/usr/share/pyshared/carrot/backends/pyamqplib.py is in python-carrot 0.10.7-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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`amqplib`_ backend for carrot.
.. _`amqplib`: http://barryp.org/software/py-amqplib/
"""
from amqplib.client_0_8 import transport
# amqplib's handshake mistakenly identifies as protocol version 1191,
# this breaks in RabbitMQ tip, which no longer falls back to
# 0-8 for unknown ids.
transport.AMQP_PROTOCOL_HEADER = "AMQP\x01\x01\x08\x00"
from amqplib import client_0_8 as amqp
from amqplib.client_0_8.exceptions import AMQPChannelException
from amqplib.client_0_8.serialization import AMQPReader, AMQPWriter
from carrot.backends.base import BaseMessage, BaseBackend
from itertools import count
import warnings
import weakref
DEFAULT_PORT = 5672
class Connection(amqp.Connection):
def drain_events(self, allowed_methods=None, timeout=None):
"""Wait for an event on any channel."""
return self.wait_multi(self.channels.values(), timeout=timeout)
def wait_multi(self, channels, allowed_methods=None, timeout=None):
"""Wait for an event on a channel."""
chanmap = dict((chan.channel_id, chan) for chan in channels)
chanid, method_sig, args, content = self._wait_multiple(
chanmap.keys(), allowed_methods, timeout=timeout)
channel = chanmap[chanid]
if content \
and channel.auto_decode \
and hasattr(content, 'content_encoding'):
try:
content.body = content.body.decode(content.content_encoding)
except Exception:
pass
amqp_method = channel._METHOD_MAP.get(method_sig, None)
if amqp_method is None:
raise Exception('Unknown AMQP method (%d, %d)' % method_sig)
if content is None:
return amqp_method(channel, args)
else:
return amqp_method(channel, args, content)
def read_timeout(self, timeout=None):
if timeout is None:
return self.method_reader.read_method()
sock = self.transport.sock
prev = sock.gettimeout()
sock.settimeout(timeout)
try:
return self.method_reader.read_method()
finally:
sock.settimeout(prev)
def _wait_multiple(self, channel_ids, allowed_methods, timeout=None):
for channel_id in channel_ids:
method_queue = self.channels[channel_id].method_queue
for queued_method in method_queue:
method_sig = queued_method[0]
if (allowed_methods is None) \
or (method_sig in allowed_methods) \
or (method_sig == (20, 40)):
method_queue.remove(queued_method)
method_sig, args, content = queued_method
return channel_id, method_sig, args, content
# Nothing queued, need to wait for a method from the peer
while True:
channel, method_sig, args, content = self.read_timeout(timeout)
if (channel in channel_ids) \
and ((allowed_methods is None) \
or (method_sig in allowed_methods) \
or (method_sig == (20, 40))):
return channel, method_sig, args, content
# Not the channel and/or method we were looking for. Queue
# this method for later
self.channels[channel].method_queue.append((method_sig,
args,
content))
#
# If we just queued up a method for channel 0 (the Connection
# itself) it's probably a close method in reaction to some
# error, so deal with it right away.
#
if channel == 0:
self.wait()
class QueueAlreadyExistsWarning(UserWarning):
"""A queue with that name already exists, so a recently changed
``routing_key`` or other settings might be ignored unless you
rename the queue or restart the broker."""
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
for attr_name in ("body",
"delivery_tag",
"content_type",
"content_encoding",
"delivery_info"):
kwargs[attr_name] = getattr(amqp_message, attr_name, None)
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:
connection = self.connection.connection
self._channel_ref = weakref.ref(connection.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
return Connection(host=conninfo.host,
userid=conninfo.userid,
password=conninfo.password,
virtual_host=conninfo.virtual_host,
insist=conninfo.insist,
ssl=conninfo.ssl,
connect_timeout=conninfo.connect_timeout)
def close_connection(self, connection):
"""Close the AMQP broker connection."""
connection.close()
def queue_exists(self, queue):
"""Check if a queue has been declared.
:rtype bool:
"""
try:
self.channel.queue_declare(queue=queue, passive=True)
except AMQPChannelException, e:
if e.amqp_reply_code == 404:
return False
raise e
else:
return True
def queue_delete(self, queue, if_unused=False, if_empty=False):
"""Delete queue by name."""
return self.channel.queue_delete(queue, if_unused, if_empty)
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, arguments=None):
"""Declare a named queue."""
if warn_if_exists and self.queue_exists(queue):
warnings.warn(QueueAlreadyExistsWarning(
QueueAlreadyExistsWarning.__doc__))
return self.channel.queue_declare(queue=queue,
durable=durable,
exclusive=exclusive,
auto_delete=auto_delete,
arguments=arguments)
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,
nowait=nowait)
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.wait()
yield True
def cancel(self, consumer_tag):
"""Cancel a channel by consumer tag."""
if not self.channel.connection:
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."""
message = amqp.Message(message_data, priority=priority,
content_type=content_type,
content_encoding=content_encoding)
message.properties["delivery_mode"] = delivery_mode
return message
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."""
self.channel.basic_qos(prefetch_size, prefetch_count,
apply_global)
def flow(self, active):
"""Enable/disable flow from peer."""
self.channel.flow(active)
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