logging.INFO      when          - how to split the log file by time interval                      'S' : Seconds                      'M' : Minutes                      'H' : Hours                      'D' : Days                      'W' : Week day                      default value: 'D'      format        - format of the log                      default format:                      %(levelname)s: %(asctime)s: %(filename)s:%(lineno)d * %(thread)d %(message)s                      INFO: 12-09 18:02:42: log.py:40 * 139814749787872 HELLO WORLD      backup        - how many backup file to keep                      default value: 7    Raises:        OSError: fail to create log directories        IOError: fail to open log file    """    formatter = logging.Formatter(format, datefmt)    if not logger:      logger = logging.getLogger()    logger.setLevel(level)    dir = os.path.dirname(log_path)    if not os.path.isdir(dir):        os.makedirs(dir)    handler = logging.handlers.TimedRotatingFileHandler(log_path + ".log",                                                        when=when,                                                        backupCount=backup)    handler.setLevel(level)    handler.setFormatter(formatter)    logger.addHandler(handler)    handler = logging.handlers.TimedRotatingFileHandler(log_path + ".log.wf",                                                        when=when,                                                        backupCount=backup)    handler.setLevel(logging.WARNING)    handler.setFormatter(formatter)    logger.addHandler(handler)

参考

Flask logging not working at all
Using Flask and native Python logging?

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