在龙卷风请求处理程序中处理错误的更好方法 [英] Better way to handle errors in tornado request handler
问题描述
有两个类似的处理程序:AgeHandler1 和 AgeHandler2.在第一个中，我们只是引发一个特定的异常以返回错误消息，在第二个中 - 我们手动返回一个错误消息.您如何看待这两种方法?对于大型项目，哪种方法更可取?还有其他最佳做法吗?
There are two similar handlers: AgeHandler1 and AgeHandler2. In the first one we simply raise a specific exception to return an error message, in the second - we manually return an error message. What You think about these two methods? Which method is preferable for a large project? Any other best practices?
import logging
import os.path
import traceback
from sys import exc_info
from tornado import web, options, ioloop
logger = logging.getLogger(__name__)
class MyAppException(Exception):
def __init__(self, message, code=400, *args, **kwargs):
self.message = message
self.code = code
return super(MyAppException, self).__init__(*args, **kwargs)
def __str__(self):
return self.message
class MyAppBaseHandler(web.RequestHandler):
def handle_exception(self, e):
exc_type, exc_obj, exc_tb = exc_info()
logger.error(''.join([line for line in traceback.format_exception(
exc_type, exc_obj, exc_tb)]))
if isinstance(exc_obj, MyAppException):
self.set_status(exc_obj.code)
self.write({'error': {
'message': u'{exc_obj}'.format(exc_obj=exc_obj.message)}})
else:
self.set_status(500)
fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
self.write({'error': {
'message': u'{exc_obj} in {fname} at {line}'.format(
exc_obj=exc_obj, fname=fname, line=exc_tb.tb_lineno)}})
class AgeHandler1(MyAppBaseHandler):
def get(self):
try:
age = self.get_argument('age')
age = int(age)
if age < 1 or age > 200:
raise MyAppException('Wrong age value.')
self.write('Your age is {age}'.format(age=age))
except Exception as e:
self.handle_exception(e)
class AgeHandler2(MyAppBaseHandler):
def get(self):
age = self.get_argument('age')
age = int(age)
if age < 1 or age > 200:
self.set_status(400)
self.write('Wrong age value.')
return
self.write('Your age is {age}'.format(age=age))
class MyApplication(web.Application):
def __init__(self, **kwargs):
kwargs['handlers'] = [
web.url(r'/age1', AgeHandler1, name='age1'),
web.url(r'/age2', AgeHandler2, name='age2'),
]
kwargs['debug'] = False
super(MyApplication, self).__init__(**kwargs)
if __name__ == '__main__':
options.parse_command_line()
application = MyApplication()
application.listen(5000)
ioloop.IOLoop.instance().start()
回复:
"""
http://127.0.0.1:5000/age1
500: {"error": {"message": "HTTP 400: Bad Request (Missing argument age) in app.py at 44"}}
---
http://127.0.0.1:5000/age1?age=10
200: Your age is 10
---
http://127.0.0.1:5000/age1?age=201
400: {"error": {"message": "Wrong age value."}}
---
http://127.0.0.1:5000/age1?age=abc
500: {"error": {"message": "invalid literal for int() with base 10: 'abc' in app.py at 45"}}
http://127.0.0.1:5000/age2
400: <html><title>400: Bad Request</title><body>400: Bad Request</body></html>
---
http://127.0.0.1:5000/age2?age=10
200: Your age is 10
---
http://127.0.0.1:5000/age2?age=201
400: Wrong age value.
---
http://127.0.0.1:5000/age2?age=abc]
500: <html><title>500: Internal Server Error</title><body>500: Internal Server Error</body></html>
"""
推荐答案
一般来说，最好的方法是覆盖 RequestHandler.write_error.这与您的第一种方法类似，但您不需要处理程序主体中的 try/except，因为 Tornado 将为您处理此问题.
In general the best approach is to override RequestHandler.write_error. This is similar to your first approach, but you don't need the try/except in the body of the handler because Tornado will handle this for you.
像第二个示例中的那些显式测试也不错，但以这种方式捕获所有可能的错误是不切实际的，因此您总是需要一些东西来处理未捕获的异常.
Explicit tests like those in your second example are also good, but it's impractical to catch all possible errors this way so you'll always need something to handle uncaught exceptions.
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