OpenStack service specifics
In this section, we'll walk through each of the OpenStack services and outline the HA strategy for them. While most of the services can be configured as active/active behind a load balancer, some of them must be configured as active/passive and others may be configured as active/passive. Some of the configuration is dependent on a particular version of OpenStack as well, especially Ceilometer, Heat, and Neutron. The following details are current as of the Pike release of OpenStack.
OpenStack web services
As a general rule, all of the web services and the Horizon dashboard may be run active/active. These include the API services for Keystone, Glance, Nova, Cinder, Neutron, Heat, and Ceilometer. The scheduling services for Nova, Cinder, Neutron, Heat, and Ceilometer may also be deployed active/active. These services do not require a load balancer, as they respond to requests on the message bus.
Database services
All state for the OpenStack web services is stored in...