Unable to catch exception when reconnecting

[yuanmwang-wf]

I don't think it's possible to catch ExceededRetryCount when raised here by connection_lost because it's an isolated task that's never handled?

Example code

async def on_message(frame, message):
    print('on message')
    print(message)
    return True


async def on_error(err):
    print('on error')
    print(err)


async def main():
    client = AioStomp('localhost',
                      '61613',
                      reconnect_max_attempts=0,
                      error_handler=on_error)
    try:
        await client.connect()
    except Exception as e:
        print(repr(e))

    print('Got a connection')
    await asyncio.sleep(10)
    print('Subscribing')

    try:
        sub = client.subscribe('/topic/foo', handler=on_message)
        print(sub.destination)
    except Exception as e:
        print('Exception when subscribing')
        print(repr(e))

if __name__ == '__main__':
    io_loop = asyncio.get_event_loop()
    io_loop.run_until_complete(main())

If I start the broker, run this script then immediately kill the broker, I got stacktraces like this:

2019-02-05 09:34:36,075 - DEBUG - Using selector: KqueueSelector
2019-02-05 09:34:36,075 - DEBUG - connect
2019-02-05 09:34:36,075 - INFO - Connecting to stomp server: localhost:61613
2019-02-05 09:34:36,082 - INFO - Connected
Got a connection
2019-02-05 09:34:39,812 - DEBUG - connection lost
2019-02-05 09:34:39,812 - INFO - Connection lost, will retry.
2019-02-05 09:34:39,813 - INFO - Connecting to stomp server: localhost:61613
2019-02-05 09:34:39,813 - DEBUG - connection lost
2019-02-05 09:34:39,815 - INFO - Connecting to stomp server failed.
2019-02-05 09:34:39,815 - ERROR - All connections attempts failed.
2019-02-05 09:34:39,815 - ERROR - Task exception was never retrieved
future: <Task finished coro=<AioStomp._reconnect() done, defined at /Users/yuanwang/.virtualenvs/frugal-asyncio/lib/python3.7/site-packages/aiostomp/aiostomp.py:132> exception=ExceededRetryCount()>
Traceback (most recent call last):
  File "/Users/yuanwang/.virtualenvs/frugal-asyncio/lib/python3.7/site-packages/aiostomp/aiostomp.py", line 141, in _reconnect
    password=self._password)
  File "/Users/yuanwang/.virtualenvs/frugal-asyncio/lib/python3.7/site-packages/aiostomp/aiostomp.py", line 431, in connect
    ssl=self.ssl_context)
  File "/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py", line 952, in create_connection
    ', '.join(str(exc) for exc in exceptions)))
OSError: Multiple exceptions: [Errno 61] Connect call failed ('::1', 61613), [Errno 61] Connect call failed ('127.0.0.1', 61613)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/yuanwang/.virtualenvs/frugal-asyncio/lib/python3.7/site-packages/aiostomp/aiostomp.py", line 162, in _reconnect
    raise ExceededRetryCount()
aiostomp.errors.ExceededRetryCount
Subscribing
/topic/foo

For background info, what I'm trying to achieve is to catch exceptions like these because I'm trying to use it with Amazon MQ Active/Standby Broker so if it can't connect with one broker it'll need to try connect with the other broker.

Ideally I'd expect error_handler would be called with ExceededRetryCount when this happens, thoughts?

[pedrokiefer]

What do you think works best, calling error_handler or having a specific connection_error_handler?

[yuanmwang-wf]

Thanks! It doesn't really matter to me - they both make sense considering I can check the exception type in error_handler.

[pedrokiefer]

Do you think ExceededRetryCount should have a reference for the AioStomp instance?

[pedrokiefer]

@yuanmwang-wf can you please review #16 ?

[yuanmwang-wf]

Do you think ExceededRetryCount should have a reference for the AioStomp instance?

It would be nice to have for me, but not necessary.

@yuanmwang-wf can you please review #16 ?

Awesome! I'll pull it down and test locally.

[pedrokiefer]

I've added a .ref to ExceededRetryCount. If you have a better name, we can change it :)

[pedrokiefer]

I've just merged that branch to master. I'll add some docs / example on how to use it and then release a new version.

[yuanmwang-wf]

Sorry something came up and I got distracted, I just pulled the latest commit and confirmed it worked as expected. Thank you so much! 💯

[pedrokiefer]

@yuanmwang-wf just released version 1.4.2.