rpc.server do not consume messages after message acknowledge failure

[QingchuanHao]

oslo_messaging._executors.impl_eventlet.py
def start(self):

    @excutils.forever_retry_uncaught_exceptions
    def _executor_thread():
        try:
         while self._running:
         incoming = self.listener.poll()
         if incoming is not None:
      self._dispatch(incoming)
        except greenlet.GreenletExit:
     return

class Connection did not a lot work to ensure the operation on a connection can recovered after a reconnection. But after we get the incoming message, connection error on message acknowledgement can be raised and caught by the excutils.forever_retry_uncaught_exceptions. At this time, do_consume will be False, which means connection will drain_events acrocss "registering" consumer on the queues. kombu.Connection.drain_events establish a connection instead of raising a connection error.
Kombu related code is listed below.
def drain_events(self, **kwargs):
    return self.transport.drain_events(self.connection, **kwargs)

@property
def connection(self):
    if not self._closed:
        if not self.connected:
            self.declared_entities.clear()
            self._default_channel = None
            self._connection = self._establish_connection()
            self._closed = False
        return self._connection