python - reconnect stomp connection when dead

Question

As per the documentation, given that I've instantiated a connection:

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

How do I monitor it so that it reconnects on c.is_connected == False?

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

Answer 1

You can wrap your connection and check if its connected every call.

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)

Test:

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()

result:

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

OK

The key is magic method __getatter__ it's called everytime you try to access an attribute that is not provided by an object. More about method __getattr__ you can find in doucmentation https://docs.python.org/2/reference/datamodel.html#object.getattr .