LVM setup fails with cryptic error message if no devices are configured

[Jason Hobbs]

This is hit if no existing cinder-volumes VG is present, and the devices configured for use in the deployment have existing partition tables and 'overwrite' is set to false. The test for 'vg_found is False and len(new_devices) >' 0 will be false, no volume group will be created, and the vgreduce call will fail with this error:

Volume group "cinder-volumes" not found

Traceback: http://pastebin.ubuntu.com/11911587/

Workaround: This issue can also be avoided by setting the cinder charm's 'overwrite' config field to 'True'.

Suggested fix: the charm should check for the condition where no valid devices are available and no volume group will be created, and should raise an error indicating this before moving on with setup that depends on the volume group's existence.

[Corey Bryant (corey.bryant)]

Jason, thanks for the thorough bug report and suggestion. I agree that we should raise an error if there is no volume group found or created, and overwrite is false.