在龙卷风中"超时"请求的正确方法

Question

我设法编写了一个相当愚蠢的bug,它会让我的一个请求处理程序运行一个非常慢的数据库查询.

有趣的一点是,我注意到即使很长时间围攻完成龙卷风仍然在通过请求(有时90年后)搅拌.(评论 - >我不是100%确定Siege的工作方式,但我很确定它关闭了连接..)

我的问题分为两部分: - 当客户端关闭连接时,Tornado会取消请求处理程序吗？ - 有没有办法在Tornado中超时请求处理程序？

我通读了代码,似乎无法找到任何东西.即使我的请求处理程序在上面的错误中异步运行,待处理请求的数量也会增加到应用程序速度变慢的水平,最好关闭连接.

Answer 1

当客户端断开连接时,Tornado不会自动关闭请求处理程序.但是,您可以覆盖on_connection_close以在客户端丢弃时收到警报,这将允许您取消您的连接.可以使用上下文管理器(或装饰器)来处理设置超时以处理请求; 用于tornado.ioloop.IOLoop.add_timeout调度某个方法,该方法将请求timeout作为__enter__上下文管理器的一部分运行,然后__exit__在上下文管理器的块中取消该回调.这是一个展示这两个想法的例子:

import time
import contextlib

from tornado.ioloop import IOLoop
import tornado.web
from tornado import gen

@gen.coroutine
def async_sleep(timeout):
    yield gen.Task(IOLoop.instance().add_timeout, time.time() + timeout)

@contextlib.contextmanager
def auto_timeout(self, timeout=2): # Seconds
    handle = IOLoop.instance().add_timeout(time.time() + timeout, self.timed_out)
    try:
        yield handle
    except Exception as e:
        print("Caught %s" % e)
    finally:
        IOLoop.instance().remove_timeout(handle)
        if not self._timed_out:
            self.finish()
        else:
            raise Exception("Request timed out") # Don't continue on passed this point

class TimeoutableHandler(tornado.web.RequestHandler):
    def initialize(self):
        self._timed_out = False

    def timed_out(self):
        self._timed_out = True
        self.write("Request timed out!\n")
        self.finish()  # Connection to client closes here.
        # You might want to do other clean up here.

class MainHandler(TimeoutableHandler):

    @gen.coroutine
    def get(self):
        with auto_timeout(self): # We'll timeout after 2 seconds spent in this block.
            self.sleeper = async_sleep(5)
            yield self.sleeper
        print("writing")  # get will abort before we reach here if we timed out.
        self.write("hey\n")

    def on_connection_close(self):
        # This isn't the greatest way to cancel a future, since it will not actually
        # stop the work being done asynchronously. You'll need to cancel that some
        # other way. Should be pretty straightforward with a DB connection (close
        # the cursor/connection, maybe?)
        self.sleeper.set_exception(Exception("cancelled"))


application = tornado.web.Application([
    (r"/test", MainHandler),
])
application.listen(8888)
IOLoop.instance().start()