""" kombu.entity ================ Exchange and Queue declarations. :copyright: (c) 2009 - 2012 by Ask Solem. :license: BSD, see LICENSE for more details. """ from __future__ import absolute_import from .abstract import MaybeChannelBound TRANSIENT_DELIVERY_MODE = 1 PERSISTENT_DELIVERY_MODE = 2 DELIVERY_MODES = {'transient': TRANSIENT_DELIVERY_MODE, 'persistent': PERSISTENT_DELIVERY_MODE} __all__ = ['Exchange', 'Queue'] 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 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. This description of AMQP exchange types was shamelessly stolen from the blog post `AMQP in 10 minutes: Part 4`_ by Rajith Attapattu. This article is recommended reading. .. _`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 delivery_mode = PERSISTENT_DELIVERY_MODE attrs = (('name', None), ('type', None), ('arguments', None), ('durable', 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=False): """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`. """ 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 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 __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 False def __repr__(self): return super(Exchange, self).__repr__('Exchange %s(%s)' % (self.name, self.type)) @property def can_cache_declaration(self): return self.durable 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`. .. 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. """ 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)) def __init__(self, name='', exchange=None, routing_key='', channel=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 # exclusive implies auto-delete. if self.exclusive: self.auto_delete = True self.maybe_bind(channel) 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.""" if self.exchange: self.exchange.declare(nowait) self.queue_declare(nowait, passive=False) # self.name should be set by queue_declare in the case that # we're working with anonymous queues if self.name: self.queue_bind(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] return ret def queue_bind(self, nowait=False): """Create the queue binding on the server.""" return self.channel.queue_bind(queue=self.name, exchange=self.exchange.name, routing_key=self.routing_key, arguments=self.binding_arguments, nowait=nowait) def get(self, no_ack=None): """Poll the server for a new message. Returns the message instance if a message was available, or :const:`None` otherwise. :keyword no_ack: If set messages received does not have to be acknowledged. 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) 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 set messages received does not have to be acknowledged. :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 unbind(self): """Delete the binding on the server.""" return self.channel.queue_unbind(queue=self.name, exchange=self.exchange.name, routing_key=self.routing_key, arguments=self.binding_arguments) 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 False def __repr__(self): return super(Queue, self).__repr__( 'Queue %s -> %s -> %s' % (self.name, self.exchange, self.routing_key)) @property def can_cache_declaration(self): return self.durable @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') 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)