OpenStack projects use an open standard for messaging middleware known as AMQP. This messaging middleware enables the OpenStack services which will exist across multiple servers to talk to each other. OpenStack Oslo RPC supports three implementations of AMQP: RabbitMQ, Qpid, and ZeroMQ.

OpenStack Oslo RPC uses RabbitMQ by default. This section discusses the configuration options that are relevant when RabbitMQ is used. The rpc_backend option is not required as long as RabbitMQ is the default messaging system. However, if it is included the configuration, it must be set to nova.openstack.common.rpc.impl_kombu. rpc_backend=nova.openstack.common.rpc.impl_kombu The following tables describe the rest of the options that can be used when RabbitMQ is used as the messaging system. You can configure the messaging communication for different installation scenarios as well as tune RabbitMQ's retries and the size of the RPC thread pool. If you want to monitor notifications through RabbitMQ, you must set the notification_driver option in nova.conf to nova.notifier.rabbit_notifier. The default for sending usage data is 60 seconds plus a randomized 0-60 seconds.

This section discusses the configuration options that are relevant if Qpid is used as the messaging system for OpenStack Oslo RPC. Qpid is not the default messaging system, so it must be enabled by setting the rpc_backend option in nova.conf. rpc_backend=nova.openstack.common.rpc.impl_qpid This next critical option points the compute nodes to the Qpid broker (server). Set qpid_hostname in nova.conf to be the hostname where the broker is running. The --qpid_hostname option accepts a value in the form of either a hostname or an IP address. qpid_hostname=hostname.example.com If the Qpid broker is listening on a port other than the AMQP default of 5672, you will need to set the qpid_port option: qpid_port=12345 If you configure the Qpid broker to require authentication, you will need to add a username and password to the configuration: qpid_username=username qpid_password=password By default, TCP is used as the transport. If you would like to enable SSL, set the qpid_protocol option: qpid_protocol=ssl The following table lists the rest of the options used by the Qpid messaging driver for OpenStack Oslo RPC. It is not common that these options are used.

This section discusses the configuration options that are relevant if ZeroMQ is used as the messaging system for OpenStack Oslo RPC. ZeroMQ is not the default messaging system, so it must be enabled by setting the rpc_backend option in nova.conf.

This section lists options that are common between both the RabbitMQ and Qpid messaging drivers.