This document is for py-amqp's development version, which can be significantly different from previous releases. Get the stable docs here: 5.0.

Source code for amqp.channel

"""AMQP Channels."""
# Copyright (C) 2007-2008 Barry Pederson <bp@barryp.org>

import logging
import socket
from collections import defaultdict
from queue import Queue

from vine import ensure_promise

from . import spec
from .abstract_channel import AbstractChannel
from .exceptions import (ChannelError, ConsumerCancelled, MessageNacked,
                         RecoverableChannelError, RecoverableConnectionError,
                         error_for_code)
from .protocol import queue_declare_ok_t

__all__ = ('Channel',)

AMQP_LOGGER = logging.getLogger('amqp')

REJECTED_MESSAGE_WITHOUT_CALLBACK = """\
Rejecting message with delivery tag %r for reason of having no callbacks.
consumer_tag=%r exchange=%r routing_key=%r.\
"""


class VDeprecationWarning(DeprecationWarning):
    pass


[docs]class Channel(AbstractChannel): """AMQP Channel. 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 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. """ _METHODS = { spec.method(spec.Channel.Close, 'BsBB'), spec.method(spec.Channel.CloseOk), spec.method(spec.Channel.Flow, 'b'), spec.method(spec.Channel.FlowOk, 'b'), spec.method(spec.Channel.OpenOk), spec.method(spec.Exchange.DeclareOk), spec.method(spec.Exchange.DeleteOk), spec.method(spec.Exchange.BindOk), spec.method(spec.Exchange.UnbindOk), spec.method(spec.Queue.BindOk), spec.method(spec.Queue.UnbindOk), spec.method(spec.Queue.DeclareOk, 'sll'), spec.method(spec.Queue.DeleteOk, 'l'), spec.method(spec.Queue.PurgeOk, 'l'), spec.method(spec.Basic.Cancel, 's'), spec.method(spec.Basic.CancelOk, 's'), spec.method(spec.Basic.ConsumeOk, 's'), spec.method(spec.Basic.Deliver, 'sLbss', content=True), spec.method(spec.Basic.GetEmpty, 's'), spec.method(spec.Basic.GetOk, 'Lbssl', content=True), spec.method(spec.Basic.QosOk), spec.method(spec.Basic.RecoverOk), spec.method(spec.Basic.Return, 'Bsss', content=True), spec.method(spec.Tx.CommitOk), spec.method(spec.Tx.RollbackOk), spec.method(spec.Tx.SelectOk), spec.method(spec.Confirm.SelectOk), spec.method(spec.Basic.Ack, 'Lb'), spec.method(spec.Basic.Nack, 'Lb'), } _METHODS = {m.method_sig: m for m in _METHODS} _ALLOWED_METHODS_WHEN_CLOSING = ( spec.Channel.Close, spec.Channel.CloseOk ) def __init__(self, connection, channel_id=None, auto_decode=True, on_open=None): if channel_id: connection._claim_channel_id(channel_id) else: channel_id = connection._get_free_channel_id() AMQP_LOGGER.debug('using channel_id: %s', channel_id) super().__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() self.on_open = ensure_promise(on_open) # 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 __slots__ = ( "is_open", "active", "returned_messages", "callbacks", "cancel_callbacks", "events", "no_ack_consumers", "on_open", "_confirm_selected", )
[docs] def then(self, on_success, on_error=None): return self.on_open.then(on_success, on_error)
def _setup_listeners(self): self._callbacks.update({ spec.Channel.Close: self._on_close, spec.Channel.CloseOk: self._on_close_ok, spec.Channel.Flow: self._on_flow, spec.Channel.OpenOk: self._on_open_ok, spec.Basic.Cancel: self._on_basic_cancel, spec.Basic.CancelOk: self._on_basic_cancel_ok, spec.Basic.Deliver: self._on_basic_deliver, spec.Basic.Return: self._on_basic_return, spec.Basic.Ack: self._on_basic_ack, spec.Basic.Nack: self._on_basic_nack, })
[docs] def collect(self): """Tear down this object. Best called after we've agreed to close with the server. """ AMQP_LOGGER.debug('Closed channel #%s', 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) try: connection._used_channel_ids.remove(channel_id) except ValueError: # channel id already removed pass self.callbacks.clear() self.cancel_callbacks.clear() self.events.clear() self.no_ack_consumers.clear()
def _do_revive(self): self.is_open = False self.open()
[docs] def close(self, reply_code=0, reply_text='', method_sig=(0, 0), argsig='BsBB'): """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 self.connection is None: return if self.connection.channels is None: return if not self.is_open: return self.is_closing = True return self.send_method( spec.Channel.Close, argsig, (reply_code, reply_text, method_sig[0], method_sig[1]), wait=spec.Channel.CloseOk, ) finally: self.is_closing = False self.connection = None
def _on_close(self, reply_code, reply_text, class_id, method_id): """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. """ self.send_method(spec.Channel.CloseOk) if not self.connection.is_closing: self._do_revive() raise error_for_code( reply_code, reply_text, (class_id, method_id), ChannelError, ) def _on_close_ok(self): """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.collect()
[docs] 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 overflowing 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 exchanging 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. """ return self.send_method( spec.Channel.Flow, 'b', (active,), wait=spec.Channel.FlowOk, )
def _on_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 overflowing 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 exchanging 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 = active 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. """ return self.send_method(spec.Channel.FlowOk, 'b', (active,))
[docs] def 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 return self.send_method( spec.Channel.Open, 's', ('',), wait=spec.Channel.OpenOk, )
def _on_open_ok(self): """Signal that the channel is ready. This method signals to the client that the channel is ready for use. """ self.is_open = True self.on_open(self) 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). #
[docs] def exchange_declare(self, exchange, type, passive=False, durable=False, auto_delete=True, nowait=False, arguments=None, argsig='BssbbbbbF'): """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. """ self.send_method( spec.Exchange.Declare, argsig, (0, exchange, type, passive, durable, auto_delete, False, nowait, arguments), wait=None if nowait else spec.Exchange.DeclareOk, )
[docs] def exchange_delete(self, exchange, if_unused=False, nowait=False, argsig='Bsbb'): """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. """ return self.send_method( spec.Exchange.Delete, argsig, (0, exchange, if_unused, nowait), wait=None if nowait else spec.Exchange.DeleteOk, )
[docs] def exchange_bind(self, destination, source='', routing_key='', nowait=False, arguments=None, argsig='BsssbF'): """Bind 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. """ return self.send_method( spec.Exchange.Bind, argsig, (0, destination, source, routing_key, nowait, arguments), wait=None if nowait else spec.Exchange.BindOk, )
[docs] def exchange_unbind(self, destination, source='', routing_key='', nowait=False, arguments=None, argsig='BsssbF'): """Unbind 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. """ return self.send_method( spec.Exchange.Unbind, argsig, (0, destination, source, routing_key, nowait, arguments), wait=None if nowait else spec.Exchange.UnbindOk, )
############# # # 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. #
[docs] def queue_bind(self, queue, exchange='', routing_key='', nowait=False, arguments=None, argsig='BsssbF'): """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. """ return self.send_method( spec.Queue.Bind, argsig, (0, queue, exchange, routing_key, nowait, arguments), wait=None if nowait else spec.Queue.BindOk, )
[docs] def queue_unbind(self, queue, exchange, routing_key='', nowait=False, arguments=None, argsig='BsssF'): """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. """ return self.send_method( spec.Queue.Unbind, argsig, (0, queue, exchange, routing_key, arguments), wait=None if nowait else spec.Queue.UnbindOk, )
[docs] def queue_declare(self, queue='', passive=False, durable=False, exclusive=False, auto_delete=True, nowait=False, arguments=None, argsig='BsbbbbbF'): """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 and consumer count """ self.send_method( spec.Queue.Declare, argsig, (0, queue, passive, durable, exclusive, auto_delete, nowait, arguments), ) if not nowait: return queue_declare_ok_t(*self.wait( spec.Queue.DeclareOk, returns_tuple=True, ))
[docs] def queue_delete(self, queue='', if_unused=False, if_empty=False, nowait=False, argsig='Bsbbb'): """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. If nowait is False, returns the number of deleted messages. """ return self.send_method( spec.Queue.Delete, argsig, (0, queue, if_unused, if_empty, nowait), wait=None if nowait else spec.Queue.DeleteOk, )
[docs] def queue_purge(self, queue='', nowait=False, argsig='Bsb'): """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 number of purged messages. """ return self.send_method( spec.Queue.Purge, argsig, (0, queue, nowait), wait=None if nowait else spec.Queue.PurgeOk, )
############# # # 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 # acknowledgments on Basic content. #
[docs] def basic_ack(self, delivery_tag, multiple=False, argsig='Lb'): """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 messages. 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. """ return self.send_method( spec.Basic.Ack, argsig, (delivery_tag, multiple), )
[docs] def basic_cancel(self, consumer_tag, nowait=False, argsig='sb'): """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 arbitrary 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) return self.send_method( spec.Basic.Cancel, argsig, (consumer_tag, nowait), wait=None if nowait else spec.Basic.CancelOk, )
def _on_basic_cancel(self, consumer_tag): """Consumer cancelled by server. Most likely the queue was deleted. """ callback = self._remove_tag(consumer_tag) if callback: callback(consumer_tag) else: raise ConsumerCancelled(consumer_tag, spec.Basic.Cancel) def _on_basic_cancel_ok(self, consumer_tag): self._remove_tag(consumer_tag) def _remove_tag(self, consumer_tag): self.callbacks.pop(consumer_tag, None) return self.cancel_callbacks.pop(consumer_tag, None)
[docs] def basic_consume(self, queue='', consumer_tag='', no_local=False, no_ack=False, exclusive=False, nowait=False, callback=None, arguments=None, on_cancel=None, argsig='BssbbbbF'): """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 acknowledgment 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. """ p = self.send_method( spec.Basic.Consume, argsig, ( 0, queue, consumer_tag, no_local, no_ack, exclusive, nowait, arguments ), wait=None if nowait else spec.Basic.ConsumeOk, returns_tuple=True ) if not nowait: # send_method() returns (consumer_tag,) tuple. # consumer_tag is returned by broker using following rules: # * consumer_tag is not specified by client, random one # is generated by Broker # * consumer_tag is provided by client, the same one # is returned by broker consumer_tag = p[0] elif nowait and not consumer_tag: raise ValueError( 'Consumer tag must be specified when nowait is True' ) 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) if not nowait: return consumer_tag else: return p
def _on_basic_deliver(self, consumer_tag, delivery_tag, redelivered, exchange, routing_key, msg): 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: AMQP_LOGGER.warning( REJECTED_MESSAGE_WITHOUT_CALLBACK, delivery_tag, consumer_tag, exchange, routing_key, ) self.basic_reject(delivery_tag, requeue=True) else: fun(msg)
[docs] def basic_get(self, queue='', no_ack=False, argsig='Bsb'): """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 acknowledgment 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 amqp.basic_message.Message object, or None if queue is empty. """ ret = self.send_method( spec.Basic.Get, argsig, (0, queue, no_ack), wait=[spec.Basic.GetOk, spec.Basic.GetEmpty], returns_tuple=True, ) if not ret or len(ret) < 2: return self._on_get_empty(*ret) return self._on_get_ok(*ret)
def _on_get_empty(self, cluster_id=None): pass def _on_get_ok(self, delivery_tag, redelivered, exchange, routing_key, message_count, msg): 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, timeout=None, confirm_timeout=None, argsig='Bssbb'): """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. When channel is in confirm mode (when Connection parameter confirm_publish is set to True), each message is confirmed. When broker rejects published message (e.g. due internal broker constrains), MessageNacked exception is raised and set confirm_timeout to wait maximum confirm_timeout second for message to confirm. 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. timeout: short timeout for publish Set timeout to wait maximum timeout second for message to publish. confirm_timeout: short confirm_timeout for publish in confirm mode When the channel is in confirm mode set confirm_timeout to wait maximum confirm_timeout second for message to confirm. """ if not self.connection: raise RecoverableConnectionError( 'basic_publish: connection closed') capabilities = self.connection. \ client_properties.get('capabilities', {}) if capabilities.get('connection.blocked', False): try: # Check if an event was sent, such as the out of memory message self.connection.drain_events(timeout=0) except socket.timeout: pass try: with self.connection.transport.having_timeout(timeout): return self.send_method( spec.Basic.Publish, argsig, (0, exchange, routing_key, mandatory, immediate), msg ) except socket.timeout: raise RecoverableChannelError('basic_publish: timed out') basic_publish = _basic_publish
[docs] def basic_publish_confirm(self, *args, **kwargs): confirm_timeout = kwargs.pop('confirm_timeout', None) def confirm_handler(method, *args): # When RMQ nacks message we are raising MessageNacked exception if method == spec.Basic.Nack: raise MessageNacked() if not self._confirm_selected: self._confirm_selected = True self.confirm_select() ret = self._basic_publish(*args, **kwargs) # Waiting for confirmation of message. timeout = confirm_timeout or kwargs.get('timeout', None) self.wait([spec.Basic.Ack, spec.Basic.Nack], callback=confirm_handler, timeout=timeout) return ret
[docs] def basic_qos(self, prefetch_size, prefetch_count, a_global, argsig='lBb'): """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 Defines a scope of QoS. Semantics of this parameter differs between AMQP 0-9-1 standard and RabbitMQ broker: MEANING IN AMQP 0-9-1: False: shared across all consumers on the channel True: shared across all consumers on the connection MEANING IN RABBITMQ: False: applied separately to each new consumer on the channel True: shared across all consumers on the channel """ return self.send_method( spec.Basic.Qos, argsig, (prefetch_size, prefetch_count, a_global), wait=spec.Basic.QosOk, )
[docs] 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. """ return self.send_method(spec.Basic.Recover, 'b', (requeue,))
[docs] def basic_recover_async(self, requeue=False): return self.send_method(spec.Basic.RecoverAsync, 'b', (requeue,))
[docs] def basic_reject(self, delivery_tag, requeue, argsig='Lb'): """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. """ return self.send_method( spec.Basic.Reject, argsig, (delivery_tag, requeue), )
def _on_basic_return(self, reply_code, reply_text, exchange, routing_key, message): """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. """ exc = error_for_code( reply_code, reply_text, spec.Basic.Return, ChannelError, ) handlers = self.events.get('basic_return') if not handlers: raise exc for callback in handlers: callback(exc, exchange, routing_key, message) ############# # # 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. # #
[docs] 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. """ return self.send_method(spec.Tx.Commit, wait=spec.Tx.CommitOk)
[docs] 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. """ return self.send_method(spec.Tx.Rollback, wait=spec.Tx.RollbackOk)
[docs] 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. """ return self.send_method(spec.Tx.Select, wait=spec.Tx.SelectOk)
[docs] def confirm_select(self, nowait=False): """Enable publisher confirms for this channel. Note: This is 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. """ return self.send_method( spec.Confirm.Select, 'b', (nowait,), wait=None if nowait else spec.Confirm.SelectOk, )
def _on_basic_ack(self, delivery_tag, multiple): for callback in self.events['basic_ack']: callback(delivery_tag, multiple) def _on_basic_nack(self, delivery_tag, multiple): for callback in self.events['basic_nack']: callback(delivery_tag, multiple)