.. nova-fake-driver:

================
Nova Fake Driver
================

One common question from OpenStack operators is that "how does the control
plane (e.g., database, messaging queue, nova-scheduler ) scales?". To answer
this question, operators setup Rally to drive workload to the OpenStack cloud.
However, without a large number of nova-compute nodes, it becomes difficult to
exercise the control performance.

Given the built-in feature of Docker container, Kolla enables standing up many
many of nova-compute nodes with nova fake driver on a single host. For example,
we can create 100 nova-compute containers on a real host to simulate the
100-hypervisor workload to the nova-conductor and the messaging queue.

Use nova-fake driver
====================

Nova fake driver can not work with all-in-one deployment. This is because the
fake neutron-openvswitch-agent for the fake nova-compute container conflicts
with neutron-openvswitch-agent on the compute nodes. Therefore, in the
inventory the network node must be different than the compute node.

By default, Kolla uses libvirt driver on the compute node. To use nova-fake
driver, edit the following parameters in ``ansible/group_vars`` or in the
command line options.

::

  enable_nova_fake: "yes"
  num_nova_fake_per_node: 5

Each compute nodes will run 5 nova-compute containers and 5
neutron-plugin-agent containers. When booting instance, there will be no real
instances created. But *nova list* shows the fake instances.