Consolidated object storage - bucket name required even if selected object storage disabled

Summary

If a user enables consolidated object storage https://docs.gitlab.com/ee/administration/object_storage.html#consolidated-object-storage-configuration, by default this enables object storage for all object types.

If a user then selectively disables some object storage types, they are still required to set a bucket name for that object type.

Our documentation does mention if you selectively disable object storage, then you still must specify a bucket name https://docs.gitlab.com/ee/administration/object_storage.html#selectively-disabling-object-storage, otherwise the reconfigure will fail. This seems very strange to me, why should the user specify a bucket name if they aren't using object storage?

Steps to reproduce

1. Enable consolidated object storage https://docs.gitlab.com/ee/administration/object_storage.html#consolidated-object-storage-configuration

2. Configure the artifacts object storage with the below:

   # Selectively disable artifacts object storage
   gitlab_rails['object_store']['objects']['artifacts']['enabled'] = false
   
   # Don't specify a bucket name for artifacts
   # gitlab_rails['object_store']['objects']['artifacts']['bucket'] = 'antons-artifacts-object-store'
   
   # Enable artifacts
   gitlab_rails['artifacts_enabled'] = true

3. Reconfigure GitLab and you see this error:

   Running handlers:
   There was an error running gitlab-ctl reconfigure:
   
   execute[clear the gitlab-rails cache] (gitlab::gitlab-rails line 426) had an error: Mixlib::ShellOut::ShellCommandFailed: Expected process to exit with [0], but received '1'
   ---- Begin output of /opt/gitlab/bin/gitlab-rake cache:clear ----
   STDOUT:
   STDERR: rake aborted!
   Object storage for artifacts must have a bucket specified
   /opt/gitlab/embedded/service/gitlab-rails/config/object_store_settings.rb:108:in `block in parse!'
   /opt/gitlab/embedded/service/gitlab-rails/config/object_store_settings.rb:101:in `each'
   /opt/gitlab/embedded/service/gitlab-rails/config/object_store_settings.rb:101:in `parse!'
   /opt/gitlab/embedded/service/gitlab-rails/config/initializers/1_settings.rb:618:in `<top (required)>'
   /opt/gitlab/embedded/service/gitlab-rails/config/environment.rb:5:in `<top (required)>'
   /opt/gitlab/embedded/bin/bundle:23:in `load'
   /opt/gitlab/embedded/bin/bundle:23:in `<main>'
   Tasks: TOP => cache:clear => cache:clear:redis => environment
   (See full trace by running task with --trace)
   ---- End output of /opt/gitlab/bin/gitlab-rake cache:clear ----
   Ran /opt/gitlab/bin/gitlab-rake cache:clear returned 1

Workaround

As per the documentation https://docs.gitlab.com/ee/administration/object_storage.html#selectively-disabling-object-storage, either specify a bucket name or disable the object type.

Example Project

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What is the current bug behavior?

When selectively disabling object storage types with consolidated object storage, the user is forced to set a bucket name.

What is the expected correct behavior?

When selectively disabling object storage types with consolidated object storage, the user should not need to specify a bucket name.

Relevant logs and/or screenshots

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Output of checks

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Results of GitLab environment info

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`sudo gitlab-rake gitlab:env:info`)

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`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

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sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

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