oslo.messaging/oslo_messaging/_drivers/pika_driver/pika_poller.py

#    Copyright 2015 Mirantis, 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.

import threading
import time

from oslo_log import log as logging
import pika_pool
import retrying
import six

from oslo_messaging._drivers.pika_driver import pika_message as pika_drv_msg

LOG = logging.getLogger(__name__)


class PikaPoller(object):
    """Provides user friendly functionality for RabbitMQ message consuming,
    handles low level connectivity problems and restore connection if some
    connectivity related problem detected
    """

    def __init__(self, pika_engine, prefetch_count, incoming_message_class):
        """Initialize required fields

        :param pika_engine: PikaEngine, shared object with configuration and
            shared driver functionality
        :param prefetch_count: Integer, maximum count of unacknowledged
            messages which RabbitMQ broker sends to this consumer
        :param incoming_message_class: PikaIncomingMessage, wrapper for
            consumed RabbitMQ message
        """
        self._pika_engine = pika_engine
        self._prefetch_count = prefetch_count
        self._incoming_message_class = incoming_message_class

        self._connection = None
        self._channel = None
        self._lock = threading.Lock()

        self._started = False

        self._queues_to_consume = None

        self._message_queue = []

    def _reconnect(self):
        """Performs reconnection to the broker. It is unsafe method for
        internal use only
        """
        self._connection = self._pika_engine.create_connection(
            for_listening=True
        )
        self._channel = self._connection.channel()
        self._channel.basic_qos(prefetch_count=self._prefetch_count)

        if self._queues_to_consume is None:
            self._queues_to_consume = self._declare_queue_binding()

        for queue, no_ack in six.iteritems(self._queues_to_consume):
            self._start_consuming(queue, no_ack)

    def _declare_queue_binding(self):
        """Is called by recovering connection logic if target RabbitMQ
        exchange and (or) queue do not exist. Should be overridden in child
        classes

        :return Dictionary, declared_queue_name -> no_ack_mode
        """
        raise NotImplementedError(
            "It is base class. Please declare exchanges and queues here"
        )

    def _start_consuming(self, queue, no_ack):
        """Is called by recovering connection logic for starting consumption
        of the RabbitMQ queue

        :param queue: String, RabbitMQ queue name for consuming
        :param no_ack: Boolean, Choose consuming acknowledgement mode. If True,
            acknowledges are not needed. RabbitMQ considers message consumed
            after sending it to consumer immediately
        """
        on_message_no_ack_callback = (
            self._on_message_no_ack_callback if no_ack
            else self._on_message_with_ack_callback
        )

        try:
            self._channel.basic_consume(on_message_no_ack_callback, queue,
                                        no_ack=no_ack)
        except Exception:
            self._queues_to_consume = None
            raise

    def _on_message_no_ack_callback(self, unused, method, properties, body):
        """Is called by Pika when message was received from queue listened with
        no_ack=True mode
        """
        self._message_queue.append(
            self._incoming_message_class(
                self._pika_engine, None, method, properties, body
            )
        )

    def _on_message_with_ack_callback(self, unused, method, properties, body):
        """Is called by Pika when message was received from queue listened with
        no_ack=False mode
        """
        self._message_queue.append(
            self._incoming_message_class(
                self._pika_engine, self._channel, method, properties, body
            )
        )

    def _cleanup(self):
        """Cleanup allocated resources (channel, connection, etc). It is unsafe
        method for internal use only
        """
        if self._channel:
            try:
                self._channel.close()
            except Exception as ex:
                if not pika_pool.Connection.is_connection_invalidated(ex):
                    LOG.exception("Unexpected error during closing channel")
            self._channel = None

        if self._connection:
            try:
                self._connection.close()
            except Exception as ex:
                if not pika_pool.Connection.is_connection_invalidated(ex):
                    LOG.exception("Unexpected error during closing connection")
            self._connection = None

        for i in six.moves.range(len(self._message_queue) - 1, -1, -1):
            message = self._message_queue[i]
            if message.need_ack():
                del self._message_queue[i]

    def poll(self, timeout=None, prefetch_size=1):
        """Main method of this class - consumes message from RabbitMQ

        :param: timeout: float, seconds, timeout for waiting new incoming
            message, None means wait forever
        :param: prefetch_size:  Integer, count of messages which we are want to
            poll. It blocks until prefetch_size messages are consumed or until
            timeout gets expired
        :return: list of PikaIncomingMessage, RabbitMQ messages
        """
        expiration_time = time.time() + timeout if timeout else None

        while True:
            with self._lock:
                if timeout is not None:
                    timeout = expiration_time - time.time()
                if (len(self._message_queue) < prefetch_size and
                        self._started and ((timeout is None) or timeout > 0)):
                    try:
                        if self._channel is None:
                            self._reconnect()
                        # we need some time_limit here, not too small to avoid
                        # a lot of not needed iterations but not too large to
                        # release lock time to time and give a chance to
                        # perform another method waiting this lock
                        self._connection.process_data_events(
                            time_limit=0.25
                        )
                    except pika_pool.Connection.connectivity_errors:
                        self._cleanup()
                        raise
                else:
                    result = self._message_queue[:prefetch_size]
                    del self._message_queue[:prefetch_size]
                    return result

    def start(self):
        """Starts poller. Should be called before polling to allow message
        consuming
        """
        self._started = True

    def stop(self):
        """Stops poller. Should be called when polling is not needed anymore to
        stop new message consuming. After that it is necessary to poll already
        prefetched messages
        """
        with self._lock:
            if not self._started:
                return

            self._started = False

    def reconnect(self):
        """Safe version of _reconnect. Performs reconnection to the broker."""
        with self._lock:
            self._cleanup()
            try:
                self._reconnect()
            except Exception:
                self._cleanup()
                raise

    def cleanup(self):
        """Safe version of _cleanup. Cleans up allocated resources (channel,
        connection, etc).
        """
        with self._lock:
            self._cleanup()


class RpcServicePikaPoller(PikaPoller):
    """PikaPoller implementation for polling RPC messages. Overrides base
    functionality according to RPC specific
    """
    def __init__(self, pika_engine, target, prefetch_count):
        """Adds target parameter for declaring RPC specific exchanges and
        queues

        :param pika_engine: PikaEngine, shared object with configuration and
            shared driver functionality
        :param target: Target, oslo.messaging Target object which defines RPC
            endpoint
        :param prefetch_count: Integer, maximum count of unacknowledged
            messages which RabbitMQ broker sends to this consumer
        """
        self._target = target

        super(RpcServicePikaPoller, self).__init__(
            pika_engine, prefetch_count=prefetch_count,
            incoming_message_class=pika_drv_msg.RpcPikaIncomingMessage
        )

    def _declare_queue_binding(self):
        """Overrides base method and perform declaration of RabbitMQ exchanges
        and queues which correspond to oslo.messaging RPC target

        :return Dictionary, declared_queue_name -> no_ack_mode
        """
        queue_expiration = self._pika_engine.rpc_queue_expiration

        queues_to_consume = {}

        for no_ack in [True, False]:
            exchange = self._pika_engine.get_rpc_exchange_name(
                self._target.exchange, self._target.topic, False, no_ack
            )
            fanout_exchange = self._pika_engine.get_rpc_exchange_name(
                self._target.exchange, self._target.topic, True, no_ack
            )
            queue = self._pika_engine.get_rpc_queue_name(
                self._target.topic, None, no_ack
            )
            server_queue = self._pika_engine.get_rpc_queue_name(
                self._target.topic, self._target.server, no_ack
            )

            queues_to_consume[queue] = no_ack
            queues_to_consume[server_queue] = no_ack

            self._pika_engine.declare_queue_binding_by_channel(
                channel=self._channel, exchange=exchange, queue=queue,
                routing_key=queue, exchange_type='direct', durable=False,
                queue_expiration=queue_expiration
            )
            self._pika_engine.declare_queue_binding_by_channel(
                channel=self._channel, exchange=exchange, queue=server_queue,
                routing_key=server_queue, exchange_type='direct',
                queue_expiration=queue_expiration, durable=False
            )
            self._pika_engine.declare_queue_binding_by_channel(
                channel=self._channel, exchange=fanout_exchange, durable=False,
                queue=server_queue, routing_key="", exchange_type='fanout',
                queue_expiration=queue_expiration
            )
        return queues_to_consume


class RpcReplyPikaPoller(PikaPoller):
    """PikaPoller implementation for polling RPC reply messages. Overrides
    base functionality according to RPC reply specific
    """
    def __init__(self, pika_engine, exchange, queue, prefetch_count):
        """Adds exchange and queue parameter for declaring exchange and queue
        used for RPC reply delivery

        :param pika_engine: PikaEngine, shared object with configuration and
            shared driver functionality
        :param exchange: String, exchange name used for RPC reply delivery
        :param queue: String, queue name used for RPC reply delivery
        :param prefetch_count: Integer, maximum count of unacknowledged
            messages which RabbitMQ broker sends to this consumer
        """
        self._exchange = exchange
        self._queue = queue

        super(RpcReplyPikaPoller, self).__init__(
            pika_engine=pika_engine, prefetch_count=prefetch_count,
            incoming_message_class=pika_drv_msg.RpcReplyPikaIncomingMessage
        )

    def _declare_queue_binding(self):
        """Overrides base method and perform declaration of RabbitMQ exchange
        and queue used for RPC reply delivery

        :return Dictionary, declared_queue_name -> no_ack_mode
        """
        self._pika_engine.declare_queue_binding_by_channel(
            channel=self._channel,
            exchange=self._exchange, queue=self._queue,
            routing_key=self._queue, exchange_type='direct',
            queue_expiration=self._pika_engine.rpc_queue_expiration,
            durable=False
        )

        return {self._queue: False}

    def start(self, timeout=None):
        """Overrides default behaviour of start method. Base start method
        does not create connection to RabbitMQ during start method (uses
        lazy connecting during first poll method call). This class should be
        connected after start call to ensure that exchange and queue for reply
        delivery are created before RPC request sending
        """
        super(RpcReplyPikaPoller, self).start()

        def on_exception(ex):
            LOG.warn(str(ex))

            return True

        retrier = retrying.retry(
            stop_max_attempt_number=self._pika_engine.rpc_reply_retry_attempts,
            stop_max_delay=None if timeout is None else timeout * 1000,
            wait_fixed=self._pika_engine.rpc_reply_retry_delay * 1000,
            retry_on_exception=on_exception,
        )

        retrier(self.reconnect)()


class NotificationPikaPoller(PikaPoller):
    """PikaPoller implementation for polling Notification messages. Overrides
    base functionality according to Notification specific
    """
    def __init__(self, pika_engine, targets_and_priorities,
                 queue_name=None, prefetch_count=100):
        """Adds targets_and_priorities and queue_name parameter
        for declaring exchanges and queues used for notification delivery

        :param pika_engine: PikaEngine, shared object with configuration and
            shared driver functionality
        :param targets_and_priorities: list of (target, priority), defines
            default queue names for corresponding notification types
        :param queue: String, alternative queue name used for this poller
            instead of default queue name
        :param prefetch_count: Integer, maximum count of unacknowledged
            messages which RabbitMQ broker sends to this consumer
        """
        self._targets_and_priorities = targets_and_priorities
        self._queue_name = queue_name

        super(NotificationPikaPoller, self).__init__(
            pika_engine, prefetch_count=prefetch_count,
            incoming_message_class=pika_drv_msg.PikaIncomingMessage
        )

    def _declare_queue_binding(self):
        """Overrides base method and perform declaration of RabbitMQ exchanges
        and queues used for notification delivery

        :return Dictionary, declared_queue_name -> no_ack_mode
        """
        queues_to_consume = {}
        for target, priority in self._targets_and_priorities:
            routing_key = '%s.%s' % (target.topic, priority)
            queue = self._queue_name or routing_key
            self._pika_engine.declare_queue_binding_by_channel(
                channel=self._channel,
                exchange=(
                    target.exchange or
                    self._pika_engine.default_notification_exchange
                ),
                queue = queue,
                routing_key=routing_key,
                exchange_type='direct',
                queue_expiration=None,
                durable=self._pika_engine.notification_persistence,
            )
            queues_to_consume[queue] = False

        return queues_to_consume