Deal with missing volume_type

[ekohl]

LVM volumes do not have a volume type and after a reload the value is set to nil. 0277e9b introduced that reload after saving. The mock driver doesn't properly show this behavior, which is why it was missed. A test is added to simulate the real world behavior.

Fixes: 0277e9b ("Correctly load volumes after creation and cloning")
Link: https://libvirt.org/formatstorage.html#storage-volume-target-elements
Link: https://libvirt.org/storage.html#valid-logical-volume-format-types

Fixes #169

[ekohl]

@nofaralfasi mind taking a look? I take https://community.theforeman.org/t/invalid-libvirt-xml-unknown-driver-format-value/43081/10 as a confirmation that it works.

[mxey]

With this reproducer, the output does not change:

require 'fog/libvirt'

compute = Fog::Compute.new(provider: :libvirt, libvirt_uri: "qemu+ssh://s098209.rz.babiel.com/system")
vol = compute.volumes.new
puts "format_type before save: #{vol.format_type.inspect}"
vol.save
puts "format_type after save: #{vol.format_type.inspect}"

Gemfile:

source 'https://rubygems.org'

gem 'fog-libvirt', github: 'ekohl/fog-libvirt', ref: 'fix-volume-format_type-handling'

$ bundle install           
$ bundle show 
Gems included by the bundle:
  * builder (3.3.0)
  * bundler (2.6.9)
  * excon (1.2.5)
  * fog-core (2.6.0)
  * fog-json (1.2.0)
  * fog-libvirt (0.13.2 1614014)
  * fog-xml (0.1.5)
  * formatador (1.1.0)
  * json (2.12.0)
  * logger (1.7.0)
  * mime-types (3.7.0)
  * mime-types-data (3.2025.0514)
  * multi_json (1.15.0)
  * nokogiri (1.18.8)
  * racc (1.8.1)
  * ruby-libvirt (0.8.4)
$ bundle exec ruby repro.rb
format_type before save: "raw"
format_type after save: nil

Changing the Gemfile back to 0.12.0, it works:

fog-libvirt LVM Bug  % bundle show
Gems included by the bundle:
  * builder (3.3.0)
  * bundler (2.6.9)
  * excon (1.2.5)
  * fog-core (2.6.0)
  * fog-json (1.2.0)
  * fog-libvirt (0.12.0)
  * fog-xml (0.1.5)
  * formatador (1.1.0)
  * json (2.12.0)
  * logger (1.7.0)
  * mime-types (3.7.0)
  * mime-types-data (3.2025.0514)
  * multi_json (1.15.0)
  * nokogiri (1.18.8)
  * racc (1.8.1)
  * ruby-libvirt (0.8.4)
fog-libvirt LVM Bug  % bundle exec ruby repro.rb
format_type before save: "raw"
/opt/homebrew/lib/ruby/gems/3.2.0/gems/fog-libvirt-0.12.0/lib/fog/libvirt/models/compute/util/util.rb:24: warning: Passing safe_level with the 2nd argument of ERB.new is deprecated. Do not use it, and specify other arguments as keyword arguments.
/opt/homebrew/lib/ruby/gems/3.2.0/gems/fog-libvirt-0.12.0/lib/fog/libvirt/models/compute/util/util.rb:24: warning: Passing trim_mode with the 3rd argument of ERB.new is deprecated. Use keyword argument like ERB.new(str, trim_mode: ...) instead.
format_type after save: "raw"

[mxey]

Handling a nil volume_type when creating the server might fix the issue with Foreman though, but it's IMO more of a workaround.

[ekohl]

@mxey as indicated in the linked resources, this is mirroring what libvirt internally does. LVM doesn't have a format type so pretending it does doesn't make sense.

[mxey]

@mxey as indicated in the linked resources, this is mirroring what libvirt internally does. LVM doesn't have a format type so pretending it does doesn't make sense.

OK, then the default format_type set to raw also does not make sense. This PR fixes the problem if used through Foreman, but it does not solve the bug as I filed it, which affects more API. I personally do not care about the other API, but maybe other users of the library do?

[ekohl]

I debated dropping the default of raw. Might still revisit that

[lestercheung]

For the record we have deployed this fix since 2025 Q3 which works for us (Foreman v3.17) and I agree with @ekohl's interpretation that LVM volume doesn't have a format from libvirt's point of view and thus shouldn't have a format type set.