This document describes the current stable version of Celery (3.1). For development docs, go here.
Source code for kombu.entity
"""
kombu.entity
================
Exchange and Queue declarations.
"""
from __future__ import absolute_import
from .abstract import MaybeChannelBound, Object
from .exceptions import ContentDisallowed
from .five import string_t
from .serialization import prepare_accept_content
TRANSIENT_DELIVERY_MODE = 1
PERSISTENT_DELIVERY_MODE = 2
DELIVERY_MODES = {'transient': TRANSIENT_DELIVERY_MODE,
'persistent': PERSISTENT_DELIVERY_MODE}
__all__ = ['Exchange', 'Queue', 'binding']
def _reprstr(s):
s = repr(s)
if isinstance(s, string_t) and s.startswith("u'"):
return s[2:-1]
return s[1:-1]
def pretty_bindings(bindings):
return '[%s]' % (', '.join(map(str, bindings)))
class Exchange(MaybeChannelBound):
"""An Exchange declaration.
:keyword name: See :attr:`name`.
:keyword type: See :attr:`type`.
:keyword channel: See :attr:`channel`.
:keyword durable: See :attr:`durable`.
:keyword auto_delete: See :attr:`auto_delete`.
:keyword delivery_mode: See :attr:`delivery_mode`.
:keyword arguments: See :attr:`arguments`.
.. attribute:: name
Name of the exchange. Default is no name (the default exchange).
.. attribute:: type
*This description of AMQP exchange types was shamelessly stolen
from the blog post `AMQP in 10 minutes: Part 4`_ by
Rajith Attapattu. Reading this article is recommended if you're
new to amqp.*
"AMQP defines four default exchange types (routing algorithms) that
covers most of the common messaging use cases. An AMQP broker can
also define additional exchange types, so see your broker
manual for more information about available exchange types.
* `direct` (*default*)
Direct match between the routing key in the message, and the
routing criteria used when a queue is bound to this exchange.
* `topic`
Wildcard match between the routing key and the routing pattern
specified in the exchange/queue binding. The routing key is
treated as zero or more words delimited by `"."` and
supports special wildcard characters. `"*"` matches a
single word and `"#"` matches zero or more words.
* `fanout`
Queues are bound to this exchange with no arguments. Hence any
message sent to this exchange will be forwarded to all queues
bound to this exchange.
* `headers`
Queues are bound to this exchange with a table of arguments
containing headers and values (optional). A special argument
named "x-match" determines the matching algorithm, where
`"all"` implies an `AND` (all pairs must match) and
`"any"` implies `OR` (at least one pair must match).
:attr:`arguments` is used to specify the arguments.
.. _`AMQP in 10 minutes: Part 4`:
http://bit.ly/amqp-exchange-types
.. attribute:: channel
The channel the exchange is bound to (if bound).
.. attribute:: durable
Durable exchanges remain active when a server restarts. Non-durable
exchanges (transient exchanges) are purged when a server restarts.
Default is :const:`True`.
.. attribute:: auto_delete
If set, the exchange is deleted when all queues have finished
using it. Default is :const:`False`.
.. attribute:: delivery_mode
The default delivery mode used for messages. The value is an integer,
or alias string.
* 1 or `"transient"`
The message is transient. Which means it is stored in
memory only, and is lost if the server dies or restarts.
* 2 or "persistent" (*default*)
The message is persistent. Which means the message is
stored both in-memory, and on disk, and therefore
preserved if the server dies or restarts.
The default value is 2 (persistent).
.. attribute:: arguments
Additional arguments to specify when the exchange is declared.
"""
TRANSIENT_DELIVERY_MODE = TRANSIENT_DELIVERY_MODE
PERSISTENT_DELIVERY_MODE = PERSISTENT_DELIVERY_MODE
name = ''
type = 'direct'
durable = True
auto_delete = False
passive = False
delivery_mode = PERSISTENT_DELIVERY_MODE
attrs = (
('name', None),
('type', None),
('arguments', None),
('durable', bool),
('passive', bool),
('auto_delete', bool),
('delivery_mode', lambda m: DELIVERY_MODES.get(m) or m),
)
def __init__(self, name='', type='', channel=None, **kwargs):
super(Exchange, self).__init__(**kwargs)
self.name = name or self.name
self.type = type or self.type
self.maybe_bind(channel)
def __hash__(self):
return hash('E|%s' % (self.name, ))
def declare(self, nowait=False, passive=None):
"""Declare the exchange.
Creates the exchange on the broker.
:keyword nowait: If set the server will not respond, and a
response will not be waited for. Default is :const:`False`.
"""
passive = self.passive if passive is None else passive
if self.name:
return self.channel.exchange_declare(
exchange=self.name, type=self.type, durable=self.durable,
auto_delete=self.auto_delete, arguments=self.arguments,
nowait=nowait, passive=passive,
)
def bind_to(self, exchange='', routing_key='',
arguments=None, nowait=False, **kwargs):
"""Binds the exchange to another exchange.
:keyword nowait: If set the server will not respond, and the call
will not block waiting for a response. Default is :const:`False`.
"""
if isinstance(exchange, Exchange):
exchange = exchange.name
return self.channel.exchange_bind(destination=self.name,
source=exchange,
routing_key=routing_key,
nowait=nowait,
arguments=arguments)
def unbind_from(self, source='', routing_key='',
nowait=False, arguments=None):
"""Delete previously created exchange binding from the server."""
if isinstance(source, Exchange):
source = source.name
return self.channel.exchange_unbind(destination=self.name,
source=source,
routing_key=routing_key,
nowait=nowait,
arguments=arguments)
def Message(self, body, delivery_mode=None, priority=None,
content_type=None, content_encoding=None,
properties=None, headers=None):
"""Create message instance to be sent with :meth:`publish`.
:param body: Message body.
:keyword delivery_mode: Set custom delivery mode. Defaults
to :attr:`delivery_mode`.
:keyword priority: Message priority, 0 to 9. (currently not
supported by RabbitMQ).
:keyword content_type: The messages content_type. If content_type
is set, no serialization occurs as it is assumed this is either
a binary object, or you've done your own serialization.
Leave blank if using built-in serialization as our library
properly sets content_type.
:keyword content_encoding: The character set in which this object
is encoded. Use "binary" if sending in raw binary objects.
Leave blank if using built-in serialization as our library
properly sets content_encoding.
:keyword properties: Message properties.
:keyword headers: Message headers.
"""
properties = {} if properties is None else properties
dm = delivery_mode or self.delivery_mode
properties['delivery_mode'] = \
DELIVERY_MODES[dm] if (dm != 2 and dm != 1) else dm
return self.channel.prepare_message(body,
properties=properties,
priority=priority,
content_type=content_type,
content_encoding=content_encoding,
headers=headers)
def publish(self, message, routing_key=None, mandatory=False,
immediate=False, exchange=None):
"""Publish message.
:param message: :meth:`Message` instance to publish.
:param routing_key: Routing key.
:param mandatory: Currently not supported.
:param immediate: Currently not supported.
"""
exchange = exchange or self.name
return self.channel.basic_publish(message,
exchange=exchange,
routing_key=routing_key,
mandatory=mandatory,
immediate=immediate)
def delete(self, if_unused=False, nowait=False):
"""Delete the exchange declaration on server.
:keyword if_unused: Delete only if the exchange has no bindings.
Default is :const:`False`.
:keyword nowait: If set the server will not respond, and a
response will not be waited for. Default is :const:`False`.
"""
return self.channel.exchange_delete(exchange=self.name,
if_unused=if_unused,
nowait=nowait)
def binding(self, routing_key='', arguments=None, unbind_arguments=None):
return binding(self, routing_key, arguments, unbind_arguments)
def __eq__(self, other):
if isinstance(other, Exchange):
return (self.name == other.name and
self.type == other.type and
self.arguments == other.arguments and
self.durable == other.durable and
self.auto_delete == other.auto_delete and
self.delivery_mode == other.delivery_mode)
return NotImplemented
def __ne__(self, other):
return not self.__eq__(other)
def __repr__(self):
return super(Exchange, self).__repr__(str(self))
def __str__(self):
return 'Exchange %s(%s)' % (_reprstr(self.name) or repr(''), self.type)
@property
def can_cache_declaration(self):
return not self.auto_delete
class binding(Object):
"""Represents a queue or exchange binding.
:keyword exchange: Exchange to bind to.
:keyword routing_key: Routing key used as binding key.
:keyword arguments: Arguments for bind operation.
:keyword unbind_arguments: Arguments for unbind operation.
"""
attrs = (
('exchange', None),
('routing_key', None),
('arguments', None),
('unbind_arguments', None)
)
def __init__(self, exchange=None, routing_key='',
arguments=None, unbind_arguments=None):
self.exchange = exchange
self.routing_key = routing_key
self.arguments = arguments
self.unbind_arguments = unbind_arguments
def declare(self, channel, nowait=False):
"""Declare destination exchange."""
if self.exchange and self.exchange.name:
ex = self.exchange(channel)
ex.declare(nowait=nowait)
def bind(self, entity, nowait=False):
"""Bind entity to this binding."""
entity.bind_to(exchange=self.exchange,
routing_key=self.routing_key,
arguments=self.arguments,
nowait=nowait)
def unbind(self, entity, nowait=False):
"""Unbind entity from this binding."""
entity.unbind_from(self.exchange,
routing_key=self.routing_key,
arguments=self.unbind_arguments,
nowait=nowait)
def __repr__(self):
return '<binding: %s>' % (self, )
def __str__(self):
return '%s->%s' % (
_reprstr(self.exchange.name), _reprstr(self.routing_key),
)
class Queue(MaybeChannelBound):
"""A Queue declaration.
:keyword name: See :attr:`name`.
:keyword exchange: See :attr:`exchange`.
:keyword routing_key: See :attr:`routing_key`.
:keyword channel: See :attr:`channel`.
:keyword durable: See :attr:`durable`.
:keyword exclusive: See :attr:`exclusive`.
:keyword auto_delete: See :attr:`auto_delete`.
:keyword queue_arguments: See :attr:`queue_arguments`.
:keyword binding_arguments: See :attr:`binding_arguments`.
:keyword on_declared: See :attr:`on_declared`
.. attribute:: name
Name of the queue. Default is no name (default queue destination).
.. attribute:: exchange
The :class:`Exchange` the queue binds to.
.. attribute:: routing_key
The routing key (if any), also called *binding key*.
The interpretation of the routing key depends on
the :attr:`Exchange.type`.
* direct exchange
Matches if the routing key property of the message and
the :attr:`routing_key` attribute are identical.
* fanout exchange
Always matches, even if the binding does not have a key.
* topic exchange
Matches the routing key property of the message by a primitive
pattern matching scheme. The message routing key then consists
of words separated by dots (`"."`, like domain names), and
two special characters are available; star (`"*"`) and hash
(`"#"`). The star matches any word, and the hash matches
zero or more words. For example `"*.stock.#"` matches the
routing keys `"usd.stock"` and `"eur.stock.db"` but not
`"stock.nasdaq"`.
.. attribute:: channel
The channel the Queue is bound to (if bound).
.. attribute:: durable
Durable queues remain active when a server restarts.
Non-durable queues (transient queues) are purged if/when
a server restarts.
Note that durable queues do not necessarily hold persistent
messages, although it does not make sense to send
persistent messages to a transient queue.
Default is :const:`True`.
.. attribute:: exclusive
Exclusive queues may only be consumed from by the
current connection. Setting the 'exclusive' flag
always implies 'auto-delete'.
Default is :const:`False`.
.. attribute:: auto_delete
If set, the queue is deleted when all consumers have
finished using it. Last consumer can be cancelled
either explicitly or because its channel is closed. If
there was no consumer ever on the queue, it won't be
deleted.
.. attribute:: queue_arguments
Additional arguments used when declaring the queue.
.. attribute:: binding_arguments
Additional arguments used when binding the queue.
.. attribute:: alias
Unused in Kombu, but applications can take advantage of this.
For example to give alternate names to queues with automatically
generated queue names.
.. attribute:: on_declared
Optional callback to be applied when the queue has been
declared (the ``queue_declare`` operation is complete).
This must be a function with a signature that accepts at least 3
positional arguments: ``(name, messages, consumers)``.
"""
ContentDisallowed = ContentDisallowed
name = ''
exchange = Exchange('')
routing_key = ''
durable = True
exclusive = False
auto_delete = False
no_ack = False
attrs = (
('name', None),
('exchange', None),
('routing_key', None),
('queue_arguments', None),
('binding_arguments', None),
('durable', bool),
('exclusive', bool),
('auto_delete', bool),
('no_ack', None),
('alias', None),
('bindings', list),
)
def __init__(self, name='', exchange=None, routing_key='',
channel=None, bindings=None, on_declared=None,
**kwargs):
super(Queue, self).__init__(**kwargs)
self.name = name or self.name
self.exchange = exchange or self.exchange
self.routing_key = routing_key or self.routing_key
self.bindings = set(bindings or [])
self.on_declared = on_declared
# allows Queue('name', [binding(...), binding(...), ...])
if isinstance(exchange, (list, tuple, set)):
self.bindings |= set(exchange)
if self.bindings:
self.exchange = None
# exclusive implies auto-delete.
if self.exclusive:
self.auto_delete = True
self.maybe_bind(channel)
def bind(self, channel):
on_declared = self.on_declared
bound = super(Queue, self).bind(channel)
bound.on_declared = on_declared
return bound
def __hash__(self):
return hash('Q|%s' % (self.name, ))
def when_bound(self):
if self.exchange:
self.exchange = self.exchange(self.channel)
def declare(self, nowait=False):
"""Declares the queue, the exchange and binds the queue to
the exchange."""
# - declare main binding.
if self.exchange:
self.exchange.declare(nowait)
self.queue_declare(nowait, passive=False)
if self.exchange and self.exchange.name:
self.queue_bind(nowait)
# - declare extra/multi-bindings.
for B in self.bindings:
B.declare(self.channel)
B.bind(self, nowait=nowait)
return self.name
def queue_declare(self, nowait=False, passive=False):
"""Declare queue on the server.
:keyword nowait: Do not wait for a reply.
:keyword passive: If set, the server will not create the queue.
The client can use this to check whether a queue exists
without modifying the server state.
"""
ret = self.channel.queue_declare(queue=self.name,
passive=passive,
durable=self.durable,
exclusive=self.exclusive,
auto_delete=self.auto_delete,
arguments=self.queue_arguments,
nowait=nowait)
if not self.name:
self.name = ret[0]
if self.on_declared:
self.on_declared(*ret)
return ret
def queue_bind(self, nowait=False):
"""Create the queue binding on the server."""
return self.bind_to(self.exchange, self.routing_key,
self.binding_arguments, nowait=nowait)
def bind_to(self, exchange='', routing_key='',
arguments=None, nowait=False):
if isinstance(exchange, Exchange):
exchange = exchange.name
return self.channel.queue_bind(queue=self.name,
exchange=exchange,
routing_key=routing_key,
arguments=arguments,
nowait=nowait)
def get(self, no_ack=None, accept=None):
"""Poll the server for a new message.
Must return the message if a message was available,
or :const:`None` otherwise.
:keyword no_ack: If enabled the broker will automatically
ack messages.
:keyword accept: Custom list of accepted content types.
This method provides direct access to the messages in a
queue using a synchronous dialogue, designed for
specific types of applications where synchronous functionality
is more important than performance.
"""
no_ack = self.no_ack if no_ack is None else no_ack
message = self.channel.basic_get(queue=self.name, no_ack=no_ack)
if message is not None:
m2p = getattr(self.channel, 'message_to_python', None)
if m2p:
message = m2p(message)
if message.errors:
message._reraise_error()
message.accept = prepare_accept_content(accept)
return message
def purge(self, nowait=False):
"""Remove all ready messages from the queue."""
return self.channel.queue_purge(queue=self.name,
nowait=nowait) or 0
def consume(self, consumer_tag='', callback=None,
no_ack=None, nowait=False):
"""Start a queue consumer.
Consumers last as long as the channel they were created on, or
until the client cancels them.
:keyword consumer_tag: Unique identifier for the consumer. The
consumer tag is local to a connection, so two clients
can use the same consumer tags. If this field is empty
the server will generate a unique tag.
:keyword no_ack: If enabled the broker will automatically ack
messages.
:keyword nowait: Do not wait for a reply.
:keyword callback: callback called for each delivered message
"""
if no_ack is None:
no_ack = self.no_ack
return self.channel.basic_consume(queue=self.name,
no_ack=no_ack,
consumer_tag=consumer_tag or '',
callback=callback,
nowait=nowait)
def cancel(self, consumer_tag):
"""Cancel a consumer by consumer tag."""
return self.channel.basic_cancel(consumer_tag)
def delete(self, if_unused=False, if_empty=False, nowait=False):
"""Delete the queue.
:keyword if_unused: If set, the server will only delete the queue
if it has no consumers. A channel error will be raised
if the queue has consumers.
:keyword if_empty: If set, the server will only delete the queue
if it is empty. If it is not empty a channel error will be raised.
:keyword nowait: Do not wait for a reply.
"""
return self.channel.queue_delete(queue=self.name,
if_unused=if_unused,
if_empty=if_empty,
nowait=nowait)
def queue_unbind(self, arguments=None, nowait=False):
return self.unbind_from(self.exchange, self.routing_key,
arguments, nowait)
def unbind_from(self, exchange='', routing_key='',
arguments=None, nowait=False):
"""Unbind queue by deleting the binding from the server."""
return self.channel.queue_unbind(queue=self.name,
exchange=exchange.name,
routing_key=routing_key,
arguments=arguments,
nowait=nowait)
def __eq__(self, other):
if isinstance(other, Queue):
return (self.name == other.name and
self.exchange == other.exchange and
self.routing_key == other.routing_key and
self.queue_arguments == other.queue_arguments and
self.binding_arguments == other.binding_arguments and
self.durable == other.durable and
self.exclusive == other.exclusive and
self.auto_delete == other.auto_delete)
return NotImplemented
def __ne__(self, other):
return not self.__eq__(other)
def __repr__(self):
s = super(Queue, self).__repr__
if self.bindings:
return s('Queue {name} -> {bindings}'.format(
name=_reprstr(self.name),
bindings=pretty_bindings(self.bindings),
))
return s(
'Queue {name} -> {0.exchange!r} -> {routing_key}'.format(
self, name=_reprstr(self.name),
routing_key=_reprstr(self.routing_key),
),
)
@property
def can_cache_declaration(self):
return not self.auto_delete
@classmethod
def from_dict(self, queue, **options):
binding_key = options.get('binding_key') or options.get('routing_key')
e_durable = options.get('exchange_durable')
if e_durable is None:
e_durable = options.get('durable')
e_auto_delete = options.get('exchange_auto_delete')
if e_auto_delete is None:
e_auto_delete = options.get('auto_delete')
q_durable = options.get('queue_durable')
if q_durable is None:
q_durable = options.get('durable')
q_auto_delete = options.get('queue_auto_delete')
if q_auto_delete is None:
q_auto_delete = options.get('auto_delete')
e_arguments = options.get('exchange_arguments')
q_arguments = options.get('queue_arguments')
b_arguments = options.get('binding_arguments')
bindings = options.get('bindings')
exchange = Exchange(options.get('exchange'),
type=options.get('exchange_type'),
delivery_mode=options.get('delivery_mode'),
routing_key=options.get('routing_key'),
durable=e_durable,
auto_delete=e_auto_delete,
arguments=e_arguments)
return Queue(queue,
exchange=exchange,
routing_key=binding_key,
durable=q_durable,
exclusive=options.get('exclusive'),
auto_delete=q_auto_delete,
no_ack=options.get('no_ack'),
queue_arguments=q_arguments,
binding_arguments=b_arguments,
bindings=bindings)
def as_dict(self, recurse=False):
res = super(Queue, self).as_dict(recurse)
if not recurse:
return res
bindings = res.get('bindings')
if bindings:
res['bindings'] = [b.as_dict(recurse=True) for b in bindings]
return res
