The CONF.compute.max_disk_devices_to_attach option controls the maximum
number of disk devices allowed to attach to an instance. If it is set
to 0, it will literally allow no disk device for instances, preventing
them from being able to boot.
This adds a note to the config option help to call this out and changes
nova-compute to raise InvalidConfiguration during init_host if
[compute]max_disk_devices_to_attach has been set to 0. The nova-compute
service will fail to start if the option is set to 0.
Note: there doesn't appear to be any way to disallow particular values
in a oslo.config IntOpt other than the min/max values. Here we need the
min value to be -1 to represent unlimited. There is a 'choices' kwarg
available but that is only for enumerating valid values and we need to
allow any integer >= 1 as well.
Change-Id: I6e30468bc28f661ddc17937ab1de04a706f05063
Closes-Bug: #1897950
(cherry picked from commit 25a632a4e1)
(cherry picked from commit 8e12b81839)
(cherry picked from commit 4ad7e5e263)
62bf0ef129