
# Copyright 2011 OpenStack Foundation.
# All Rights Reserved.
# Copyright 2013 Red Hat, Inc.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""
Notification drivers for sending notifications via messaging.

The messaging drivers publish notification messages to notification
listeners.

The driver will block the notifier's thread until the notification message has
been passed to the messaging transport.  There is no guarantee that the
notification message will be consumed by a notification listener.

Notification messages are sent 'at-most-once' - ensuring that they are not
duplicated.

If the connection to the messaging service is not active when a notification is
sent this driver will block waiting for the connection to complete.  If the
connection fails to complete, the driver will try to re-establish that
connection. By default this will continue indefinitely until the connection
completes. However, the retry parameter can be used to have the notification
send fail with a MessageDeliveryFailure after the given number of retries.
"""

import logging

import oslo_messaging
from oslo_messaging.notify import notifier

LOG = logging.getLogger(__name__)


class MessagingDriver(notifier.Driver):

    """Send notifications using the 1.0 message format.

    This driver sends notifications over the configured messaging transport,
    but without any message envelope (also known as message format 1.0).

    This driver should only be used in cases where there are existing consumers
    deployed which do not support the 2.0 message format.
    """

    def __init__(self, conf, topics, transport, version=1.0):
        super(MessagingDriver, self).__init__(conf, topics, transport)
        self.version = version

    def notify(self, ctxt, message, priority, retry):
        priority = priority.lower()
        for topic in self.topics:
            target = oslo_messaging.Target(topic='%s.%s' % (topic, priority))
            try:
                self.transport._send_notification(target, ctxt, message,
                                                  version=self.version,
                                                  retry=retry)
            except Exception:
                LOG.exception("Could not send notification to %(topic)s. "
                              "Payload=%(message)s",
                              {'topic': topic, 'message': message})


class MessagingV2Driver(MessagingDriver):

    "Send notifications using the 2.0 message format."

    def __init__(self, conf, **kwargs):
        super(MessagingV2Driver, self).__init__(conf, version=2.0, **kwargs)
