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Configure the Oslo RPC messaging system
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OpenStack projects use AMQP, an open standard for messaging middleware.
This messaging middleware enables the OpenStack services that run on
multiple servers to talk to each other. OpenStack Oslo RPC supports
three implementations of AMQP: ``RabbitMQ``, ``Qpid``, and ``ZeroMQ``.

Configure RabbitMQ
~~~~~~~~~~~~~~~~~~

OpenStack Oslo RPC uses ``RabbitMQ`` by default.
Use these options to configure the ``RabbitMQ`` message system.
The ``rpc_backend`` option is not required as long as ``RabbitMQ``
is the default messaging system. However, if it is included in
the configuration, you must set it to ``rabbit``.

.. code-block:: ini

   rpc_backend=rabbit

You can use these additional options to configure the ``RabbitMQ``
messaging system. You can configure messaging communication for
different installation scenarios, tune retries for RabbitMQ, and
define the size of the RPC thread pool. To monitor notifications
through ``RabbitMQ``, you must set the ``notification_driver`` option to
``nova.openstack.common.notifier.rpc_notifier`` in the ``nova.conf`` file.
The default for sending usage data is sixty seconds plus a random
number of seconds from zero to sixty.

.. include:: ../tables/nova-rabbitmq.rst

Configure Qpid
~~~~~~~~~~~~~~

Use these options to configure the ``Qpid`` messaging system for
OpenStack Oslo RPC. ``Qpid`` is not the default messaging system,
so you must enable it by setting the ``rpc_backend`` option in the
``nova.conf`` file.

.. code-block:: ini

   rpc_backend=qpid

.. warning::

   The Qpid driver has been deprecated.
   The driver is planned to be removed during the Mitaka development cycle.

This critical option points the compute nodes to the ``Qpid`` broker (server).
Set ``qpid_hostname`` to the host name where the broker runs in the
``nova.conf`` file.

.. note::

   The :option:`--qpid_hostname` parameter accepts a host name or IP address value.

.. code-block:: ini

   qpid_hostname=hostname.example.com

If the ``Qpid`` broker listens on a port other than the AMQP default of
``5672``, you must set the ``qpid_port`` option to that value:

.. code-block:: ini

   qpid_port=12345

If you configure the ``Qpid`` broker to require authentication,
you must add a user name and password to the configuration:

.. code-block:: ini

   qpid_username=username
   qpid_password=password

By default, TCP is used as the transport.
To enable SSL, set the ``qpid_protocol`` option:

.. code-block:: ini

   qpid_protocol=ssl

This table lists additional options that can be used to configure the Qpid
messaging driver for OpenStack Oslo RPC. These options are used infrequently.

.. include:: ../tables/nova-qpid.rst

Configure ZeroMQ
~~~~~~~~~~~~~~~~

Use these options to configure the ``ZeroMQ`` messaging system for OpenStack
Oslo RPC. ``ZeroMQ`` is not the default messaging system, so you must enable
it by setting the ``rpc_backend`` option in the ``nova.conf`` file.

.. include:: ../tables/nova-zeromq.rst

Configure messaging
~~~~~~~~~~~~~~~~~~~

Use these options to configure the ``RabbitMQ`` and ``Qpid``
messaging drivers.

.. include:: ../tables/nova-amqp.rst
.. include:: ../tables/nova-rpc.rst