[2.5, upgrade-series] prepare sub-command applied to machine with no units produces awkward output

[Peter Matulis]

When the `upgrade-series prepare` command affects a machine without any units (controller) the output is awkward due to much whitespace. Perhaps text such as "no units found" is apropos here.

$ juju upgrade-series -m controller prepare 0 bionic

WARNING This command will mark machine "0" as being upgraded to series "bionic"
This operation cannot be reverted or canceled once started. The units
of machine "0" will also be upgraded. These units include:

Continue [y/N]?y
machine-0 started upgrade series from series xenial to series bionic
machine-0 all necessary binaries and service files written

Juju is now ready for the series to be updated.
Perform any manual steps required along with "do-release-upgrade".
When ready run the following to complete the upgrade series process:

juju upgrade-series complete 0

[Peter Matulis (petermatulis)]

LP modified the original text to remove 2 blank lines. There are actually 3 blank lines above the
"Continue" line.

[Peter Matulis (petermatulis)]

I now understand that a controller (machine without units) is not supported by `upgrade-series`.

Would it make sense to prevent the 'prepare' of a controller machine?

[Tim Penhey (thumper)]

We should have better support for machines without units, as this is
entirely valid, if unusual, in normal models.

We should also have early exit for attempting to upgrade controllers.

The reason for the the current restrictions around upgrading controllers
is around the underlying Juju database, and having to upgrade the
content from one version of mongo to another. Also we are unsure how HA
would work across mongo version skew - likely answer is that it doesn't
very well at all.

On 12/10/18 07:33, Peter Matulis wrote:
> I now understand that a controller (machine without units) is not
> supported by `upgrade-series`.
>
> Would it make sense to prevent the 'prepare' of a controller machine?
>

[Ian Booth (wallyworld)]

Just to clarify comment #2 - a controller can have units. People can and do deploy to the controller machine.

[Richard Harding (rharding)]

I've added a task to fail early on controller machines and we can do better for output on machines w/o units.

[Joseph Phillips (manadart)]

https://github.com/juju/juju/pull/9375 causes the section on affected units to be omitted from the confirmation prompt where there are none on the machine.