python

Question

根据 documentation，假设我已经实例化了一个连接：

>>> import stomp
>>> c = stomp.Connection([('127.0.0.1', 62615)])
>>> c.start()
>>> c.connect('admin', 'password', wait=True)

如何监控它以便它在 c.is_connected == False 重新连接？

>>> reconnect_on_dead_connection(c)
...
>>> [1479749503] reconnected dead connection

Answer 1

您可以包装您的连接并检查它是否连接到每个呼叫。

import stomp


def reconnect(connection):
    """reconnect here"""


class ReconnectWrapper(object):
    def __init__(self, connection):
        self.__connection = connection

    def __getattr__(self, item):
        if not self.__connection.is_connected:
            reconnect(self.__connection)
        return getattr(self.__connection, item)


if __name__ == '__main__':
    c = stomp.Connection([('127.0.0.1', 62615)])
    c.start()
    c.connect('admin', 'password', wait=True)
    magic_connection = ReconnectWrapper(c)

测试：

from scratch_35 import ReconnectWrapper
import unittest
import mock


class TestReconnection(unittest.TestCase):

    def setUp(self):
        self.connection = mock.MagicMock()
        self.reconnect_patcher = mock.patch("scratch_35.reconnect")
        self.reconnect = self.reconnect_patcher.start()

    def tearDown(self):
        self.reconnect_patcher.stop()

    def test_pass_call_to_warapped_connection(self):
        connection = ReconnectWrapper(self.connection)
        connection.send("abc")
        self.reconnect.assert_not_called()
        self.connection.send.assert_called_once_with("abc")

    def test_reconnect_when_disconnected(self):
        self.connection.is_connected = False
        connection = ReconnectWrapper(self.connection)
        connection.send("abc")
        self.reconnect.assert_called_once_with(self.connection)
        self.connection.send.assert_called_once_with("abc")


if __name__ == '__main__':
    unittest.main()

结果：

..
----------------------------------------------------------------------
Ran 2 tests in 0.004s

OK

关键是魔术方法 __getatter__ 每次您尝试访问对象未提供的属性时都会调用它。有关方法 __getattr__ 的更多信息，您可以在文档 https://docs.python.org/2/reference/datamodel.html#object.getattr 中找到。

Answer 2

如果您使用 Stomp 作为发件人：

def reconnect_on_dead_connection(c):
    if c.is_connected():
        c.connect('admin', 'password', wait=True)

并在发送 Stomp 消息之前调用它。

如果您使用的是 ConnectionListener class 扩展，请使用 on_disconnected 回调重新连接。

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