Reduce db calls when presenting processes (#4889)

Eager load apps, buildpack_lifecycle_data, and cnb_lifecycle_data. This
data is needed to determine if the process belongs to a docker app to
then either get the run_action_user from the execution_metadata or
return a default user name.

Also remove the check if a droplet belongs to a docker app in
'docker_user'. This issues one or two db requests (check if
buildpack_lifecycle_data or cnb_lifecycle_data exists) and it is only
called from process_model and task_model (docker_run_action_user) after
it has already been verified that it's a docker app.

Author: philippthun

app/models/runtime/droplet_model.rb

@@ -126,8 +126,6 @@ def docker_ports
     end
 
     def docker_user
-      return '' unless docker?
-
       container_user = ''
       if execution_metadata.present?
         begin

app/presenters/v3/process_presenter.rb

@@ -8,6 +8,13 @@ module V3
       class ProcessPresenter < BasePresenter
         include VCAP::CloudController::Presenters::Mixins::MetadataPresentationHelpers
 
+        class << self
+          # :labels and :annotations come from MetadataPresentationHelpers
+          def associated_resources
+            super + [{ app: %i[buildpack_lifecycle_data cnb_lifecycle_data] }]
+          end
+        end
+
         def to_hash
           health_check_data = { timeout: process.health_check_timeout, invocation_timeout: process.health_check_invocation_timeout, interval: process.health_check_interval }
           health_check_data[:endpoint] = process.health_check_http_endpoint if process.health_check_type == HealthCheckTypes::HTTP

spec/request/processes_spec.rb

@@ -83,6 +83,23 @@
       allow(instances_reporters).to receive(:instances_for_processes).and_return(instances_for_processes)
     end
 
+    context 'eager loading' do
+      let(:cnb_app) { VCAP::CloudController::AppModel.make(:cnb, space:) }
+      let!(:cnb_process_1) { VCAP::CloudController::ProcessModel.make(:cnb, app: cnb_app) }
+      let!(:cnb_process_2) { VCAP::CloudController::ProcessModel.make(:cnb, app: cnb_app) }
+      let(:get_processes) { -> { get '/v3/processes', nil, developer_headers } }
+
+      it 'eager loads associated data needed to present processes' do
+        expect { get_processes.call }.to have_queried_db_times(/SELECT .* FROM .processes. /i, 1)
+        expect(last_response.status).to eq(200)
+        expect(parsed_response['resources'].count).to eq(4)
+
+        expect { get_processes.call }.to have_queried_db_times(/SELECT .* FROM .apps. /i, 1) # instead of 4 w/o eager loading
+        expect { get_processes.call }.to have_queried_db_times(/SELECT .* FROM .buildpack_lifecycle_data. /i, 1) # instead of 4 w/o eager loading
+        expect { get_processes.call }.to have_queried_db_times(/SELECT .* FROM .cnb_lifecycle_data. /i, 1) # instead of 2 w/o eager loading
+      end
+    end
+
     it_behaves_like 'list query endpoint' do
       let(:message) { VCAP::CloudController::ProcessesListMessage }
       let(:request) { '/v3/processes' }

spec/unit/controllers/v3/processes_controller_spec.rb

@@ -17,7 +17,7 @@
       it 'eager loads associated resources that the presenter specifies' do
         expect(VCAP::CloudController::ProcessListFetcher).to receive(:fetch_for_app).with(
           an_instance_of(VCAP::CloudController::ProcessesListMessage),
-          hash_including(eager_loaded_associations: %i[labels annotations])
+          hash_including(eager_loaded_associations: [:labels, :annotations, { app: %i[buildpack_lifecycle_data cnb_lifecycle_data] }])
         ).and_call_original
 
         get :index, params: { app_guid: app.guid }
@@ -103,7 +103,7 @@
         it 'eager loads associated resources that the presenter specifies' do
           expect(VCAP::CloudController::ProcessListFetcher).to receive(:fetch_all).with(
             an_instance_of(VCAP::CloudController::ProcessesListMessage),
-            hash_including(eager_loaded_associations: %i[labels annotations])
+            hash_including(eager_loaded_associations: [:labels, :annotations, { app: %i[buildpack_lifecycle_data cnb_lifecycle_data] }])
           ).and_call_original
 
           get :index

spec/unit/models/runtime/droplet_model_spec.rb

@@ -349,12 +349,6 @@ module VCAP::CloudController
     describe '#docker_user' do
       let(:droplet_model) { DropletModel.make }
 
-      context 'when the droplet DOES NOT belong to a Docker lifecycle app' do
-        it 'returns an empty string' do
-          expect(droplet_model.docker_user).to eq('')
-        end
-      end
-
       context 'when the droplet belongs to a Docker lifecycle app' do
         let(:droplet_execution_metadata) { '{"entrypoint":["/image-entrypoint.sh"],"user":"cnb"}' }
         let(:droplet_model) { DropletModel.make(:docker, execution_metadata: droplet_execution_metadata) }