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/ channel.py
"""AMQP Channels"""
# Copyright (C) 2007-2008 Barry Pederson <bp@barryp.org>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
from __future__ import absolute_import
import logging
from collections import defaultdict
from warnings import warn
from .abstract_channel import AbstractChannel
from .exceptions import (
ChannelError, ConsumerCancelled, NotConfirmed, error_for_code,
)
from .five import Queue
from .protocol import basic_return_t, queue_declare_ok_t
from .serialization import AMQPWriter
__all__ = ['Channel']
AMQP_LOGGER = logging.getLogger('amqp')
EXCHANGE_AUTODELETE_DEPRECATED = """\
The auto_delete flag for exchanges has been deprecated and will be removed
from py-amqp v1.5.0.\
"""
class VDeprecationWarning(DeprecationWarning):
pass
class Channel(AbstractChannel):
"""Work with channels
The channel class provides methods for a client to establish a
virtual connection - a channel - to a server and for both peers to
operate the virtual connection thereafter.
GRAMMAR::
channel = open-channel *use-channel close-channel
open-channel = C:OPEN S:OPEN-OK
use-channel = C:FLOW S:FLOW-OK
/ S:FLOW C:FLOW-OK
/ functional-class
close-channel = C:CLOSE S:CLOSE-OK
/ S:CLOSE C:CLOSE-OK
"""
def __init__(self, connection, channel_id=None, auto_decode=True):
"""Create a channel bound to a connection and using the specified
numeric channel_id, and open on the server.
The 'auto_decode' parameter (defaults to True), indicates
whether the library should attempt to decode the body
of Messages to a Unicode string if there's a 'content_encoding'
property for the message. If there's no 'content_encoding'
property, or the decode raises an Exception, the message body
is left as plain bytes.
"""
if channel_id:
connection._claim_channel_id(channel_id)
else:
channel_id = connection._get_free_channel_id()
AMQP_LOGGER.debug('using channel_id: %d', channel_id)
super(Channel, self).__init__(connection, channel_id)
self.is_open = False
self.active = True # Flow control
self.returned_messages = Queue()
self.callbacks = {}
self.cancel_callbacks = {}
self.auto_decode = auto_decode
self.events = defaultdict(set)
self.no_ack_consumers = set()
# set first time basic_publish_confirm is called
# and publisher confirms are enabled for this channel.
self._confirm_selected = False
if self.connection.confirm_publish:
self.basic_publish = self.basic_publish_confirm
self._x_open()
def _do_close(self):
"""Tear down this object, after we've agreed to close
with the server."""
AMQP_LOGGER.debug('Closed channel #%d', self.channel_id)
self.is_open = False
channel_id, self.channel_id = self.channel_id, None
connection, self.connection = self.connection, None
if connection:
connection.channels.pop(channel_id, None)
connection._avail_channel_ids.append(channel_id)
self.callbacks.clear()
self.cancel_callbacks.clear()
self.events.clear()
self.no_ack_consumers.clear()
def _do_revive(self):
self.is_open = False
self._x_open()
def close(self, reply_code=0, reply_text='', method_sig=(0, 0)):
"""Request a channel close
This method indicates that the sender wants to close the
channel. This may be due to internal conditions (e.g. a forced
shut-down) or due to an error handling a specific method, i.e.
an exception. When a close is due to an exception, the sender
provides the class and method id of the method which caused
the exception.
RULE:
After sending this method any received method except
Channel.Close-OK MUST be discarded.
RULE:
The peer sending this method MAY use a counter or timeout
to detect failure of the other peer to respond correctly
with Channel.Close-OK..
PARAMETERS:
reply_code: short
The reply code. The AMQ reply codes are defined in AMQ
RFC 011.
reply_text: shortstr
The localised reply text. This text can be logged as an
aid to resolving issues.
class_id: short
failing method class
When the close is provoked by a method exception, this
is the class of the method.
method_id: short
failing method ID
When the close is provoked by a method exception, this
is the ID of the method.
"""
try:
if not self.is_open or self.connection is None:
return
args = AMQPWriter()
args.write_short(reply_code)
args.write_shortstr(reply_text)
args.write_short(method_sig[0]) # class_id
args.write_short(method_sig[1]) # method_id
self._send_method((20, 40), args)
return self.wait(allowed_methods=[
(20, 40), # Channel.close
(20, 41), # Channel.close_ok
])
finally:
self.connection = None
def _close(self, args):
"""Request a channel close
This method indicates that the sender wants to close the
channel. This may be due to internal conditions (e.g. a forced
shut-down) or due to an error handling a specific method, i.e.
an exception. When a close is due to an exception, the sender
provides the class and method id of the method which caused
the exception.
RULE:
After sending this method any received method except
Channel.Close-OK MUST be discarded.
RULE:
The peer sending this method MAY use a counter or timeout
to detect failure of the other peer to respond correctly
with Channel.Close-OK..
PARAMETERS:
reply_code: short
The reply code. The AMQ reply codes are defined in AMQ
RFC 011.
reply_text: shortstr
The localised reply text. This text can be logged as an
aid to resolving issues.
class_id: short
failing method class
When the close is provoked by a method exception, this
is the class of the method.
method_id: short
failing method ID
When the close is provoked by a method exception, this
is the ID of the method.
"""
reply_code = args.read_short()
reply_text = args.read_shortstr()
class_id = args.read_short()
method_id = args.read_short()
self._send_method((20, 41))
self._do_revive()
raise error_for_code(
reply_code, reply_text, (class_id, method_id), ChannelError,
)
def _close_ok(self, args):
"""Confirm a channel close
This method confirms a Channel.Close method and tells the
recipient that it is safe to release resources for the channel
and close the socket.
RULE:
A peer that detects a socket closure without having
received a Channel.Close-Ok handshake method SHOULD log
the error.
"""
self._do_close()
def flow(self, active):
"""Enable/disable flow from peer
This method asks the peer to pause or restart the flow of
content data. This is a simple flow-control mechanism that a
peer can use to avoid oveflowing its queues or otherwise
finding itself receiving more messages than it can process.
Note that this method is not intended for window control. The
peer that receives a request to stop sending content should
finish sending the current content, if any, and then wait
until it receives a Flow restart method.
RULE:
When a new channel is opened, it is active. Some
applications assume that channels are inactive until
started. To emulate this behaviour a client MAY open the
channel, then pause it.
RULE:
When sending content data in multiple frames, a peer
SHOULD monitor the channel for incoming methods and
respond to a Channel.Flow as rapidly as possible.
RULE:
A peer MAY use the Channel.Flow method to throttle
incoming content data for internal reasons, for example,
when exchangeing data over a slower connection.
RULE:
The peer that requests a Channel.Flow method MAY
disconnect and/or ban a peer that does not respect the
request.
PARAMETERS:
active: boolean
start/stop content frames
If True, the peer starts sending content frames. If
False, the peer stops sending content frames.
"""
args = AMQPWriter()
args.write_bit(active)
self._send_method((20, 20), args)
return self.wait(allowed_methods=[
(20, 21), # Channel.flow_ok
])
def _flow(self, args):
"""Enable/disable flow from peer
This method asks the peer to pause or restart the flow of
content data. This is a simple flow-control mechanism that a
peer can use to avoid oveflowing its queues or otherwise
finding itself receiving more messages than it can process.
Note that this method is not intended for window control. The
peer that receives a request to stop sending content should
finish sending the current content, if any, and then wait
until it receives a Flow restart method.
RULE:
When a new channel is opened, it is active. Some
applications assume that channels are inactive until
started. To emulate this behaviour a client MAY open the
channel, then pause it.
RULE:
When sending content data in multiple frames, a peer
SHOULD monitor the channel for incoming methods and
respond to a Channel.Flow as rapidly as possible.
RULE:
A peer MAY use the Channel.Flow method to throttle
incoming content data for internal reasons, for example,
when exchangeing data over a slower connection.
RULE:
The peer that requests a Channel.Flow method MAY
disconnect and/or ban a peer that does not respect the
request.
PARAMETERS:
active: boolean
start/stop content frames
If True, the peer starts sending content frames. If
False, the peer stops sending content frames.
"""
self.active = args.read_bit()
self._x_flow_ok(self.active)
def _x_flow_ok(self, active):
"""Confirm a flow method
Confirms to the peer that a flow command was received and
processed.
PARAMETERS:
active: boolean
current flow setting
Confirms the setting of the processed flow method:
True means the peer will start sending or continue
to send content frames; False means it will not.
"""
args = AMQPWriter()
args.write_bit(active)
self._send_method((20, 21), args)
def _flow_ok(self, args):
"""Confirm a flow method
Confirms to the peer that a flow command was received and
processed.
PARAMETERS:
active: boolean
current flow setting
Confirms the setting of the processed flow method:
True means the peer will start sending or continue
to send content frames; False means it will not.
"""
return args.read_bit()
def _x_open(self):
"""Open a channel for use
This method opens a virtual connection (a channel).
RULE:
This method MUST NOT be called when the channel is already
open.
PARAMETERS:
out_of_band: shortstr (DEPRECATED)
out-of-band settings
Configures out-of-band transfers on this channel. The
syntax and meaning of this field will be formally
defined at a later date.
"""
if self.is_open:
return
args = AMQPWriter()
args.write_shortstr('') # out_of_band: deprecated
self._send_method((20, 10), args)
return self.wait(allowed_methods=[
(20, 11), # Channel.open_ok
])
def _open_ok(self, args):
"""Signal that the channel is ready
This method signals to the client that the channel is ready
for use.
"""
self.is_open = True
AMQP_LOGGER.debug('Channel open')
#############
#
# Exchange
#
#
# work with exchanges
#
# Exchanges match and distribute messages across queues.
# Exchanges can be configured in the server or created at runtime.
#
# GRAMMAR::
#
# exchange = C:DECLARE S:DECLARE-OK
# / C:DELETE S:DELETE-OK
#
# RULE:
#
# The server MUST implement the direct and fanout exchange
# types, and predeclare the corresponding exchanges named
# amq.direct and amq.fanout in each virtual host. The server
# MUST also predeclare a direct exchange to act as the default
# exchange for content Publish methods and for default queue
# bindings.
#
# RULE:
#
# The server SHOULD implement the topic exchange type, and
# predeclare the corresponding exchange named amq.topic in
# each virtual host.
#
# RULE:
#
# The server MAY implement the system exchange type, and
# predeclare the corresponding exchanges named amq.system in
# each virtual host. If the client attempts to bind a queue to
# the system exchange, the server MUST raise a connection
# exception with reply code 507 (not allowed).
#
def exchange_declare(self, exchange, type, passive=False, durable=False,
auto_delete=True, nowait=False, arguments=None):
"""Declare exchange, create if needed
This method creates an exchange if it does not already exist,
and if the exchange exists, verifies that it is of the correct
and expected class.
RULE:
The server SHOULD support a minimum of 16 exchanges per
virtual host and ideally, impose no limit except as
defined by available resources.
PARAMETERS:
exchange: shortstr
RULE:
Exchange names starting with "amq." are reserved
for predeclared and standardised exchanges. If
the client attempts to create an exchange starting
with "amq.", the server MUST raise a channel
exception with reply code 403 (access refused).
type: shortstr
exchange type
Each exchange belongs to one of a set of exchange
types implemented by the server. The exchange types
define the functionality of the exchange - i.e. how
messages are routed through it. It is not valid or
meaningful to attempt to change the type of an
existing exchange.
RULE:
If the exchange already exists with a different
type, the server MUST raise a connection exception
with a reply code 507 (not allowed).
RULE:
If the server does not support the requested
exchange type it MUST raise a connection exception
with a reply code 503 (command invalid).
passive: boolean
do not create exchange
If set, the server will not create the exchange. The
client can use this to check whether an exchange
exists without modifying the server state.
RULE:
If set, and the exchange does not already exist,
the server MUST raise a channel exception with
reply code 404 (not found).
durable: boolean
request a durable exchange
If set when creating a new exchange, the exchange will
be marked as durable. Durable exchanges remain active
when a server restarts. Non-durable exchanges
(transient exchanges) are purged if/when a server
restarts.
RULE:
The server MUST support both durable and transient
exchanges.
RULE:
The server MUST ignore the durable field if the
exchange already exists.
auto_delete: boolean
auto-delete when unused
If set, the exchange is deleted when all queues have
finished using it.
RULE:
The server SHOULD allow for a reasonable delay
between the point when it determines that an
exchange is not being used (or no longer used),
and the point when it deletes the exchange. At
the least it must allow a client to create an
exchange and then bind a queue to it, with a small
but non-zero delay between these two actions.
RULE:
The server MUST ignore the auto-delete field if
the exchange already exists.
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
arguments: table
arguments for declaration
A set of arguments for the declaration. The syntax and
semantics of these arguments depends on the server
implementation. This field is ignored if passive is
True.
"""
arguments = {} if arguments is None else arguments
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(exchange)
args.write_shortstr(type)
args.write_bit(passive)
args.write_bit(durable)
args.write_bit(auto_delete)
args.write_bit(False) # internal: deprecated
args.write_bit(nowait)
args.write_table(arguments)
self._send_method((40, 10), args)
if auto_delete:
warn(VDeprecationWarning(EXCHANGE_AUTODELETE_DEPRECATED))
if not nowait:
return self.wait(allowed_methods=[
(40, 11), # Channel.exchange_declare_ok
])
def _exchange_declare_ok(self, args):
"""Confirms an exchange declaration
This method confirms a Declare method and confirms the name of
the exchange, essential for automatically-named exchanges.
"""
pass
def exchange_delete(self, exchange, if_unused=False, nowait=False):
"""Delete an exchange
This method deletes an exchange. When an exchange is deleted
all queue bindings on the exchange are cancelled.
PARAMETERS:
exchange: shortstr
RULE:
The exchange MUST exist. Attempting to delete a
non-existing exchange causes a channel exception.
if_unused: boolean
delete only if unused
If set, the server will only delete the exchange if it
has no queue bindings. If the exchange has queue
bindings the server does not delete it but raises a
channel exception instead.
RULE:
If set, the server SHOULD delete the exchange but
only if it has no queue bindings.
RULE:
If set, the server SHOULD raise a channel
exception if the exchange is in use.
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
"""
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(exchange)
args.write_bit(if_unused)
args.write_bit(nowait)
self._send_method((40, 20), args)
if not nowait:
return self.wait(allowed_methods=[
(40, 21), # Channel.exchange_delete_ok
])
def _exchange_delete_ok(self, args):
"""Confirm deletion of an exchange
This method confirms the deletion of an exchange.
"""
pass
def exchange_bind(self, destination, source='', routing_key='',
nowait=False, arguments=None):
"""This method binds an exchange to an exchange.
RULE:
A server MUST allow and ignore duplicate bindings - that
is, two or more bind methods for a specific exchanges,
with identical arguments - without treating these as an
error.
RULE:
A server MUST allow cycles of exchange bindings to be
created including allowing an exchange to be bound to
itself.
RULE:
A server MUST not deliver the same message more than once
to a destination exchange, even if the topology of
exchanges and bindings results in multiple (even infinite)
routes to that exchange.
PARAMETERS:
reserved-1: short
destination: shortstr
Specifies the name of the destination exchange to
bind.
RULE:
A client MUST NOT be allowed to bind a non-
existent destination exchange.
RULE:
The server MUST accept a blank exchange name to
mean the default exchange.
source: shortstr
Specifies the name of the source exchange to bind.
RULE:
A client MUST NOT be allowed to bind a non-
existent source exchange.
RULE:
The server MUST accept a blank exchange name to
mean the default exchange.
routing-key: shortstr
Specifies the routing key for the binding. The routing
key is used for routing messages depending on the
exchange configuration. Not all exchanges use a
routing key - refer to the specific exchange
documentation.
no-wait: bit
arguments: table
A set of arguments for the binding. The syntax and
semantics of these arguments depends on the exchange
class.
"""
arguments = {} if arguments is None else arguments
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(destination)
args.write_shortstr(source)
args.write_shortstr(routing_key)
args.write_bit(nowait)
args.write_table(arguments)
self._send_method((40, 30), args)
if not nowait:
return self.wait(allowed_methods=[
(40, 31), # Channel.exchange_bind_ok
])
def exchange_unbind(self, destination, source='', routing_key='',
nowait=False, arguments=None):
"""This method unbinds an exchange from an exchange.
RULE:
If a unbind fails, the server MUST raise a connection
exception.
PARAMETERS:
reserved-1: short
destination: shortstr
Specifies the name of the destination exchange to
unbind.
RULE:
The client MUST NOT attempt to unbind an exchange
that does not exist from an exchange.
RULE:
The server MUST accept a blank exchange name to
mean the default exchange.
source: shortstr
Specifies the name of the source exchange to unbind.
RULE:
The client MUST NOT attempt to unbind an exchange
from an exchange that does not exist.
RULE:
The server MUST accept a blank exchange name to
mean the default exchange.
routing-key: shortstr
Specifies the routing key of the binding to unbind.
no-wait: bit
arguments: table
Specifies the arguments of the binding to unbind.
"""
arguments = {} if arguments is None else arguments
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(destination)
args.write_shortstr(source)
args.write_shortstr(routing_key)
args.write_bit(nowait)
args.write_table(arguments)
self._send_method((40, 40), args)
if not nowait:
return self.wait(allowed_methods=[
(40, 51), # Channel.exchange_unbind_ok
])
def _exchange_bind_ok(self, args):
"""Confirm bind successful
This method confirms that the bind was successful.
"""
pass
def _exchange_unbind_ok(self, args):
"""Confirm unbind successful
This method confirms that the unbind was successful.
"""
pass
#############
#
# Queue
#
#
# work with queues
#
# Queues store and forward messages. Queues can be configured in
# the server or created at runtime. Queues must be attached to at
# least one exchange in order to receive messages from publishers.
#
# GRAMMAR::
#
# queue = C:DECLARE S:DECLARE-OK
# / C:BIND S:BIND-OK
# / C:PURGE S:PURGE-OK
# / C:DELETE S:DELETE-OK
#
# RULE:
#
# A server MUST allow any content class to be sent to any
# queue, in any mix, and queue and delivery these content
# classes independently. Note that all methods that fetch
# content off queues are specific to a given content class.
#
def queue_bind(self, queue, exchange='', routing_key='',
nowait=False, arguments=None):
"""Bind queue to an exchange
This method binds a queue to an exchange. Until a queue is
bound it will not receive any messages. In a classic
messaging model, store-and-forward queues are bound to a dest
exchange and subscription queues are bound to a dest_wild
exchange.
RULE:
A server MUST allow ignore duplicate bindings - that is,
two or more bind methods for a specific queue, with
identical arguments - without treating these as an error.
RULE:
If a bind fails, the server MUST raise a connection
exception.
RULE:
The server MUST NOT allow a durable queue to bind to a
transient exchange. If the client attempts this the server
MUST raise a channel exception.
RULE:
Bindings for durable queues are automatically durable and
the server SHOULD restore such bindings after a server
restart.
RULE:
The server SHOULD support at least 4 bindings per queue,
and ideally, impose no limit except as defined by
available resources.
PARAMETERS:
queue: shortstr
Specifies the name of the queue to bind. If the queue
name is empty, refers to the current queue for the
channel, which is the last declared queue.
RULE:
If the client did not previously declare a queue,
and the queue name in this method is empty, the
server MUST raise a connection exception with
reply code 530 (not allowed).
RULE:
If the queue does not exist the server MUST raise
a channel exception with reply code 404 (not
found).
exchange: shortstr
The name of the exchange to bind to.
RULE:
If the exchange does not exist the server MUST
raise a channel exception with reply code 404 (not
found).
routing_key: shortstr
message routing key
Specifies the routing key for the binding. The
routing key is used for routing messages depending on
the exchange configuration. Not all exchanges use a
routing key - refer to the specific exchange
documentation. If the routing key is empty and the
queue name is empty, the routing key will be the
current queue for the channel, which is the last
declared queue.
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
arguments: table
arguments for binding
A set of arguments for the binding. The syntax and
semantics of these arguments depends on the exchange
class.
"""
arguments = {} if arguments is None else arguments
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(queue)
args.write_shortstr(exchange)
args.write_shortstr(routing_key)
args.write_bit(nowait)
args.write_table(arguments)
self._send_method((50, 20), args)
if not nowait:
return self.wait(allowed_methods=[
(50, 21), # Channel.queue_bind_ok
])
def _queue_bind_ok(self, args):
"""Confirm bind successful
This method confirms that the bind was successful.
"""
pass
def queue_unbind(self, queue, exchange, routing_key='',
nowait=False, arguments=None):
"""Unbind a queue from an exchange
This method unbinds a queue from an exchange.
RULE:
If a unbind fails, the server MUST raise a connection exception.
PARAMETERS:
queue: shortstr
Specifies the name of the queue to unbind.
RULE:
The client MUST either specify a queue name or have
previously declared a queue on the same channel
RULE:
The client MUST NOT attempt to unbind a queue that
does not exist.
exchange: shortstr
The name of the exchange to unbind from.
RULE:
The client MUST NOT attempt to unbind a queue from an
exchange that does not exist.
RULE:
The server MUST accept a blank exchange name to mean
the default exchange.
routing_key: shortstr
routing key of binding
Specifies the routing key of the binding to unbind.
arguments: table
arguments of binding
Specifies the arguments of the binding to unbind.
"""
arguments = {} if arguments is None else arguments
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(queue)
args.write_shortstr(exchange)
args.write_shortstr(routing_key)
args.write_table(arguments)
self._send_method((50, 50), args)
if not nowait:
return self.wait(allowed_methods=[
(50, 51), # Channel.queue_unbind_ok
])
def _queue_unbind_ok(self, args):
"""Confirm unbind successful
This method confirms that the unbind was successful.
"""
pass
def queue_declare(self, queue='', passive=False, durable=False,
exclusive=False, auto_delete=True, nowait=False,
arguments=None):
"""Declare queue, create if needed
This method creates or checks a queue. When creating a new
queue the client can specify various properties that control
the durability of the queue and its contents, and the level of
sharing for the queue.
RULE:
The server MUST create a default binding for a newly-
created queue to the default exchange, which is an
exchange of type 'direct'.
RULE:
The server SHOULD support a minimum of 256 queues per
virtual host and ideally, impose no limit except as
defined by available resources.
PARAMETERS:
queue: shortstr
RULE:
The queue name MAY be empty, in which case the
server MUST create a new queue with a unique
generated name and return this to the client in
the Declare-Ok method.
RULE:
Queue names starting with "amq." are reserved for
predeclared and standardised server queues. If
the queue name starts with "amq." and the passive
option is False, the server MUST raise a connection
exception with reply code 403 (access refused).
passive: boolean
do not create queue
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.
RULE:
If set, and the queue does not already exist, the
server MUST respond with a reply code 404 (not
found) and raise a channel exception.
durable: boolean
request a durable queue
If set when creating a new queue, the queue will be
marked as 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.
RULE:
The server MUST recreate the durable queue after a
restart.
RULE:
The server MUST support both durable and transient
queues.
RULE:
The server MUST ignore the durable field if the
queue already exists.
exclusive: boolean
request an exclusive queue
Exclusive queues may only be consumed from by the
current connection. Setting the 'exclusive' flag
always implies 'auto-delete'.
RULE:
The server MUST support both exclusive (private)
and non-exclusive (shared) queues.
RULE:
The server MUST raise a channel exception if
'exclusive' is specified and the queue already
exists and is owned by a different connection.
auto_delete: boolean
auto-delete queue when unused
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.
RULE:
The server SHOULD allow for a reasonable delay
between the point when it determines that a queue
is not being used (or no longer used), and the
point when it deletes the queue. At the least it
must allow a client to create a queue and then
create a consumer to read from it, with a small
but non-zero delay between these two actions. The
server should equally allow for clients that may
be disconnected prematurely, and wish to re-
consume from the same queue without losing
messages. We would recommend a configurable
timeout, with a suitable default value being one
minute.
RULE:
The server MUST ignore the auto-delete field if
the queue already exists.
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
arguments: table
arguments for declaration
A set of arguments for the declaration. The syntax and
semantics of these arguments depends on the server
implementation. This field is ignored if passive is
True.
Returns a tuple containing 3 items:
the name of the queue (essential for automatically-named queues)
message count
consumer count
"""
arguments = {} if arguments is None else arguments
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(queue)
args.write_bit(passive)
args.write_bit(durable)
args.write_bit(exclusive)
args.write_bit(auto_delete)
args.write_bit(nowait)
args.write_table(arguments)
self._send_method((50, 10), args)
if not nowait:
return self.wait(allowed_methods=[
(50, 11), # Channel.queue_declare_ok
])
def _queue_declare_ok(self, args):
"""Confirms a queue definition
This method confirms a Declare method and confirms the name of
the queue, essential for automatically-named queues.
PARAMETERS:
queue: shortstr
Reports the name of the queue. If the server generated
a queue name, this field contains that name.
message_count: long
number of messages in queue
Reports the number of messages in the queue, which
will be zero for newly-created queues.
consumer_count: long
number of consumers
Reports the number of active consumers for the queue.
Note that consumers can suspend activity
(Channel.Flow) in which case they do not appear in
this count.
"""
return queue_declare_ok_t(
args.read_shortstr(),
args.read_long(),
args.read_long(),
)
def queue_delete(self, queue='',
if_unused=False, if_empty=False, nowait=False):
"""Delete a queue
This method deletes a queue. When a queue is deleted any
pending messages are sent to a dead-letter queue if this is
defined in the server configuration, and all consumers on the
queue are cancelled.
RULE:
The server SHOULD use a dead-letter queue to hold messages
that were pending on a deleted queue, and MAY provide
facilities for a system administrator to move these
messages back to an active queue.
PARAMETERS:
queue: shortstr
Specifies the name of the queue to delete. If the
queue name is empty, refers to the current queue for
the channel, which is the last declared queue.
RULE:
If the client did not previously declare a queue,
and the queue name in this method is empty, the
server MUST raise a connection exception with
reply code 530 (not allowed).
RULE:
The queue must exist. Attempting to delete a non-
existing queue causes a channel exception.
if_unused: boolean
delete only if unused
If set, the server will only delete the queue if it
has no consumers. If the queue has consumers the
server does does not delete it but raises a channel
exception instead.
RULE:
The server MUST respect the if-unused flag when
deleting a queue.
if_empty: boolean
delete only if empty
If set, the server will only delete the queue if it
has no messages. If the queue is not empty the server
raises a channel exception.
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
"""
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(queue)
args.write_bit(if_unused)
args.write_bit(if_empty)
args.write_bit(nowait)
self._send_method((50, 40), args)
if not nowait:
return self.wait(allowed_methods=[
(50, 41), # Channel.queue_delete_ok
])
def _queue_delete_ok(self, args):
"""Confirm deletion of a queue
This method confirms the deletion of a queue.
PARAMETERS:
message_count: long
number of messages purged
Reports the number of messages purged.
"""
return args.read_long()
def queue_purge(self, queue='', nowait=False):
"""Purge a queue
This method removes all messages from a queue. It does not
cancel consumers. Purged messages are deleted without any
formal "undo" mechanism.
RULE:
A call to purge MUST result in an empty queue.
RULE:
On transacted channels the server MUST not purge messages
that have already been sent to a client but not yet
acknowledged.
RULE:
The server MAY implement a purge queue or log that allows
system administrators to recover accidentally-purged
messages. The server SHOULD NOT keep purged messages in
the same storage spaces as the live messages since the
volumes of purged messages may get very large.
PARAMETERS:
queue: shortstr
Specifies the name of the queue to purge. If the
queue name is empty, refers to the current queue for
the channel, which is the last declared queue.
RULE:
If the client did not previously declare a queue,
and the queue name in this method is empty, the
server MUST raise a connection exception with
reply code 530 (not allowed).
RULE:
The queue must exist. Attempting to purge a non-
existing queue causes a channel exception.
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
if nowait is False, returns a message_count
"""
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(queue)
args.write_bit(nowait)
self._send_method((50, 30), args)
if not nowait:
return self.wait(allowed_methods=[
(50, 31), # Channel.queue_purge_ok
])
def _queue_purge_ok(self, args):
"""Confirms a queue purge
This method confirms the purge of a queue.
PARAMETERS:
message_count: long
number of messages purged
Reports the number of messages purged.
"""
return args.read_long()
#############
#
# Basic
#
#
# work with basic content
#
# The Basic class provides methods that support an industry-
# standard messaging model.
#
# GRAMMAR::
#
# basic = C:QOS S:QOS-OK
# / C:CONSUME S:CONSUME-OK
# / C:CANCEL S:CANCEL-OK
# / C:PUBLISH content
# / S:RETURN content
# / S:DELIVER content
# / C:GET ( S:GET-OK content / S:GET-EMPTY )
# / C:ACK
# / C:REJECT
#
# RULE:
#
# The server SHOULD respect the persistent property of basic
# messages and SHOULD make a best-effort to hold persistent
# basic messages on a reliable storage mechanism.
#
# RULE:
#
# The server MUST NOT discard a persistent basic message in
# case of a queue overflow. The server MAY use the
# Channel.Flow method to slow or stop a basic message
# publisher when necessary.
#
# RULE:
#
# The server MAY overflow non-persistent basic messages to
# persistent storage and MAY discard or dead-letter non-
# persistent basic messages on a priority basis if the queue
# size exceeds some configured limit.
#
# RULE:
#
# The server MUST implement at least 2 priority levels for
# basic messages, where priorities 0-4 and 5-9 are treated as
# two distinct levels. The server MAY implement up to 10
# priority levels.
#
# RULE:
#
# The server MUST deliver messages of the same priority in
# order irrespective of their individual persistence.
#
# RULE:
#
# The server MUST support both automatic and explicit
# acknowledgements on Basic content.
#
def basic_ack(self, delivery_tag, multiple=False):
"""Acknowledge one or more messages
This method acknowledges one or more messages delivered via
the Deliver or Get-Ok methods. The client can ask to confirm
a single message or a set of messages up to and including a
specific message.
PARAMETERS:
delivery_tag: longlong
server-assigned delivery tag
The server-assigned and channel-specific delivery tag
RULE:
The delivery tag is valid only within the channel
from which the message was received. I.e. a client
MUST NOT receive a message on one channel and then
acknowledge it on another.
RULE:
The server MUST NOT use a zero value for delivery
tags. Zero is reserved for client use, meaning "all
messages so far received".
multiple: boolean
acknowledge multiple messages
If set to True, the delivery tag is treated as "up to
and including", so that the client can acknowledge
multiple messages with a single method. If set to
False, the delivery tag refers to a single message.
If the multiple field is True, and the delivery tag
is zero, tells the server to acknowledge all
outstanding mesages.
RULE:
The server MUST validate that a non-zero delivery-
tag refers to an delivered message, and raise a
channel exception if this is not the case.
"""
args = AMQPWriter()
args.write_longlong(delivery_tag)
args.write_bit(multiple)
self._send_method((60, 80), args)
def basic_cancel(self, consumer_tag, nowait=False):
"""End a queue consumer
This method cancels a consumer. This does not affect already
delivered messages, but it does mean the server will not send
any more messages for that consumer. The client may receive
an abitrary number of messages in between sending the cancel
method and receiving the cancel-ok reply.
RULE:
If the queue no longer exists when the client sends a
cancel command, or the consumer has been cancelled for
other reasons, this command has no effect.
PARAMETERS:
consumer_tag: shortstr
consumer tag
Identifier for the consumer, valid within the current
connection.
RULE:
The consumer tag is valid only within the channel
from which the consumer was created. I.e. a client
MUST NOT create a consumer in one channel and then
use it in another.
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
"""
if self.connection is not None:
self.no_ack_consumers.discard(consumer_tag)
args = AMQPWriter()
args.write_shortstr(consumer_tag)
args.write_bit(nowait)
self._send_method((60, 30), args)
return self.wait(allowed_methods=[
(60, 31), # Channel.basic_cancel_ok
])
def _basic_cancel_notify(self, args):
"""Consumer cancelled by server.
Most likely the queue was deleted.
"""
consumer_tag = args.read_shortstr()
callback = self._on_cancel(consumer_tag)
if callback:
callback(consumer_tag)
else:
raise ConsumerCancelled(consumer_tag, (60, 30))
def _basic_cancel_ok(self, args):
"""Confirm a cancelled consumer
This method confirms that the cancellation was completed.
PARAMETERS:
consumer_tag: shortstr
consumer tag
Identifier for the consumer, valid within the current
connection.
RULE:
The consumer tag is valid only within the channel
from which the consumer was created. I.e. a client
MUST NOT create a consumer in one channel and then
use it in another.
"""
consumer_tag = args.read_shortstr()
self._on_cancel(consumer_tag)
def _on_cancel(self, consumer_tag):
self.callbacks.pop(consumer_tag, None)
return self.cancel_callbacks.pop(consumer_tag, None)
def basic_consume(self, queue='', consumer_tag='', no_local=False,
no_ack=False, exclusive=False, nowait=False,
callback=None, arguments=None, on_cancel=None):
"""Start a queue consumer
This method asks the server to start a "consumer", which is a
transient request for messages from a specific queue.
Consumers last as long as the channel they were created on, or
until the client cancels them.
RULE:
The server SHOULD support at least 16 consumers per queue,
unless the queue was declared as private, and ideally,
impose no limit except as defined by available resources.
PARAMETERS:
queue: shortstr
Specifies the name of the queue to consume from. If
the queue name is null, refers to the current queue
for the channel, which is the last declared queue.
RULE:
If the client did not previously declare a queue,
and the queue name in this method is empty, the
server MUST raise a connection exception with
reply code 530 (not allowed).
consumer_tag: shortstr
Specifies the 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.
RULE:
The tag MUST NOT refer to an existing consumer. If
the client attempts to create two consumers with
the same non-empty tag the server MUST raise a
connection exception with reply code 530 (not
allowed).
no_local: boolean
do not deliver own messages
If the no-local field is set the server will not send
messages to the client that published them.
no_ack: boolean
no acknowledgement needed
If this field is set the server does not expect
acknowledgments for messages. That is, when a message
is delivered to the client the server automatically and
silently acknowledges it on behalf of the client. This
functionality increases performance but at the cost of
reliability. Messages can get lost if a client dies
before it can deliver them to the application.
exclusive: boolean
request exclusive access
Request exclusive consumer access, meaning only this
consumer can access the queue.
RULE:
If the server cannot grant exclusive access to the
queue when asked, - because there are other
consumers active - it MUST raise a channel
exception with return code 403 (access refused).
nowait: boolean
do not send a reply method
If set, the server will not respond to the method. The
client should not wait for a reply method. If the
server could not complete the method it will raise a
channel or connection exception.
callback: Python callable
function/method called with each delivered message
For each message delivered by the broker, the
callable will be called with a Message object
as the single argument. If no callable is specified,
messages are quietly discarded, no_ack should probably
be set to True in that case.
"""
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(queue)
args.write_shortstr(consumer_tag)
args.write_bit(no_local)
args.write_bit(no_ack)
args.write_bit(exclusive)
args.write_bit(nowait)
args.write_table(arguments or {})
self._send_method((60, 20), args)
if not nowait:
consumer_tag = self.wait(allowed_methods=[
(60, 21), # Channel.basic_consume_ok
])
self.callbacks[consumer_tag] = callback
if on_cancel:
self.cancel_callbacks[consumer_tag] = on_cancel
if no_ack:
self.no_ack_consumers.add(consumer_tag)
return consumer_tag
def _basic_consume_ok(self, args):
"""Confirm a new consumer
The server provides the client with a consumer tag, which is
used by the client for methods called on the consumer at a
later stage.
PARAMETERS:
consumer_tag: shortstr
Holds the consumer tag specified by the client or
provided by the server.
"""
return args.read_shortstr()
def _basic_deliver(self, args, msg):
"""Notify the client of a consumer message
This method delivers a message to the client, via a consumer.
In the asynchronous message delivery model, the client starts
a consumer using the Consume method, then the server responds
with Deliver methods as and when messages arrive for that
consumer.
RULE:
The server SHOULD track the number of times a message has
been delivered to clients and when a message is
redelivered a certain number of times - e.g. 5 times -
without being acknowledged, the server SHOULD consider the
message to be unprocessable (possibly causing client
applications to abort), and move the message to a dead
letter queue.
PARAMETERS:
consumer_tag: shortstr
consumer tag
Identifier for the consumer, valid within the current
connection.
RULE:
The consumer tag is valid only within the channel
from which the consumer was created. I.e. a client
MUST NOT create a consumer in one channel and then
use it in another.
delivery_tag: longlong
server-assigned delivery tag
The server-assigned and channel-specific delivery tag
RULE:
The delivery tag is valid only within the channel
from which the message was received. I.e. a client
MUST NOT receive a message on one channel and then
acknowledge it on another.
RULE:
The server MUST NOT use a zero value for delivery
tags. Zero is reserved for client use, meaning "all
messages so far received".
redelivered: boolean
message is being redelivered
This indicates that the message has been previously
delivered to this or another client.
exchange: shortstr
Specifies the name of the exchange that the message
was originally published to.
routing_key: shortstr
Message routing key
Specifies the routing key name specified when the
message was published.
"""
consumer_tag = args.read_shortstr()
delivery_tag = args.read_longlong()
redelivered = args.read_bit()
exchange = args.read_shortstr()
routing_key = args.read_shortstr()
msg.channel = self
msg.delivery_info = {
'consumer_tag': consumer_tag,
'delivery_tag': delivery_tag,
'redelivered': redelivered,
'exchange': exchange,
'routing_key': routing_key,
}
try:
fun = self.callbacks[consumer_tag]
except KeyError:
pass
else:
fun(msg)
def basic_get(self, queue='', no_ack=False):
"""Direct access to a queue
This method provides a direct access to the messages in a
queue using a synchronous dialogue that is designed for
specific types of application where synchronous functionality
is more important than performance.
PARAMETERS:
queue: shortstr
Specifies the name of the queue to consume from. If
the queue name is null, refers to the current queue
for the channel, which is the last declared queue.
RULE:
If the client did not previously declare a queue,
and the queue name in this method is empty, the
server MUST raise a connection exception with
reply code 530 (not allowed).
no_ack: boolean
no acknowledgement needed
If this field is set the server does not expect
acknowledgments for messages. That is, when a message
is delivered to the client the server automatically and
silently acknowledges it on behalf of the client. This
functionality increases performance but at the cost of
reliability. Messages can get lost if a client dies
before it can deliver them to the application.
Non-blocking, returns a message object, or None.
"""
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(queue)
args.write_bit(no_ack)
self._send_method((60, 70), args)
return self.wait(allowed_methods=[
(60, 71), # Channel.basic_get_ok
(60, 72), # Channel.basic_get_empty
])
def _basic_get_empty(self, args):
"""Indicate no messages available
This method tells the client that the queue has no messages
available for the client.
PARAMETERS:
cluster_id: shortstr
Cluster id
For use by cluster applications, should not be used by
client applications.
"""
cluster_id = args.read_shortstr() # noqa
def _basic_get_ok(self, args, msg):
"""Provide client with a message
This method delivers a message to the client following a get
method. A message delivered by 'get-ok' must be acknowledged
unless the no-ack option was set in the get method.
PARAMETERS:
delivery_tag: longlong
server-assigned delivery tag
The server-assigned and channel-specific delivery tag
RULE:
The delivery tag is valid only within the channel
from which the message was received. I.e. a client
MUST NOT receive a message on one channel and then
acknowledge it on another.
RULE:
The server MUST NOT use a zero value for delivery
tags. Zero is reserved for client use, meaning "all
messages so far received".
redelivered: boolean
message is being redelivered
This indicates that the message has been previously
delivered to this or another client.
exchange: shortstr
Specifies the name of the exchange that the message
was originally published to. If empty, the message
was published to the default exchange.
routing_key: shortstr
Message routing key
Specifies the routing key name specified when the
message was published.
message_count: long
number of messages pending
This field reports the number of messages pending on
the queue, excluding the message being delivered.
Note that this figure is indicative, not reliable, and
can change arbitrarily as messages are added to the
queue and removed by other clients.
"""
delivery_tag = args.read_longlong()
redelivered = args.read_bit()
exchange = args.read_shortstr()
routing_key = args.read_shortstr()
message_count = args.read_long()
msg.channel = self
msg.delivery_info = {
'delivery_tag': delivery_tag,
'redelivered': redelivered,
'exchange': exchange,
'routing_key': routing_key,
'message_count': message_count
}
return msg
def _basic_publish(self, msg, exchange='', routing_key='',
mandatory=False, immediate=False):
"""Publish a message
This method publishes a message to a specific exchange. The
message will be routed to queues as defined by the exchange
configuration and distributed to any active consumers when the
transaction, if any, is committed.
PARAMETERS:
exchange: shortstr
Specifies the name of the exchange to publish to. The
exchange name can be empty, meaning the default
exchange. If the exchange name is specified, and that
exchange does not exist, the server will raise a
channel exception.
RULE:
The server MUST accept a blank exchange name to
mean the default exchange.
RULE:
The exchange MAY refuse basic content in which
case it MUST raise a channel exception with reply
code 540 (not implemented).
routing_key: shortstr
Message routing key
Specifies the routing key for the message. The
routing key is used for routing messages depending on
the exchange configuration.
mandatory: boolean
indicate mandatory routing
This flag tells the server how to react if the message
cannot be routed to a queue. If this flag is True, the
server will return an unroutable message with a Return
method. If this flag is False, the server silently
drops the message.
RULE:
The server SHOULD implement the mandatory flag.
immediate: boolean
request immediate delivery
This flag tells the server how to react if the message
cannot be routed to a queue consumer immediately. If
this flag is set, the server will return an
undeliverable message with a Return method. If this
flag is zero, the server will queue the message, but
with no guarantee that it will ever be consumed.
RULE:
The server SHOULD implement the immediate flag.
"""
args = AMQPWriter()
args.write_short(0)
args.write_shortstr(exchange)
args.write_shortstr(routing_key)
args.write_bit(mandatory)
args.write_bit(immediate)
self._send_method((60, 40), args, msg)
basic_publish = _basic_publish
def basic_publish_confirm(self, *args, **kwargs):
if not self._confirm_selected:
self._confirm_selected = True
self.confirm_select()
ret = self._basic_publish(*args, **kwargs)
# Basic.Ack / Basic.Nack
self.wait([(60, 80), (60, 120)])
return ret
def basic_qos(self, prefetch_size, prefetch_count, a_global):
"""Specify quality of service
This method requests a specific quality of service. The QoS
can be specified for the current channel or for all channels
on the connection. The particular properties and semantics of
a qos method always depend on the content class semantics.
Though the qos method could in principle apply to both peers,
it is currently meaningful only for the server.
PARAMETERS:
prefetch_size: long
prefetch window in octets
The client can request that messages be sent in
advance so that when the client finishes processing a
message, the following message is already held
locally, rather than needing to be sent down the
channel. Prefetching gives a performance improvement.
This field specifies the prefetch window size in
octets. The server will send a message in advance if
it is equal to or smaller in size than the available
prefetch size (and also falls into other prefetch
limits). May be set to zero, meaning "no specific
limit", although other prefetch limits may still
apply. The prefetch-size is ignored if the no-ack
option is set.
RULE:
The server MUST ignore this setting when the
client is not processing any messages - i.e. the
prefetch size does not limit the transfer of
single messages to a client, only the sending in
advance of more messages while the client still
has one or more unacknowledged messages.
prefetch_count: short
prefetch window in messages
Specifies a prefetch window in terms of whole
messages. This field may be used in combination with
the prefetch-size field; a message will only be sent
in advance if both prefetch windows (and those at the
channel and connection level) allow it. The prefetch-
count is ignored if the no-ack option is set.
RULE:
The server MAY send less data in advance than
allowed by the client's specified prefetch windows
but it MUST NOT send more.
a_global: boolean
apply to entire connection
By default the QoS settings apply to the current
channel only. If this field is set, they are applied
to the entire connection.
"""
args = AMQPWriter()
args.write_long(prefetch_size)
args.write_short(prefetch_count)
args.write_bit(a_global)
self._send_method((60, 10), args)
return self.wait(allowed_methods=[
(60, 11), # Channel.basic_qos_ok
])
def _basic_qos_ok(self, args):
"""Confirm the requested qos
This method tells the client that the requested QoS levels
could be handled by the server. The requested QoS applies to
all active consumers until a new QoS is defined.
"""
pass
def basic_recover(self, requeue=False):
"""Redeliver unacknowledged messages
This method asks the broker to redeliver all unacknowledged
messages on a specified channel. Zero or more messages may be
redelivered. This method is only allowed on non-transacted
channels.
RULE:
The server MUST set the redelivered flag on all messages
that are resent.
RULE:
The server MUST raise a channel exception if this is
called on a transacted channel.
PARAMETERS:
requeue: boolean
requeue the message
If this field is False, the message will be redelivered
to the original recipient. If this field is True, the
server will attempt to requeue the message,
potentially then delivering it to an alternative
subscriber.
"""
args = AMQPWriter()
args.write_bit(requeue)
self._send_method((60, 110), args)
def basic_recover_async(self, requeue=False):
args = AMQPWriter()
args.write_bit(requeue)
self._send_method((60, 100), args)
def _basic_recover_ok(self, args):
"""In 0-9-1 the deprecated recover solicits a response."""
pass
def basic_reject(self, delivery_tag, requeue):
"""Reject an incoming message
This method allows a client to reject a message. It can be
used to interrupt and cancel large incoming messages, or
return untreatable messages to their original queue.
RULE:
The server SHOULD be capable of accepting and process the
Reject method while sending message content with a Deliver
or Get-Ok method. I.e. the server should read and process
incoming methods while sending output frames. To cancel a
partially-send content, the server sends a content body
frame of size 1 (i.e. with no data except the frame-end
octet).
RULE:
The server SHOULD interpret this method as meaning that
the client is unable to process the message at this time.
RULE:
A client MUST NOT use this method as a means of selecting
messages to process. A rejected message MAY be discarded
or dead-lettered, not necessarily passed to another
client.
PARAMETERS:
delivery_tag: longlong
server-assigned delivery tag
The server-assigned and channel-specific delivery tag
RULE:
The delivery tag is valid only within the channel
from which the message was received. I.e. a client
MUST NOT receive a message on one channel and then
acknowledge it on another.
RULE:
The server MUST NOT use a zero value for delivery
tags. Zero is reserved for client use, meaning "all
messages so far received".
requeue: boolean
requeue the message
If this field is False, the message will be discarded.
If this field is True, the server will attempt to
requeue the message.
RULE:
The server MUST NOT deliver the message to the
same client within the context of the current
channel. The recommended strategy is to attempt
to deliver the message to an alternative consumer,
and if that is not possible, to move the message
to a dead-letter queue. The server MAY use more
sophisticated tracking to hold the message on the
queue and redeliver it to the same client at a
later stage.
"""
args = AMQPWriter()
args.write_longlong(delivery_tag)
args.write_bit(requeue)
self._send_method((60, 90), args)
def _basic_return(self, args, msg):
"""Return a failed message
This method returns an undeliverable message that was
published with the "immediate" flag set, or an unroutable
message published with the "mandatory" flag set. The reply
code and text provide information about the reason that the
message was undeliverable.
PARAMETERS:
reply_code: short
The reply code. The AMQ reply codes are defined in AMQ
RFC 011.
reply_text: shortstr
The localised reply text. This text can be logged as an
aid to resolving issues.
exchange: shortstr
Specifies the name of the exchange that the message
was originally published to.
routing_key: shortstr
Message routing key
Specifies the routing key name specified when the
message was published.
"""
self.returned_messages.put(basic_return_t(
args.read_short(),
args.read_shortstr(),
args.read_shortstr(),
args.read_shortstr(),
msg,
))
#############
#
# Tx
#
#
# work with standard transactions
#
# Standard transactions provide so-called "1.5 phase commit". We
# can ensure that work is never lost, but there is a chance of
# confirmations being lost, so that messages may be resent.
# Applications that use standard transactions must be able to
# detect and ignore duplicate messages.
#
# GRAMMAR::
#
# tx = C:SELECT S:SELECT-OK
# / C:COMMIT S:COMMIT-OK
# / C:ROLLBACK S:ROLLBACK-OK
#
# RULE:
#
# An client using standard transactions SHOULD be able to
# track all messages received within a reasonable period, and
# thus detect and reject duplicates of the same message. It
# SHOULD NOT pass these to the application layer.
#
#
def tx_commit(self):
"""Commit the current transaction
This method commits all messages published and acknowledged in
the current transaction. A new transaction starts immediately
after a commit.
"""
self._send_method((90, 20))
return self.wait(allowed_methods=[
(90, 21), # Channel.tx_commit_ok
])
def _tx_commit_ok(self, args):
"""Confirm a successful commit
This method confirms to the client that the commit succeeded.
Note that if a commit fails, the server raises a channel
exception.
"""
pass
def tx_rollback(self):
"""Abandon the current transaction
This method abandons all messages published and acknowledged
in the current transaction. A new transaction starts
immediately after a rollback.
"""
self._send_method((90, 30))
return self.wait(allowed_methods=[
(90, 31), # Channel.tx_rollback_ok
])
def _tx_rollback_ok(self, args):
"""Confirm a successful rollback
This method confirms to the client that the rollback
succeeded. Note that if an rollback fails, the server raises a
channel exception.
"""
pass
def tx_select(self):
"""Select standard transaction mode
This method sets the channel to use standard transactions.
The client must use this method at least once on a channel
before using the Commit or Rollback methods.
"""
self._send_method((90, 10))
return self.wait(allowed_methods=[
(90, 11), # Channel.tx_select_ok
])
def _tx_select_ok(self, args):
"""Confirm transaction mode
This method confirms to the client that the channel was
successfully set to use standard transactions.
"""
pass
def confirm_select(self, nowait=False):
"""Enables publisher confirms for this channel (an RabbitMQ
extension).
Can now be used if the channel is in transactional mode.
:param nowait:
If set, the server will not respond to the method.
The client should not wait for a reply method. If the
server could not complete the method it will raise a channel
or connection exception.
"""
args = AMQPWriter()
args.write_bit(nowait)
self._send_method((85, 10), args)
if not nowait:
self.wait(allowed_methods=[
(85, 11), # Confirm.select_ok
])
def _confirm_select_ok(self, args):
"""With this method the broker confirms to the client that
the channel is now using publisher confirms."""
pass
def _basic_ack_recv(self, args):
delivery_tag = args.read_longlong()
multiple = args.read_bit()
self._apply_callbacks('basic_ack', delivery_tag, multiple)
def _apply_callbacks(self, event, *args):
return [callback(*args) for callback in self.events[event]]
def _basic_nack(self, args):
delivery_tag = args.read_longlong()
multiple = args.read_bit()
requeue = args.read_bit()
if not self._apply_callbacks(
'basic_nack', delivery_tag, multiple, requeue):
raise NotConfirmed(delivery_tag, (60, 120), 'basic.nack')
_METHOD_MAP = {
(20, 11): _open_ok,
(20, 20): _flow,
(20, 21): _flow_ok,
(20, 40): _close,
(20, 41): _close_ok,
(40, 11): _exchange_declare_ok,
(40, 21): _exchange_delete_ok,
(40, 31): _exchange_bind_ok,
(40, 51): _exchange_unbind_ok,
(50, 11): _queue_declare_ok,
(50, 21): _queue_bind_ok,
(50, 31): _queue_purge_ok,
(50, 41): _queue_delete_ok,
(50, 51): _queue_unbind_ok,
(60, 11): _basic_qos_ok,
(60, 21): _basic_consume_ok,
(60, 30): _basic_cancel_notify,
(60, 31): _basic_cancel_ok,
(60, 50): _basic_return,
(60, 60): _basic_deliver,
(60, 71): _basic_get_ok,
(60, 72): _basic_get_empty,
(60, 80): _basic_ack_recv,
(60, 120): _basic_nack,
(60, 111): _basic_recover_ok,
(85, 11): _confirm_select_ok,
(90, 11): _tx_select_ok,
(90, 21): _tx_commit_ok,
(90, 31): _tx_rollback_ok,
}
_IMMEDIATE_METHODS = [
(60, 50), # basic_return
]