Twisted reactor.callLater() 未被尝试捕获，仅在某些机器上除外

Question

我正在使用 Twisted python 并且代码基本上如下所示：

class TimeoutException(Exception):
    pass


def timeout(msg):
    raise TimeoutExpection(msg)

def create_timeout(len, msg):
    return reactor.callLater(len, timeout, msg)

在代码的其他地方...

try:
    timeout_call = create_timeout(10, "timeout")
    db_res = yield some_large_io_request()
except Exception as e:
    print e
    raise web.HTTPError(408) # cyclone error
else:
    if timeout_call.active():
        timeout_call.cancel()

这是运行在 Docker 容器中，但是在某些机器上，try except 有效，在其他机器上，我收到类型 TimeoutException 的未处理错误，但我仍然收到 408 .我不清楚how/why它是断断续续的，有什么想法吗？

Answer 1

reactor.callLaterreturns马上。它唯一做的就是安排一个函数在未来某个时间点被事件循环调用。

考虑：

from twisted.internet.task import react
from twisted.internet.defer import Deferred

def foo():
    raise Exception("oh no")

def main(reactor):
    try:
        call = reactor.callLater(0, foo)
    except:
        print("Handling an exception!")
    else:
        print("Not handling an exception at all.")
        print("Got {}".format(call))
    print("Goodbye.")
    return Deferred()

react(main, [])

这个程序总是产生这个输出：

Not handling an exception at all.
Got <DelayedCall 0x7fd082e28758 [-3.71932983398e-05s] called=0 cancelled=0 foo()>
Goodbye.
Unhandled Error
Traceback (most recent call last):
  File "/tmp/junk.py", line 18, in <module>
    react(main, [])
  File "/usr/lib/python2.7/dist-packages/twisted/internet/task.py", line 936, in react
    _reactor.run()
  File "/usr/lib/python2.7/dist-packages/twisted/internet/base.py", line 1195, in run
    self.mainLoop()
  File "/usr/lib/python2.7/dist-packages/twisted/internet/base.py", line 1204, in mainLoop
    self.runUntilCurrent()
--- <exception caught here> ---
  File "/usr/lib/python2.7/dist-packages/twisted/internet/base.py", line 825, in runUntilCurrent
    call.func(*call.args, **call.kw)
  File "/tmp/junk.py", line 5, in foo
    raise Exception("oh no")
exceptions.Exception: oh no

因此，您永远不能使用 try/except 来处理您使用 callLater 安排的函数引发的异常。

Twisted reactor.callLater() 未被尝试捕获，仅在某些机器上除外

Twisted reactor.callLater() not caught in try except only on some machines

python

twisted

try-except