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 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 log
if __name__ == '__main__':
log.init_log('./log/app')
log.init_log('./log/app', app.logger)
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)
参考
Flask logging not working at all
Using Flask and native Python logging? | 
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