Plugins » Discovery

Lukas Zapletal wrote:

Shim added (#16646) the ability for plugins to modify the scope used to get hosts for #index action. This is needed if a plugin wants to add more includes or eager_load statements, so Active Record won't try to lazy load additional relations and create N+1 queries.

Discovery should take advantage of this.

@Lukas Zapletal

`ScopesPerAction` can be used once the pull request(https://github.com/theforeman/foreman/pull/3887) gets merged(probably once conflicts are resolved) into foreman, right ?

ScopesPerAction concern is needed if you want to add the ability to customize actions in your controller.
If you want to customize the scope for existing controller (HostsController is the only one that uses ScopesPerAction right now), you will need to register your scope filter in the plugin declaration:

    Foreman::Plugin.register :test_hosts_controller_action_scope do
      add_controller_action_scope HostsController, :test_action, &mock_scope
    end

Shimon Shtein wrote:

ScopesPerAction concern is needed if you want to add the ability to customize actions in your controller.

This looks more of refactoring step.

If you want to customize the scope for existing controller (HostsController is the only one that uses ScopesPerAction right now), you will need to register your scope filter in the plugin declaration:
[...]

So if we take an example from foreman_discovery plugin.
https://github.com/theforeman/foreman_discovery/blob/develop/app/controllers/discovered_hosts_controller.rb#L20-L25

The `includes` method chained in DiscoveredHostsController#index would be removed and instead the plugin scope will come into play ?

## The index action would look like:

  def index
    @hosts = resource_base.search_for(params[:search], :order => params[:order]).paginate(:page => params[:page])
    fact_array = @hosts.collect do |host|
      [host.id, Hash[host.fact_values.joins(:fact_name).where('fact_names.name' => Setting::Discovered.discovery_fact_column_array).pluck(:name, :value)]]
    end
    @host_facts = Hash[fact_array]
  end

## Some initializer:

  Foreman::Plugin.register :my_plugin do                                                                                                                                                      
    add_controller_action_scope(DiscoveredHostsController, :index) { |base_scope|                                                                                                             
      base_scope.includes([                                                                                                                                                                   
                            :location,                                                                                                                                                        
                            :organization,                                                                                                                                                    
                            :model,                                                                                                                                                           
                            :discovery_attribute_set                                                                                                                                          
                          ], {:interfaces => :subnet}) }                                                                                                                                      
  end