documentation: auto recovery method need not evacuate instance to a host within same segment

[Hemanth Nakkina]

The documentation claims for a compute host failure, the instances are moved to compute host within same segment [1].

The statement is true for recovery method 'reserved_host' but need not be accurate for other recovery methods especially auto. When auto recovery method is involved, the scheduler can evacuate the instance to any compute node (without considering failover segment).

There is an open bug on this in masakari [2] (may be called as new feature as the code is never intended to failover to same segment since inception) but based on code review comments in the patch this is not likely to get fixed until consensus is achieved in masakari community.

Ask here is to change documentation [1] about evacuation to compute host in same segment until the bug is fixed.

Also given the auto recovery method current functionality, it does not make sense for operator to create multiple AUTO recovery segments. A single segment for AUTO failover mechanism is sufficient. This can be discussed further in the existing bug https://bugs.launchpad.net/charm-masakari/+bug/1898115

[1] https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-masakari.html#instance-evacuation-recovery-methods
[2] https://launchpad.net/bugs/1870305
[3] https://review.opendev.org/c/openstack/masakari/+/825286

[Khoi (khoinh5)]

Yes, We need recover instance same segment when having multi segments.