summaryrefslogtreecommitdiff
path: root/kombu/entity.py
blob: 5e6419ae6d297213704babe57943bbd964341d04 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
"""Exchange and Queue declarations."""

from __future__ import annotations

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


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))

    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,
            )

    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,
        )

    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,
        )

    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)

    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,
        )

    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)

    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),
        )


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)

    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}')

    def when_bound(self):
        if self.exchange:
            self.exchange = self.exchange(self.channel)

    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)

    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

    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)

    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,
        )

    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

    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.

        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)

    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.

        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)

    def queue_unbind(self, arguments=None, nowait=False, channel=None):
        return self.unbind_from(self.exchange, self.routing_key,
                                arguments, nowait, channel)

    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

    @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)

    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