# Connection

The `Connection` class implements the base behavior that all connection adapters extend.

class `pika.connection.``Connection`(parameters=None, on_open_callback=None, on_open_error_callback=None, on_close_callback=None)

  This is the core class that implements communication with RabbitMQ. This class should not be invoked directly but rather through the use of an adapter such as SelectConnection or BlockingConnection.

  Parameters:

  - parameters (pika.connection.Parameters) – Connection parameters
  - on_open_callback (method) – Called when the connection is opened
  - on_open_error_callback (method) – Called if the connection cant be opened
  - on_close_callback (method) – Called when the connection is closed

  `add_backpressure_callback`(callback_method)

    Call method “callback” when pika believes backpressure is being applied.

    Parameters: | callback_method (method) – The method to call

  `add_on_close_callback`(callback_method)

    Add a callback notification when the connection has closed. The callback will be passed the connection, the reply_code (int) and the reply_text (str), if sent by the remote server.

    Parameters: | callback_method (method) – Callback to call on close

  `add_on_connection_blocked_callback`(callback_method)

    Add a callback to be notified when RabbitMQ has sent a `Connection.Blocked` frame indicating that RabbitMQ is low on resources. Publishers can use this to voluntarily suspend publishing, instead of relying on back pressure throttling. The callback will be passed the `Connection.Blocked` method frame.

    See also ConnectionParameters.blocked_connection_timeout.

    Parameters: | callback_method (method) – Callback to call on Connection.Blocked, having the signature callback_method(pika.frame.Method), where the method frame’s method member is of type pika.spec.Connection.Blocked

  `add_on_connection_unblocked_callback`(callback_method)

    Add a callback to be notified when RabbitMQ has sent a `Connection.Unblocked` frame letting publishers know it’s ok to start publishing again. The callback will be passed the `Connection.Unblocked` method frame.

    Parameters: | callback_method (method) – Callback to call on Connection.Unblocked, having the signature callback_method(pika.frame.Method), where the method frame’s method member is of type pika.spec.Connection.Unblocked

  `add_on_open_callback`(callback_method)

    Add a callback notification when the connection has opened.

    Parameters: | callback_method (method) – Callback to call when open

  `add_on_open_error_callback`(callback_method, remove_default=True)

    Add a callback notification when the connection can not be opened.

    The callback method should accept the connection object that could not connect, and an optional error message.

    Parameters:

    - callback_method (method) – Callback to call when can’t connect
    - remove_default (bool) – Remove default exception raising callback

  `add_timeout`(deadline, callback_method)

    Adapters should override to call the callback after the specified number of seconds have elapsed, using a timer, or a thread, or similar.

    Parameters:

    - deadline (int) – The number of seconds to wait to call callback
    - callback_method (method) – The callback method

  `basic_nack`

    Specifies if the server supports basic.nack on the active connection.

    Return type: | bool

  `channel`(on_open_callback, channel_number=None)

    Create a new channel with the next available channel number or pass in a channel number to use. Must be non-zero if you would like to specify but it is recommended that you let Pika manage the channel numbers.

    Parameters:

    - on_open_callback (method) – The callback when the channel is opened
    - channel_number (int) – The channel number to use, defaults to the next available.

    Return type: | pika.channel.Channel

  `close`(reply_code=200, reply_text='Normal shutdown')

    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:

    - reply_code (int) – The code number for the close
    - reply_text (str) – The text reason for the close

  `connect`()

    Invoke if trying to reconnect to a RabbitMQ server. Constructing the Connection object should connect on its own.

  `consumer_cancel_notify`

    Specifies if the server supports consumer cancel notification on the active connection.

    Return type: | bool

  `exchange_exchange_bindings`

    Specifies if the active connection supports exchange to exchange bindings.

    Return type: | bool

  `is_closed`

    Returns a boolean reporting the current connection state.

  `is_closing`

    Returns True if connection is in the process of closing due to client-initiated close request, but closing is not yet complete.

  `is_open`

    Returns a boolean reporting the current connection state.

  `publisher_confirms`

    Specifies if the active connection can use publisher confirmations.

    Return type: | bool

  `remove_timeout`(timeout_id)

    Adapters should override: Remove a timeout

    Parameters: | timeout_id (str) – The timeout id to remove

  `set_backpressure_multiplier`(value=10)

    Alter the backpressure multiplier value. We set this to 10 by default. This value is used to raise warnings and trigger the backpressure callback.

    Parameters: | value (int) – The multiplier value to set