Channel

The Channel class provides a wrapper for interacting with RabbitMQ implementing the methods and behaviors for an AMQP Channel.

Channel

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.

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

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

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)

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

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.Channel

• method: pika.spec.Basic.Return

• properties: pika.spec.BasicProperties

• body: bytes

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.

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 –

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.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 –

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.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 –

basic_nack(delivery_tag=0, 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.

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

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 –

basic_reject(delivery_tag=0, 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

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 –

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

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:

https://www.rabbitmq.com/confirms.html

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 consumer_tags

Property method that returns a list of currently active consumers

Return type

list

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 –

exchange_declare(exchange, exchange_type=ExchangeType.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 –

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 –

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 –

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 –

property is_closed

Returns True if the channel is closed.

Return type

bool

property is_closing

Returns True if client-initiated closing of the channel is in progress.

Return type

bool

property is_open

Returns True if the channel is open.

Return type

bool

open()

Open the channel

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 –

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 –

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 –

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 –

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 –

tx_commit(callback=None)

Commit a transaction

Parameters

callback (callable) – The callback for delivery confirmations

Raises

ValueError –

tx_rollback(callback=None)

Rollback a transaction.

Parameters

callback (callable) – The callback for delivery confirmations

Raises

ValueError –

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 –