1 日誌應用場景

基於flask開發的應用程式通常有三類日誌，按照一次HTTP請求的處理順序依次為：

1. url handler處理HTTP請求時列印的地址
2. handler使用的類的方法列印的日誌
3. flask的web server列印的HTTP請求和響應日誌

@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 starts
INFO: 07-09 17:42:30: app.py:16 * 10348 Util do_something
INFO: 07
 
-09 17:42:30: app.py:23 * 10348 handler_home ends
INFO: 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

在基於flask開發的應用中使用日誌需要初始化兩個logger：

1. flask的app物件自身有一個logger物件，它是用來列印HTTP請求響應日誌，如果debug=True時還列印除錯資訊。這個日誌是flask框架的內部程式碼自己列印的，業務程式碼不需要關心
2. 業務程式碼（包括handler以及自己寫的類中列印的日誌）使用logging模組的logger物件，通過logging.{warn,info,debug}等介面列印即可。位於單獨的py檔案中的類，import logging即可。

例：日誌handler為定時切割方式，flask和業務程式碼的日誌也可以分別列印到不同的檔案中。

import log
if __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.py
import os
import logging
import logging.handlers

def 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)

參考