/usr/share/pyshared/carrot/backends/librabbitmq.py is in python-carrot 0.10.7-1ubuntu1.
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`amqplib`_ backend for carrot.
.. _`amqplib`: http://barryp.org/software/py-amqplib/
"""
import pylibrabbitmq as amqp
from pylibrabbitmq import ChannelError, ConnectionError
from carrot.backends.base import BaseMessage, BaseBackend
from itertools import count
import warnings
import weakref
DEFAULT_PORT = 5672
class Message(BaseMessage):
"""A message received by the broker.
Usually you don't insantiate message objects yourself, but receive
them using a :class:`carrot.messaging.Consumer`.
:param backend: see :attr:`backend`.
:param amqp_message: see :attr:`_amqp_message`.
.. attribute:: body
The message body.
.. attribute:: delivery_tag
The message delivery tag, uniquely identifying this message.
.. attribute:: backend
The message backend used.
A subclass of :class:`carrot.backends.base.BaseBackend`.
.. attribute:: _amqp_message
A :class:`amqplib.client_0_8.basic_message.Message` instance.
This is a private attribute and should not be accessed by
production code.
"""
def __init__(self, backend, amqp_message, **kwargs):
self._amqp_message = amqp_message
self.backend = backend
kwargs["body"] = amqp_message.body
properties = amqp_message.properties
kwargs["content_type"] = properties["content_type"]
kwargs["content_encoding"] = properties["content_encoding"]
kwargs["delivery_info"] = amqp_message.delivery_info
kwargs["delivery_tag"] = amqp_message.delivery_info["delivery_tag"]
super(Message, self).__init__(backend, **kwargs)
class Backend(BaseBackend):
"""amqplib backend
:param connection: see :attr:`connection`.
.. attribute:: connection
A :class:`carrot.connection.BrokerConnection` instance. An established
connection to the broker.
"""
default_port = DEFAULT_PORT
Message = Message
def __init__(self, connection, **kwargs):
self.connection = connection
self.default_port = kwargs.get("default_port", self.default_port)
self._channel_ref = None
@property
def _channel(self):
return callable(self._channel_ref) and self._channel_ref()
@property
def channel(self):
"""If no channel exists, a new one is requested."""
if not self._channel:
self._channel_ref = weakref.ref(self.connection.get_channel())
return self._channel
def establish_connection(self):
"""Establish connection to the AMQP broker."""
conninfo = self.connection
if not conninfo.hostname:
raise KeyError("Missing hostname for AMQP connection.")
if conninfo.userid is None:
raise KeyError("Missing user id for AMQP connection.")
if conninfo.password is None:
raise KeyError("Missing password for AMQP connection.")
if not conninfo.port:
conninfo.port = self.default_port
conn = amqp.Connection(host=conninfo.hostname,
port=conninfo.port,
userid=conninfo.userid,
password=conninfo.password,
virtual_host=conninfo.virtual_host)
return conn
def close_connection(self, connection):
"""Close the AMQP broker connection."""
connection.close()
def queue_exists(self, queue):
return True
def queue_delete(self, queue, if_unused=False, if_empty=False):
"""Delete queue by name."""
pass
def queue_purge(self, queue, **kwargs):
"""Discard all messages in the queue. This will delete the messages
and results in an empty queue."""
return self.channel.queue_purge(queue=queue)
def queue_declare(self, queue, durable, exclusive, auto_delete,
warn_if_exists=False):
"""Declare a named queue."""
return self.channel.queue_declare(queue=queue,
durable=durable,
exclusive=exclusive,
auto_delete=auto_delete)
def exchange_declare(self, exchange, type, durable, auto_delete):
"""Declare an named exchange."""
return self.channel.exchange_declare(exchange=exchange,
type=type,
durable=durable,
auto_delete=auto_delete)
def queue_bind(self, queue, exchange, routing_key, arguments=None):
"""Bind queue to an exchange using a routing key."""
return self.channel.queue_bind(queue=queue,
exchange=exchange,
routing_key=routing_key,
arguments=arguments)
def message_to_python(self, raw_message):
"""Convert encoded message body back to a Python value."""
return self.Message(backend=self, amqp_message=raw_message)
def get(self, queue, no_ack=False):
"""Receive a message from a declared queue by name.
:returns: A :class:`Message` object if a message was received,
``None`` otherwise. If ``None`` was returned, it probably means
there was no messages waiting on the queue.
"""
raw_message = self.channel.basic_get(queue, no_ack=no_ack)
if not raw_message:
return None
return self.message_to_python(raw_message)
def declare_consumer(self, queue, no_ack, callback, consumer_tag,
nowait=False):
"""Declare a consumer."""
return self.channel.basic_consume(queue=queue,
no_ack=no_ack,
callback=callback,
consumer_tag=consumer_tag)
def consume(self, limit=None):
"""Returns an iterator that waits for one message at a time."""
for total_message_count in count():
if limit and total_message_count >= limit:
raise StopIteration
if not self.channel.is_open:
raise StopIteration
self.channel.conn.drain_events()
yield True
def cancel(self, consumer_tag):
"""Cancel a channel by consumer tag."""
if not self.channel.conn:
return
self.channel.basic_cancel(consumer_tag)
def close(self):
"""Close the channel if open."""
if self._channel and self._channel.is_open:
self._channel.close()
self._channel_ref = None
def ack(self, delivery_tag):
"""Acknowledge a message by delivery tag."""
return self.channel.basic_ack(delivery_tag)
def reject(self, delivery_tag):
"""Reject a message by deliver tag."""
return self.channel.basic_reject(delivery_tag, requeue=False)
def requeue(self, delivery_tag):
"""Reject and requeue a message by delivery tag."""
return self.channel.basic_reject(delivery_tag, requeue=True)
def prepare_message(self, message_data, delivery_mode, priority=None,
content_type=None, content_encoding=None):
"""Encapsulate data into a AMQP message."""
return amqp.Message(message_data, properties={
"delivery_mode": delivery_mode,
"priority": priority,
"content_type": content_type,
"content_encoding": content_encoding})
def publish(self, message, exchange, routing_key, mandatory=None,
immediate=None, headers=None):
"""Publish a message to a named exchange."""
if headers:
message.properties["headers"] = headers
ret = self.channel.basic_publish(message, exchange=exchange,
routing_key=routing_key,
mandatory=mandatory,
immediate=immediate)
if mandatory or immediate:
self.close()
def qos(self, prefetch_size, prefetch_count, apply_global=False):
"""Request specific Quality of Service."""
pass
#self.channel.basic_qos(prefetch_size, prefetch_count,
# apply_global)
def flow(self, active):
"""Enable/disable flow from peer."""
pass
#self.channel.flow(active)
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