The nova-conductor
service enables OpenStack to function without compute nodes
accessing the database. Conceptually, it implements a new
layer on top of nova-compute. It should not be deployed on
compute nodes, or else the security benefits of removing
database access from nova-compute are negated. Just like
other nova services such as nova-api or nova-scheduler, it can be scaled
horizontally. You can run multiple instances of nova-conductor on different
machines as needed for scaling purposes.
The methods exposed by nova-conductor are relatively
simple methods used by nova-compute to offload its database
operations. Places where nova-compute previously performed database
access are now talking to nova-conductor. However, we have plans in
the medium to long term to move more and more of what is
currently in nova-compute up to the nova-conductor layer. The
Compute service will start to look like a less intelligent
slave service to nova-conductor. The conductor service will
implement long running complex operations, ensuring forward
progress and graceful error handling. This will be especially
beneficial for operations that cross multiple compute nodes,
such as migrations or resizes.
To customize the Conductor, use the configuration option settings documented in Table 4.23, “Description of conductor configuration options”.
