Regions And Device Ownership; Failover Behavior Within A Region - HP HPE VAN SDN Controller 2.7 Administrator's Manual

NOTE:
IPv6 addresses occurring in any region field are not supported and will cause the region to
be ignored.
All region configuration operations (create, update, refresh, and delete) using the
REST API require that every controller specified in the team, including the master controller
and all slave controllers, be in an active state. If any controller in the region is in a
suspended or unreacheable state, then the region configuration operations are disallowed.

Regions and device ownership

Regions in standalone environments
In a standalone environment, regions are not enforced, and devices are owned by the standalone
controller.
Regions in teamed environments
In a teamed environment, assigning devices and controllers to regions can ensure controller
availability to devices when one of the following situations occur:
A single controller fails.
A single controller is disconnected from the other controllers in the team.
A single device is disconnected from one or two controllers in the team.
Each region is configured with a prioritized list of controllers, which are used by the Device Owner
Service to assign specific roles to each controller:
master
The highest-priority controller is the configured master controller. The controller that has the
role of master for a region is also considered the owner of the devices in the region. For a
given device, only the controller that currently has the role of master controller can write to
or modify the device. The controller that has the role of master at any given time might not
be the configured master controller. For example, the configured master controller might be
offline.
slave
Controllers with this role can read the configurations of the network devices that are managed
by the region, but cannot write or modify those configurations. The slave controllers, in priority
order, are the configured primary slave and the configured secondary slave. Controllers with
a configured role of slave can be assigned the role of master controller temporarily, such as
when the configured master controller is offline or a device has lost connection to both the
configured master controller and the primary slave controller.

Failover behavior within a region

Device Owner Service triggers the failover operation in two cases:
Controller failure: The Device Owner Service detects a controller failure in a team through
notifications from the teaming subsystem. If Device Owner Service determines that the failed
controller instance was a master for any devices within a region, it immediately elects an
appropriate backup (slave) controller to assume the master role over the affected devices.
Device disconnect: The Device Owner Service instance in a controller is notified of a
communication failure with network device(s) through the Controller Service notifications. It
instantly communicates with all Device Owner Service instances in the team to determine
if the network device(s) in question are still connected to any of the backup (slave) controllers
within the team. If that is the case, it elects one of the slaves to assume the master role over
the affected network device(s).
The first slave will be chosen as master if it still has connectivity with the device(s), and the
second slave will be chosen as master if neither the configured master or first slave have
connectivity with the device(s).
Team configuration using curl commands 189