如何用 gevent 捕获异常？答案

【问题标题】：How to catch an exception with gevent?如何用 gevent 捕获异常？
【发布时间】：2018-02-12 19:38:33
【问题描述】：

我有以下服务器在flask 之上运行gevent：

import gevent.monkey
gevent.monkey.patch_all()
import flask
import gevent.wsgi

app = flask.Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

gevent.wsgi.WSGIServer(('127.0.0.1', 5000), app, keyfile='my.key', certfile='my.cer').serve_forever()

调用https://127.0.0.1:5000 时运行良好，但调用http://127.0.0.1:5000 时崩溃。原因是在 HTTPS 上下文中未正确处理 HTTP 调用：

Traceback (most recent call last):
  File "C:\Users\aaa\AppData\Local\Programs\Python\Python35-32\lib\site-packages\gevent\greenlet.py", line 536, in run
    result = self._run(*self.args, **self.kwargs)
  File "C:\Users\aaa\AppData\Local\Programs\Python\Python35-32\lib\site-packages\gevent\baseserver.py", line 26, in _handle_and_close_when_done
    return handle(*args_tuple)
  File "C:\Users\aaa\AppData\Local\Programs\Python\Python35-32\lib\site-packages\gevent\server.py", line 173, in wrap_socket_and_handle
    ssl_socket = self.wrap_socket(client_socket, **self.ssl_args)
  File "C:\Users\aaa\AppData\Local\Programs\Python\Python35-32\lib\site-packages\gevent\_ssl3.py", line 646, in wrap_socket
    ciphers=ciphers)
  File "C:\Users\aaa\AppData\Local\Programs\Python\Python35-32\lib\site-packages\gevent\_ssl3.py", line 229, in __init__
    raise x
  File "C:\Users\aaa\AppData\Local\Programs\Python\Python35-32\lib\site-packages\gevent\_ssl3.py", line 225, in __init__
    self.do_handshake()
  File "C:\Users\aaa\AppData\Local\Programs\Python\Python35-32\lib\site-packages\gevent\_ssl3.py", line 549, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [SSL: HTTP_REQUEST] http request (_ssl.c:645)
Mon Sep  4 16:19:01 2017 <Greenlet at 0x4631c60: _handle_and_close_when_done(<bound method StreamServer.wrap_socket_and_handle , <bound method StreamServer.do_close of <WSGIServer, (<gevent._socket3.socket [closed]  object, fd=-1, )> failed with SSLError

在这样的循环中捕获异常的正确方法是什么 (.serve_forever())？

我尝试了天真

try:
    gevent.wsgi.WSGIServer(('127.0.0.1', 5000), app, keyfile='my.key', certfile='my.cer').serve_forever()
except Exception as e:
    print("got exception {e}".format(e=e))

但它没有被抓住（我挥手的印象是 serve_forever() 循环运行时，try/except 对还没有到位（永远不会）

【问题讨论】：

标签： python python-3.x flask exception-handling gevent

【解决方案1】：

您可以生成一个 greenlet 并将异常处理程序附加到它：

g = gevent.spawn(WSGIServer(...).serve_forever)
def exception_callback(g):
    """Process gevent exception"""
    try:
        g.get()
    except Exception as exc:
        pass

g.link_exception(exception_callback)

【讨论】：