BlockingConnection¶
The blocking connection adapter module implements blocking semantics on top of Pika’s core AMQP driver. While most of the asynchronous expectations are removed when using the blocking connection adapter, it attempts to remain true to the asynchronous RPC nature of the AMQP protocol, supporting server sent RPC commands.
The user facing classes in the module consist of the
BlockingConnection
and the BlockingChannel
classes.
Be sure to check out examples in Usage Examples.
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class
pika.adapters.blocking_connection.
BlockingConnection
(parameters=None)[source]¶ The BlockingConnection creates a layer on top of Pika’s asynchronous core providing methods that will block until their expected response has returned. Due to the asynchronous nature of the Basic.Deliver and Basic.Return calls from RabbitMQ to your application, you can still implement continuation-passing style asynchronous methods if you’d like to receive messages from RabbitMQ using
basic_consume
or if you want to be notified of a delivery failure when usingbasic_publish
.Basic.Get is a blocking call which will either return the Method Frame, Header Frame and Body of a message, or it will return a Basic.GetEmpty frame as the method frame.
For more information about communicating with the blocking_connection adapter, be sure to check out the
BlockingChannel
class which implements theChannel
based communication for the blocking_connection adapter.-
add_backpressure_callback
(callback_method)¶ Call method “callback” when pika believes backpressure is being applied.
Parameters: callback_method (method) – The method to call
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add_on_close_callback
(callback_method_unused)[source]¶ This is not supported in BlockingConnection. When a connection is closed in BlockingConnection, a pika.exceptions.ConnectionClosed exception will raised instead.
Parameters: callback_method_unused (method) – Unused Raises: NotImplementedError
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add_on_open_callback
(callback_method_unused)[source]¶ This method is not supported in BlockingConnection.
Parameters: callback_method_unused (method) – Unused Raises: NotImplementedError
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add_on_open_error_callback
(callback_method_unused, remove_default=False)[source]¶ This method is not supported in BlockingConnection.
A pika.exceptions.AMQPConnectionError will be raised instead.
Parameters: callback_method_unused (method) – Unused Raises: NotImplementedError
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add_timeout
(deadline, callback_method)[source]¶ Add the callback_method to the IOLoop timer to fire after deadline seconds. Returns a handle to the timeout. Do not confuse with Tornado’s timeout where you pass in the time you want to have your callback called. Only pass in the seconds until it’s to be called.
Parameters: - deadline (int) – The number of seconds to wait to call callback
- callback_method (method) – The callback method
Return type:
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channel
(channel_number=None)[source]¶ Create a new channel with the next available or specified channel #.
Parameters: channel_number (int) – Specify the channel number
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close
(reply_code=200, reply_text='Normal shutdown')[source]¶ Disconnect from RabbitMQ. If there are any open channels, it will attempt to close them prior to fully disconnecting. Channels which have active consumers will attempt to send a Basic.Cancel to RabbitMQ to cleanly stop the delivery of messages prior to closing the channel.
Parameters:
-
connect
()[source]¶ Invoke if trying to reconnect to a RabbitMQ server. Constructing the Connection object should connect on its own.
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consumer_cancel_notify
¶ Specifies if the server supports consumer cancel notification on the active connection.
Return type: bool
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exchange_exchange_bindings
¶ Specifies if the active connection supports exchange to exchange bindings.
Return type: bool
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is_closed
¶ Returns a boolean reporting the current connection state.
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is_closing
¶ Returns a boolean reporting the current connection state.
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is_open
¶ Returns a boolean reporting the current connection state.
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process_data_events
()[source]¶ Will make sure that data events are processed. Your app can block on this method.
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publisher_confirms
¶ Specifies if the active connection can use publisher confirmations.
Return type: bool
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remove_timeout
(timeout_id)[source]¶ Remove the timeout from the IOLoop by the ID returned from add_timeout.
Parameters: timeout_id (str) – The id of the timeout to remove
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send_method
(channel_number, method_frame, content=None)[source]¶ Constructs a RPC method frame and then sends it to the broker.
Parameters:
-
-
class
pika.adapters.blocking_connection.
BlockingChannel
(connection, channel_number)[source]¶ The BlockingChannel implements blocking semantics for most things that one would use callback-passing-style for with the
Channel
class. In addition, the BlockingChannel class implements a generator that allows you to consume messages without using callbacks.Example of creating a BlockingChannel:
import pika # Create our connection object connection = pika.BlockingConnection() # The returned object will be a blocking channel channel = connection.channel()
Parameters: - connection (BlockingConnection) – The connection
- channel_number (int) – The channel number for this instance
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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:
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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 (method) – The method to call on callback
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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, the reply_code (int) and the reply_text (int) sent by the server describing why the channel was closed.
Parameters: callback (method) – The method to call on callback
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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 (method) – The method to call on callback
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add_on_return_callback
(callback)¶ Pass a callback function that will be called when basic_publish as sent a message that has been rejected and returned by the server. The callback handler should receive a method, header and body frame. The base signature for the callback should be the same as the method signature one creates for a basic_consume callback.
Parameters: callback (method) – The method to call on callback
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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 (int) – 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='', nowait=False)[source]¶ 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:
-
basic_consume
(consumer_callback, queue='', no_ack=False, exclusive=False, consumer_tag=None, arguments=None)¶ Sends the AMQP 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: http://www.rabbitmq.com/amqp-0-9-1-reference.html#basic.consume
Parameters: - consumer_callback (method) – The method to callback when consuming
- queue (str or unicode) – The queue to consume from
- no_ack (bool) – Tell the broker to not expect a response
- exclusive (bool) – Don’t allow other consumers on the queue
- consumer_tag (str or unicode) – Specify your own consumer tag
- arguments (dict) – Custom key/value pair arguments for the consume
Return type:
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basic_get
(queue=None, no_ack=False)[source]¶ Get a single message from the AMQP broker. The callback method signature should have 3 parameters: The method frame, header frame and the body, like the consumer callback for Basic.Consume.
Parameters: - queue (str or unicode) – The queue to get a message from
- no_ack (bool) – Tell the broker to not expect a reply
Return type: (None, None, None)|(spec.Basic.Get, spec.Basic.Properties, str or unicode)
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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 (int) – 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, immediate=False)[source]¶ Publish to the channel with the given exchange, routing key and body. Returns a boolean value indicating the success of the operation. 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:
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basic_qos
(prefetch_size=0, prefetch_count=0, all_channels=False)[source]¶ 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 if the no-ack option is set.
- 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 if the no-ack option is set.
- all_channels (bool) – Should the QoS apply to all channels
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basic_recover
(requeue=False)[source]¶ 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.
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basic_reject
(delivery_tag=None, 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:
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cancel
()[source]¶ Cancel the consumption of a queue, rejecting all pending messages. This should only work with the generator based BlockingChannel.consume method. If you’re looking to cancel a consumer issues with BlockingChannel.basic_consume then you should call BlockingChannel.basic_cancel.
Return int: The number of messages requeued by Basic.Nack
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close
(reply_code=0, reply_text='Normal Shutdown')[source]¶ Will invoke a clean shutdown of the channel with the AMQP Broker.
Parameters:
-
confirm_delivery
(nowait=False)[source]¶ Turn on Confirm mode in the channel.
- For more information see:
- http://www.rabbitmq.com/extensions.html#confirms
Parameters: nowait (bool) – Do not send a reply frame (Confirm.SelectOk)
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consume
(queue, no_ack=False, exclusive=False)[source]¶ Blocking consumption of a queue instead of via a callback. This method is a generator that returns messages a tuple of method, properties, and body.
Example:
- for method, properties, body in channel.consume(‘queue’):
- print body channel.basic_ack(method.delivery_tag)
You should call BlockingChannel.cancel() when you escape out of the generator loop. Also note this turns on forced data events to make sure that any acked messages actually get acked.
Parameters: Return type: tuple(spec.Basic.Deliver, spec.BasicProperties, str or unicode)
Property method that returns a list of currently active consumers
Return type: list
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exchange_bind
(destination=None, source=None, routing_key='', nowait=False, arguments=None)[source]¶ Bind an exchange to another exchange.
Parameters:
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exchange_declare
(exchange=None, exchange_type='direct', passive=False, durable=False, auto_delete=False, internal=False, nowait=False, arguments=None, type=None)[source]¶ 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 or unicode) – 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
- nowait (bool) – Do not expect an Exchange.DeclareOk response
- arguments (dict) – Custom key/value pair arguments for the exchange
- type (str) – The deprecated exchange type parameter
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exchange_delete
(exchange=None, if_unused=False, nowait=False)[source]¶ Delete the exchange.
Parameters:
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exchange_unbind
(destination=None, source=None, routing_key='', nowait=False, arguments=None)[source]¶ Unbind an exchange from another exchange.
Parameters: - destination (str or unicode) – The destination exchange to unbind
- source (str or unicode) – The source exchange to unbind from
- routing_key (str or unicode) – The routing key to unbind
- nowait (bool) – Do not wait for an Exchange.UnbindOk
- arguments (dict) – Custom key/value pair arguments for the binding
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flow
(callback, active)¶ 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: - callback (method) – The callback method
- active (bool) – Turn flow on or off
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force_data_events
(enable)[source]¶ Turn on and off forcing the blocking adapter to stop and look to see if there are any frames from RabbitMQ in the read buffer. By default the BlockingChannel will check for a read after every RPC command which can cause performance to degrade in scenarios where you do not care if RabbitMQ is trying to send RPC commands to your client connection.
Examples of RPC commands of this sort are:
- Heartbeats
- Connection.Close
- Channel.Close
- Basic.Return
- Basic.Ack and Basic.Nack when using delivery confirmations
Turning off forced data events can be a bad thing and prevents your client from properly communicating with RabbitMQ. Forced data events were added in 0.9.6 to enforce proper channel behavior when communicating with RabbitMQ.
Note that the BlockingConnection also has the constant WRITE_TO_READ_RATIO which forces the connection to stop and try and read after writing the number of frames specified in the constant. This is a way to force the client to received these types of frames in a very publish/write IO heavy workload.
Parameters: enable (bool) – Set to False to disable
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queue_bind
(queue, exchange, routing_key=None, nowait=False, arguments=None)[source]¶ Bind the queue to the specified exchange
Parameters:
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queue_declare
(queue='', passive=False, durable=False, exclusive=False, auto_delete=False, nowait=False, arguments=None)[source]¶ 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.
Leave the queue name empty for a auto-named queue in RabbitMQ
Parameters: - queue (str or unicode) – The 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
- nowait (bool) – Do not wait for a Queue.DeclareOk
- arguments (dict) – Custom key/value arguments for the queue
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queue_delete
(queue='', if_unused=False, if_empty=False, nowait=False)[source]¶ Delete a queue from the broker.
Parameters:
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queue_purge
(queue='', nowait=False)[source]¶ Purge all of the messages from the specified queue
Parameters: - queue (str or unicode) – The queue to purge
- nowait (bool) – Do not expect a Queue.PurgeOk response
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queue_unbind
(queue='', exchange=None, routing_key=None, arguments=None)[source]¶ Unbind a queue from an exchange.
Parameters: - queue (str or unicode) – The queue to unbind from the exchange
- exchange (str or unicode) – The source exchange to bind from
- routing_key (str or unicode) – The routing key to unbind
- arguments (dict) – Custom key/value pair arguments for the binding