python-3.x - 如何让 Flask 记录未处理异常中的链式异常？

Question

Python 3 引入了异常链，因此:

import logging

logger = logging.getLogger(__name__)

class MyException(Exception):
    pass

def blow_up():
    try:
        impossible = 42 / 0
    except ZeroDivisionError as zde:
        raise MyException('Uh oh!') from zde

try:
    blow_up()
except:
    logger.exception('It blew up!')

产生这个:

It blew up!
Traceback (most recent call last):
  File "ka-boom.py", line 10, in blow_up
    impossible = 42 / 0
ZeroDivisionError: division by zero

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "ka-boom.py", line 15, in <module>
    blow_up()
  File "ka-boom.py", line 12, in blow_up
    raise MyException('Uh oh!') from zde
MyException: Uh oh!

但是当在 Flask View 方法中抛出未处理的异常时，__cause__ 不会被记录，这使得调试变得困难。

我能做到:

@app.errorhandler(Exception)
def better_exception_handler(error):
    current_app.logger.exception('Whoopsie!')
    return 'Internal server error', 500

但是我觉得像这样捕捉所有的异常不太舒服，感觉不太优雅。有没有办法让 Flask 的内置异常处理程序记录链接的异常？

Answer 1

你能提供你正在使用的 Python 和 Flask 的版本吗？使用 Python 3.5.2 和 Flask 0.12.1 我明白你所说的应该发生什么。

from flask import Flask
app = Flask(__name__)


@app.route('/error')
def error_out():
    try:
        blow_up()
    except:
        app.logger.exception('it blew up!')
        return 'something went wrong'
    return 'everything is a-ok!'


def blow_up():
    try:
        impossible = 42 / 0
    except ZeroDivisionError as zde:
        raise MyExc('Uh oh!') from zde


class MyExc(Exception):
    pass


if __name__ == "__main__":
    app.run()

为我点击 localhost:5000/error 将在控制台中记录以下内容:

Seaking:flask-err rdbaker $ ~/.pyenv/versions/3.5.2/bin/python app.py 
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
[2017-05-15 12:19:52,229] ERROR in app: it blew up!
Traceback (most recent call last):
  File "app.py", line 21, in blow_up
    impossible = 42 / 0
ZeroDivisionError: division by zero

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "app.py", line 12, in error_out
    blow_up()
  File "app.py", line 23, in blow_up
    raise MyExc('Uh oh!') from zde
MyExc: Uh oh!
127.0.0.1 - - [15/May/2017 12:19:52] "GET /error HTTP/1.1" 200 -

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