This document is for Kombu's development version, which can be significantly different from previous releases. Get the stable docs here: 5.0.
Source code for kombu.entity
"""Exchange and Queue declarations."""
import numbers
from .abstract import MaybeChannelBound, Object
from .exceptions import ContentDisallowed
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', 'maybe_delivery_mode')
INTERNAL_EXCHANGE_PREFIX = ('amq.',)
def _reprstr(s):
s = repr(s)
if isinstance(s, str) and s.startswith("u'"):
return s[2:-1]
return s[1:-1]
def pretty_bindings(bindings):
return '[{}]'.format(', '.join(map(str, bindings)))
def maybe_delivery_mode(
v, modes=None, default=PERSISTENT_DELIVERY_MODE):
"""Get delivery mode by name (or none if undefined)."""
modes = DELIVERY_MODES if not modes else modes
if v:
return v if isinstance(v, numbers.Integral) else modes[v]
return default
[docs]class Exchange(MaybeChannelBound):
"""An Exchange declaration.
Arguments:
name (str): See :attr:`name`.
type (str): See :attr:`type`.
channel (kombu.Connection, ChannelT): See :attr:`channel`.
durable (bool): See :attr:`durable`.
auto_delete (bool): See :attr:`auto_delete`.
delivery_mode (enum): See :attr:`delivery_mode`.
arguments (Dict): See :attr:`arguments`.
no_declare (bool): See :attr:`no_declare`
Attributes:
name (str): Name of the exchange.
Default is no name (the default exchange).
type (str):
*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`:
https://bit.ly/2rcICv5
channel (ChannelT): The channel the exchange is bound to (if bound).
durable (bool): Durable exchanges remain active when a server restarts.
Non-durable exchanges (transient exchanges) are purged when a
server restarts. Default is :const:`True`.
auto_delete (bool): If set, the exchange is deleted when all queues
have finished using it. Default is :const:`False`.
delivery_mode (enum): 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).
arguments (Dict): Additional arguments to specify when the exchange
is declared.
no_declare (bool): Never declare this exchange
(:meth:`declare` does nothing).
"""
TRANSIENT_DELIVERY_MODE = TRANSIENT_DELIVERY_MODE
PERSISTENT_DELIVERY_MODE = PERSISTENT_DELIVERY_MODE
name = ''
type = 'direct'
durable = True
auto_delete = False
passive = False
delivery_mode = None
no_declare = False
attrs = (
('name', None),
('type', None),
('arguments', None),
('durable', bool),
('passive', bool),
('auto_delete', bool),
('delivery_mode', lambda m: DELIVERY_MODES.get(m) or m),
('no_declare', bool),
)
def __init__(self, name='', type='', channel=None, **kwargs):
super().__init__(**kwargs)
self.name = name or self.name
self.type = type or self.type
self.maybe_bind(channel)
def __hash__(self):
return hash(f'E|{self.name}')
def _can_declare(self):
return not self.no_declare and (
self.name and not self.name.startswith(
INTERNAL_EXCHANGE_PREFIX))
[docs] def declare(self, nowait=False, passive=None, channel=None):
"""Declare the exchange.
Creates the exchange on the broker, unless passive is set
in which case it will only assert that the exchange exists.
Argument:
nowait (bool): If set the server will not respond, and a
response will not be waited for. Default is :const:`False`.
"""
if self._can_declare():
passive = self.passive if passive is None else passive
return (channel or 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,
)
[docs] def bind_to(self, exchange='', routing_key='',
arguments=None, nowait=False, channel=None, **kwargs):
"""Bind the exchange to another exchange.
Arguments:
nowait (bool): 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 (channel or self.channel).exchange_bind(
destination=self.name,
source=exchange,
routing_key=routing_key,
nowait=nowait,
arguments=arguments,
)
[docs] def unbind_from(self, source='', routing_key='',
nowait=False, arguments=None, channel=None):
"""Delete previously created exchange binding from the server."""
if isinstance(source, Exchange):
source = source.name
return (channel or self.channel).exchange_unbind(
destination=self.name,
source=source,
routing_key=routing_key,
nowait=nowait,
arguments=arguments,
)
[docs] def Message(self, body, delivery_mode=None, properties=None, **kwargs):
"""Create message instance to be sent with :meth:`publish`.
Arguments:
body (Any): Message body.
delivery_mode (bool): Set custom delivery mode.
Defaults to :attr:`delivery_mode`.
priority (int): Message priority, 0 to broker configured
max priority, where higher is better.
content_type (str): 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.
content_encoding (str): 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.
properties (Dict): Message properties.
headers (Dict): Message headers.
"""
properties = {} if properties is None else properties
properties['delivery_mode'] = maybe_delivery_mode(self.delivery_mode)
if (isinstance(body, str) and
properties.get('content_encoding', None)) is None:
kwargs['content_encoding'] = 'utf-8'
return self.channel.prepare_message(
body,
properties=properties,
**kwargs)
[docs] def publish(self, message, routing_key=None, mandatory=False,
immediate=False, exchange=None):
"""Publish message.
Arguments:
message (Union[kombu.Message, str, bytes]):
Message to publish.
routing_key (str): Message routing key.
mandatory (bool): Currently not supported.
immediate (bool): Currently not supported.
"""
if isinstance(message, str):
message = self.Message(message)
exchange = exchange or self.name
return self.channel.basic_publish(
message,
exchange=exchange,
routing_key=routing_key,
mandatory=mandatory,
immediate=immediate,
)
[docs] def delete(self, if_unused=False, nowait=False):
"""Delete the exchange declaration on server.
Arguments:
if_unused (bool): Delete only if the exchange has no bindings.
Default is :const:`False`.
nowait (bool): 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)
[docs] 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 self._repr_entity(self)
def __str__(self):
return 'Exchange {}({})'.format(
_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.
Arguments:
exchange (Exchange): Exchange to bind to.
routing_key (str): Routing key used as binding key.
arguments (Dict): Arguments for bind operation.
unbind_arguments (Dict): 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:
self.exchange.declare(channel=channel, nowait=nowait)
def bind(self, entity, nowait=False, channel=None):
"""Bind entity to this binding."""
entity.bind_to(exchange=self.exchange,
routing_key=self.routing_key,
arguments=self.arguments,
nowait=nowait,
channel=channel)
def unbind(self, entity, nowait=False, channel=None):
"""Unbind entity from this binding."""
entity.unbind_from(self.exchange,
routing_key=self.routing_key,
arguments=self.unbind_arguments,
nowait=nowait,
channel=channel)
def __repr__(self):
return f'<binding: {self}>'
def __str__(self):
return '{}->{}'.format(
_reprstr(self.exchange.name), _reprstr(self.routing_key),
)
[docs]class Queue(MaybeChannelBound):
"""A Queue declaration.
Arguments:
name (str): See :attr:`name`.
exchange (Exchange, str): See :attr:`exchange`.
routing_key (str): See :attr:`routing_key`.
channel (kombu.Connection, ChannelT): See :attr:`channel`.
durable (bool): See :attr:`durable`.
exclusive (bool): See :attr:`exclusive`.
auto_delete (bool): See :attr:`auto_delete`.
queue_arguments (Dict): See :attr:`queue_arguments`.
binding_arguments (Dict): See :attr:`binding_arguments`.
consumer_arguments (Dict): See :attr:`consumer_arguments`.
no_declare (bool): See :attr:`no_declare`.
on_declared (Callable): See :attr:`on_declared`.
expires (float): See :attr:`expires`.
message_ttl (float): See :attr:`message_ttl`.
max_length (int): See :attr:`max_length`.
max_length_bytes (int): See :attr:`max_length_bytes`.
max_priority (int): See :attr:`max_priority`.
Attributes:
name (str): Name of the queue.
Default is no name (default queue destination).
exchange (Exchange): The :class:`Exchange` the queue binds to.
routing_key (str): 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"`.
channel (ChannelT): The channel the Queue is bound to (if bound).
durable (bool): 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`.
exclusive (bool): Exclusive queues may only be consumed from by the
current connection. Setting the 'exclusive' flag
always implies 'auto-delete'.
Default is :const:`False`.
auto_delete (bool): If set, the queue is deleted when all consumers
have finished using it. Last consumer can be canceled
either explicitly or because its channel is closed. If
there was no consumer ever on the queue, it won't be
deleted.
expires (float): Set the expiry time (in seconds) for when this
queue should expire.
The expiry time decides how long the queue can stay unused
before it's automatically deleted.
*Unused* means the queue has no consumers, the queue has not been
redeclared, and ``Queue.get`` has not been invoked for a duration
of at least the expiration period.
See https://www.rabbitmq.com/ttl.html#queue-ttl
**RabbitMQ extension**: Only available when using RabbitMQ.
message_ttl (float): Message time to live in seconds.
This setting controls how long messages can stay in the queue
unconsumed. If the expiry time passes before a message consumer
has received the message, the message is deleted and no consumer
will see the message.
See https://www.rabbitmq.com/ttl.html#per-queue-message-ttl
**RabbitMQ extension**: Only available when using RabbitMQ.
max_length (int): Set the maximum number of messages that the
queue can hold.
If the number of messages in the queue size exceeds this limit,
new messages will be dropped (or dead-lettered if a dead letter
exchange is active).
See https://www.rabbitmq.com/maxlength.html
**RabbitMQ extension**: Only available when using RabbitMQ.
max_length_bytes (int): Set the max size (in bytes) for the total
of messages in the queue.
If the total size of all the messages in the queue exceeds this
limit, new messages will be dropped (or dead-lettered if a dead
letter exchange is active).
**RabbitMQ extension**: Only available when using RabbitMQ.
max_priority (int): Set the highest priority number for this queue.
For example if the value is 10, then messages can delivered to
this queue can have a ``priority`` value between 0 and 10,
where 10 is the highest priority.
RabbitMQ queues without a max priority set will ignore
the priority field in the message, so if you want priorities
you need to set the max priority field to declare the queue
as a priority queue.
**RabbitMQ extension**: Only available when using RabbitMQ.
queue_arguments (Dict): Additional arguments used when declaring
the queue. Can be used to to set the arguments value
for RabbitMQ/AMQP's ``queue.declare``.
binding_arguments (Dict): Additional arguments used when binding
the queue. Can be used to to set the arguments value
for RabbitMQ/AMQP's ``queue.declare``.
consumer_arguments (Dict): Additional arguments used when consuming
from this queue. Can be used to to set the arguments value
for RabbitMQ/AMQP's ``basic.consume``.
alias (str): Unused in Kombu, but applications can take advantage
of this, for example to give alternate names to queues with
automatically generated queue names.
on_declared (Callable): 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)``.
no_declare (bool): Never declare this queue, nor related
entities (:meth:`declare` does nothing).
"""
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),
('consumer_arguments', None),
('durable', bool),
('exclusive', bool),
('auto_delete', bool),
('no_ack', None),
('alias', None),
('bindings', list),
('no_declare', bool),
('expires', float),
('message_ttl', float),
('max_length', int),
('max_length_bytes', int),
('max_priority', int)
)
def __init__(self, name='', exchange=None, routing_key='',
channel=None, bindings=None, on_declared=None,
**kwargs):
super().__init__(**kwargs)
self.name = name or self.name
if isinstance(exchange, str):
self.exchange = Exchange(exchange)
elif isinstance(exchange, Exchange):
self.exchange = 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)
[docs] def bind(self, channel):
on_declared = self.on_declared
bound = super().bind(channel)
bound.on_declared = on_declared
return bound
def __hash__(self):
return hash(f'Q|{self.name}')
[docs] def declare(self, nowait=False, channel=None):
"""Declare queue and exchange then binds queue to exchange."""
if not self.no_declare:
# - declare main binding.
self._create_exchange(nowait=nowait, channel=channel)
self._create_queue(nowait=nowait, channel=channel)
self._create_bindings(nowait=nowait, channel=channel)
return self.name
def _create_exchange(self, nowait=False, channel=None):
if self.exchange:
self.exchange.declare(nowait=nowait, channel=channel)
def _create_queue(self, nowait=False, channel=None):
self.queue_declare(nowait=nowait, passive=False, channel=channel)
if self.exchange and self.exchange.name:
self.queue_bind(nowait=nowait, channel=channel)
def _create_bindings(self, nowait=False, channel=None):
for B in self.bindings:
channel = channel or self.channel
B.declare(channel)
B.bind(self, nowait=nowait, channel=channel)
[docs] def queue_declare(self, nowait=False, passive=False, channel=None):
"""Declare queue on the server.
Arguments:
nowait (bool): Do not wait for a reply.
passive (bool): 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.
"""
channel = channel or self.channel
queue_arguments = channel.prepare_queue_arguments(
self.queue_arguments or {},
expires=self.expires,
message_ttl=self.message_ttl,
max_length=self.max_length,
max_length_bytes=self.max_length_bytes,
max_priority=self.max_priority,
)
ret = channel.queue_declare(
queue=self.name,
passive=passive,
durable=self.durable,
exclusive=self.exclusive,
auto_delete=self.auto_delete,
arguments=queue_arguments,
nowait=nowait,
)
if not self.name:
self.name = ret[0]
if self.on_declared:
self.on_declared(*ret)
return ret
[docs] def queue_bind(self, nowait=False, channel=None):
"""Create the queue binding on the server."""
return self.bind_to(self.exchange, self.routing_key,
self.binding_arguments,
channel=channel, nowait=nowait)
[docs] def bind_to(self, exchange='', routing_key='',
arguments=None, nowait=False, channel=None):
if isinstance(exchange, Exchange):
exchange = exchange.name
return (channel or self.channel).queue_bind(
queue=self.name,
exchange=exchange,
routing_key=routing_key,
arguments=arguments,
nowait=nowait,
)
[docs] def get(self, no_ack=None, accept=None):
"""Poll the server for a new message.
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.
Returns:
~kombu.Message: if a message was available,
or :const:`None` otherwise.
Arguments:
no_ack (bool): If enabled the broker will
automatically ack messages.
accept (Set[str]): Custom list of accepted content types.
"""
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
[docs] def purge(self, nowait=False):
"""Remove all ready messages from the queue."""
return self.channel.queue_purge(queue=self.name,
nowait=nowait) or 0
[docs] 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.
Arguments:
consumer_tag (str): 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.
no_ack (bool): If enabled the broker will automatically
ack messages.
nowait (bool): Do not wait for a reply.
callback (Callable): 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,
arguments=self.consumer_arguments)
[docs] def cancel(self, consumer_tag):
"""Cancel a consumer by consumer tag."""
return self.channel.basic_cancel(consumer_tag)
[docs] def delete(self, if_unused=False, if_empty=False, nowait=False):
"""Delete the queue.
Arguments:
if_unused (bool): 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.
if_empty (bool): If set, the server will only delete the queue if
it is empty. If it is not empty a channel error will be raised.
nowait (bool): Do not wait for a reply.
"""
return self.channel.queue_delete(queue=self.name,
if_unused=if_unused,
if_empty=if_empty,
nowait=nowait)
[docs] def queue_unbind(self, arguments=None, nowait=False, channel=None):
return self.unbind_from(self.exchange, self.routing_key,
arguments, nowait, channel)
[docs] def unbind_from(self, exchange='', routing_key='',
arguments=None, nowait=False, channel=None):
"""Unbind queue by deleting the binding from the server."""
return (channel or 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.consumer_arguments == other.consumer_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):
if self.bindings:
return self._repr_entity('Queue {name} -> {bindings}'.format(
name=_reprstr(self.name),
bindings=pretty_bindings(self.bindings),
))
return self._repr_entity(
'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):
if self.queue_arguments:
expiring_queue = "x-expires" in self.queue_arguments
else:
expiring_queue = False
return not expiring_queue and not self.auto_delete
[docs] @classmethod
def from_dict(cls, 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')
c_arguments = options.get('consumer_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,
consumer_arguments=c_arguments,
bindings=bindings)
[docs] def as_dict(self, recurse=False):
res = super().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
