2.3. High Availability with pacemaker and DVR
In addition to the required HA profile, Red Hat recommends that you deploy OVN with DVR to ensure the availability of networking services. With the HA profile enabled, the OVN database servers start on all the Controllers, and pacemaker
then selects one controller to serve in the master role.
The ovsdb-server
service does not currently support active-active mode. It does support HA with the master-slave mode, which is managed by Pacemaker using the resource agent Open Cluster Framework (OCF) script. Having ovsdb-server
run in master mode allows write access to the database, while all the other slave ovsdb-server
services replicate the database locally from the master, and do not allow write access.
The YAML file for this profile is the tripleo-heat-templates/environments/services/neutron-ovn-dvr-ha.yaml
file. When enabled, the OVN database servers are managed by Pacemaker, and puppet-tripleo
creates a pacemaker OCF resource named ovn:ovndb-servers
.
The OVN database servers are started on each Controller node, and the controller owning the virtual IP address (OVN_DBS_VIP
) runs the OVN DB servers in master mode. The OVN ML2 mechanism driver and ovn-controller
then connect to the database servers using the OVN_DBS_VIP
value. In the event of a failover, Pacemaker moves the virtual IP address (OVN_DBS_VIP
) to another controller, and also promotes the OVN database server running on that node to master.