Channel¶
The Channel class provides a wrapper for interacting with RabbitMQ implementing the methods and behaviors for an AMQP Channel.
Channel¶
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class
pika.channel.
Channel
(connection, channel_number, on_open_callback)¶ A Channel is the primary communication method for interacting with RabbitMQ. It is recommended that you do not directly invoke the creation of a channel object in your application code but rather construct a channel by calling the active connection’s channel() method.
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add_callback
(callback, replies, one_shot=True)¶ Pass in a callback handler and a list replies from the RabbitMQ broker which you’d like the callback notified of. Callbacks should allow for the frame parameter to be passed in.
- Parameters
callback (callable) – The callback to call
replies (list) – The replies to get a callback for
one_shot (bool) – Only handle the first type callback
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add_on_cancel_callback
(callback)¶ Pass a callback function that will be called when the basic_cancel is sent by the server. The callback function should receive a frame parameter.
- Parameters
callback (callable) – The callback to call on Basic.Cancel from broker
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add_on_close_callback
(callback)¶ Pass a callback function that will be called when the channel is closed. The callback function will receive the channel and an exception describing why the channel was closed.
If the channel is closed by broker via Channel.Close, the callback will receive ChannelClosedByBroker as the reason.
If graceful user-initiated channel closing completes successfully ( either directly of indirectly by closing a connection containing the channel) and closing concludes gracefully without Channel.Close from the broker and without loss of connection, the callback will receive ChannelClosedByClient exception as reason.
If channel was closed due to loss of connection, the callback will receive another exception type describing the failure.
- Parameters
callback (callable) – The callback, having the signature: callback(Channel, Exception reason)
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add_on_flow_callback
(callback)¶ Pass a callback function that will be called when Channel.Flow is called by the remote server. Note that newer versions of RabbitMQ will not issue this but instead use TCP backpressure
- Parameters
callback (callable) – The callback function
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add_on_return_callback
(callback)¶ Pass a callback function that will be called when basic_publish is sent a message that has been rejected and returned by the server.
- Parameters
callback (callable) – The function to call, having the signature callback(channel, method, properties, body) where channel: pika.Channel method: pika.spec.Basic.Return properties: pika.spec.BasicProperties body: bytes
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basic_ack
(delivery_tag=0, multiple=False)¶ Acknowledge one or more messages. When sent by the client, this method acknowledges one or more messages delivered via the Deliver or Get-Ok methods. When sent by server, this method acknowledges one or more messages published with the Publish method on a channel in confirm mode. The acknowledgement can be for a single message or a set of messages up to and including a specific message.
- Parameters
delivery_tag (integer) – int/long The server-assigned delivery tag
multiple (bool) – If set to True, the delivery tag is treated as “up to and including”, so that multiple messages can be acknowledged with a single method. If set to False, the delivery tag refers to a single message. If the multiple field is 1, and the delivery tag is zero, this indicates acknowledgement of all outstanding messages.
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basic_cancel
(consumer_tag='', callback=None)¶ 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. It may also be sent from the server to the client in the event of the consumer being unexpectedly cancelled (i.e. cancelled for any reason other than the server receiving the corresponding basic.cancel from the client). This allows clients to be notified of the loss of consumers due to events such as queue deletion.
- Parameters
consumer_tag (str) – Identifier for the consumer
callback (callable) – callback(pika.frame.Method) for method Basic.CancelOk. If None, do not expect a Basic.CancelOk response, otherwise, callback must be callable
- Raises
ValueError –
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basic_consume
(queue, on_message_callback, auto_ack=False, exclusive=False, consumer_tag=None, arguments=None, callback=None)¶ Sends the AMQP 0-9-1 command Basic.Consume to the broker and binds messages for the consumer_tag to the consumer callback. If you do not pass in a consumer_tag, one will be automatically generated for you. Returns the consumer tag.
For more information on basic_consume, see: Tutorial 2 at http://www.rabbitmq.com/getstarted.html http://www.rabbitmq.com/confirms.html http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.consume
- Parameters
queue (str) – The queue to consume from. Use the empty string to specify the most recent server-named queue for this channel
on_message_callback (callable) –
The function to call when consuming with the signature on_message_callback(channel, method, properties, body), where
channel: pika.Channel method: pika.spec.Basic.Deliver properties: pika.spec.BasicProperties body: bytes
auto_ack (bool) – if set to True, automatic acknowledgement mode will be used (see http://www.rabbitmq.com/confirms.html). This corresponds with the ‘no_ack’ parameter in the basic.consume AMQP 0.9.1 method
exclusive (bool) – Don’t allow other consumers on the queue
consumer_tag (str) – Specify your own consumer tag
arguments (dict) – Custom key/value pair arguments for the consumer
callback (callable) – callback(pika.frame.Method) for method Basic.ConsumeOk.
- Returns
Consumer tag which may be used to cancel the consumer.
- Return type
str
- Raises
ValueError –
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basic_get
(queue, callback, auto_ack=False)¶ Get a single message from the AMQP broker. If you want to be notified of Basic.GetEmpty, use the Channel.add_callback method adding your Basic.GetEmpty callback which should expect only one parameter, frame. Due to implementation details, this cannot be called a second time until the callback is executed. For more information on basic_get and its parameters, see:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.get
- Parameters
queue (str) – The queue from which to get a message. Use the empty string to specify the most recent server-named queue for this channel
callback (callable) – The callback to call with a message that has the signature callback(channel, method, properties, body), where: channel: pika.Channel method: pika.spec.Basic.GetOk properties: pika.spec.BasicProperties body: bytes
auto_ack (bool) – Tell the broker to not expect a reply
- Raises
ValueError –
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basic_nack
(delivery_tag=None, multiple=False, requeue=True)¶ This method allows a client to reject one or more incoming messages. It can be used to interrupt and cancel large incoming messages, or return untreatable messages to their original queue.
- Parameters
delivery-tag (integer) – int/long The server-assigned delivery tag
multiple (bool) – If set to True, the delivery tag is treated as “up to and including”, so that multiple messages can be acknowledged with a single method. If set to False, the delivery tag refers to a single message. If the multiple field is 1, and the delivery tag is zero, this indicates acknowledgement of all outstanding messages.
requeue (bool) – If requeue is true, the server will attempt to requeue the message. If requeue is false or the requeue attempt fails the messages are discarded or dead-lettered.
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basic_publish
(exchange, routing_key, body, properties=None, mandatory=False)¶ Publish to the channel with the given exchange, routing key and body. For more information on basic_publish and what the parameters do, see:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.publish
- Parameters
exchange (str) – The exchange to publish to
routing_key (str) – The routing key to bind on
body (bytes) – The message body
properties (pika.spec.BasicProperties) – Basic.properties
mandatory (bool) – The mandatory flag
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basic_qos
(prefetch_size=0, prefetch_count=0, global_qos=False, callback=None)¶ 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 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.
- Parameters
prefetch_size (int) – This field specifies the prefetch window size. 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 by consumers who have enabled the no-ack option.
prefetch_count (int) – 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 by consumers who have enabled the no-ack option.
global_qos (bool) – Should the QoS apply to all channels on the connection.
callback (callable) – The callback to call for Basic.QosOk response
- Raises
ValueError –
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basic_recover
(requeue=False, callback=None)¶ This method asks the server to redeliver all unacknowledged messages on a specified channel. Zero or more messages may be redelivered. This method replaces the asynchronous Recover.
- Parameters
requeue (bool) – If False, the message will be redelivered to the original recipient. If True, the server will attempt to requeue the message, potentially then delivering it to an alternative subscriber.
callback (callable) – Callback to call when receiving Basic.RecoverOk
callback – callback(pika.frame.Method) for method Basic.RecoverOk
- Raises
ValueError –
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basic_reject
(delivery_tag, requeue=True)¶ 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.
- Parameters
delivery-tag (integer) – int/long The server-assigned delivery tag
requeue (bool) – If requeue is true, the server will attempt to requeue the message. If requeue is false or the requeue attempt fails the messages are discarded or dead-lettered.
- Raises
TypeError
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close
(reply_code=0, reply_text='Normal shutdown')¶ Invoke a graceful shutdown of the channel with the AMQP Broker.
If channel is OPENING, transition to CLOSING and suppress the incoming Channel.OpenOk, if any.
- Parameters
reply_code (int) – The reason code to send to broker
reply_text (str) – The reason text to send to broker
- Raises
ChannelWrongStateError – if channel is closed or closing
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confirm_delivery
(ack_nack_callback, callback=None)¶ Turn on Confirm mode in the channel. Pass in a callback to be notified by the Broker when a message has been confirmed as received or rejected (Basic.Ack, Basic.Nack) from the broker to the publisher.
- For more information see:
- Parameters
ack_nack_callback (callable) – Required callback for delivery confirmations that has the following signature: callback(pika.frame.Method), where method_frame contains either method spec.Basic.Ack or spec.Basic.Nack.
callback (callable) – callback(pika.frame.Method) for method Confirm.SelectOk
- Raises
ValueError –
Property method that returns a list of currently active consumers
- Return type
list
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exchange_bind
(destination, source, routing_key='', arguments=None, callback=None)¶ Bind an exchange to another exchange.
- Parameters
destination (str) – The destination exchange to bind
source (str) – The source exchange to bind to
routing_key (str) – The routing key to bind on
arguments (dict) – Custom key/value pair arguments for the binding
callback (callable) – callback(pika.frame.Method) for method Exchange.BindOk
- Raises
ValueError –
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exchange_declare
(exchange, exchange_type='direct', passive=False, durable=False, auto_delete=False, internal=False, arguments=None, callback=None)¶ 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.
If passive set, the server will reply with Declare-Ok if the exchange already exists with the same name, and raise an error if not and if the exchange does not already exist, the server MUST raise a channel exception with reply code 404 (not found).
- Parameters
exchange (str) – The exchange name consists of a non-empty sequence of these characters: letters, digits, hyphen, underscore, period, or colon
exchange_type (str) – The exchange type to use
passive (bool) – Perform a declare or just check to see if it exists
durable (bool) – Survive a reboot of RabbitMQ
auto_delete (bool) – Remove when no more queues are bound to it
internal (bool) – Can only be published to by other exchanges
arguments (dict) – Custom key/value pair arguments for the exchange
callback (callable) – callback(pika.frame.Method) for method Exchange.DeclareOk
- Raises
ValueError –
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exchange_delete
(exchange=None, if_unused=False, callback=None)¶ Delete the exchange.
- Parameters
exchange (str) – The exchange name
if_unused (bool) – only delete if the exchange is unused
callback (callable) – callback(pika.frame.Method) for method Exchange.DeleteOk
- Raises
ValueError –
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exchange_unbind
(destination=None, source=None, routing_key='', arguments=None, callback=None)¶ Unbind an exchange from another exchange.
- Parameters
destination (str) – The destination exchange to unbind
source (str) – The source exchange to unbind from
routing_key (str) – The routing key to unbind
arguments (dict) – Custom key/value pair arguments for the binding
callback (callable) – callback(pika.frame.Method) for method Exchange.UnbindOk
- Raises
ValueError –
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flow
(active, callback=None)¶ Turn Channel flow control off and on. Pass a callback to be notified of the response from the server. active is a bool. Callback should expect a bool in response indicating channel flow state. For more information, please reference:
http://www.rabbitmq.com/amqp-0-9-1-reference.html#channel.flow
- Parameters
active (bool) – Turn flow on or off
callback (callable) – callback(bool) upon completion
- Raises
ValueError –
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property
is_closed
¶ Returns True if the channel is closed.
- Return type
bool
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property
is_closing
¶ Returns True if client-initiated closing of the channel is in progress.
- Return type
bool
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property
is_open
¶ Returns True if the channel is open.
- Return type
bool
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open
()¶ Open the channel
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queue_bind
(queue, exchange, routing_key=None, arguments=None, callback=None)¶ Bind the queue to the specified exchange
- Parameters
queue (str) – The queue to bind to the exchange
exchange (str) – The source exchange to bind to
routing_key (str) – The routing key to bind on
arguments (dict) – Custom key/value pair arguments for the binding
callback (callable) – callback(pika.frame.Method) for method Queue.BindOk
- Raises
ValueError –
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queue_declare
(queue, passive=False, durable=False, exclusive=False, auto_delete=False, arguments=None, callback=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.
Use an empty string as the queue name for the broker to auto-generate one
- Parameters
queue (str) – The queue name; if empty string, the broker will create a unique queue name
passive (bool) – Only check to see if the queue exists
durable (bool) – Survive reboots of the broker
exclusive (bool) – Only allow access by the current connection
auto_delete (bool) – Delete after consumer cancels or disconnects
arguments (dict) – Custom key/value arguments for the queue
callback (callable) – callback(pika.frame.Method) for method Queue.DeclareOk
- Raises
ValueError –
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queue_delete
(queue, if_unused=False, if_empty=False, callback=None)¶ Delete a queue from the broker.
- Parameters
queue (str) – The queue to delete
if_unused (bool) – only delete if it’s unused
if_empty (bool) – only delete if the queue is empty
callback (callable) – callback(pika.frame.Method) for method Queue.DeleteOk
- Raises
ValueError –
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queue_purge
(queue, callback=None)¶ Purge all of the messages from the specified queue
- Parameters
queue (str) – The queue to purge
callback (callable) – callback(pika.frame.Method) for method Queue.PurgeOk
- Raises
ValueError –
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queue_unbind
(queue, exchange=None, routing_key=None, arguments=None, callback=None)¶ Unbind a queue from an exchange.
- Parameters
queue (str) – The queue to unbind from the exchange
exchange (str) – The source exchange to bind from
routing_key (str) – The routing key to unbind
arguments (dict) – Custom key/value pair arguments for the binding
callback (callable) – callback(pika.frame.Method) for method Queue.UnbindOk
- Raises
ValueError –
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tx_commit
(callback=None)¶ Commit a transaction
- Parameters
callback (callable) – The callback for delivery confirmations
- Raises
ValueError –
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tx_rollback
(callback=None)¶ Rollback a transaction.
- Parameters
callback (callable) – The callback for delivery confirmations
- Raises
ValueError –
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tx_select
(callback=None)¶ 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.
- Parameters
callback (callable) – The callback for delivery confirmations
- Raises
ValueError –
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